Дисертації: "Seismic surface wave"

1

Malladi, Subrahmanya Sastry Venkata. "Modeling and Algorithm Performance For Seismic Surface Wave Velocity Estimation." University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1194630399.

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2

Ruan, Youyi. "Surface wave propagation in 3-D anelastic media." Diss., Virginia Tech, 2012. http://hdl.handle.net/10919/28945.

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Lateral perturbations in anelasticity (Q) and wave speed together provide important constraints on thermal and chemical structures in the mantle. In present-day tomography studies of global wave speed and anelasticity, the significance of 3-D wave speed and 3-D Q structures on surface wave travel times and amplitudes has not been well understood. In this dissertation, the effects of lateral perturbations in anelasticity (Q) and wave speed on surface wave observables are quantified based upon wave propagation simulations in 3-D earth models using a Spectral Element Method. Comparison between phase delays caused by 3-D wave speed structures and those caused by 3-D Q variations show that anelastic dispersion due to lateral perturbation in Q is important in long-period surface wave and can account for 15-20% observed phase delays. For amplitude perturbations, elastic focusing/defocusing effects associated with 3-D wave speed structures are dominant while energy dissipation is important in short-period (â ¼ 50 s) surface waves but decreases quickly with increasing wave period. Anelastic focusing/defocusing associated with 3-D anelastic dispersion becomes more important than wave attenuation in longer period surface waves. In tomography studies, ray theory breaks down and finite frequency effects become important when the length scale of heterogenities are smaller than seismic wavelength. Finite frequency effects in 3-D earth models are investigated by comparing theoretical predictions of travel times and amplitudes with â ground truthâ measurements made on synthetic seismograms generated in SEM simulations. The comparisons show that finite frequency effects are stronger in amplitudes than in phases, especially at long periods.
Ph. D.

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3

Liu, Kui. "Surface Wave Propagation and Global Crustal Tomography." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25428.

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In this thesis, a finite-frequency theory is developed to calculate Born sensitivity kernels for Rayleigh-wave phase and amplitude measurements that are valid in regions near seismic stations. Calculations of sensitivity kernels for inter-station measurements show that exact travelling-wave representation of Green tensor is necessary when station spacing is close to or smaller than the seismic wavelength. This finite-frequency theory will allow us to take advantage of dense seismic arrays to obtain high-resolution surface-wave tomography using inter-station measurements. The non-linear dependence of surface wave phase upon large perturbations in crustal thickness as well as finite-frequency effects in global surface-wave tomography are investigated using wave propagation simulations. Calculations show that non-linearity as well as finite-frequency effects can be accounted for by using 2D phase-velocity kernels for boundary perturbations. A 3D-reference tomographic approach is developed for iterative inversions of global crustal structure where Frechet kernels are calculated in 3D reference models. A global dataset of minor-arc and major-arc Rayleigh wave dispersion measurements at periods between 25 seconds and 100 seconds are built and global phase velocity maps based on the dataset are obtained using diffractional tomography. The phase velocity model confirms many general features associated with surface tectonics including the ocean-continent dichotomy and the signature of lithospheric cooling in oceanic plates. There are significant differences between the phase velocity model and calculations based on a current global model CRUST2.0+S20RTS in oceanic regions, Archean and Proterozoic cratons as well as orogenic belts. In addition, the high resolution phase velocity maps reveal a major change in the distribution of small scale anomalies in the Pacific at different wave periods.
Ph. D.

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4

Hebeler, Gregory L. "Site characterization in Shelby County, Tennessee using advanced surface wave methods." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/20996.

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5

BATTAGLIA, ENZO. "Seismic reflection imaging of near surface structures using the Common Reflection Surface (CRS) Stack Method." Doctoral thesis, Università degli Studi di Cagliari, 2014. http://hdl.handle.net/11584/266406.

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This PhD thesis aims to evaluate whether the Common-Refl ection-Surface (CRS) stack method can be considered as a more cost efficient processing alternative to the conventionally used Common Midpoint (CMP) stack method for processing of shallow and ultrashallow reflection data. The CRS stack is a seismic imaging method established for oil and gas exploration that is similar in concept to the conventional CMP stack method. Unlike the CMP stack, the CRS stack process is not confined to single CMP gathers (offset direction), but also includes neighbouring CMPs (midpoint direction) into the so-called CRS supergathers. The use of CRS supergathers enables stable \data-driven", i.e. without human interactions, velocity analysis and residual static corrections, avoiding the poorly-automated and time-consuming processing steps that are instead required when implementing conventional CMP processing. This makes the seismic imaging process more compatible with budgets available for near-surface geophysical investigations. Improving seismic imaging of near-surface reflection data, while at the same time reducing processing costs and human interaction during processing was the principal objective which guided my work. To investigate the advantages and limitations of exporting the CRS stack from the hydrocarbon exploration field to the near-surface scale, I have firstly analysed and adapted the characteristics of the CRS to the requirements of near-surface reflection data. Then, I have compared the results (seismic sections and velocity fields) obtained by processing with the CMP and the CRS stack methods for two real field datasets (P- and SH-wave)and two synthetic datasets that exhibited very large vertical velocity changes. Finally, I have proposed some original solutions that overcome several of the issues encountered when using CRS stack with near-surface data. The P-wave dataset was collected as part of a hydrogeological investigation with the aim of delineating the hydrogeological framework of a paleolake environment to a depth of few hundred metres. Using the CMP method, several nearly horizontal reectors with onsets from 60 to about 250 ms were imaged. The CRS stack produced a stacked section with greater coherency and lateral continuity than the CMP section, but also spurious alignments of seismic energy which hinder interpretation. Weighing the CRS stacked section with the corresponding CRS coherence and number of CRS stacked traces leads to a considerable reduction of the spurious alignments, resulting in a seismic section more suited to delineate the aquifer and its confining units. The SH-wave ultrashallow dataset was collected to support a geotechnical study to a depth of 10 m. The obtained CMP stacked section imaged a dipping bedrock interface below four horizontal re ectors in unconsolidated, very low velocity sediments. The vertical and lateral resolution was very high, so that despite the very shallow depth the resulting CMP stacked section showed the well-defined pinchout of two layers at less than 10 m depth. The CRS stack improved the continuity of the shallowest reector but showed an excessive smearing effect with some reector portions, including the pinchout, unresolved and not as well defined as in the (very detailed) CMP counterpart. Restricting the CRS stack process to single CMP gathers, preserving the CRS-supergather for the search of stacking parameters, produced a time section very similar to the CMP counterpart. In both cases, I swiftly obtained the CRS stacked sections in a fully automatic way, so with a cost/benefit ratio considerably more advantageous than that of the CMP sections, which required time-consuming prestack velocity analysis as well as residual static corrections. Moreover, using the kinematic wave field attributes determined for each stacking operation I reconstructed velocity fields matching the ones estimated with the CMP processing, even if this required a greater amount of work than that required to produce the CRS stacked sections. Finally, using two synthetic datasets, I addressed the issue of the crossing reection events that appear in data acquired in soils characterized by strong vertical velocity gradients. Although a matter debate for decades, this is an issue still unresolved by use of the conventional CMP method. Using the first synthetic dataset I showed that unlike in conventional CMP processing which cannot accurately process crossing reflection events without generating distortions and artefacts, the data-driven CRS stack imaging process considerably restricts their generation, limiting the reduction of signal-to-noise ratio and of temporal resolution in stacked traces. With the second synthetic dataset I simulated a data acquisition reproducing a case history with a high-velocity contrast in the first 5 m depth. The CRS results that I obtained from the modelled data demonstrated that the CRS stack method may be a reliable alternative for processing crossing reection events, definitely easier and faster than the construction of complicated velocity functions and/or the separated processing of the crossing events. By comparing these results with those obtained using the CMP method I obtained other interesting results, which, however, to validate would necessitate the use of real datasets. The findings of this present study demonstrates that the CRS stack could represent a significant step forward for the reduction of the costs involved in shallow and ultrashallow seismic reflection data processing, one which does not compromise the quality of results. Both these conditions being essential to the increased acceptance of the seismic reection method as a routine investigation method for use in shallow and ultrashallow seismics.

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6

Almayahi, Ali Z. "SHEAR-WAVE IMAGING AND BIREFRINGENCE IN A COMPLEX NEAR-SURFACE GEOLOGICAL ENVIRONMENT." UKnowledge, 2013. http://uknowledge.uky.edu/ees_etds/12.

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Multiple geophysical and geological data sets were compiled, reprocessed, and interpreted using state-of-the-art signal processing and modeling algorithms to characterize the complex post-Paleozoic geology that overlies the southwestern projection of the Fluorspar Area Fault Complex (FAFC) in western Kentucky. Specific data included 21.5 km of SH-wave seismic reflection, 1.5 km of P-wave seismic reflection, 2 km of electrical resistivity, vertical seismic profiles, Vp and Vs sonic-suspension logs, and 930 lithologic borehole logs. The resultant model indicates three general northeast–southwest-oriented fault zones pass through the study area as southwestern extensions of parts of the FAFC. These fault zones form two significant subparallel grabens with ancillary substructures. The geometry of the interpreted fault zones indicates that they have undergone episodic tectonic deformation since their first formation. Evidence of thickening and steeply dipping reflectors within Tertiary and Quaternary sediment in the downthrown blocks indicate syndepositional movement. Subtle thickening and lack of steeply dipping intraformational reflectors in the Cretaceous suggest a more quiescent period, with sediment deposition unconformably draping and filling the earlier Paleozoic structural surface. There is also evidence that the Tertiary and early Quaternary reactivation was associated with an extensional to compressional regional stress reversal, as manifested by the antiformal folds seen in the hanging wall reflectors and the potential small-amplitude force folds in the Quaternary alluvium, as well as a clear displacement inversion along the Metropolis-loess seismic horizon in two high-resolution reflection images. A surface shear-wave splitting experiment proved to be an efficient and effective tool for characterizing shallow subsurface azimuthally anisotropic geologic inclusions in low-impedance water-saturated sediment environments. The measured azimuthal anisotropy across a well-constrained N60ºE-striking fault exhibited a natural coordinate system that had a fast direction coincident with the fault strike and an orthogonal slow direction. This is also one indicator that faults inactive during significant geologic intervals (i.e., Holocene) do not "heal". Integrated shear-wave velocity models and electrical resistivity tomography profiles across the fault zones exhibit lower shear-wave velocities and resistivities within the deformation zones compared with values outside the boundaries. This is additional evidence that the deformed sediment does not reconsolidate or heal, but that the sediment particle configuration remains more loosely packed, providing an increase in the overall porosity (i.e., hydraulic conductivity). This can wholly or in large part explain the anomalous contaminant plume migration path that is coincident with the deformed zones of the regional gravel groundwater aquifer.

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7

Liu, Faqi. "Surface multiple attenuation operators in the plane wave domain : theory and applications /." Digital version accessible at:, 1999. http://wwwlib.umi.com/cr/utexas/main.

