Tesis sobre el tema "Seismic tomography"
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Lo, Tien-when. "Seismic borehole tomography". Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/54325.
Texto completoNurhandoko, Bagus Endar Bachtiar. "Fresnel zone seismic tomography". Kyoto University, 2000. http://hdl.handle.net/2433/180954.
Texto completoYang, Ting. "Seismic constraints on structure beneath hotspots : earthquake tomography & finite frequency tomography approaches /". View online ; access limited to URI, 2006. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3232466.
Texto completoZhang, Qie Sandvol Eric Alan. "Seismic tomography and anisotropy: studies of intraplate seismic zones". Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6855.
Texto completoLees, Jonathan Matthew. "Seismic tomography in western Washington /". Thesis, Connect to this title online; UW restricted, 1989. http://hdl.handle.net/1773/6829.
Texto completoDyer, Benjamin Charles. "Seismic transmission and reflection tomography". Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47042.
Texto completoDumont-Kristiansen, Frédéric-Nicolas. "Spatial variability in seismic depth tomography". Thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-9501.
Texto completoThe location of a reflector or medium in the subsurface is correlated with the high wavenumbers or high frequencies in the velocity field. Indeed, the determination of the high frequencies of the velocity field both normally and laterally is the key step for improving seimic data and then get a better insight of the position of a reflector in the subsurface. This project focus on the velocity data processing part involved in seismic tomography. We describe, compare and implement several highpass operators based on finite-difference and the Hamming window in order to filter a seismic velocity dataset. In fact, we study their behaviour in the frequency domain by examining their spectrums. The main contribution of this project is to construct two dimensional anisotropic operators by rotating a one dimensional operator based on linear interpolation. We test all the operators on a synthetic seismic velocity dataset and compare the results obtained between the isotropic filtering method and the anisotropic filtering method. We show that anisotropic filters can be useful in certain geological circumstances. Finally we attempt to scale the different operators in order to fully incorporate them in the seismic tomography inversion problem by using a Bayesian method. We show that it is possible to decide the strength of the constraint in which we want to filter the seismic dataset by using a regularization parameter.
Gruber, Thomas. "Crosshole seismic tomography incorporating later arrivals /". Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phg885.pdf.
Texto completoGaletti, Erica. "Seismic interferometry and non-linear tomography". Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/10506.
Texto completoTrinks, Immo. "Traveltime tomography of densely sampled seismic data". Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615782.
Texto completoIvansson, Sven. "Applications of seismic tomography to geophysical exploration". Licentiate thesis, Luleå tekniska universitet, 1987. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26497.
Texto completoLoveday, David Carl. "Resolving Small Objects Using Seismic Traveltime Tomography". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/35032.
Texto completoMaster of Science
McCaughey, Michael. "Travel-time tomography of wide-angle seismic data". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389868.
Texto completoFoss, Stig-Kyrre. "Depth consistent pp and ps seismic angle tomography". Doctoral thesis, Norwegian University of Science and Technology, Department of Mathematical Sciences, 2004. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-318.
Texto completoThis thesis addressed the problem of finding background models yielding depth consistent migrated PP and PS images, i.e. geologically equivalent reflectors should be imaged at the same depth in the two images. The tomographic approach in search of a background medium, is performed as a combination of migration velocity analysis by differential semblance in angle and map migration. A practical strategy for obtaining estimates of all parameter values in a transversely isotropic medium with a known symmetry axis is presented. The approach combines the search of a background medium yielding optimum focusing ability by differential semblance and the matching of PP and PS key reflectors in depth by means of map migration. This can also be used to match the imaged reflectors with known depths e.g. from well markers.
For the purpose of fast and computationally inexpensive imaging and tomography in angle, a complete review and analysis for the 2.5-D case is performed. The theory is also extended to anisotropic media under necessary and sufficient assumptions. An analysis is performed with regards to parameter issues in 2.5-D in anisotropic media. All inversion and migration results are derived in the natural coordinate system, namely scattering/reflection angle at the imaging point by means of the generalized Radon transform.
Hope, Victoria. "Applications of seismic transmission tomography in civil engineering". Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/842729/.
