Dissertations / Theses on the topic 'Wide Angle Reflection'
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Harsha, Senusi Mohamed. "Interpretation of Southern Georgia coastal plain velocity structure using refraction and wide-angle reflection methods." Thesis, Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/25886.
Full textHananto, Nugroho. "Architecture and Evolution of North Sumatra Subduction Zone based on long Offset Seismic Reflection and Wide Angle Seismic Refraction / Reflection Data." Institut de physique du globe (Paris), 2011. http://www.theses.fr/2011GLOB1203.
Full textOueity, Jounada. "Near-vertical and wide-angle seismic reflection studies of the Moho and sub-crustal lithosphere in NW Canada." Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/28903.
Full textHughes, Stephen. "Crustal structure of northeastern North America : results from the Ontario-New York-New England seismic refraction/wide-angle reflection experiment." Thesis, University of Leicester, 1992. http://hdl.handle.net/2381/35043.
Full textMeléndez, i. Catalán Adrià. "Development of a New Parallel Code for 3-D Joint Refraction and Reflection Travel-Time Tomography of Wide-Angle Seismic Data. Synthetic and Real Data Applications to the Study of Subduction Zones." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/289786.
Full textAquesta tesi està dedicada a la tomografia sísmica. Concretament, he implementat una eina de modelització 3D per a la tomografia conjunta de temps de trajecte de refraccions i reflexions (TOMO3D). La raó darrere d'aquest objectiu és l'evidència de que la informació basada en dades sísmiques 2D no permet copsar la complexitat de gran part dels cossos geològics, i en particular de la zona sismogènica en marges de subducció. El desenvolupament del TOMO3D es basa en el TOMO2D, un codi d'avantguarda per a la tomografia conjunta de refraccions i reflexions en 2D. Els arxius de codi han estat reescrits, redefinint i introduint les funcions necessàries per dur a terme la inversió 3D. Els testos fets amb la versió seqüencial del codi posen de manifest la necessitat de paral·lelització ja que l'increment de la mida dels conjunts de dades així com la modelització de la dimensió espacial afegida fan que les inversions siguin computacionalment exigents. La versió paral·lelitzada del TOMO3D ha sigut aplicada a un cas sintètic complex que simula una zona de subducció. Aquesta primera aplicació 3D serveix per avaluar la correcció de la programació del codi, i com a descripció pas a pas del procediment de modelització. Els resultats demostren la capacitat del codi per recuperar acuradament la distribució de velocitat i la geometria dels dos reflectors. Finalment, el TOMO3D és aplicat a un conjunt 3D de dades de sísmica de gran angle adquirit al marge pacífic d'Equador i Colòmbia per extreure'n un model 3D de la velocitat de les plaques cavalcant i subduïda, que és comparat amb el resultat obtingut amb un codi 3D de tomografia de temps de trajecte de refraccions (FAST). La comparació indica que el TOMO3D és més acurat que el FAST però al mateix temps és computacionalment més exigent. Tot i així, la paral·lelització del TOMO3D permet utilitzar plataformes de supercomputació, a diferència del que passa amb el FAST i la majoria de codis existents.
Biari, Youssef. "Structure profonde de la marge Nord-Ouest Africaine." Thesis, Brest, 2015. http://www.theses.fr/2015BRES0080/document.
