Relevant bibliographies by topics / Crustal tomography

Academic literature on the topic 'Crustal tomography'

Author: Grafiati
Published: 11 March 2023

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Journal articles on the topic "Crustal tomography"

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Hable, Sarah, Karin Sigloch, Eléonore Stutzmann, Sergey Kiselev, and Guilhem Barruol. "Tomography of crust and lithosphere in the western Indian Ocean from noise cross-correlations of land and ocean bottom seismometers." Geophysical Journal International 219, no. 2 (July 26, 2019): 924–44. http://dx.doi.org/10.1093/gji/ggz333.

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SUMMARY We use seismic noise cross-correlations to obtain a 3-D tomography model of SV-wave velocities beneath the western Indian Ocean, in the depth range of the oceanic crust and uppermost mantle. The study area covers 2000 × 2000 km2 between Madagascar and the three spreading ridges of the Indian Ocean, centred on the volcanic hotspot of La Réunion. We use seismograms from 38 ocean bottom seismometers (OBSs) deployed by the RHUM-RUM project and 10 island stations on La Réunion, Madagascar, Mauritius, Rodrigues, and Tromelin. Phase cross-correlations are calculated for 1119 OBS-to-OBS, land-to-OBS, and land-to-land station pairs, and a phase-weighted stacking algorithm yields robust group velocity measurements in the period range of 3–50 s. We demonstrate that OBS correlations across large interstation distances of >2000 km are of sufficiently high quality for large-scale tomography of ocean basins. Many OBSs yielded similarly good group velocity measurements as land stations. Besides Rayleigh waves, the noise correlations contain a low-velocity wave type propagating at 0.8–1.5 km s−1 over distances exceeding 1000 km, presumably Scholte waves travelling through seafloor sediments. The 100 highest-quality group velocity curves are selected for tomographic inversion at crustal and lithospheric depths. The inversion is executed jointly with a data set of longer-period, Rayleigh-wave phase and group velocity measurements from earthquakes, which had previously yielded a 3-D model of Indian Ocean lithosphere and asthenosphere. Robust resolution tests and plausible structural findings in the upper 30 km validate the use of noise-derived OBS correlations for adding crustal structure to earthquake-derived tomography of the oceanic mantle. Relative to crustal reference model CRUST1.0, our new shear-velocity model tends to enhance both slow and fast anomalies. It reveals slow anomalies at 20 km depth beneath La Réunion, Mauritius, Rodrigues Ridge, Madagascar Rise, and beneath the Central Indian spreading ridge. These structures can clearly be associated with increased crustal thickness and/or volcanic activity. Locally thickened crust beneath La Réunion and Mauritius is probably related to magmatic underplating by the hotspot. In addition, these islands are characterized by a thickened lithosphere that may reflect the depleted, dehydrated mantle regions from which the crustal melts where sourced. Our tomography model is available as electronic supplement.
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Crowder, E., N. Rawlinson, D. G. Cornwell, C. Sammarco, E. Galetti, and A. Curtis. "New insights into North Sea deep crustal structure and extension from transdimensional ambient noise tomography." Geophysical Journal International 224, no. 2 (October 10, 2020): 1197–210. http://dx.doi.org/10.1093/gji/ggaa475.