Texto completoRao, Ying. "Seismic tomography for velocity and attenuation model reconstruction". Thesis, Imperial College London, 2007. http://hdl.handle.net/10044/1/11882.
Texto completoTape, Carl Clayton Robert W. Tromp Jeroen. "Seismic tomography of Southern California using adjoint methods /". Diss., Pasadena, Calif. : California Institute of Technology, 2009. http://resolver.caltech.edu/CaltechETD:etd-05062009-183823.
Texto completoCarannante, Simona <1976>. "Multiresolution spherical wavelet analysis in global seismic tomography". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/871/1/Tesi_Carannante_Simona.pdf.
Texto completoCarannante, Simona <1976>. "Multiresolution spherical wavelet analysis in global seismic tomography". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/871/.
Texto completoLegovini, Paride <1983>. "Ambient seismic noise tomography of the Antarctic continent". Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amsdottorato.unibo.it/9023/1/tesi-legovini.pdf.
Texto completoEllis, Grant Andrew. "Subsurface electromagnetic sensing in the presence of the air-earth interface using a cross-borehole configuration /". Thesis, Connect to this title online; UW restricted, 1995. http://hdl.handle.net/1773/6058.
Texto completoChan, Ne Xun. "One- and Three-dimensional P- and S-wave Velocity Models of Central and Southern Sweden Based on SNSN Data". Thesis, Uppsala universitet, Geofysik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-231929.
Texto completoGhaychi, Afrouz Setareh. "Seismic Wave Velocity Variations in Deep Hard Rock Underground Mines by Passive Seismic Tomography". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97890.
Texto completoDoctor of Philosophy
Mining activities unbalance the stress distribution underground, which is called mining induced stress. The stability of the underground mines is jeopardized due to accumulation of induced stress thus it is critical for the safety of the miners to prevent excessive induced stress accumulation. Hence it is important to continuously monitor the rock mass performance under the induced stress which can form cracks or slide along the existing discontinuities in rock mass. Cracking or sliding releases energy as the source of the seismic wave propagation in underground rocks, known as a seismic event. The velocity of seismic wave propagation can be recorded and monitored by installing seismic sensors such as geophones underground. The seismic events are similar to earthquakes but on a much smaller scale. The strength of seismic events is measured on a scale of moment magnitude. The strongest earthquakes in the world are around magnitude 9, most destructive earthquakes are magnitude 7 or higher, and earthquakes below magnitude 5 generally do not cause significant damage. The moment magnitude of mining induced seismic events is typically less than 3. In order to monitor mining induced stress variations, the propagated seismic wave velocity in rock mass is measured by a series of mathematical computations on recorded seismic waves called passive seismic tomography, which is similar to the medical CT-scan machine. Seismic wave velocity is like the velocity of the vibrating particles of rock due to the released energy from a seismic event. This study proposes to investigate trends of seismic velocity variations before and after each seismic event. The areas which are highly stressed have higher seismic velocities compared to the average seismic velocity of the entire area. Therefore, early recognition of highly stressed zones, based on the seismic velocity amount prior the occurrence of major seismic events, will be helpful to apply optimization of mining practices to prevent progression of high stress zones which can be ended to rock failures. For this purpose, time-dependent seismic velocity of a synthetic mine was compared to its stress numerically. Then, the seismic data of a narrow vein mine is evaluated to determine the seismic velocity trends prior to the occurrence of at least five major seismic events as the case study.
Papaleo, Elvira. "The north Anatolian fault, Turkey : insights from seismic tomography". Thesis, University of Aberdeen, 2018. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=239855.
Texto completoLu, Jing S. M. Massachusetts Institute of Technology. "Seismic tomography and surface deformation in Krýsuvík, SW Iceland". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/87506.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 59-62).