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8

Schlottmann, Robert Brian. "A path integral formulation of elastic wave propagation /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004372.

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9

Baumann-Wilke, Maria. "Combining body wave tomography, surface wave inversion, seismic interferometry and laboratory measurements to characterize the black shales on Bornholm at different scales." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2013/6900/.

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Black shales are sedimentary rocks with a high content of organic carbon, which leads to a dark grayish to black color. Due to their potential to contain oil or gas, black shales are of great interest for the support of the worldwide energy supply. An integrated seismic investigation of the Lower Palaeozoic black shales was carried out at the Danish island Bornholm to locate the shallow-lying Alum Shale layer and its surrounding formations and to characterize its potential as a source rock. Therefore, two seismic experiments at a total of three crossing profiles were carried out in October 2010 and in June 2012 in the southern part of the island. Two different active measurements were conducted with either a weight drop source or a minivibrator. Additionally, the ambient noise field was recorded at the study location over a time interval of about one day, and also a laboratory analysis of borehole samples was carried out. The seismic profiles were positioned as close as possible to two scientific boreholes which were used for comparative purposes. The seismic field data was analyzed with traveltime tomography, surface wave inversion and seismic interferometry to obtain the P-wave and S-wave velocity models of the subsurface. The P-wave velocity models which were determined for all three profiles clearly locate the Alum Shale layer between the Komstad Limestone layer on top and the Læså Sandstone Formation at the base of the models. The black shale layer has P-wave velocities around 3 km/s which are lower compared to the adjacent formations. Due to a very good agreement of the sonic log and the vertical velocity profiles of the two seismic lines, which are directly crossing the borehole where the sonic log was conducted, the reliability of the traveltime tomography is proven. A correlation of the seismic velocities with the content of organic carbon is an important task for the characterization of the reservoir properties of a black shale formation. It is not possible without calibration but in combination with a full 2D tomographic image of the subsurface it gives the subsurface distribution of the organic material. The S-wave model obtained with surface wave inversion of the vibroseis data of one of the profiles images the Alum Shale layer also very well with S-wave velocities around 2 km/s. Although individual 1D velocity models for each of the source positions were determined, the subsurface S-wave velocity distribution is very uniform with a good match between the single models. A really new approach described here is the application of seismic interferometry to a really small study area and a quite short time interval. Also new is the selective procedure of only using time windows with the best crosscorrelation signals to achieve the final interferograms. Due to the small scale of the interferometry even P-wave signals can be observed in the final crosscorrelations. In the laboratory measurements the seismic body waves were recorded for different pressure and temperature stages. Therefore, samples of different depths of the Alum Shale were available from one of the scientific boreholes at the study location. The measured velocities have a high variance with changing pressure or temperature. Recordings with wave propagation both parallel and perpendicular to the bedding of the samples reveal a great amount of anisotropy for the P-wave velocity, whereas the S-wave velocity is almost independent of the wave direction. The calculated velocity ratio is also highly anisotropic with very low values for the perpendicular samples and very high values for the parallel ones. Interestingly, the laboratory velocities of the perpendicular samples are comparable to the velocities of the field experiments indicating that the field measurements are sensitive to wave propagation in vertical direction. The velocity ratio is also calculated with the P-wave and S-wave velocity models of the field experiments. Again, the Alum Shale can be clearly separated from the adjacent formations because it shows overall very low vP/vS ratios around 1.4. The very low velocity ratio indicates the content of gas in the black shale formation. With the combination of all the different methods described here, a comprehensive interpretation of the seismic response of the black shale layer can be made and the hydrocarbon source rock potential can be estimated.
Schwarzschiefer sind Sedimentgesteine, die einen hohen Gehalt an organischem Kohlenstoff aufweisen, was zu einer dunkelgrauen bis schwarzen Färbung führt. Da Schwarzschiefer das Potenzial besitzen, Öl oder Gas zu enthalten und somit zur weltweiten Energieversorgung beitragen könnten, sind sie von großem Interesse. Mit Hilfe der Kombination verschiedener seismischer Messverfahren wurden die Schwarzschiefer des Unteren Paläozoikums auf der dänischen Insel Bornholm untersucht um den oberflächennahen Alaunschiefer und dessen Umgebungsgestein dort zu lokalisieren und sein Potenzial als Muttergestein abzuschätzen. Dafür wurden im Oktober 2010 und im Juni 2012 im südlichen Teil der Insel zwei seismische Experimente auf insgesamt drei sich kreuzenden Profilen durchgeführt. Für zwei aktive seismische Messungen wurden ein Fallgewicht und ein Minivibrator als Quellen genutzt. Zusätzlich wurde im Messgebiet noch das Wellenfeld des umgebenden Rauschens über einen Zeitraum von etwa einem Tag aufgezeichnet. Außerdem wurden Labormessungen an Bohrkernen aus dem Alaunschiefer durchgeführt. Die seismischen Messprofile befanden sich so nah wie möglich an zwei wissenschaftlichen Bohrungen, die für Vergleichszwecke genutzt wurden. Um die P- und S-Wellengeschwindigkeitsmodelle des Untergrundes zu erhalten wurden die seismischen Felddaten mittels Laufzeittomographie, Oberflächenwelleninversion und seismischer Interferometrie ausgewertet. Die P-Wellenmodelle, die für alle drei seismischen Profile erstellt wurden, zeigen den Alaunschiefer zwischen dem Komstad Kalkstein, der den Alaunschiefer überdeckt, und der Læså Sandsteinformation, die die Basis der Modelle bildet. Für die Schwarzschieferschicht ergeben sich mit rund 3 km/s deutlich geringere P-Wellengeschwindigkeiten als für die umgebenden Gesteine. Zwei seismische Profile liegen direkt an einer der Bohrungen, für die verschiedene Bohrloch-Logs durchgeführt wurden. Der Vergleich des Sonic-Logs mit den vertikalen Geschwindigkeitsprofilen beider Modelle am Bohrpunkt zeigt eine sehr gute übereinstimmung aller Geschwindigkeiten. Dies ist ein Indiz für die Plausibilität der durchgeführten Laufzeittomographie. Um die Reservoireigenschaften der Schwarzschieferschicht einordnen zu können, wurde versucht, die seismischen Geschwindigkeiten mit dem Gehalt an organischem Material zu korrelieren. Ohne geeignete Kalibrierung ist diese Korrelation schwierig, kann aber mit Hilfe der Tomographieergebnisse ein zweidimensionales Abbild der Verteilung des organischen Materials im Untergrund liefern. Auch das S-Wellengeschwindigkeitsmodell, welches mit der Oberflächenwelleninversion der Vibroseisdaten erstellt wurde, bildet den Alaunschiefer gut ab. Hierbei zeigen sich S-Wellengeschwindigkeiten um 2 km/s. Obwohl jeweils nur 1D-Modelle für jede Quellposition bestimmt wurden, ergibt sich für die gesamte Untergrundstruktur des untersuchten Profils ein einheitliches Bild der Geschwindigkeiten. Einen sehr neuen Ansatz bildet die Anwendung der seismischen Interferometrie auf ein sehr kleines Untersuchungsgebiet und über einen sehr kurzen Zeitraum. Neu ist außerdem, dass für die Bestimmung der endgültigen Interferogramme nur Zeitfenster der Kreuzkorrelationen ausgewählt werden, in denen die Signalqualität hinreichend gut ist. In den berechneten Kreuzkorrelationen sind sogar P-Wellen enthalten, was auf die geringen Abstände der seismischen Rekorder zurück zu führen ist. Bei den Labormessungen wurden die Raumwellen für verschiedene Drücke und Temperaturen aufgezeichnet. Die Messungen der Geschwindigkeiten sowohl parallel als auch senkrecht zur Schichtung der Proben zeigen eine starke Anisotropie für die P-Welle. Dagegen scheint die S-Wellengeschwindigkeit fast unabhängig von der Ausbreitungsrichtung der Wellen zu sein. Auch das Verhältnis der Geschwindigkeiten weist starke Anisotropie auf. Für die Wellenausbreitung senkrecht zur Schichtung zeigen sich sehr niedrige Werte, die Werte für die Messungen parallel zur Schichtung sind dagegen deutlich erhöht. Ein interessanter Aspekt der aus den Labormessungen resultiert ist, dass die Geschwindigkeit der Messungen senkrecht zur Schichtung mit den Geschwindigkeitswerten der Feldmessungen übereinstimmen. Damit scheinen die Feldmessungen besonders die Ausbreitung der Wellen in vertikaler Richtung zu registrieren. Das Geschwindigkeitsverhältnis wurde auch mit den P- und S-Wellenmodellen der Feldexperimente berechnet. Auch hier hebt sich der Alaunschiefer mit deutlich verringerten Werten um 1.4 vom Umgebungsgestein ab. Solch geringe Werte für das Verhältnis der Geschwindigkeiten deutet auf den Gehalt von Gas im Schwarzschiefer. Mit der Kombination der verschiedenen Methoden ist es möglich, die seismische Antwort der Schwarzschieferschicht umfassend zu beschreiben und Schlussfolgerungen darüber zu ziehen, ob die hier untersuchte Schwarzschieferschicht das Potenzial hat als Kohlenwasserstofflagerstätte zu fungieren.

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10

Martin, Brian E. "Seismic surface-wave ray tracing for anisotropic and laterally varying Earth models." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq20671.pdf.

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11

Bjurström, Henrik. "Non-contact surface wave measurements on pavements." Doctoral thesis, KTH, Jord- och bergmekanik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201147.

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In this thesis, nondestructive surface wave measurements are presented for characterization of dynamic modulus and layer thickness on different pavements and cement concrete slabs. Air-coupled microphones enable rapid data acquisition without physical contact with the pavement surface. Quality control of asphalt concrete pavements is crucial to verify the specified properties and to prevent premature failure. Testing today is primarily based on destructive testing and the evaluation of core samples to verify the degree of compaction through determination of density and air void content. However, mechanical properties are generally not evaluated since conventional testing is time-consuming, expensive, and complicated to perform. Recent developments demonstrate the ability to accurately determine the complex modulus as a function of loading time (frequency) and temperature using seismic laboratory testing. Therefore, there is an increasing interest for faster, continuous field data evaluation methods that can be linked to the results obtained in the laboratory, for future quality control of pavements based on mechanical properties. Surface wave data acquisition using accelerometers has successfully been used to determine dynamic modulus and thickness of the top asphalt concrete layer in the field. However, accelerometers require a new setup for each individual measurement and are therefore slow when testing is performed in multiple positions. Non-contact sensors, such as air-coupled microphones, are in this thesis established to enable faster surface wave testing performed on-the-fly. For this project, a new data acquisition system is designed and built to enable rapid surface wave measurements while rolling a data acquisition trolley. A series of 48 air-coupled micro-electro-mechanical sensor (MEMS) microphones are mounted on a straight array to realize instant collection of multichannel data records from a single impact. The data acquisition and evaluation is shown to provide robust, high resolution results comparable to conventional accelerometer measurements. The importance of a perfect alignment between the tested structure’s surface and the microphone array is investigated by numerical analyses. Evaluated multichannel measurements collected in the field are compared to resonance testing on core specimens extracted from the same positions, indicating small differences. Rolling surface wave measurements obtained in the field at different temperatures also demonstrate the strong temperature dependency of asphalt concrete. A new innovative method is also presented to determine the thickness of plate like structures. The Impact Echo (IE) method, commonly applied to determine thickness of cement concrete slabs using an accelerometer, is not ideal when air-coupled microphones are employed due to low signal-to-noise ratio. Instead, it is established how non-contact receivers are able to identify the frequency of propagating waves with counter-directed phase velocity and group velocity, directly linked to the IE thickness resonance frequency. The presented non-contact surface wave testing indicates good potential for future rolling quality control of asphalt concrete pavements.