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SUMMARY The deep crustal structure beneath the North Sea is poorly understood since it is constrained by only a few seismic reflection and refraction profiles. However, it is widely acknowledged that the mid to lower crust plays important roles in rift initiation and evolution, particularly when large-scale sutures and/or terrane boundaries are present, since these inherited features can focus strain or act as inhibitors to extensional deformation. Ancient tectonic features are known to exist beneath the iconic failed rift system of the North Sea, making it an ideal location to investigate the complex interplay between pre-existing regional heterogeneity and rifting. To this end, we produce a 3-D shear wave velocity model from transdimensional ambient seismic noise tomography to constrain crustal properties to ∼30 km depth beneath the North Sea and its surrounding landmasses. Major North Sea sedimentary basins appear as low shear wave velocity zones that are a good match to published sediment thickness maps. We constrain relatively thin crust (13–18 km) beneath the Central Graben depocentres that contrasts with crust elsewhere at least 25–30 km thick. Significant variations in crustal structure and rift symmetry are identified along the failed rift system that appears to be related to the locations of Laurentia–Avalonia–Baltica palaeoplate boundaries. We constrain first-order differences in structure between palaeoplates; with strong lateral gradients in crustal velocity related to Laurentia–Avalonia–Baltica plate juxtaposition and reduced lower crustal velocities in the vicinity of the Thor suture, possibly representing the remnants of a Caledonian accretionary complex. Our results provide fresh insight into the pivotal roles that ancient terranes can play in the formation and failure of continental rifts and may help explain the characteristics of other similar continental rifts globally.
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Rezaeifar, M., and E. Kissling. "Regional 3-D lithosphere structure of the northern half of Iran by local earthquake tomography." Geophysical Journal International 223, no. 3 (September 11, 2020): 1956–72. http://dx.doi.org/10.1093/gji/ggaa431.

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SUMMARY The 3-D P-wave velocity structure of the northern half of Iran crust has been determined from the local earthquake tomography using a high-quality data set of semi-automatically re-picked arrival times. The quality and quantity of these re-picked phase data allow the 3-D imaging of large parts of the northern half of Iran lithosphere between 0 and 60 km depth. Our new P-wave tomography model represents a major improvement over existing models in terms of reliability, resolution and consistency. First-order anomalies such as the crustal roots of the Zagros and Alborz Mountains are clearly resolved. In addition, several shallow smaller-scale features like the Central Iran sedimentary basin and volcanic and igneous rocks are visible in the tomographic image. Our results show deep Moho depressions beneath the Central Alborz and Zagros mountain ranges that are part of the Arabia–Iranian–Eurasia continental collision zone and locally this Moho topography agrees very well with existing models of other studies. The observed P-wave velocity structure suggests that compared to the Sanandaj-Sirjan and Zagros mountain ranges there is a minor crustal thickening beneath the Alborz mountain range and Kopeh Dagh region.
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Li, Mengkui, and Tengfei Wu. "Ps-splitting analysis reveals differential crustal deformation beneath the Qinling Orogenic Belt and its surrounding areas." Geophysical Journal International 229, no. 2 (December 17, 2021): 853–61. http://dx.doi.org/10.1093/gji/ggab509.

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SUMMARY Crustal anisotropy parameters beneath the Qinling Orogenic Belt (QOB) and its surrounding areas (including the northeastern Tibetan Plateau) are investigated by harmonic fitting the arrival times of the P-to-S converted phase from the Moho and an intracrustal discontinuity. The measurements reveal strong and spatially varying crustal anisotropy beneath the study region, with an average splitting time of 0.50 ± 0.17 s. The eastern Kunlun Orogen (EKLO), western part of QOB (WWQL) and Longmenshan block (LMB) present relatively larger crustal anisotropy, and the fast orientations changed gradually from NWW–SEE in EKLO and WWQL to NEE–SWW in LMB. The crustal anisotropy measurements, combined with the results from ambient-noise tomography and gravity inversion, suggest that the middle-lower crustal flow induced by the inhomogeneous crustal thickening during the early stage of plateau growth exists beneath these areas. The fast orientations beneath the eastern part of the QOB are predominantly NNE–SSW, nearly orthogonal to that from local shear wave splitting and teleseismic XKS splitting. The crustal anisotropy measurements suggest a layered deformation beneath the eastern QOB. The upper crust retains the fossil deformation formed during the main orogeny, the middle-to-lower crust is dominated by the N–S oriented subduction, collision and continued convergence between the North China Block, South China Block and Qinling microblocks; the upper mantle is decoupled from the crust and mainly controlled by the mantle flow from the Tibetan Plateau.
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Acevedo, Jorge, Gabriela Fernández-Viejo, Sergio Llana-Fúnez, Carlos López-Fernández, and Javier Olona. "Ambient noise tomography of the southern sector of the Cantabrian Mountains, NW Spain." Geophysical Journal International 219, no. 1 (July 8, 2019): 479–95. http://dx.doi.org/10.1093/gji/ggz308.