Full textThe NE American margin represents one of the best studied margins in the world, it was the subject of several scientific programs. In comparison, the conjugate NW African margin remains fairly unknown, only two deep seismic cruises were acquired: the SISMAR cruise (2001) offshore the Meseta and the DAKHLA cruise (2002) offshore the Sahara. The deep structure of the Canadian margin is known due to the SMART wide-angle seismic profiles 1, 2 and 3. The first objective of the MIRROR project was to acquire combined wide-angle and deep reflection seismic data offshore a segment conjugate to the SMART-1 profile. The comparison between the homologous segments of these two margins aimed to better understand the opening mechanism of the Central Atlantic Ocean. A comparison between Sismar, Dakhla and Mirror models shows that the continental crust is thicker in the north and thins toward the south. The width of the transition zone is narrower south and Sismar profiles are located on a sedimentary basin placed on a very thinned continental crust. Comparing the Mirror profile with that of the Canadian conjugate margin (Smart 1) shows that the thickness, the structure of the continental crust and the thinning is very similar. However, zones of exhumed and serpentinized mantle were imaged along the Canadian profile that have no conjugate on the African margin. Moreover, the thickness of the oceanic crust is variable with 8 km on the African side and only 3-4 km on the Canadian margin. Several hypotheses have been proposed to explain this difference (a) an age difference between the two types of crust (b) thickening associated with the passage of the Canary hotspot (c) an asymmetric accretion or (d) an accretion at slow to ultra-slow speading centers
Bouyahiaoui, Boualem. "Structure profonde et réactivation de la marge est-algérienne et du bassin adjacent (secteur d'Annaba), contraintes par sismique réflexion multitrace et grand-angle terre-mer." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4116/document.
Full textIn this study, we determine the deep structure of the eastern Algerian basin and its southern margin in the Annaba region (easternmost Algeria), to better constrain the plate kinematic reconstruction in this region. This study is based on new geophysical data collected during the SPIRAL cruise in 2009 that included a wide-angle, 240-km-long, onshore-offshore seismic profile, multichannel seismic reflection lines, and gravity and magnetic data, which was complemented by the available geophysical data for the study area. The analysis and modeling of the wide-angle seismic data using travel-times and amplitudes, and integrated with the multichannel seismic lines, reveal the detailed structure of an ocean-to-continent transition. In the deep basin, there is an ~5.5-km-thick oceanic crust that is composed of two layers. The upper layer of the crust is defined by a high velocity gradient and P-wave velocities between 4.8 km/s and 6.0 km/s from the top to the bottom. The lower crust is defined by a lower velocity gradient and P-wave velocity between 6.0 km/s and 7.1 km/s. The Poisson ratio in the lower crust deduced from S-wave modeling is 0.28, which indicates that the lower crust is composed mainly of gabbros. Below the continental edge, a typical continental crust with P-wave velocities between 5.2 km/s and 7.0 km/s from the top to the bottom shows a gradual seaward thinning of ~15 km over an ~35-km distance
Laurencin, Muriel. "Etude de la géométrie, de la nature et des déformations de la zone de subduction des Petites Antilles du Nord." Thesis, Brest, 2017. http://www.theses.fr/2017BRES0096/document.
Full textIn subduction zones, the 3D geometry of the plate interface is one of the key parameters that controls margin tectonic deformation, interplate coupling and seismogenic behavior. The North American plate subducts below the Caribbean plate with a convergence rate of 20 mm/y. The seismic activity is heterogeneous and increases locally under the Virgin Islands platform. The northward increasing convergence obliquity is favorable in partitioning which deformations were not really observed. This PhD confirms that the forearc crust is a crust of oceanic affinity thickened by hotspot magmatism and poorly affected by subduction magmatism. Two structures accommodating the partitioning of the deformation were identified. The Bunce Fault is a 850-kmlength sinistral strike-slip fault extending from Hispaniola to the east of Barbuda decoupling the accretionary prism from the Caribbean substratum. The Anegada Passage, whose extension towards the NE is highlighted, entailed deeply the forearc. The structures are reactivated in sinistral strike-slip faults compatible with the partitioning of the deformation after formation in extension due to the collision of the Bahamas Bank with the northern margin. We image for the first time the characteristics of a slow ridge formation (partly complex core and partly oceanic grain) entering in subduction. It affects the morphology of the accretion prism and probably the seismogenic potential of the subduction interface. We have highlighted a shallower slab which is located under the NE Anegada Passage and where earthquakes and partitioning deformations increase locally. Thus, the shallowing slab might results in a local greater interplate coupling favoring seismic activity and tectonic partitioning beneath the Anegada Passage
Brancatelli, Giuseppe. "Analisi di dati acquisiti con OBS." Doctoral thesis, Università degli studi di Trieste, 2010. http://hdl.handle.net/10077/3458.