QC 20170209

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12

Chaiprakaikeow, Susit. "New Methods for Engineering Site Characterization Using Reflection and Surface wave Seismic Surveys." DigitalCommons@USU, 2012. https://digitalcommons.usu.edu/etd/1273.

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This study presents two new seismic testing methods for engineering application, a new shallow seismic reflection method and Time Filtered Analysis of Surface Waves (TFASW). Both methods are described in this dissertation. The new shallow seismic reflection was developed to measure reflection at a single point using two to four receivers, assuming homogeneous, horizontal layering. It uses one or more shakers driven by a swept sine function as a source, and the cross-correlation technique to identify wave arrivals. The phase difference between the source forcing function and the ground motion due to the dynamic response of the shaker-ground interface was corrected by using a reference geophone. Attenuated high frequency energy was also recovered using the whitening in frequency domain. The new shallow seismic reflection testing was performed at the crest of Porcupine Dam in Paradise, Utah. The testing used two horizontal Vibroseis sources and four receivers for spacings between 6 and 300 ft. Unfortunately, the results showed no clear evidence of the reflectors despite correction of the magnitude and phase of the signals. However, an improvement in the shape of the cross-correlations was noticed after the corrections. The results showed distinct primary lobes in the corrected cross-correlated signals up to 150 ft offset. More consistent maximum peaks were observed in the corrected waveforms. TFASW is a new surface (Rayleigh) wave method to determine the shear wave velocity profile at a site. It is a time domain method as opposed to the Spectral Analysis of Surface Waves (SASW) method, which is a frequency domain method. This method uses digital filtering to optimize bandwidth used to determine the dispersion curve. Results from testings at three different sites in Utah indicated good agreement with the dispersion curves measured using both TFASW and SASW methods. The advantage of TFASW method is that the dispersion curves had less scatter at long wavelengths as a result from wider bandwidth used in those tests.

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13

Sadeghisorkhani, Hamzeh. "Analyses and Application of Ambient Seismic Noise in Sweden : Source, Interferometry, Tomography." Doctoral thesis, Uppsala universitet, Geofysik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-320169.

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Ambient seismic noise from generation to its application for determination of sub-surface velocity structures is analyzed using continuous data recordings from the Swedish National Seismic Network (SNSN). The fundamental aim of the thesis is to investigate the applicability of precise velocity measurements from ambient noise data. In the ambient noise method, a form of interferometry, the seismic signal is constructed from long-term cross correlation of a random noise field. Anisotropy of the source distribution causes apparent time shifts (velocity bias) in the interferometric signals. The velocity bias can be important for the study area (Sweden) which has relatively small velocity variations. This work explores the entire data path, from investigating the noise-source distribution to a tomographic study of southern Sweden. A new method to invert for the azimuthal source distribution from cross-correlation envelopes is introduced. The method provides quantitative estimates of the azimuthal source distribution which can be used for detailed studies of source generation processes. An advantage of the method is that it uses few stations to constrain azimuthal source distributions. The results show that the source distribution is inhomogeneous, with sources concentrated along the western coast of Norway. This leads to an anisotropic noise field, especially for the secondary microseisms. The primary microseismic energy comes mainly from the northeast. The deduced azimuthal source distributions are used to study the level of expected bias invelocity estimates within the SNSN. The results indicate that the phase-velocity bias is less than 1% for most station pairs but can be larger for small values of the ratio of inter-station distance over wavelength. In addition, the nature of velocity bias due to a heterogeneous source field is investigated in terms of high and finite-frequency regimes. Graphical software for phase-velocity dispersion measurements based on new algorithms is presented and validated with synthetic data and by comparisons to other methods. The software is used for phase-velocity measurements, and deduced azimuthal source distributions are used for velocity-bias correction. Derived phase-velocity dispersion curves are used to construct two-dimensional velocity maps of southern Sweden at different periods based on travel-time tomography. The effect of the bias correction is investigated, and velocity maps are interpreted in comparison to previous geological and geophysical information.

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14

Sabey, Lindsay Erin. "Body and surface wave ambient noise seismic interferometry across the Salton Sea Geothermal Field, California." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/51185.

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Virtual source gathers were generated using the principles of seismic interferometry from 135 hours of ambient noise recorded during a controlled-source survey across the Salton Sea Geothermal Field in southern California. The non-uniform nature of the noise sources violated a primary assumption of the method and generated artifacts in the data. The artifacts generated by the high-energy impulsive sources (e.g. earthquakes, shots) were removable using traditional methods of amplitude normalization prior to cross-correlation. The continuous source artifacts generated by the geothermal wells and highways required an unconventional approach of utilizing only normalized impulsive sources to successfully reduce the artifacts. Virtual source gathers were produced successfully that contained strong surface waves at 0.4-2.5 Hz, an order of magnitude below the corner frequency of the geophones, and modest body waves at 22-30 Hz, which are generally more difficult to obtain due to the need for many large, well-distributed subsurface sources. The virtual source gathers compare well to nearby explosive shots and are more densely spaced, but have a much lower signal-to-noise ratio. Analysis of the surface waves was complicated by strong higher-order modes. Spectral analysis of virtual source gathers required utilization of the geothermal plant energy, which produced usable signal at offsets required for mode separation. The virtual source dispersion curve compared well to a dispersion curve from a nearby explosive shot. P-waves were observed on the virtual source gathers. Creation of a low-quality multichannel reflection stack revealed two weak reflectors in the upper 2 km.
Master of Science

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15

Rosenblad, Brent Lyndon. "Experimental and theoretical studies in support of implementing the spectral-analysis-of-surface-wave (SASW) method offshore /." Digital version accessible at:, 2000. http://wwwlib.umi.com/cr/utexas/main.

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16

Kalinski, Michael E. "Determination of in situ V[subscript s] and G[subscript max] using surface wave measurements in cased and uncased boreholes /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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17

Bailey, Jonathan Pqul. "Development of shear wave velocity profiles in the deep sediments of the Mississippi Embayment using surface wave and spectral ratio methods." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5635.

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Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 10, 2009 Includes bibliographical references.

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18

Zaccherini, Rachele. "Surface waves attenuation in granular media through a small-scale Metabarrier." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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The present thesis describes a small-scale experiment, carried out in the laboratory of the Swiss Federal Institute of Technology of Zurich (ETH). The research focuses on metamaterials, locally resonant structures able to affect the propagation of waves passing through them. The present thesis investigates an innovative method to attenuate Rayleigh waves through the insertion of a barrier of scaled resonators into the soil, capable of generating a bandgap in the dispersion relation. Waves, whose frequency fall within the bandgap, cannot propagate through the resonant structure. Each resonator is constituted by a steel mass mounted on top of a spring made with 16 beams forming a truss. Taking advantage of the results of A. Palermo et al [1] as a starting point, we carried out a small-scale experiment in a big wooden box filled with glass beads in order to investigate the effectiveness of the designed metabarrier in attenuating surface waves generated by a metal rod exciting the surface every 300 ms. We found a stop-band in the dispersion relation inside the metabarrier, generated by the coupling between the vertical component of Rayleigh waves and the longitudinal resonances of the resonators. In parallel with the laboratory experiment, some numerical simulations have been performed with the software Comsol Multiphysics in order to compare the results obtained experimentally.

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19

Casey, Thomas J. "Shear wave data collection in mid America using an automated surface source during seismic cone testing." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/32804.

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van, Heijst Hendrik Jan. "New constraints on the seismic structure of the earth from surface wave overtone phase velocity measurements." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242041.

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21

Winsborrow, G. "The estimation of shear wave statics using in situ seismic measurements in near-surface marine sediments." Thesis, Bangor University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.275155.

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22

GAROFALO, FLORA. "Physically Constrained joint inversion of seismic and electrical data for near surface applications." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2549137.

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Geophysical methods require the solution of inverse problems that lead to the estimation of physical properties of the subsurface (model parameters) based on the minimization of the misfit function between theoretical and the experimental data. The inverse problems are often non-linear, ill-posed and affected by solution non-uniqueness and this leads to interpretation ambiguities. These criticisms can be mitigated with a joint inversion of different geophysical data to obtain a final multi-parametric model and to exploit the different sensitivity of each method to the different model parameters. This can also mitigate the inherent limitations which are peculiar of each technique. The joint inversion can be performed or by imposing the same structure of the subsurface to all the methods (structural approach) or using physical relationships among the model parameters (physical approach). The latter ensures the internal physical consistency of the model. The algorithm I propose imposes either the same structure as well as some physical relationships and it involves seismic data, related to geometrical dispersion of surface waves and refracted P-wave traveltimes, and apparent resistivity data. Such data allow respectively S-wave velocity, P-wave velocity and resistivity to be retrieved. The algorithm is based on a collection of 1D layered models located along the line and each model is linked to the neighbour ones trough spatial constraints. Also a priori information on the model parameters is taken into account. The physical relationships are introduced by imposing constraints on the Poisson’s ratio, that is expressed as function of S- and P- wave velocities, and by imposing equality between the porosity value estimated from seismic velocities and the porosity value estimated from resistivity. The algorithm was applied to both synthetic and field data and three examples were proposed combining different kind of data and physical relationships. The starting point was an existing algorithm on the joint inversion of surface wave and refracted P-wave data for S- and P- wave velocities and including the Poisson’s ratio as physical link between those model parameters. This algorithm was applied on experimental data acquired along a line crossing a fault in New Zealand and the seismic dataset was exploited not only to extract surface wave and refracted P-wave data, but also to perform a lateral variability assessment to tune the geometric regularization. Then the vertical electrical sounding was included in the algorithm and hence the apparent resistivity data were added to the data vector as well as the resistivity to the model one. The algorithm was tested on synthetic and field data related to a case study regarding a site in Norway affected by instability due to quick clay. Based on a 1D model, the third example is on the use of the porosity as link between the seismic and resistivity model parameters testing it on a synthetic and field data related to a saturated sand deposit. All of these examples show how the joint inversion provide a more reliable and physically consistent final model than the results from individual inversions. In addition, even if the Poisson’s ratio and the porosity are not primary objectives of the inversion, the final model, being internally consistent, provides a more reliable estimation of those physical parameters than the one from the results of the individual inversions.