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SUMMARY This study presents the first detailed analysis of ambient noise tomography in an area of the continental upper crust in the Cantabrian Mountains (NW Spain), where a confluence of crustal scale faults occurs at depth. Ambient noise data from two different seismic networks have been analysed. In one side, a 10-short-period station network was set recording continuously for 19 months. A second set of data from 13 broad-band stations was used to extend at depth the models. The phase cross-correlation processing technique was used to compute in total more than 34 000 cross-correlations from 123 station pairs. The empirical Green's functions were obtained by applying the time–frequency, phase-weighted stacking methodology and provided the emergence of Rayleigh waves. After measuring group velocities, Rayleigh-wave group velocity tomographic maps were computed at different periods and then they were inverted in order to calculate S-wave velocities as a function of depth, reaching the first 12 km of the crust. The results show that shallow velocity patterns are dominated by geological features that can be observed at the surface, particularly bedding and/or lithology and fracturing associated with faults. In contrast, velocity patterns below 4 km depth seem to be segmented by large structures, which show a velocity reduction along fault zones. The best example is the visualization in the tomography of the frontal thrust of the Cantabrian Mountains at depth, which places higher velocity Palaeozoic rocks over Cenozoic sediments of the foreland Duero basin. One of the major findings in the tomographic images is the reduction of seismic velocities above the area in the crust where one seismicity cluster is nucleated within the otherwise quiet seismic area of the range. The noise tomography reveals itself as a valuable technique to identify shear zones associated with crustal scale fractures and hence, lower strain areas favourable to seismicity.
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Bozdağ, Ebru, and Jeannot Trampert. "On crustal corrections in surface wave tomography." Geophysical Journal International 172, no. 3 (March 2008): 1066–82. http://dx.doi.org/10.1111/j.1365-246x.2007.03690.x.

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Hearn, Thomas M. "Crustal attenuation from USArray ML amplitude tomography." Geophysical Journal International 224, no. 1 (September 19, 2020): 199–206. http://dx.doi.org/10.1093/gji/ggaa445.

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SUMMARY Seismic attenuation across the US is estimated using station ML magnitude data from the USArray. Station magnitudes are recalibrated back to amplitude and back projected in a 2-D tomography. Data represent the amplitudes of the horizontal components of the Lg phase. The western US shows regions of very high attenuation and contrasts with the lesser attenuation of the eastern US. Individual attenuation anomalies can be clearly tied to regional geology. Station gains show broad regional variations that match geographic regions. Most of the high-attenuation areas are regions of high geothermal activity suggesting that intrinsic attenuation dominates over scattering attenuation. An exception is the central San Andreas Fault zone because it lacks any localized heat-flow anomaly. The US east of the Rocky Mountains is bland and contains none of the high-attenuation regions of the western US. Instead, the central US has low-attenuation patches that do not obviously correspond to geologic province. Sediments of the Gulf Coast Plain, Willison Basin and Michigan Basin do show up as intermediate attenuation while the Illinois Basin, Appalachian Basin and other basins are not apparent. In Alaska, attenuation is generally less than the western US, but still much greater than the eastern US. In southeast Alaska, the Wrangell Volcanic Field causes a sizeable high-attenuation zone. The volcanic Aleutian Mountains also have high attenuation. However, moderate to high attenuation also correlates with the tertiary sedimentary basins in Alaska. The North Slope Basin does not seem to attenuate. Thicker crust and mountain roots tend to show less attenuation, if anything, but this correspondence is most likely due to differences in temperature and seismic velocity. Heat, scattering and young sedimentary basins create seismic attenuation in the continental crust.
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Got, Jean Luc, Vadim Monteiller, Jean Virieux, and Paul Okubo. "Estimating Crustal Heterogeneity from Double-difference Tomography." Pure and Applied Geophysics 163, no. 2-3 (March 2006): 405–30. http://dx.doi.org/10.1007/s00024-005-0022-x.