Full textGli OBS (Ocean Bottom Seismometer) sono ampiamente utilizzati negli studi sismici crostali attraverso l’utilizzo delle registrazioni di onde rifratte e riflesse a grande offset (Wide Angle Reflection/Refraction, WAR/R). L'analisi di questi dati comporta, solitamente, l'impiego di modellistica diretta e/o inversa al fine di giungere alle velocità dei singoli strati e alle profondità delle interfacce. In questa tesi, invece, si presenta un approccio diverso che prevede: 1) costruzione di modelli di velocità dall’analisi dei segnali rifratti; 2) elaborazione dei dati OBS al fine di ottenere immagini sismiche a riflessione. In particolare, gli OBS e gli scoppi sono stati riportati ad uno stesso datum (superficie del mare), utilizzando il Wave Equation Datuming (WED). Dopo il WED è stato possibile applicare l'elaborazione tipica della sismica a riflessione. I profili OBS analizzati sono stati acquisiti nell'area dell'Arco Ellenico e, i risultati ottenuti, hanno permesso di riconoscere le strutture geologiche principali e i meccanismi dell’evoluzione tettonica. L'utilizzo del WED ha migliorato la risoluzione delle sezioni finali rispetto a quanto ottenibile con le correzioni statiche classiche. Per confronto è stata applicata la metodologia WED anche a dati simici ad alta risoluzione a terra, risolvendo problemi di correzioni statiche e di strutturazioni tettoniche apparenti nell'area della Bassa Pianura Friulana.
XXII Ciclo
1979
Leprêtre, Angélique. "Contraintes par imagerie sismique pénétrante sur l'évolution d'une marge Cénozoïque réactivée en compression (cas de la marge algérienne, secteur de Tipaza)." Thesis, Brest, 2012. http://www.theses.fr/2012BRES0079/document.
Full textThe inversion of passive margins appears to be one of the first steps towards the initiation of new subduction zones. This crucial step in plate tectonics nevertheless still raises many questions. The study of margins currently reactivated by compressional tectonics is thus essential to better understand this process. These margins are uncommon, located in different geodynamic settings, and the factors determining their evolution are poorly constrained. The Algerian margin, located in North Africa, is one of handful of modern examples worldwide. The evolution of this margin, rifted during the Miocene, in a back-arc setting, is part ofthe complex puzzle of the western Mediterranean. Since a few million years, the margin has suffered inversion and compression in the framework of slow on going convergence between the European and African plates. This convergence generates moderate to strong earthquakes in North Algeria. The relatively young age of the Algerian basin, the large sediment load, and the compressive forces, constitute favorable conditions to the formation of a future subduction zone. Studies from the past ten years indicate, that themain unresolved questions are related to (1) the deep structure of the Algerian basin and its southern margin (the type of margin, the nature of the basement, the dimension and nature of the ocean-continent transition, the style and the distribution of the compressional deformation), and (2) the history of the kinematic and geodynamic evolution of the basin. All of these unknowns have prevented a complete and thorough analysis of modalities of the Algerian margin inversion. This study focuses on the Central Algerian margin, in the area of Tipaza (West of Algiers), a key region to understand the mechanism of the opening of the Algerian basin. Processing and analysis of a deep wide-angle and multichannel seismic new data set acquired in the context of the French-Algerian project SPIRAL (Sismique profonde et Investigation Régionales en Algérie, 2009)have enabled us to determine the crustal structure of the Algerian basin and its southern continental margin,as well as the pseudo-3D structure of a specific feature in the study area: the submarine topographic highformed by the Khayr-al-Din bank. The analysis of the deep structure of the margin reveals features inherited from its complex evolution: (1) a crust of continental nature of more than 15 km thick at the upper margin(Khayr-al-Din Bank), (2) a thin crust of oceanic nature, 5-6 thick in the deep basin, including slightly high velocities at its base (7.2 km/s - 7.3 km/s), (3) similarities with margins formed in context of transform deformation, (4) a progressive deepening of the whole sedimentary cover and the thickening of the Plio-Quaternary sediments, from the distal deep basin towards the margin foot, coeval with (5) a long wavelengthflexuration of the basement in the basin. Results from this study provide new constraints on (1) the geometryand nature of the margin and the basin, (2) the evolution of the margin, suggesting a multiphased history including a stage of rifting and/or oceanic spreading, a transcurrent episode due to the westward migration of the Alboran block, and a diffuse Plio-Quaternary compressional reactivation distributed from the deep basinto the upper margin; (3) the mechanisms of the reactivation marked by newly formed south-dipping blind-thrusts, especially at the foot of the Khayr-al-Din bank, and suggesting a Plio-Quaternary uplift of the bankof 0.2 mm/y to 0.75 mm/y and the early stages of imbricate thrusting of crustal scales
Mihoubi, Abdelhafid. "Imagerie sismique de la structure profonde de la marge Algérienne orientale (secteur de Jijel) : implications en terme de potentiel pétrolier." Thesis, Brest, 2014. http://www.theses.fr/2014BRES0037/document.