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23

Käestle, Emanuel David. "High-resolution ambient-noise and earthquake surface-wave tomography of the Alps Apennines and Dinarides." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066307/document.

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La collision alpine a créé des structures complexes comme des chaînes de montagnes très arqués et des interactions compliquées entre les slabs subduits. La polarité de subduction est inversée à la transition entre les Alpes et les Apennins et les Alpes et les Dinarides. Le fait que la plaque Adria subducte en même temps vers l'ouest et vers l'est avec un fort pendage, presque verticalement, suggèrent une flexion importante de cette plaque. Notamment, si on considère de plus la proposition qu'Adria subducte aussi vers le nord sous les Alpes de l'est, ce qui est toujours sujet de discussion. Des déchirures dans le slab adriatique sous les Dinarides du nord à plus de 150 km de profondeur et sous les Apennins à moins de 200 km, pourraient être des signes d'une forte tension et, en conséquence, un détachement de la plaque adriatique. La plaque européenne pourrait aussi avoir subi plusieurs déchirures le long des Alpes. Cette hypothèse sujette à débat nécessite de nouveaux modèles tomographiques. Le modèle tomographique présenté dans cette thèse se base sur les vitesses de phase des ondes de surface pour donner un modèle 3-D à haute résolution des vitesses de cisaillement de la surface jusqu'à 200 km de profondeur. Ce modèle est unique de par sa haute résolution dans le manteau lithosphérique où des modèles antérieurs montrent de fortes incertitudes. Afin d'imager la croûte et le manteau supérieur en même temps, une combinaison des données de vitesses de phase des ondes de surface mesurés à partir des bruits ambiants ainsi que des séismes est utilisée dans cette thèse.Pour tester la validité de cette procédure, une comparaison détaillée des mesures de vitesses de phases et des structures imagées avec les deux méthodes est présentée. De l’analyse résulte un faible biais qui montre des vitesses plus élevées avec les données se basant sur des séismes par rapport aux données se basant sur le bruit ambiant. En comparant avec des travaux antérieurs, il est apparu que ce biais est dû à une différence méthodologique. Plusieurs paramètres qui pourraient influencer les mesures du bruit ambiant sont testés numériquement. Une cause unique n'a pu être identifiée. L'explication la plus probable pour le biais est une combinaison entre différentes sensibilités des méthodes aux structures et l'influence des modes supérieurs. Néanmoins, l'écart est suffisamment faible par rapport aux variations structurales pour être négligé.Un modèle final de vitesse de cisaillement de la région alpine est obtenu avec une résolution latérale d'environ 25 km dans la croûte peu profonde. Les tests synthétiques donnent une résolution approximative de profondeur estimée à 2 km près de la surface et de 5 km à la profondeur du Moho. Dans le manteau supérieur, la résolution baisse rapidement mais les structures principales des panneaux plongeants restent bien imagées jusqu'à une profondeur de 200 km le long des Alpes et des Apennins.La partie crustale du modèle donne des informations à haute résolution sur la taille et la profondeur des bassins sédimentaires et du corps d’Ivrée ainsi que sur la profondeur et la structure du Moho. Ce modèle de vitesses de cisaillement est le premier montrant autant de détails et couvrant les Alpes entières, il est proposé que le modèle pourrait servir comme référence pour la région.Le modèle montre les limites des zones de subduction et les régions de basses vitesses asthénosphèriques montants sous les bassins Ligure et pannonien. Des structures connues comme les déchirures de slabs sous les Apennins et les Dinarides sont imagés. Des découvertes supplémentaires ont été mises en évidence : une petite zone de faible vitesse qui coupe la lithosphère au nord des Dinarides est interprété comme l'expression d'une grande faille décrochante
The plate collision in the Alps and adjacent orogens has created a complex picture of highly arcuate mountain belts and complicated interactions of subduction slabs. The subduction polarity is reversed from European to Adriatic subduction in the transition of the Alps to the Apennines and to the Dinarides. The subduction of Adria both to the west and east and the almost vertical dip of the slabs implies an important flexure of this plate. Even more so if one considers the proposed subduction of Adria also to the north under the eastern Alps, which is still a matter of discussion. Gaps in the Adriatic slab under the northern Dinarides, below 150~km depth and in the southern Apennines above 200~km may be signs of the stresses and the consequent tearing that the Adriatic plate is exposed to.Also the European plate has supposedly undergone one or several break-offs all along the Alpine arc. Especially in the eastern and western Alps it is still an open question whether the European slab is detached below the lithosphere. New tomographic models are thus needed.The herein presented tomographic model is based on surface-wave phase velocities and gives a picture of the shear-velocity structure from the surface to 200 km depth. It is the first high-resolution shear-velocity model of the entire Alpine crust and upper mantle. It is also unique in its good resolution in the lithospheric mantle, where previous body-wave models are subject to high uncertainties. In order to be able to image both crust and upper mantle, a combination of ambient-noise and earthquake-based phase-velocity measurements is used in the present thesis.The validity of this approach is tested by a detailed comparison of the phase-velocity measurements and the structures that are imaged from each method individually. A small bias between the methods results in slightly elevated velocities from earthquake measurements. By comparison with earlier works it appears that this bias is due to methodological differences. Several effects that may influence the ambient-noise records are tested with synthetic experiments, but no unique cause is found. The most likely explanation for the bias between the two methods is a combination of different structural sensitivities and the influence of higher modes. Nevertheless, the discrepancy is sufficiently small with respect to the structural variations that the bias can be neglected.A final shear-velocity model of the Alpine region is obtained which has a lateral resolution in the shallow crust of approximately 25 km. From synthetic tests, the average depth resolution is estimated to be 2~km close to the surface and 5 km for the Moho depth. In the upper mantle the resolution decreases significantly, but main slab structures are well imaged in the central Alps and the Apennines down to the bottom of the model at 200 km depth.Highlights of the crustal part of the model are size and depth of sedimentary basins, the Ivrea body and the Moho structure. Being the first shear-velocity model of this detail and extend it is proposed to serve as reference for the Alps

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Calkins, Josh A. "An Investigation of Lithospheric Structure and Evolution in Convergent Orogenic Systems using Seismic Receiver Functions and Surface Wave Analysis." Diss., The University of Arizona, 2008. http://hdl.handle.net/10150/195366.

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Whether by accretion, magmatic addition, or refinement of more mafic lithologies, continental arcs are likely zones for the creation of "average" continental crust with intermediate silica content. This dissertation contains the results of broadband seismic studies carried out in two field areas, an active subduction zone and the remnants of an extinct arc, with the aim of understanding lithospheric evolution at convergent margins. The analytical techniques of receiver function calculation and surface wave tomography are applied to data sets collected above the Andean subduction zone in Chile and western Argentina and in the Coast Mountains Batholith of central British Columbia. We present the first in-depth comparison of receiver functions calculated using the high frequencies available in records of intermediate-depth local earthquakes with those calculated from the lower frequency data in records of larger teleseismic events. The comparison reveals that the lower crust beneath the Western Sierras Pampeanas contains a gradational velocity increase over ~20km above a small velocity step at the Moho. Surface wave tomography confirms the existence of an unusually high velocity anomaly in the mantle above the slab and yields estimates of slab thickness on the order of 50 km. To the south of the flat slab region, we see evidence of active mantle wedge convection above the steep slab, but no evidence of the lithosphere-asthenosphere boundary beneath the subducting Nazca plate. In the Coast Mountains Batholith (CMB), receiver functions image a bright, continuous Moho throughout the study region. Combined with petrologic modeling, the receiver function data point toward convective removal of any ultramafic root that formed beneath the CMB. Low absolute shear wave velocities in the upper mantle resolved via surface wave analysis strengthen the case for root removal beneath the eastern section of the CMB. On the far western edge of the CMB, we find evidence of a partially reformed lithosphere outboard of a major tectonic boundary. These observations shed light on the distillation of felsic to intermediate continental crust from more mafic primary magmas in active subduction zones and the eventual return of the complementary ultramafic residuals to the convecting mantle.

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Kuehnert, Julian. "Simulation of High Frequency Seismic Waves generated by Rockfalls on Real Topography." Thesis, Université de Paris (2019-....), 2019. https://theses.md.univ-paris-diderot.fr/KUEHNERT_Julian_va2.pdf.