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Ritter, J. R. R., and U. Achauer. "Crustal tomography of the central kenya rift." Tectonophysics 236, no. 1-4 (September 1994): 291–304. http://dx.doi.org/10.1016/0040-1951(94)90181-3.

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Koulakov, I., I. Zabelina, I. Amanatashvili, and V. Meskhia. "Nature of orogenesis and volcanism in the Caucasus region based on results of regional tomography." Solid Earth 3, no. 2 (October 17, 2012): 327–37. http://dx.doi.org/10.5194/se-3-327-2012.

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Abstract. In the paper, we discuss the problem of continental collision and related volcanism in the Caucasus and surrounding areas based on the analysis of the upper mantle seismic structure in a recently derived model by Koulakov (2011). This model, which includes P and S-velocity anomalies down to 1000 km depth, was obtained from tomographic inversion of worldwide travel time data from the catalogue of the International Seismological Center. It can be seen that the Caucasus region is squeezed between two continental plates, Arabian to the south and European to the north, which are displayed in the tomographic model as high-velocity bodies down to about 200–250 km depth. On the contrary, a very bright low-velocity anomaly beneath the collision area implies that the lithosphere in this zone is very thin, which is also supported by strong horizontal deformations and crustal thickening indicating weak properties of the lithosphere. In the contact between stable continental and collision zones, we observe a rather complex alternation of seismic anomalies having the shapes of sinking drops. We propose that the convergence process causes crustal thickening and transformation of the lower crust material into the dense eclogite. When achieving a critical mass, the dense eclogitic drops trigger detachment of the mantle lithosphere and its delamination. The observed high-velocity bodies in the upper mantle may indicate the parts of the descending mantle lithosphere which were detached from the edges of the continental lithosphere plates. Very thin, or even absent, mantle parts of the lithosphere leads to the presence of hot asthenosphere just below the crust. The crustal shortening and eclogitisation of the lower crustal layer leads to the dominantly felsic composition of the crust which is favourable for the upward heat transport from the mantle. This, and also the factors of frictional heating and the radioactivity of felsic rocks, may be the origin of volcanic centres in the Caucasus and surrounding collisional areas.
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Dissertations / Theses on the topic "Crustal tomography"

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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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Lynner, Colton, and Robert W. Porritt. "Crustal structure across the eastern North American margin from ambient noise tomography." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625356.

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Passive tectonic margins, like the eastern North American margin (ENAM), represent the meeting of oceanic and continental material where no active deformation is occurring. The recent ENAM Community Seismic Experiment provides an opportunity to examine the crustal structure across the ENAM owing to the simultaneous deployment of offshore and onshore seismic instrumentation. Using Rayleigh wave phase and group velocities derived from ambient noise data, we invert for shear velocity across the ENAM. We observe a region of transitional crustal thicknesses that connects the oceanic and continental crusts. Associated with the transitional crust is a localized positive gravitational anomaly. Farther east, the East Coast magnetic anomaly (ECMA) is located at the intersection of the transitional and oceanic crusts. We propose that underplating of dense magmatic material along the bottom of the transitional crust is responsible for the gravitational anomaly and that the ECMA demarks the location of initial oceanic crustal formation.
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Villagomez, Diaz Darwin R. 1973. "Crustal and upper mantle structure beneath the Galapagos arechipelago from seismic tomography." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/11071.