The Krýsuvík region of southwestern Iceland is a region of high potential for geothermal energy that is currently experiencing seismic swarm activity and active surface deformation. Understanding the subsurface structure of the area is of great scientific and practical significance. Using permanent and temporary seismic stations deployed in the region, we captured an earthquake swarm from Nov. 2010 to Feb. 2011 clustered around the center of the Krýsuvík volcanic system. We studied the seismicity and Vp, Vs and Vp/Vs ratio in this region by applying double difference tomography. Our tomography result indicates a low velocity zone at a depth of about 6 kin, directly beneath the earthquake swarm. At the same time, our relocation result delineates strike-slip and dip-slip faults above and around this low velocity zone. Brittle-ductile transition is delineated based on the distribution of the earthquakes in this area. In order to understand the relation between the subsurface structure and the surface deformation, we modeled surface deformation using the input parameters constrained from our tomography results. We found that the main deformation is well captured by a pressure source yielding a volume expansion of about 30x 106 m3 at the depth of about 6 km, centered on the low velocity zone detected in tomography. And the secondary deformation could be explained by the normal and the right-lateral slip faults, whose patterns are delineated by the earthquake relocations. The combination of the local stress caused by the expanding source and regional stress that yields a combination of left-lateral shear and extension might have triggered the earthquakes. Based on the low Vp, Vs and possibly high Vp/Vs ratio at depth of ~6 km and its expanding property, the possibilities of supercritical water, H₂O-rich partial melting with magma intrusion are discussed. The results of this thesis provide new insights to understand the seismicity and surface deformation in volcanic zones as well as provided important reference in exploration of new geothermal areas.
by Jing Liu.
S.M. in Geophysics
Hosa, Aleksandra M. "Imaging of the Hellenic subduction zone by seismic tomography". Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/114344.
Texto completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 24-25).
The Hellenic subduction zone is a complicated tectonic boundary, along which transitions in the nature of subducted material are believed to occur. The objective of this study was to better constrain the subsurface geometry of the Hellenic subduction zone by increasing the resolution of an existing tomographic model of the region. Increase in resolution is important for understanding the effects of inferred transitions in subducted material at depth. Nonlinear inversion of P-wave travel times was used on a global dataset expanded by temporary array data collected in southern Greece. Results show a vertically continuous slab, with a break at the depth 200-400 km detected only in the NW portion of the system. At depth above 400 kin, there is a lateral discontinuity marked by the Central Hellenic Shear Zone and Kephalonia Transform Fault, with slab more pronounced in southern part of the system. Our study supports the hypothesis of the change in subduction mode between northern and southern part of Hellenic arc in late Pliocene.
by Aleksandra M. Hosa.
S.B.
Mohamadian, Sarvandani Mohamadhasan. "Seismic tomography of an amagmatic ultra-slow spreading ridge". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS467.
Texto completoUltra-slow spreading ridges are a new category of spreading ridges characterized by quasi-amagmatic crustal accretion, exposing considerable amounts of mantle derived peridotites on the seafloor. Investigating the contributions of tectonic, magmatic, and other involved processes is necessary to gain a comprehensive conceptual model of ultra-slow spreading ridges. Imaging the crustal and upper mantle structures can help us to understand the past and current geological activities in the ultra-slow spreading ridges. The aim of the project is to understand the oceanic crust formed in an ultra-slow spreading ridge called the Southwest Indian Ridge with a low melt supply. Our research project is based on the processing and modeling of the active and passive seismic data in the easternmost part of Southwest Indian Ridge. The data acquisition took place in 2014 during the SISMOSMOOTH cruise. We analyzed vertical component recordings from 43 ocean-bottom seismometers in our passive seismic approach and the hydrophone components of 16 ocean-bottom seismometers in the active seismic approach. Ambient-noise interferometry and full-waveform inversion (FWI) of refraction data were used to image the internal structures of the lithosphere. In the modeling of ambient-noise interferometry, we find an average crustal thickness of 7 km with a shallow layer of low shear velocities. Moreover, we infer that the uppermost 2 km are highly porous and may be strongly serpentinized. The average shear wave velocity between the base of the crust and the maximum depth of our model (15 km) was less than the global reference value of 4.5 km/s and was explained by the younger age of the seafloor in our area. Our two-dimensional P-wave velocity model obtained from FWI suggests considerable variations in the upper lithospheric compositions along the axis-parallel profile. A transition is expected at a distance of ∼65-95 km along the profile from the predominantly volcanic domain in the western zone to variable serpentinized peridotite in the eastern zone. Dike injections are predicted in this area. A westward increase in melt supply is proposed in the seafloor accretion mode. The serpentinization and P-wave velocity model suggests that the Moho is a gradual transition from hydrated to unaltered peridotite
Ecoublet, Philippe. "Bent-ray travel-time tomography and migration without ray tracing". Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263006.