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Les risques d'éboulements doivent être évalués et surveillés afin de prévenir les pertes de vies humaines et dommages aux infrastructures. A cet égard, il est important de créer des catalogues d'événements et de comprendre la dynamique des éboulements. Les ondes sismiques peuvent être utiles à cette fin, car elles transmettent des informations précieuses sur l'événement. Elles sont générées lorsque des éboulements touchent le sol et peuvent être utilisées pour détecter, classer et localiser des événements. Plus encore, on peut déduire des propriétés des éboulements telles que leur volumes et leur comportement dynamique. Cependant, les signaux sismiques hautes fréquences (>1Hz) sont mal compris. En effet, ils sont associés à des sources sismiques complexes qui sont réparties dans l'espace et peuvent varier rapidement dans le temps. De plus, les ondes sismiques hautes fréquences sont susceptibles d'être diffusées et diffractées en raison des interactions avec les hétérogénéités du sol ou la topographie de surface. Cette thèse franchit une étape importante dans la compréhension des signaux sismiques hautes fré-quences des éboulements en simulant la propagation des ondes sismiques en utilisant la méthode des éléments spectraux (SEM) avec des profils de vitesse réalistes et des topographies de surface 3D. L'influence de la topographie sur le champ des ondes sismiques est étudiée. On constate que l'ampli-fication induite par la topographie est sensiblement différente entre les sources situées en profondeurs et celles situées en surface. En effet, les ondes de surface générées par des sources peu profondes sont exposées à une diffusion et à une diffraction constantes lorsqu'elles se déplacent le long de la surface. La désintégration de l'énergie le long de la surface est étudiée pour différents modèles de vitesse et des équations sont dérivées pour calculer rétroactivement l'énergie sismique totale rayonnée par la source. Ceci est intéressant du fait du lien entre l'énergie sismique et le volume d'éboulement. Afin de tenir compte des effets topographiques, il est proposé un facteur de correction qui peut être introduit dans le calcul de l'énergie. Les signaux sismiques générés par les éboulements du cratère Dolomieu du Piton de la Fournaise, à La Réunion, sont analysés. Les sismogrammes synthétiques sont utilisés pour identifier et interpréter les signaux observés qui sont générés par des impacts uniques. L'influence de la topographie sur les formes d'onde est démontrée et la sensibilité avec l'emplacement et la direction de la source est évaluée. Les caractéristiques du signal telles que les amplitudes et le contenu fréquentiel sont expliquées sur la base de la théorie du contact de Hertz. De plus, les rapports spectraux entre stations, calculés à partir des signaux sismiques d'éboulement, sont considérés comme caractéristiques de la position de la source. La comparaison avec les rapports spectraux simulés suggère qu'ils sont dominés par la propagation le long de la topographie plutôt que par le mécanisme de la source. Sur la base de ces résultats, une méthode est proposée pour la localisation des éboulements à l'aide de rapports énergétiques simulés entre stations. La méthode est appliquée pour localiser les éboulements dans le cratère de Dolomieu. La mise en œuvre de la méthode implique une fenêtre temporelle glissante qui permet une application simple sur des signaux sismiques continus. L'accent est mis sur la capacité de la méthode à surveiller l'activité des éboulements en temps réel
Rockfall hazard has to be evaluated and monitored in order to prevent loss of life and infrastructure. In this regard it is important to create event catalogs and understand rockfall dynamics. Seismic waves can help for this purpose as they carry valuable information of the event. They are generated when rockfalls impact the ground and can be used to detect, classify and locate events. Beyond that, rockfall properties such as their volume and their dynamic behavior can be inferred. Yet, high frequency seismic signals (>1Hz) are poorly understood. This is because they are associated to complex seismic sources which are spatially distributed and can rapidly vary over time. On top of this, high frequency seismic waves are prone to be scattered and diffracted due to interactions with soil heterogeneities or surface topography. This thesis takes an important step forward to enhance understanding of high frequency rockfall seismic signals by simulating seismic wave propagation on domains with realistic velocity profiles and 3D surface topographies using the Spectral Element Method (SEM). The influence of the topography on the seismic wave field is investigated. It is found that topography induced amplification is substantially different between deep sources and sources located at the surface. This is because surface waves generated by shallow sources are exposed to constant scattering and diffraction when traveling along the surface. The energy decay along the surface is investigated for different velocity models and equations are derived to back-calculate the total seismic energy radiated by the source. This is of interest as the rockfall seismic energy is related to the rockfall volume. In order to account for topography effects, a correction factor is proposed which can be introduced in the energy calculation. Observed seismic signals generated by rockfall at Dolomieu crater on Piton de la Fournaise volcano, La Réunion, are analyzed. Synthetic seismograms are used to identify and interpret observed signals generated by single impacts. The influence of topography on the waveforms is demonstrated and the sensitivity on source location as well as source direction is evaluated. Signal characteristics such as amplitudes and frequency content are explained based on Hertz contact theory. Additionally, inter-station spectral ratios computed from rockfall seismic signals are shown to be characteristic of the source position. Comparison with simulated spectral ratios suggest that they are dominated by the propagation along the topography rather than the mechanism of the source. Based on these findings, a method is proposed for the localization of rockfalls using simulated inter-station energy ratios. The method is applied to localize rockfalls at Dolomieu crater. The implementation of the method involves a sliding time window which allows a straightforward application on continuous seismic signals. The potential of the method to monitor rockfall activity in real-time is emphasized

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26

Fader, Amelia Erin. "Integration of surface seismic waves, laboratory measurements, and downhole acoustic televiewer imaging, in geotechnical characterization: Ogden, KS." Thesis, Kansas State University, 2012. http://hdl.handle.net/2097/15118.

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Master of Science
Department of Geology
Abdelmoneam Raef
Geotechnical site characteristics are a function of the subsurface elastic moduli and the geologic structures. This study integrates borehole, surface and laboratory measurements for a geotechnical investigation that is focused on investigating shear-wave velocity (Vs) variation and its implication to geotechnical aspects of the Ogden test site in eastern Kansas. The area has a potential of seismicity due to the seismic zone associated with the Nemaha formation where earthquakes pose a moderate hazard. This study is in response to recent design standards for bridge structures require integrating comprehensive geotechnical site characterization. Furthermore, evaluation of dynamic soil properties is important for proper seismic response analysis and soil modeling programs. In this study, near surface geophysical site characterization in the form of 2D shear-wave velocity (Vs) structure that is compared with laboratory measurements of elastic moduli and earth properties at simulated in situ overburden pressure conditions and synergy with downhole Acoustic Televiewer time and amplitude logs, proved very robust “validated” workflow in site characterization for geotechnical purposes. An important component of a geotechnical site characterization is the evaluation of in-situ shear modulus, Poisson’s ratio and reliable and accurate elastic modulus ([lambda]) and shear modulus ([mu]) estimates are important in a good geotechnical site characterization. The geophysical site characterization, undertaken in this study, will complement and help in extrapolating drilling and core-based properties deduced by the geotechnical engineers interested at the test site.

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Baumann-Wilke, Maria [Verfasser], and Michael [Akademischer Betreuer] Weber. "Combining body wave tomography, surface wave inversion, seismic interferometry and laboratory measurements to characterize the black shales on Bornholm at different scales / Maria Baumann-Wilke. Betreuer: Michael Weber." Potsdam : Universitätsbibliothek der Universität Potsdam, 2013. http://d-nb.info/1045780693/34.

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Ahammod, Shamim. "Determination of Vp, Vs, Glacial Drift Thickness and Poisson’s Ratio at a Site in Jay County, Indiana, Using Seismic Refraction and Multichannel Analysis of Surface Wave (MASW) Analysis on a Common Data Set." Wright State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=wright1451337593.

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29

Duffy, Brendan Gilbert. "Development of Multichannel Analysis of Surface Waves (MASW) for Characterising the Internal Structure of Active Fault Zones as a Predictive Method of Identifying the Distribution of Ground Deformation." Thesis, University of Canterbury. Geological Sciences, 2008. http://hdl.handle.net/10092/2051.

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Bulk rock strength is greatly dependent on fracture density, so that reductions in rock strength associated with faulting and fracturing should be reflected by reduced shear coupling and hence S-wave velocity. This study is carried out along the Canterbury rangefront and in Otago. Both lie within the broader plate boundary deformation zone in the South Island of New Zealand. Therefore built structures are often, , located in areas where there are undetected or poorly defined faults with associated rock strength reduction. Where structures are sited near to, or across, such faults or fault-zones, they may sustain both shaking and ground deformation damage during an earthquake. Within this zone, management of seismic hazards needs to be based on accurate identification of the potential fault damage zone including the likely width of off-plane deformation. Lateral S-wave velocity variability provides one method of imaging and locating damage zones and off-plane deformation. This research demonstrates the utility of Multi-Channel Analysis of Surface Waves (MASW) to aid land-use planning in such fault-prone settings. Fundamentally, MASW uses surface wave dispersive characteristics to model a near surface profile of S-wave velocity variability as a proxy for bulk rock strength. The technique can aid fault-zone planning not only by locating and defining the extent of fault-zones, but also by defining within-zone variability that is readily correlated with measurable rock properties applicable to both foundation design and the distribution of surface deformation. The calibration sites presented here have well defined field relationships and known fault-zone exposure close to potential MASW survey sites. They were selected to represent a range of progressively softer lithologies from intact and fractured Torlesse Group basement hard rock (Dalethorpe) through softer Tertiary cover sediments (Boby’s Creek) and Quaternary gravels. This facilitated initial calibration of fracture intensity at a high-velocity-contrast site followed by exploration of the limits of shear zone resolution at lower velocity contrasts. Site models were constructed in AutoCAD in order to demonstrate spatial correlations between S-wave velocity and fault zone features. Site geology was incorporated in the models, along with geomorphology, river profiles, scanline locations and crosshole velocity measurement locations. Spatial data were recorded using a total-station survey. The interpreted MASW survey results are presented as two dimensional snapshot cross-sections of the three dimensional calibration-site models. These show strong correlations between MASW survey velocities and site geology, geomorphology, fluvial profiles and geotechnical parameters and observations. Correlations are particularly pronounced where high velocity contrasts exist, whilst weaker correlations are demonstrated in softer lithologies. Geomorphic correlations suggest that off-plane deformation can be imaged and interpreted in the presence of suitable topographic survey data. A promising new approach to in situ and laboratory soft-rock material and mass characterisation is also presented using a Ramset nail gun. Geotechnical investigations typically involve outcrop and laboratory scale determination of rock mass and material properties such as fracture density and unconfined compressive strength (UCS). This multi-scale approach is espoused by this study, with geotechnical and S-wave velocity data presented at multiple scales, from survey scale sonic velocity measurements, through outcrop scale scanline and crosshole sonic velocity measurements to laboratory scale property determination and sonic velocity measurements. S-wave velocities invariably increased with decreasing scale. These scaling relationships and strategies for dealing with them are investigated and presented. Finally, the MASW technique is applied to a concealed fault on the Taieri Ridge in Macraes Flat, Central Otago. Here, high velocity Otago Schist is faulted against low velocity sheared Tertiary and Quaternary sediments. This site highlights the structural sensitivity of the technique by apparently constraining the location of the principal fault, which had been ambiguous after standard processing of the seismic reflection data. Processing of the Taieri Ridge dataset has further led to the proposal of a novel surface wave imaging technique termed Swept Frequency Imaging (SFI). This inchoate technique apparently images the detailed structure of the fault-zone, and is in agreement with the conventionally-determined fault location and an existing partial trench. Overall, the results are promising and are expected to be supported by further trenching in the near future.

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Dudchenko, Aleksandr. "Analyse numérique de l’interaction des ondes de Rayleigh en surface avec des barrières sismiques et des champs de pieux prenant en compte le comportement élastoplastique du sol." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI102/document.