Full textThis thesis has been conducted within the framework of the Algerian-French research cooperation program SPIRAL (Sismique Profonde et Investigations Régionales du Nord de l’Algérie). This project aims to study the deep structure of the Algerian margin. The area covered by this study focuses in the region of Jijel in eastern Algerian margin.The main objective of our thesis is to improve depth imaging of the Algerian margin using a combined approach of seismic techniques; wide-angle and multi- channel seismic data. The purpose of this thesis is to bring new knowledge to answer some questions about the nature of the crust, the area of continental -oceanic transition, the presence of Messinian salt, its distribution and relationship between surface sedimentary formations and crustal structures.This study presents the results of a deep seismic survey across the north Algerian margin, based on the combination of 2D multi-channel and wide-angle seismic data simultaneously recorded by 41 ocean bottom seismometers deployed along a North-South line extending 180 km off Jijel into the Algerian offshore basin, and 25 land stations deployed along a 100 km-long line, cutting through the Lesser Kabylia and the Tellian thrust-belt.In this study, our approach is a joint inversion of wide-angle seismic recordings (OBS, ocean bottom seismometers) and multi- channel seismic data (MCS). We conducted a series of first arrivals tomography, a joint inversion of reflected and refracted arrivals and gravity modelling. Since the solution of the inverse problem is not unique, two tomography programs were applied using the same data for the same study area; FAST (First Arrival Seismic Tomography) and Tomo2D. Tomography was followed by a joint inversion of reflected and refracted arrivals following an approach based on the combination of Kirchhoff prestack depth migration (PSDM) for MCS data and forward modelling of OBS. To check the consistency of the velocity model with gravity data, the free air anomaly was modeled.The final model obtained using forward modelling of the wide-angle data and pre-stack depth migration of the seismic reflection data provides an unprecedented view of the sedimentary and crustal structure of the margin. The sedimentary layers in the Algerian basin are 3.75 km thick to the north and up to 4.5 to 5 km thick at the foot of the margin. They are characterised by seismic velocities from 1.9 km/s to 3.8 km/s. Messinian salt formations are about 1 km thick in the study area, and are modelled and imaged using a velocity between 3.7 km/s to 3.8 km/s. The crust in the deep sea basin is about 4.5 km thick and of oceanic origin, presenting two distinct layers with a high gradient upper crust (4.7 km/s - 6.1 km) and a low gradient lower crust (6.2 km/s - 7.1 km/s). The upper mantle velocity is constrained to 7.9 km/s. The ocean-continent transition zone is very narrow between 15 km to 20 km wide. The continental crust reaches 25 km thickness as imaged from the most landward station and thins to 5 km over a less than 70 km distance. The continental crust presents steep and asymmetric upper and lower crustal geometry, possibly due to either asymmetric rifting of the margin, an underplated body, or flow of lower crustal material towards the ocean basin. Present-time deformation, as imaged from 3 additional seismic profiles, is characterized by an interplay of gravity-driven mobile-salt creep and active thrusting at the foot of the tectonically inverted Algerian margin
Chiu, Chi-Kai, and 丘志凱. "The Numerical Study of Ideal Anti-Reflection For Wide Angle Incidence." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/92618453859248113473.