Texto completoFurniss, Matthew David. "Quantitative Comparison of Seismic Velocity Tomography With Seismic Activity Around a Deep Coal Longwall Panel". Thesis, Virginia Tech, 2009. http://hdl.handle.net/10919/32659.
Texto completoMaster of Science
Muchaidze, Iana. "Imaging in karst terrain using electrical resistivity tomography". Diss., Rolla, Mo. : Missouri University of Science and Technology, 2008. http://scholarsmine.mst.edu/thesis/pdf/Muchaidze_09007dcc80534d1b.pdf.
Texto completoVita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 26, 2008) Includes bibliographical references (p. 66-67).
Whiting, Peter Mark. "Reflection traveltime tomography and the maximum entropy principle". Thesis, The University of Sydney, 1993. https://hdl.handle.net/2123/26623.
Texto completoSymons, Neill. "Seismic velocity structure of the Puget Sound Region from 3-D non-linear tomography /". Thesis, Connect to this title online; UW restricted, 1998. http://hdl.handle.net/1773/6813.
Texto completoHerwanger, Jorg. "Seismic and electric crosshole tomography for fracture detection and characterization". Thesis, Imperial College London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367577.
Texto completoValentine, Andrew P. "Imaging the Earth : Methods and algorithms for global seismic tomography". Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.533890.
Texto completoRobertson, Graham Scott. "Shear wave heterogeneity in the lower mantle from seismic tomography". Thesis, University of Oxford, 1994. http://ora.ox.ac.uk/objects/uuid:99ea6162-a1d5-4544-8f52-8deed81d065f.
Texto completoThompson, Delaine Rebecca. "Nonlinear waveform tomography : theory and application to crosshole seismic data". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12666.
Texto completoIncludes bibliographical references (p. 175-183).
by Delaine Rebecca Thompson.
Ph.D.
Kárason, Hrafnkell 1970. "Constraints on mantle convection from seismic tomography and flow modeling". Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8059.
Texto completoIncludes bibliographical references (p. 205-224).
In this thesis I combine high resolution seismic tomography and realistic flow modeling to constrain mantle convection. The bulk of the data used in the tomographic imaging are millions of P, pP and pwP travel time residuals, read from high frequency seismic records. The distribution of earthquakes and stations results in uneven data coverage and to improve the model I use core phases (PKP, Pdiff) for the deep mantle and surface reflected phases (PP) for the shallow mantle. Since narrow rays are not adequate for low frequency measurements, I construct broad 3-D sensitivity kernels to relate some of the added data to earth's structure. Furthermore, the parameterization of the tomographic model is adapted to data density and the model shows, among other details, the varying style of subduction in the shallow mantle and complex flow patterns around the transition zone between the upper and lower mantle. I develop a novel and efficient method of modeling buoyancy driven mantle flow in spherical geometry. Here, the linear Stokes equation is solved using a Green's function approach and 3-D surfaces, representing the boundaries of dense material, such as subducting slabs, are tracked through time.
by Hrafnkell Kárason.
(cont.) I describe the basis of the approach, represent tests, and investigate the thickening and slowing of subducting slabs for different viscosity contrasts between the upper and lower mantle. I compare seismic tomography, flow modeling and reconstructed plate motions associated with the collision of India to mainland Asia, in particular, the south and south-west motion of the Sunda block. This way I can evaluate subduction scenarios and make quantitative comparison between tomography and plate reconstructions. I conclude that a viscosity increase of -200 in the lower mantle, resulting in -10 times higher viscosity than previously estimated, best fits the observations. Juxtaposing the tomography, the flow models and inversion tests using the flow models as input, indicates that the results are robust.
Ph.D.
Fang, Lihua. "Rayleigh wave tomography in North-China from ambient seismic noise". Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3623.