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xv, 151 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.
To explain the origin of several distinct aspects of the Galápagos volcanic hotspot, such as the broad geographical extent of recent volcanism and the unusual pattern of geochemical anomalies, we conducted seismic tomography studies of the upper mantle and crust beneath the Galápagos Archipelago. The studies combine measurements of group and phase velocities of surface waves and delay times of body waves. We find that upper mantle seismic velocities are lower than those beneath other regions of comparable age in the Pacific and consistent with an excess temperature of 30 to 150°C and ∼0.5% melt. We attribute the excess temperature and presence of melt to an upwelling thermal mantle plume. Crustal seismic velocity is up to 25% lower than that of very young crust at the East Pacific Rise (EPR) and is comparable to that of Hawaii, which we attribute to heating by increased intrusive activity above the Galápagos plume and the construction of a highly porous volcanic platform. In addition, we find that the Galápagos hotspot is underlain by a high-velocity region whose thickness varies from 40 to 100 km. The tomographic images reveal that the upwelling mantle plume tilts northward (towards the nearby Galápagos Spreading Center) as it rises and then spreads laterally when it reaches the bottom the lid. The lid, which we attribute to residuum from melting, is thickest where it is farthest from the spreading center, suggesting that ridge processes may affect the generation and amount of thinning of the residuum layer. In addition, the thickness of the lid correlates well with the geographical pattern of geochemical anomalies of erupted lavas, suggesting that the lid may control the final depth of decompression melting. We conclude that many of the distinct characteristics of the Galápagos can be attributed to the interaction of the upwelling plume with the lid and the nearby ridge. We further suggest that the ridge affects the geometry of plume upwelling in the upper mantle and also the pattern of lateral spreading of the plume due to its effect on the thickness of the residuum layer. This dissertation includes previously published co-authored material.
Committee in charge: Dr. Douglas R. Toomey, Chairperson; Dr. Eugene Humphreys, Member; Dr. Emilie Hooft Toomey, Member; Dr. Paul Wallace, Member; Dr. John Conery, Outside Member
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Day, Anthony James. "Seismic imaging of crustal structure at mid-ocean ridges : a three-dimensional approach." Thesis, Durham University, 2001. http://etheses.dur.ac.uk/4274/.

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Over recent years geological, geochemical and geophysical surveys of mid-ocean ridges have revealed a significant degree of along-axis variability not only in seabed morphology, but also in crustal structure, particularly Numerous geophysical surveys of the Valu Fa Ridge, southwest Pacific, have mapped the extent of an axial mid-crustal reflector. This reflector has been interpreted as representing the top of a sill-like melt lens, comprising a high percentage of partial melt, lying at the top of a crustal magma chamber. In 1995, a controlled-source, wide-angle seismic dataset was acquired at the Valu Fa Ridge during RN Maurice Ewing cruise EW9512, to investigate the mid-deep crustal structure at this ridge, and particularly the crustal magma chamber associated with the melt lens beneath the ridge axis. The EW9512 acquisition geometry was primarily two-dimensional in design, and modelling of these 2-D profiles revealed the presence of an axial low velocity zone beneath the melt lens. This low velocity zone is thought to represent a region of crystal mush comprising a much lower percentage of partial melt than is present in the overlying melt lens. Similar structures have been modelled beneath a number of other mid-ocean ridges. The primary aim of this study was to build on this 2-D interpretation by taking advantage of three-dimensional ray coverage in the axial region in order to assess the along-axis continuity of the magmatic system, correlate this to any ridge segmentation apparent in the seabed morphology, and determine if ridge segmentation is related to the magma supply. The 3-D data were analysed using a tomographic inversion technique. The inversion results suggest that the axial low velocity zone may be segmented on a scale of 5-10 km, which correlates with the morphological segmentation of the ridge crest and is believed to reflect episodic magma supply with different ridge segments at different stages of a cycle of magmatic and amagmatic extension. However, three- dimensional ray coverage is not ideal owing to the dominantly 2-D acquisition geometry. Therefore a detailed assessment of data uncertainty and resolution was undertaken to enable a meaningful interpretation of the inversion results in terms of which features have a geological origin and which are artefacts of the inversion process. P-S mode converted arrivals arising from mid-crustal interfaces were also modelled in order to obtain improved geological constraints on the crustal structure than is possible from P-wave studies alone. This modelling indicates that the uppermost crust is pervaded by thin cracks. In addition, techniques were developed for modeling the polarisation of 5-wave arrivals with low signal strength. Application of these methods suggests that the thin cracks have a preferred orientation parallel to the ridge crest on-axis, and oblique to the ridge crest off-axis which is thought to reflect the pattern of southward propagation of the ridge system inferred from regional tectonic and bathymetric studies. Modelling of P-S mode converted arrivals arising from conversion at the top of the melt lens provided additional constraints on the properties of the melt lens. In conjunction with the 3-D tomographic results, this work suggests that the southernmost ridge segment in the study area has recently become magmatically active following a period of amagmatic extension suggested by its morphology, thus providing evidence for episodic melt supply at this ridge. As part of the suggestions for further work, a theoretical investigation of survey resolution was undertaken to test commonly adopted acquisition geometries with a view to optimising the design and cost-effectiveness of future 3-D controlled-source tomographic experiments.
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Beachly, Matthew William 1986. "The Upper Crustal P-wave Velocity Structure of Newberry Volcano, Central Oregon." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11475.