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Le travail présent est axé sur la simulation numérique et l'analyse de l'interaction des ondes de surface de Rayleigh avec des barrières sismiques verticales (murs souterrains, écrans, tranchées, etc.) ainsi que des champs de pieux dans des modèles de matériaux mécaniques élastiques et plastiques linéaires. Le but de la recherche est d'estimer le degré de protection que les barrières verticales et les champs de pieux fournissent contre les vibrations transférées par les ondes de surface de Rayleigh et générées par diverses sources. L'idée principale de ce type de protection est d'éviter que les ondes sismiques ne transmettent l'énergie des vagues dans la zone protégée, diminuant les amplitudes de déplacements, les vitesses et les accélérations aux points situés derrière la barrière (champ de pieux). Les principaux complexes sans dimension sont formulés. L'attention est portée sur les ondes de Rayleigh car elles peuvent être générées à la fois par des sources de vibrations externes (situées à la surface de la Terre) et internes (situées sous la surface de la Terre) et ses ondes peuvent transmettre une portion significative de l’énergie de source de la vibration.Premièrement, des simulations numériques de l'interaction des ondes de Rayleigh avec les barrières sismiques verticales et les champs de pieux sont effectuées en supposant que le sol et les matériaux de barrière se comportent conformément à la loi de comportement linéaire élastique. Cela concerne les vibrations qui induisent des contraintes de cisaillement dans le sol n'excédant pas 0.00001 lors de leur propagation. Les principaux complexes sans dimension sont formulés sur cette base. Des paramètres géométriques et mécaniques de la barrière (champ de pieux) déterminant l'effet de réduction de vibration sont identifiés. Les résultats obtenus révèlent la validité de cette onde de protection contre les vibrations. En outre, l’approche de l’optimisation de la barrière sismique verticale (qui peut également être étendue au champ de pieux) est adoptée sous forme de différences finies pour des conditions de sol particulières et une fréquence de vibration de conception.Plusieurs modèles de comportement du sol sont analysés et leur validité, ainsi que l'applicabilité à l'approximation du comportement dynamique réel du sol, ainsi que le mécanisme de dissipation d'énergie des vibrations, sont identifiés. Sur la base de cette analyse, modèle de Mohr-Coulomb a été choisie car elle dispose d’une base de données expérimentale étendue pour divers sols et reflète de manière appropriée la réduction du module de cisaillement avec l’augmentation de la contrainte de cisaillement ainsi que les effets de dissipation d’énergie. Par la suite, ce modèle est utilisé dans l'analyse de l'interaction des ondes de Rayleigh avec les barrières verticales et les champs de pieux, en tenant compte du caractère non linéaire de la déformation du sol à différents niveaux de déformation de cisaillement. En conséquence, l'influence du niveau de contrainte de cisaillement sur l'efficacité des moyens de protection contre les vibrations considérés est démontrée et les conditions appropriées pour utiliser ces méthodes sont identifiées dans le cadre de cette recherche
The present work is focused on numerical simulation (FEM) and analysis of surface Rayleigh wave interaction with vertical seismic barriers (underground walls, screens, trenches, etc.) as well as pile fields within the framework of linear elastic and plastic mechanical material models. The aim of the research is to estimate the degree of protection that vertical barriers and pile fields provide against vibrations transferred by surface Rayleigh waves and generated by various sources. The main idea behind this type of protection is to prevent seismic waves form transmitting wave energy into the protected zone, decreasing the amplitude of displacements, velocities and accelerations at the points behind the barrier (pile field). The attention is paid to Rayleigh waves as they can be generated by both external (located on the Earth's surface) and internal (located beneath the Earth's surface) vibration sources and this type of waves can transfer a significant portion of vibration source energy.First, numerical simulations of Rayleigh wave interaction with vertical seismic barriers and pile fields are performed assuming the soil and barrier materials to behave according to the linearly-elastic constitutive law. This regards the vibrations that induce shear strains in the soil not exceeding 0.00001 during their propagation. Based on this, the principal dimensionless complexes are formulated. Geometrical along with mechanical parameters of the barrier (pile field), that determine vibration reduction effect, are identified. The obtained results reveal the validity of this way of vibration protection. In addition to that, the approach towards vertical seismic barrier optimization (which can also be extended to the pile field) is adopted in finite difference form to use for particular soil conditions and design vibration frequency.Several models of soil behaviour are analysed and their validity as well the applicability to approximate real dynamic soil behaviour along with the mechanism of vibration energy dissipation are identified. Based on this analysis, Mohr-Coulomb constitutive model is selected as it has a broad experimental database for various soils and appropriately reflects shear modulus reduction with an increase in the shear strain as well as energy dissipation effects. Afterwards, this model is used in the analysis of Rayleigh wave interaction with the vertical barriers and pile fields accounting for non-linear character of soil deformation at different shear strain level. As a results, the influence of shear strain level on the effectiveness of the considered ways of vibration protections is shown and the appropriate conditions to use these methods are identified within the scope of this research

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Eker, Mert Arif. "Determination Of The Dynamic Characteristics And Local Site Conditions Of The Plio-quarternary Sediments Situated Towards The North Of Ankara Through Surface Wave Testing Methods." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610824/index.pdf.

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The purpose of this study is to assess the engineering geological and geotechnical characteristics and to perform seismic hazard studies of the Upper Pliocene to Quaternary (Plio-Quaternary) deposits located towards the north of Ankara through surface wave testing methods. Based on a general engineering geological and seismic site characterization studies, site classification systems are assigned in seismic hazard assessments. The objective of the research is to determine the regional and local seismic soil conditions (i.e., shear wave velocities, soil predominant periods and soil amplification factors) and to characterize the soil profile of the sites in this region by the help of surface geophysical methods. These studies have been supported by engineering geological and geotechnical field studies carried out prior to and during this study. By integrating these studies, local soil conditions and dynamic soil characteristics for the study area have been assessed by detailed soil characterization in the region. As a result, seismic hazard assessments have been performed for Ç
ubuk and its close vicinity with the aid of Geographical Information Systems (GIS) through establishing seismic characterization and local soil conditions of the area.

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32

Maupin, Valérie. "Etude des caracteristiques des ondes de surface en milieu anisotrope : application a l'analyse d'anomalies de polarisation a la station de port-aux-francais." Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13035.

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Dispersion et polarisation des ondes de surface dans des structures anisotropes lateralement homogenes. L'equation des ondes elastiques dans des structures planes isotropes est perturbee par l'introduction de coefficients elastiques anisotropes. On en deduit l'anomalie de vitesse de phase et l'anomalie de polarisation decomposee sur les modes propres de la structure isotrope de reference. Ces resultats sont illustres par le calcul d'anomalies de vitesse et de polarisation dans des modeles oceaniques ou l'anisotropie est cree par orientation de fissures dans la croute ou de cristaux d'olivine dans le manteau

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33

Montagner, Jean-Paul. "Etude de la structure profonde de la terre a partir des ondes de surface de longue periode." Paris 6, 1986. http://www.theses.fr/1986PA066188.

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Differentes methodes d'inversion de la vitesse de ces ondes sont appliquees a plusieurs regions du globe: ocean pacifique, afrique, ocean indien. La regionalisation suivant l'age du fond oceanique montre que des heterogeneites laterales de vitesse existent jusqu'a au moins 400 km de profondeur et que la correlation entre la tectonique de surface et la structure profonde est meilleure sous l'ocean pacifique que sous l'ocean indien

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Pasquet, Sylvain. "Apport des méthodes sismiques à l'hydrogéophysique : importance du rapport Vp/Vs et contribution des ondes de surface." Thesis, Paris 6, 2014. http://www.theses.fr/2014PA066495/document.

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La caractérisation et le monitoring des ressources en eau souterraine et des processus d'écoulement et de transport associés reposent principalement sur la mise en place de forages (piézomètres). Mais la variété des échelles auxquelles se déroulent ces processus et leur variabilité dans l'espace et dans le temps limitent l'interprétation des observations hydrogéologiques. Dans un tel contexte, l'hydrogéophysique fait appel aux méthodes de prospection géophysique afin, notamment, d'améliorer la très faible résolution spatiale des données de forage et de limiter leur caractère destructif. Parmi les outils géophysiques appliqués à l'hydrogéologie, les méthodes sismiques sont régulièrement utilisées à différentes échelles. Mais la réponse sismique dans le contexte de la caractérisation des aquifères reste complexe. L'interprétation des vitesses estimées est souvent délicate à cause de leur variabilité en fonction de la lithologie de l'aquifère (paramètres mécaniques intrinsèques et géométrie des milieux poreux le constituant, influence du degré de saturation, etc). La perméabilité du milieu a également un effet sur la géométrie d'un réservoir hydrologique dont les contours peuvent varier en espace comme en temps, compliquant ainsi l'interprétation des données sismiques.Les géophysiciens cherchent à pallier ces limites, notamment à travers l'étude conjointe des vitesses (Vp et Vs) des ondes compression (P) et de cisaillement (S), dont l'évolution est par définition fortement découplée en présence de fluides. D'un point de vue théorique, cette approche se révèle appropriée à la caractérisation de certains aquifères, en particulier grâce à l'estimation des rapports Vp/Vs ou du coefficient de Poisson. L'évaluation de ces rapports peut être pratiquée de manière systématique grâce à la tomographie sismique en réfraction en utilisant parallèlement ondes P et S. Mais d'un point de vue pratique, la mesure de Vs reste délicate à mettre en oeuvre car les ondes S sont souvent difficiles à générer et à identifier sur les enregistrements sismiques. Une alternative est proposée par l’estimation indirecte de Vs à partir de l’inversion de la dispersion des ondes de surface, réalisée à partir de mesures de la vitesse des ondes de surface contenues dans les enregistrements sismiques classiques. Bien que généralement proposée pour la caractérisation de milieux 1D, la prospection par ondes de surface peut être déployée le long de sections linéaires dans le but de reconstruire un modèle 2D de distribution des Vs du sous-sol.Une méthodologie a été mise au point afin d'exploiter simultanément et de façon optimale les ondes P et les ondes de surface à partir des mêmes enregistrements sismiques. Lors de sa mise en oeuvre sur le terrain, cette acquisition « en ondes P » a été systématiquement suivie d'une acquisition « en ondes SH » afin de comparer les vitesses Vs obtenues par analyse de la dispersion des ondes de surface et par tomographie en ondes SH. L'utilisation de cette méthodologie dans différents contextes géologiques et hydrogéologiques a permis d'estimer les variations latérales et temporelles du rapport Vp/Vs, en bon accord avec les informations géologiques a priori et les données géophysiques et piézométriques existantes. L'utilisation de l'interférométrie laser a également permis de mettre ces techniques de traitement en application sur des modèles physiques parfaitement contrôlés afin d'étudier la propagation des ondes élastiques dans des « analogues » réalistes de milieux poreux partiellement saturés
Characterisation and monitoring of groundwater resources and associated flow and transport processes mainly rely on the implementation of wells (piezometers). The interpretation of hydrogeological observations is however limited by the variety of scales at which these processes occur and by their variability in space and in time. In such a context, using geophysical methods often improves the very low spatial resolution of borehole data and limits their destructive nature. Among the geophysical tools applied to hydrogeology, seismic methods are commonly used at different scales. However, the seismic response in the context of aquifer characterisation remains complex. The interpretation of the estimated velocities is often difficult because of their variability depending on the aquifer lithology (intrinsic mechanical parameters and geometry of the constituting porous media, influence of the degree of saturation, etc). The permeability of the medium also affects the geometry of a hydrological reservoir whose contours may vary in space and in time, thus complicating the interpretation of seismic data. Geophysicists seek to overcome these limitations, especially through the joint study of compression (P-) and shear (S-) wave velocities (Vp and Vs), whose evolution is by definition highly decoupled in the presence of fluids. From a theoretical point of view, this approach proves suitable for the characterisation of aquifers, especially by estimating Vp/Vs or Poisson's ratio. The evaluation of these ratios can be systematically carried out with seismic refraction tomography using both P- and S-waves. However, retrieving Vs remains practically delicate because S-waves are usually difficult to generate and identify on seismic records. As an alternative, indirect estimation of Vs is commonly achieved thanks to surface-wave dispersion inversion, carried out from measurements of surface waves phase velocities contained in typical seismic records. Although it is usually proposed for the characterisation of 1D media, surface-wave prospecting can be deployed along linear sections in order to build 2D models of Vs distribution in the ground. A specific methodology has been developed for the combined and optimised exploitation of P- and surface waves present on single seismic records. When deployed on the field, this "P-wave" acquisition has been systematically followed by a "SH-wave" acquisition in order to compare Vs models obtained from surface-wave dispersion analysis and SH-wave refraction tomography. The use of this methodology in several geological and hydrogeological contexts allowed for estimating Vp/Vs ratio lateral and temporal variations in good agreement with a priori geological information and existing geophysical and piezometric data. Laser-based ultrasonic techniques were also proposed to put these processing techniques in practice on perfectly controlled physical models and study elastic wave propagation in partially saturated porous media

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35

Moueddene, Kada. "Analyse d'images en sismique : pretraitement et extraction d'informations par la morphologie mathematique." Toulouse 3, 1987. http://www.theses.fr/1987TOU30006.