Texto completoThe theory and methodology of ambient noise tomography has been studied and applied to North-China successfully. Continuous vertical-component seismograms, spanning the period from January 1, 2007 to February 28, 2008 recorded by 190 broadband stations and 10 very broadband stations, have been used. The cross correlation technique has been applied to ambient noise data recorded by North-China Seismic Array for each station pairs of the array. Rayleigh wave group velocity dispersion curves are measured at periods between 4 s and 40 s by multiple filter technique. We obtain 5630 high quality dispersion curves. Surface wave tomography is conducted to generate group velocity maps with a grid spacing of 0.25º×0.25º. These maps display higher resolution and extend to shorter periods than previous surface wave tomography maps. Then genetic algorithm is used to invert pure path dispersion curves. The 3-D shear wave velocity structure from 0 to 50 km depth is readily constructed. To the authors' knowledge, the resolution presented here is, so far, the highest one in China mainland. The original results of this thesis are: 1, The SNR of Green Function is proportional to the square root of observation time and can be enhanced by using the symmetric component. The inhomogeneous distribution of seismic noise gives rise to the asymmetry of Green Function. Using more than one year's data, one can get more symmetric and higher SNR Green Function. 2, The characteristics of ambient seismic noise are different for different period bands. In 4-10 s, a coherent phase with large amplitude near zero lag time is observed. In 10-20 s, the sources of ambient seismic noise have a very clear seasonal variability. The azimuthal distributions of noise share a great similarity with the map of average ocean wave height map obtained by TOPEX-Poseidon. In 20-50s range, Rayleigh wave Green Functions are almost symmetrical and show less seasonal variation in both signal strength and directivity, which indicates that the distribution of noise is - ii - almost homogeneous. In 4-20s range, the amplitudes of positive and negative components of Green Functions are obviously asymmetrical, but the arrival times are almost identical, indicating that the distribution of noise has much influence on the amplitude of Green Function, but less influence on arrival time. 3, Tomographic maps at short periods reveal an evident lateral heterogeneity in the curst of North-China, quite well in agreement with known geological and tectonic features. The North China Basin is imaged as a broad low velocity area, while the Taihangshan and Yanshan uplifts and Ordos block are imaged as high velocity zones, and the Quaternary intermountain basins show up as small low-velocity anomalies. 4, The 3-D S-wave crustal velocity model in North China shows a distinct low velocity belt with NW trend at 10 km of depth near Zhangjiakou-Bohai seismic zone. This low velocity belt and the southern margin of Yanshan high velocity anomaly draw the outline of Zhangjiakou-Bohai seismic zone and its northern border line. There is a well-defined low velocity zone in middle-to-lower crust (15-25 km) in the Beijing-Tianjin-Tangshan region, which may be caused by intrusion of hot mantle materials. 5, We analyzed the seismogenic structure near Tangshan,Luanxian and Ninghe earthquake region. We infer that these three earthquakes are mainly caused by vertical deformation of upper mantle and material exchange between crust and upper mantle. The magma intrudes the crust along faults near the boundary of crust and upper mantle, which leads to the low velocity anomaly in the uppermost mantle. The magma intrusion heats up the lower crustal material and drops its viscosity. Some minerals are dehydrated. The water moves up and is trapped in the middle crust. The existence of liquid affects the structure and composition of the fault zone, further changes the stress state, weakens the seismotectonic region and triggers the earthquakes.
XXI Ciclo
1981
Pucciarelli, Giuseppe. "Seismic tomography of Italy (with special regard to Southern Tyrrhenian)". Doctoral thesis, Universita degli studi di Salerno, 2017. http://hdl.handle.net/10556/2569.