Full text國立清華大學
材料科學工程學系
91
Researches of AR coating had been studied for a long time, but most of them focused on vertical-incident part. In this paper, we would find out the kind of ideal AR coating which could be used for every incident angle. Based on the characteristic matrix theory, we wrote the computer program to calculate the average reflectance for p- and s-polarization of different AR coating structures on the glass for visible spectral. We designed the ideal AR coating by using of the inhomogeneous structure with refractive index changing from air to substrate. The numerical results were discussed by discussing the distribution of index change, the numbers of layers and the thickness of coatings to obtain the most effective AR coating. After series of discussion, we obtain the best refractive index distribution for 10-layers. The average reflectance was less than 0.01 over the whole spectral region up to 80°, and its result was close to that of the ideal AR coating. we also develop the best index distribution for 5-layers structure. For practical manufacturing, we decreased numbers of layers and raised the initial index of coating, however the effects were better than that of the traditional 4-layers AR coating. At last we brought up some methods to fabricate ideal AR coating for the future work.
HSIEH, WEI-CHIEH, and 謝維傑. "Design and Fabrication of Optical Cut-off Filter for Wide Angle Reflection Mirror." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/76592980213817627314.
Full text中華大學
機械工程學系碩士班
100
Traditional wide-angle refractive mirror is not transparent for visible light, it is not possible to take photography day or night behind the mirror. This study aims to design reflective cut-off filter for wide angle mirror with day and night photography function. The Essential Macleod software was utilized to design the cut-off filter with day and night photography features. The practical cut-off filter multilayer film was carried out by sputtering and sol-gel processes. The PC (Polycarbonate) was used as the substrate material. The alternated TiO2 and SiO2 dielectric films were selected to be deposited on the PC substrate acted as the cut-off filter. It is expected that the ideal cut-off filter with a high reflectivity in visible light region (~ 80% reflectivity or 20% transmittance), and a high transmittance of 90% in infrared wavelength range. The optimal modeling results show that the transmittance of visible light is in the range of 20 to 40 % and infrared transmittance achieves 95%. The practical measured results for sputtered cut filter film show that the average transmittance of visible light approach 25% and the infrared transmittance reaches 95% at wavelength above 750 nm. The sol-gel process was also utilized to deposit alternated TiO2 and SiO2 dielectric films on glass plate as a cut-off filter. The simulation results show that the transmittance of visible light is in the range of 10~20% and infrared transmittance reaches 80%. The practical sol-gel coated results are not satisfied due to the difficulty to control the thickness and uniformity of TiO2 and SiO2 layers.
Khalifa, Mohamed Omran Mohamed. "Wide-angle seismic reflection studies of the Elberton granite and Carolina Terrane, southern Appalachians, northeast Georgia." 2002. http://purl.galileo.usg.edu/uga%5Fetd/khalifa%5Fmohamed%5Fo%5F200208%5Fphd.
Full textWidiyansari, Roma, and 維蒂利. "Body- and Surface-waves Wavefield Inversion in Southern Taiwan: Application to TAIGER T4b Wide Angle Refraction/Reflection Data." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3x93q2.