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Techniques de traitement d'images appliquees aux diagraphies sismiques. En particulier, utilisation des operateurs de morphologie mathematique pour les problemes de pretraitement et d'extraction d'informations. Deux exemples d'application sont presentes: tir de bruits pour l'extraction des spectres de vitesses et tir au centre pour le filtrage des ondes de surface et des arrivees refractees

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36

Lucena, Rodrigo Ferreira de. "Avaliações e testes dos métodos MASW e ReMi por meio do tratamento de dados empíricos e sintéticos em um programa de processamento e inversão desenvolvido em MATLAB e sua implicação em um problema geológico na Bacia de Taubaté." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/44/44138/tde-17062016-135652/.

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Os métodos de ondas superficiais com ênfase nas ondas Rayleigh foram utilizados como o núcleo desse trabalho de Doutorado. Inicialmente, as ondas Rayleigh foram modeladas permitindo o estudo de sensibilidade de suas curvas de dispersão sob diferentes configurações de parâmetros físicos representando diversos modelos de camadas, em que pôde ser observado parâmetros com maior e menor sensibilidade e também alguns efeitos provocados por baixas razões de Poisson. Além disso, na fase de inversão dos dados a modelagem das ondas Rayleigh foi utilizada para a construção da função objeto, que agregada ao método de mínimos quadrados, a partir do método de Levenberg-Marquardt, permitiu a implementação de um algoritmo de busca local responsável pela inversão de dados das ondas superficiais. Por se tratar de um procedimento de busca local, o algoritmo de inversão foi complementado por uma etapa de pré-inversão com a geração de um modelo inicial para que o procedimento de inversão fosse mais rápido e eficiente. Visando uma eficiência ainda maior do procedimento de inversão, principalmente em modelos de camadas com inversão de velocidades, foi implementado um algoritmo de pós-inversão baseado em um procedimento de tentativa e erro minimizando os valores relativos da raiz quadrada do erro quadrático médio (REQMr) da inversão dos dados. Mais de 50 modelos de camadas foram utilizados para testar a modelagem, a pré-inversão, inversão e pós-inversão dos dados permitindo o ajuste preciso de parâmetros matemáticos e físicos presentes nos diversos scripts implementados em Matlab. Antes de inverter os dados adquiridos em campo, os mesmos precisaram ser tratados na etapa de processamento de dados, cujo objetivo principal é a extração da curva de dispersão originada devido às ondas superficiais. Para isso, foram implementadas, também em Matlab, três metodologias de processamento com abordagens matemáticas distintas. Essas metodologias foram testadas e avaliadas com dados sintéticos e reais em que foi possível constatar as virtudes e deficiências de cada metodologia estudada, bem como as limitações provocadas pela discretização dos dados de campo. Por último, as etapas de processamento, pré-inversão, inversão e pós-inversão dos dados foram unificadas para formar um programa de tratamento de dados de ondas superficiais (Rayleigh). Ele foi utilizado em dados reais originados pelo estudo de um problema geológico na Bacia de Taubaté em que foi possível mapear os contatos geológicos ao longo dos pontos de aquisição sísmica e compará-los a um modelo inicial existente baseado em observações geomorfológicas da área de estudos, mapa geológico da região e informações geológicas globais e locais dos movimentos tectônicos na região. As informações geofísicas associadas às geológicas permitiram a geração de um perfil analítico da região de estudos com duas interpretações geológicas confirmando a suspeita de neotectônica na região em que os contatos geológicos entre os depósitos Terciários e Quaternários foram identificados e se encaixaram no modelo inicial de hemi-graben com mergulho para Sudeste.
The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical The surface wave methods to Rayleigh waves were used as the center of this Doctoral work. Initially, the Rayleigh waves were modeled, what enabled the study of the sensitivity of dispersion curves about different sets of physical parameters representing several layer models, wherein it could be observed parameters with higher and lower sensitivity and also some effects caused by low Poisson ratios. Moreover, in the data inversion step the Rayleigh modeling was used for the construction of the object function, that aggregate to the least-squares method, by Levenberg-Marquardt, allowed the implementation of a local search algorithm responsible for data inversion of the surface waves. By reason of being a local search procedure, the data inversion algorithm was complemented with a pre-inversion step wherein an initial model was generated so that the inversion procedure was faster and efficient. Seeking a more efficiency of the inversion procedure, mainly to layer models with velocities inversion, it was implemented a post-inversion algorithm based in a trial and error procedure minimizing the values of the relative Root Mean Squared Error (rRMSE) of the data inversion. More than 50 layer models were used to test the data modeling, pre-inversion, inversion and post-inversion allowing the precise fit of the mathematical and physical parameters present in the several scripts implemented in Matlab. Before to invert the field-acquired data, they need to be treated in the data processing step, whose main aim is the extraction of the dispersion curve caused due the surface waves. For this, three processing methodologies with different mathematical approaches were implemented, also in Matlab. These methodologies were tested and evaluated with synthetic and real data and it was possible to find their strengths and weaknesses, as well as the limitations caused by discretization of the field data. Lastly, the data processing, pre-inversion, inversion and post-inversion steps were unified to form a complete data treatment program of surface waves (Rayleigh). It was used to real data originated by study of a geological problem in the Bacia de Taubaté wherein it was possible to map the geologic contacts along of the seismic acquisition points. The results were compared to an existing initial model based in geomorphological observations of the study area, geological map and global and local geologic information of the tectonic movements in the region. The geophysical information associated with geological information allowed the generation of an analytical profile of the study region with two geological interpretation confirming the suspect of neotectonic movements in the region wherein the geological contacts between the quaternary and tertiary deposits were identified and they agreed with the initial model of a hemi-graben with dip to Southeast.

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Carcolé, Carrubé Eduard. "Three-dimensional spatial distribution of scatterers in the crust by inversion analysis of s-wave coda envelopes. A case study of Gauribidanur seismic array site (Southern india) and Galeras volcano (South-western Colombia)." Doctoral thesis, Universitat Ramon Llull, 2006. http://hdl.handle.net/10803/9321.

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In this thesis, coda waves recorded by local seismographic networks will be analyzed to estimate the three-dimensional spatial distribution of scatterers (SDS). This will be done by using the single scattering approximation. This approach leads to a huge system of equations that can not be solved by traditional methods. For the first time, we will use the Simultaneous Iterative Reconstructive Technique (SIRT) to solve this kind of system in seismological applications. SIRT is slow but provides a means to carry out the inversion with greater accuracy. There is also a very fast non-iterative method that allows to carry out the inversion 102 times faster, with a higher resolution and reasonable accuracy: the Filtered Back-Projection (FBP). If one wishes to use this technique it is necessary to adapt it to the geometry of our problem. This will be done for the first time in this thesis. The theory necessary to carry out the adaptation will be developed and a simple expression will be derived to carry out the inversion.

FBP and SIRT are then used to determine the SDS in southern India. Results are almost independent of the inversion method used and they are frequency dependent. They show a remarkably uniform distribution of the scattering strength in the crust around GBA. However, a shallow (0-24 km) strong scattering structure, which is only visible at low frequencies, seems to coincide with de Closepet granitic batholith which is the boundary between the eastern and western parts of the Dharwar craton.

Also, the SDS is estimated for the Galeras volcano, Colombia. Results reveal a highly non-uniform SDS. Strong scatterers show frequency dependence, which is interpreted in terms if the scale of the heterogeneities producing scattering. Two zones of strong scattering are detected: the shallower one is located at a depth from 4 km to 8 km under the summit whereas the deeper one is imaged at a depth of ~37 km from the Earth's surface. Both zones may be correlated with the magmatic plumbing system beneath Galeras volcano. The second strong scattering zone may be probably related to the deeper magma reservoir that feeds the system.

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BIGNARDI, Samuel. "Complete Waveform Inversion Approach To Seismic Surface Waves And Adjoint Active Surfaces." Doctoral thesis, Università degli studi di Ferrara, 2011. http://hdl.handle.net/11392/2388824.

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The idea to exploit the dispersive mechanism of surface waves as a probing tool for investigating subsurface structure was introduced about 30 years ago, and afterwards a very intense research field has developed. Currently many methods known generally as Surface Wave Methods exist, and are well established, most of them assuming layered or depth dependent ground models. In most cases the parallel layer assumption is correct because the soil structure is expected to negligibly depart from a layered structure at a typical surface testing scale for engineering and geotechnical purposes however to exploit the amount of information achievable, it is necessary to extend the research, relaxing at least one of the underlying model assumptions. Indeed in classical SWM’s, surface waves are assumed to be Rayleigh waves, this means that a parallel layered model has been implicitly assumed. As a consequence search for a soil model geometry other than the assumed one can only result in slight perturbations. The only possible deduction is that overcoming limitations of layered models requires to exploit P and S waves which are indeed general solutions of the elastodynamic problem. Geometry can then be retrived by a complete waveform inversion based on a forward model capable of successfully reproducing all of the features of the displacement field in presence of complex scattering phenomena. In this research effort an inversion approach has been introduced which exploits the Boundary Element Method as forward model. Such approach is appealing from a theoretical point of view and is computationally efficient. Although in the present work a monochromatic signal traveling in a system constituted by a layer over an half space was investigated, this method is suitable for any number of layers, and multi-frequency environments. The boundary element approach can be easily generalized to three-dimensional modeling; moreover viscoelasticity can be introduced by the elasticviscoelastic principle of correspondence. Finally BEM can be easily implemented for parallel computing architecture. Synthetic cases of high and low impedance Jump were investigated for typical SWM setups and a first example of application on real data was performed. Finally an elegant analytic form of the minimization flow named Adjoint Active Surfaces was obtained combining Computer Vision technique of Active surfaces and the Adjoint Field method.

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39

Dangeard, Marine. "Développement d'une approche « time-lapse » des méthodes sismiques pour l'hydrogéophysique et la compréhension de la dynamique des hydrosystèmes." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS476.