Texto completoThe topic of my PhD thesis is a seismic tomography which has as object of investigation Italy, particularly Southern Italy and Southern Tyrrhenian. This tomography has been obtained by means of inversion of teleseismic data. Seismic tomography is a method of investigation which is considerably stabilized in the field of Geophysics. Its goal is the achievement of a tridimensional velocity model of a subsoil of a determined area. For reaching this aim, it is necessary to gather arrival times of seismic events registered by seismic stations that are distributed in an opportune way on the area subject to process of investigation and an one-dimensional velocity model (that is, velocity only in function of depth). Through this last one, there is the computation of theoretical travel times for each pair seismic event – seismic station. This particular phase of method is called forward problem. Then, there is the computation of the difference between observed travel times and these theoretical travel times, a difference named residual. This is the description of so-called inverse problem. The computation happens in an iterative way and it stops when the residual is minimum. Obtained tridimensional velocity model corresponds with the model where residual is minimum. The entire process of operation of a seismic tomography is completely described in first chapter of this thesis. The second chapter describes the phenomen of subduction, that is of a particular process which happens, under determined conditions, at convergent boundaries of plates. I have dedicated a chapter to this phenomen because the area subject to this research, the basin of Southern Tyrrhenian, is a result of a roll-back subducting Ionian slab. After a paragraph dedicated to a general description of tectonic plates theory, other paragraphs describe the kinematics and the dynamics of subduction processes. This seismic tomography has been obtained by inversion of teleseismic travel times. This particular kind of choice has been made because teleseismic ray travel in upper mantle at high depths, so their inversion could supply us a good resolution of an area that we want to investigate until depth of 500-600 km. The third chapter of my PhD thesis is dedicated to teleseisms. In particular, there is a description of classification of seismic events according to their epicentral distance and how we can interpretate various seismic phases on a teleseismic seismogram. A paragraph is about the nomenclature of same seismic phases deriving from the reflection and the refraction of the waves on the discontinuity surfaces present in Earth's inner. The fourth and last chapter of my PhD thesis contains the results of research and their interpretation. First paragraph is dedicated to a brief summary of geological history of Southern Tyrrhenian. Second paragraph is dedicated to a description of software used for the research, that is FMTT (Fast Marching Teleseismic Transform), created by Nick Rawlinson in 2008. Third paragraph is dedicated to description of my data. I have utilised 1929 teleseisms (only P phases) recorded in period 1990-2012 by 122 southern Italian seismic station directly connected to ISC (International Seismological Centre). I have obtained several sections at various level of depth, from 25 km to 500 km and I have obtained several profiles NS and EW at fixed values of longitude from 14° to 16° and latitude, from 37° to 40° respectively. Results, compared with previous works in that area, confirm the presence of a subducting slab in Southern Tyrrhenian. Finally, my PhD thesis is enriched by various appendixes, which describe in a particular way mathematical techniques and geophysical definitions which I have used. [edited by author]
La mia tesi di Dottorato descrive una tomografia sismica dell'Italia, e in particolare di quella meridionale e del Basso Tirreno, ottenuta mediante l'inversione di dati telesismici. La tomografia sismica è oramai un metodo di indagine notevolmente consolidato nel campo della Geofisica e consiste nel ricavare un modello di velocità tridimensionale del sottosuolo di una determinata regione. Quest'ultimo si ottiene avendo a disposizione i tempi di arrivo di eventi sismici registrati da stazioni sismiche distribuite in maniera opportuna sull'area da indagare e un modello di velocità di partenza unidimensionale. Infatti, sfruttando quest'ultimo si calcolano per gli eventi sismici considerati dei tempi di arrivo teorici (questa fase prende il nome di PROBLEMA DIRETTO). Poi si calcola la differenza tra i tempi di arrivo realmente osservati e quelli teorici, che prende il nome di residuo (questa fase prende il nome di PROBLEMA INVERSO) e si procede in maniera iterativa in maniera che il residuo sia minimo. Il modello di velocità da ottenere è quello che corrisponde al residuo minimo. Il primo capitolo della tesi descrive la trattazione matematica della tomografia sismica, dopo un paragrafo introduttivo dedicato all'uso in generale dei metodi inversi in geofisica. La tomografia sismica si dice locale se gli eventi considerati sono locali. Si dice telesismica – come quella oggetto della mia tesi – se gli eventi considerati sono, lapalissianalmente, telesismi. Il secondo capitolo parla quindi dei telesismi, della loro definizione riguardo alla classificazione degli eventi sismici in base alla distanza epicentrale e delle fasi sismiche che si possono leggere da un sismogramma di un telesisma. Questo capitolo comprende un paragrafo sulla nomenclatura delle fasi sismiche e soprattutto quelle derivanti dalla riflessione e rifrazione delle onde su tutte le superfici di discontinuità presenti all'interno della Terra. E, a tal proposito, il terzo capitolo è un'introduzione alla struttura dell'interno della Terra con attenzione particolare che viene rivolta al fenomeno della subduzione. Questo perché uno slab di subduzione è presente all'interno del Basso Tirreno, zona “protagonista” della mia indagine tomografica. Il quarto capitolo è dedicato alla storia geologica del Basso Tirreno e alle evidenze delle precedenti indagini geofisiche che hanno visto questa area sotto la lente di ingrandimento. L'ultimo capitolo riguarda i risultati della mia indagine e la loro interpretazione. Ho utilizzato i tempi di arrivo di fasi P di 1929 telesismi (selezionati in base a un intervallo di magnitudo, a un minimo di stazioni registranti e all'intervallo di residuo di stazione) registrati nel periodo 1990-2012 da 122 stazioni dell'Italia centro-meridionale collegate all'ISC (International Seismological Centre). I risultati sembrerebbero, confrontati con quelli dei lavori precedenti, confermare la presenza di uno slab di subduzione nel Basso Tirreno. [a cura dell'autore]
XV n.s. (XXIX )
Liu, Kui. "Surface Wave Propagation and Global Crustal Tomography". Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25428.