Full text國立中央大學
地球科學學系
106
Surface and body waves generated by near-surface explosions and recorded along T4b line is investigated for imaging subsurface velocity structure in Southern Taiwan. Surface waves propagate only at the Earth’s surface meanwhile body waves propagate deep through the body/interior of the Earth. For crustal-scale velocity structure investigation, wave-field processing and inversion of both body and surface waves records can be very useful to image Earth’s subsurface structures without picking travel-time. Seismic dataset used in this research is a crustal-scale Wide Angle Refraction/Reflection (WARR) survey under TAiwan Integrated GEodynamics Research (TAIGER) project conducted in 2008 in Taiwan. The south main array consist of four shot points (S1, S2, S3, S4) across southern Taiwan from west to east. A total of 609 geophones was deployed with receiver interval of about 200m. We use two approaches to estimate separate Vp and Vs velocity models along T4b line. The first method is through implementation of Multichannel Analysis of Surface Wave (MASW) technique to determine near-surface velocity structure. Shear wave velocity is the best indicator of material stiffness for engineering related applications. The near-surface soil or formation shear wave velocity (Vs) characteristics can be retrieved by analyzing the dispersion curve associated with the fundamental mode of surface waves in heterogeneous media. MASW method is only applicable for shot number 1 (S1) and shot number 2(S1) that possess significant amount of ground-rolls records. The second method is based on tau-p wave-field inversion. Through wave-field transformation and downward continuation approach, application of long-offset (or local short-offset) seismic data to estimate compressional wave velocity (Vp) structures can be achieved via direct global (or localized) search algorithm. Through wave-field processing strategy, independent Vp and Vs velocity models can be obtained. From inverted shear and body wave velocity structure, we can see obvious velocity gradient exist in southwestern Taiwan Coastal Plain with the bedrock boundary is slightly west-dipping. Assume the shear wave velocity of Pliocene to Miocene bedrock is 1.5 km/s, the thickness of alluvial sediments at the west-end of western Coastal Plain is ~1.8 km and become thinner toward the east with depth ~0.9 km. The Vs30 site classification for shot S1 is Class D1 and for shot S2 is Class D3 which all corresponds to “stiff soil”. From body wave wave-field inversion, subsurface structure can be imaged up to depth of approximately 20 km. In the Western Coastal Plain, a thick sediment layer (~ 3 km) with fairly low velocity (Vp= 1.5-4 km/s and Vs=250-1500 km/s) and high gradient changes produce significant seismic reverberations (refracted free-surface multiples) shown in data S1 and S2. Evidence of strong lateral velocity changes marked the transition between Coastal Plain and Western Foothills near east side of shot point S2. Strong lateral velocity transition also can be observed between Central Range and Coastal Range at shot point S4. The contour lines for Vp values between 5.0 to 6.5 km/s highlight the general feature of crust layer which thicken in the west (depth=8 and 16 km respectively) and thinned toward the east (depth =4 and 9 km respectively). By examining the contour value of 6.0 and 6.5 km/s, a relatively flat structure feature extend from Coastal Plain to Western Foothills; thickening at the distance between 40-78 km and thinning toward Central Range and Coastal Range provide a vivid view of crustal thickening and thinning feature associate with tectonic structure along the T4b line. The 6 km/s contour shown at the depth of 13 km from Coastal Plain and reaches the depth of ~7 km at Coastal Range may highlight the potential boundary between upper and lower crust (Conrad discontinuity?). The extreme thinning (necking) of the continental crust can be occurred by a typical rift zone at continental margin. The 6.5 km/s and a high velocity lower crust layer with velocity ranging from 6.9 (or 7.0) to 7.5 km/s may show similar features and may highlight the existing boundary between lower crust and upper mantle (Moho discontinuity?) which can be identified from wavefield processing and velocity inversion studies. With more careful investigate near-surface velocity distribution within 2.5-5 km, crust thickness can be thinner than the result from tomography studies. Picking the first arrival time with trial-and-error processes are somehow tedious, not efficient and time-consuming may lead to overly smoothed model. The advantages of the proposed method are no need to manually pick travel time and automatically and stable update of velocity model. The quality of the derived model is effectively checked by the consistency between computed travel-time with seismic records. Keywords: Tau-p Transform, Tau-p Inversion, MASW, Surface Waves, Ground-roll, TAIGER Project
Hrubcová, Pavla. "Stavba kůry v českém masívu z dat seismických refrakčních experimentů." Doctoral thesis, 2010. http://www.nusl.cz/ntk/nusl-297736.
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