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Анотація:

La caractérisation et la compréhension des hydrosystèmes font partie intégrante de l’étude de la « Zone Critique » (ZC). Elles représentent un enjeu important pour la gestion et la protection des ressources en eaux de surface et en eaux souterraines. La géophysique et l’hydrogéophysique font partie des outils d’étude de cette fraction de la ZC et des processus qu’elle referme. Les méthodes sismiques de subsurface sont proposées afin de l’imager pour en définir la géométrie et la nature de ses compartiments. Comme la sismique repose sur les paramètres mécaniques du milieu, le signal mesuré est également influencé par la teneur en eau : son analyse permet donc d’en décrire la variation spatiale. L’application « time-lapse » de cette approche est proposée ici afin de suivre les variations temporelles de contenu en eau des hydrosystèmes étudiés. Une chaîne de traitements basée sur une étude statistique est développée afin de s’assurer de la significativité des variations temporelles des données par rapport aux erreurs de mesures. On démontre que lorsque les variations « time-lapse » sont supérieures aux erreurs estimées, elles reflètent les comportements hydrologiques des structures identifiées et apportent de nouvelles informations sur leur dynamique. Quantifier ces résultats par inversion des données sismiques acquises à chaque pas de temps n’est cependant pas évident, même en connaissance des erreurs de mesures, notamment par manque d’information a priori. Dans ces cas, les incertitudes a posteriori peuvent s’avérer trop élevées pour pouvoir comparer les variations temporelles des paramètres inversés. Toutefois, lorsque la zone d’étude est particulièrement bien contrainte, une inversion méticuleuse à chaque pas de temps des données estimées comme significatives par notre approche, est possible. Dans ce cas, on propose une méthode d’interpolation de la profondeur de la zone saturée au voisinage de niveaux piézométriques connus, à partir des images sismiques. Ces informations peuvent ensuite être utilisées afin de contraindre la modélisation hydrodynamique en proposant : (i) une définition « haute résolution » de la géométrie des compartiments hydrogéologiques et de leur faciès et (ii) de nouvelles conditions aux bords et initiales
The characterization and understanding of hydrosystems is part of the "Critical Zone" (CZ) study. They consist in an important issue for the management and protection of surface water and groundwater resources. Geophysics and hydrogeophysics are among the tools for studying this fraction of the CZ and its processes. The near-surface seismic methods are suggested for the imaging of the CZ in order to describe its geometry and the nature of its compartments. Since seismic methods are based on the mechanical properties of the medium, the measured signal is also influenced by the water content: its analysis therefore makes it possible to describe its spatial variation. The time-lapse application of this approach is proposed here in order to follow the temporal variations in the water content of the hydrosystems. A processing workflow based on a statistical study is developed to ensure the significance of the temporal variations in the data with respect to measurement errors. It is shown that when the time-lapse variations are greater than the estimated errors, they reflect the hydrological behaviors of the structures identified and provide new information on their dynamics. Quantifying these results by inverting the seismic data recorded at each time step is however not obvious, even in the knowledge of measurement errors, in particular due to a lack of prior information. In these cases, the posterior uncertainties may be too high to compare the temporal variations of the inverted parameters. However, when the study area is particularly constrained, a thorough inversion at each time step of the data estimated as significant by our approach is possible. In this case, we suggest a method of interpolation of the depth of the saturated zone in the vicinity of known water table levels, from the seismic images. This information can then be used to constrain the hydrodynamic modeling by proposing: (i) a "high resolution" definition of the geometry of the hydrogeological compartments and their facies and (ii) new boundary and initial conditions

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40

Carter, Andrew James. "Seismic waves from surface seismic reflection surveys : an exploration tool?" Thesis, University of Leeds, 2003. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633653.

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41

Ferreira, Ana Margarida Godinho. "Seismic surface waves in the laterally heterogeneous Earth." Thesis, University of Oxford, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426406.

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42

Ronda, Afonso Jose. "Railway formation condition assessment using seismic surface waves." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/66239.

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Анотація:

The demands of railway transport have been changing over the 150 years of existence of this type of transport in South Africa, specifically the performance requirements of the formation to cater for new traffic requirements. As such, it is important to assess the condition of this vital part of a railway track. This dissertation covers a research project conducted on two railway lines in which measurements of ground vibration were conducted in order to perform geophysical analysis and characterise the formation based on the results obtained. Measurements were taken on a 26 ton axle load track (Coal line, at Bloubank) and on a 20 ton axle load track (at Amandelbult) in South Africa. Planning and implementation of several test procedures to characterise track formation require considerable effort to minimize the impact on railway operations. Coupled with track occupation and the destructive nature of some of the test procedures, it is relevant to investigate alternative testing techniques to address the issues stated above. The use of surface waves for geotechnical characterization of sites is increasing worldwide. Applications to railway engineering have so far been limited to light load, high speed lines to minimize the use of poor geomaterials with reduced Rayleigh wave velocity. Four sites were identified where trains are operated at heavy loads, with the formation condition varying from poor to good. Seismic testing (geophysical) and conventional testing (deflection measurements) were performed at the identified sites. Seismic measurements were recorded using geophones as receivers, coupled to an amplifier and a computer. The source of the seismic events was the trains operating on the track and a hammer for impact testing. For the deflection measurements, the Remote Video Monitoring (RVM) technique was adopted. Dispersion analysis of the ground vibration experimental data was conducted using the multiple receiver method. The main conclusions reached with the analysis indicated that: __ Dispersion analysis had a good correlation with the formation deflection analysis; __ Phase velocity can be used as an indicator of the quality of a certain site; __ There are limitations when using trains as the energy source in terms of the generation of excitation frequency, which greatly reduces the phase velocity information in individual layers in the formation (i.e. wavelengths are not short enough).
Dissertation (MSc)--University of Pretoria, 2016.
Civil Engineering
MSc
Unrestricted

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43

Hwang, Sukyeon. "Acoustic seismic modeling in the slowness-time intercept domain /." Access abstract and link to full text, 1993. http://0-wwwlib.umi.com.library.utulsa.edu/dissertations/fullcit/9318174.

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44

Gonzalez-Huizar, Hector. "Insight into the physics of rupture dynamic triggering seismicity /." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.

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45

Gonzalez, John. "Estimating body and surface waves using virtual sources and receivers." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/10313.

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This research is focused on the application of both new and established seismic interferometry techniques to a single area: the Altiplano in the Andes region. This area has already been widely studied in terms of its geological evolution. Nevertheless, a single accepted theory has not yet been developed to explain why the topography of the Andes incorporates such a large area of low relief at this altitude. The Altiplano is therefore an interesting zone to study. This research introduces and analyses new concepts and methodologies, such as retrieving surface and body waves between earthquakes by using interferometry. Nevertheless, several factors, such as the quality of recordings, the separation between sources, and the velocity gradient of the medium, had to be taken into account for body and surface wave retrieval. This research also analysed the retrieval of body waves by means of seismic interferometry applied to coda wave arrivals. Results show that due to the attenuation of S waves produced by the zone of partial molten material, when using S coda waves, seismic interferometry does not achieve the objective of wave retrieval. On the other hand, P coda waves gave good results. Also, the combined methodology of interferometry by cross-correlation and convolution was shown to account for the behaviour of the retrieved waves and provided an indication of how the distribution of sources affects the Green’s functions estimates for body waves in this area. Another point covered by this research was the analysis of passive recordings in order to retrieve surface and body waves. Results indicate that surface and body waves could be retrieved. However, in order to retrieve body waves, special circumstances are required, such as lateral continuity of the Moho, a relative strong Moho impedance contrast, and simplicity of the geologic structure because these factors will contribute to a strong signal like that obtained in critical reflections making interferometry results more successful.

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46

Fox, Benjamin Daniel. "Seismic source parameter determination using regional intermediate-period surface waves." Thesis, University of Oxford, 2007. http://ora.ox.ac.uk/objects/uuid:6b89e41d-8dd0-4286-9bf0-d22c4a349bb7.

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In general, the depths of shallow earthquakes are poorly resolved in current catalogues. Variations in depth of ±10 km can significantly alter the tectonic interpretation of such earthquakes. If the depth of a seismic event is in error then moment tensor estimates can also be significantly altered. In the context of nuclear-test-ban monitoring, a seismic event whose depth can be confidently shown to exceed say, 10km, is unlikely to be an explosion. Surface wave excitation is sensitive to source depth, especially at intermediate and short periods, owing to the approximate exponential decay of surface wave displacements with depth. The radiation pattern and amplitude of surface waves are controlled by the depth variations in the six components of the strain tensor associated with the surface wave eigenfunctions. The potential exists, therefore, for improvements to be made to depth and moment tensor estimates by analysing surface wave amplitudes and radiation patterns. A new method is developed to better constrain seismic source parameters by analysing 100-20s period amplitude spectra of fundamental-mode surface waves. Synthetic amplitude spectra are generated for all double-couple sources over a suitable depth range and compared with data in a grid-search algorithm. Best fitting source parameters are calculated and appropriate bounds are placed on these results. This approach is tested and validated using a representative set of globally-distributed events. Source parameters are determined for 14 moderately-sized earthquakes (5.4 ≤ M_w ≤ 6.5), occurring in a variety of tectonic regimes with depths calculated between 4-39km. For very shallow earthquakes the use of surface wave recordings as short as 15s is shown to improve estimates of source parameters, especially depth. Analysis of aftershocks (4.8 ≤ M_w ≤ 6.0) of the 2004 great Sumatra earthquake is performed to study the depth distribution of seismicity in the region. Three distinct tectonic regimes are identified and depth estimates calculated between 3-61km, including the identification of one CMT depth estimate to be in error by some 27km.

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47

Zywicki, Daren Joseph. "Advanced signal processing methods applied to engineering analysis of seismic surface waves." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/20232.

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48

Pei, Donghong. "Modeling and inversion of dispersion curves of surface waves in shallow site investigations." abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3275830.

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49

Fenneman, Douglas. "An acoustic method for the detection of surface waves in sand." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/21802.

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50

Sullivan, Brendan. "Delayed triggering of early aftershocks by multiple surface waves circling the earth." Thesis, Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/45827.

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It is well known that direct surface waves of large earthquakes are capable of triggering shallow earthquakes and deep tremor at long-range distances. Recent studies have shown that multiple surface waves circling the earth could also remotely trigger microearthquakes. However, it is still not clear whether multiple surface waves returning back to the main shock epicenters could also trigger/modulate aftershock behavior. Here we conduct a study to search for evidence of such triggering by systematically examining aftershock patterns of earthquakes with magnitude ≥ 8 since 1990 that produce observable surface waves circling the globe repeatedly. We specifically examine the 2011 M9 Tohoku-Oki event using a composite catalog of JMA, HiNet and newly detected events obtained by waveform cross correlation. We compute the magnitude of completeness for each sequence, and stack all the sequences together to compute the seismicity and moment rates by sliding data windows. The sequences are also shuffled randomly and these rates are compared to the actual data as well as synthetic aftershock sequences to estimate the statistical significance of the results. Our results suggest that there is some moderate increase of early aftershock activity after a few hours when the surface waves return to the epicentral region. However, we could not completely rule out the possibility that such an increase is purely due to random fluctuations of aftershocks or caused by missing aftershocks in the first few hours after the mainshock.

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