Texto completoPh. D.
Adiya, Munkhsaikhan. "Seismic activity near Ulannbaatar : implication for seismic hazard assessment". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAH007/document.
Texto completoWe observe since 2005 a high seismic activity at 10 km from Ulaanbaatar that allowed us to identify a new active fault, Emeelt, in the field. After computing a 3D velocity model, I applied Double-Difference tomography to obtain a precise localization of earthquakes. They trace at least three parallel branches oriented N147° like the fault seen at surface. The seismic activity on the Main Emeelt Fault (MEF) is along at least 15 km, on the West and East branches, less active, along 10 km. The depth of the seismicity extends between 4 and 15 km. The activity seems concentrated at the intersection with Mesozoic faults and Vp/Vs contrast suggests the presence of fluids. The 10 swarms identified show an increasing activity and a spatial migration with time. The calculation of 2 possible scenarios, one M ~ 6.4 and one M ~ 7, shows an important impact on Ulaanbaatar, with a minimum intensity of VIII and IX for M=6.4 and X for M=7
Johnson, Stuart G. "Applications of global seismic tomography and analysis of variational methods for the solution of the linearly attenuating frequency domain wave equation /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1997. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823696.
Texto completoPyakurel, Sandeep. "3D P- and converted shear wave characteristics of the Morrow production trend in the Buffalo Valley field, Chaves-Eddy County, New Mexico". Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4256.
Texto completoTitle from document title page. Document formatted into pages; contains xi, 145 p. : ill. (some col.), maps (some col.). Includes abstract. Includes bibliographical references (p. 141-145).
Frommel, Jamin C. "INTEGRATED GEOPHYSICAL INVESTIGATION OF KARST FEATURES – INNER BLUEGRASS REGION OF KENTUCKY". UKnowledge, 2012. http://uknowledge.uky.edu/ees_etds/5.
Texto completoBaumann-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/.
Texto completoSchwarzschiefer 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.
Viso, Richard F. "Sequential development of the Gassaway structure in Braxton County, West Virginia". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=681.
Texto completoTitle from document title page. Document formatted into pages; contains x, 106 p. : ill. (some col.), maps Includes abstract. Includes bibliographical references (p. 100-102).
Hammond, William Charles. "Dynamics, flow and melt content of the Southern East Pacific Rise upper mantle from teleseismic tomography /". view abstract or download file of text, 2000. http://wwwlib.umi.com/cr/uoregon/fullcit?p9998033.
Texto completoTypescript. Includes vita and abstract. Includes bibliographical references (leaves 139-151). Also available for download via the World Wide Web; free to University of Oregon users.
Kelly, Irene G. "Modeling and migration of Hibernia seismic data". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0010/MQ34191.pdf.
Texto completoBoyce, Alistair. "The Proterozoic building of North America : insights from broadband seismic tomography". Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/62331.
Texto completoMa, Xu. "Passive Seismic Tomography and Seismicity Hazard Analysis in Deep Underground Mines". Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/51266.
Texto completoPh. D.