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xii, 98 p. : ill. (some col.)
The upper-crustal seismic-velocity structure of Newberry volcano, central Oregon, is imaged using P-wave travel time tomography. The inversion combines a densely-spaced seismic line collected in 2008 with two USGS seismic experiments from the 1980s. A high-velocity ring (7 km EW by 5 km NS) beneath the inner caldera faults suggests an intrusive ring complex 200 to 500 m thick. Within this ring shallow low velocities (<2 km depth) are interpreted as caldera fill and a subsided block. High velocities below 2 km depth could be intrusive complexes. There appears to be a low-velocity body at 3-6 km depth beneath the center of the volcano. This region is poorly resolved in the inversion because the ray paths bend around the low-velocity body. The 2008 data also recorded a secondary arrival that may be a delayed P-wave interacting with the low-velocity body.
Committee in charge: Emilie E.E. Hooft, Chairperson; Douglas R. Toomey, Member; Katharine V. Cashman, Member
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White, Donald John. "Shallow crustal structure beneath the Juan de Fuca ridge from 2[sup D] seismic refraction tomography." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/29317.

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The formation of oceanic lithosphere along ocean ridges, and the role that crustal magma chambers play in the accretionary process, continue to be fundamental issues in plate tectonics. To address these issues, a multi-receiver airgun/ocean bottom seismograph refraction line, designed to allow definition of lateral velocity and attenuation variations within the shallow crust, was shot across the Endeavour segment of the Juan de Fuca Ridge near 48° N, 129° W. A tomographic inversion procedure has been developed to invert the first arrival travel times and amplitudes from this profile for 2[sup D] velocity and attenuation structure. The inversion method is suited to multi-source, multi-receiver refraction profiles where source/receiver spacings are denser than for conventional profiles. The travel time-velocity inversion scheme is based on an iterative solution of the linearized problem and allows for determination of continuous velocity variations as well as geometry of subhorizontal interfaces. The iterative procedure requires a good initial estimate of the velocity model. In each iteration, two-point ray tracing is performed to construct a linear system relating travel time residuals to velocity perturbations. A damped least-squares algorithm is used to solve this system for a velocity perturbation which is used to update the current velocity estimate. Once the final velocity structure of the model has been determined, amplitudes can be inverted directly for attenuation. Tests to ascertain resolution of the method reveal horizontal smearing of the solution due to ray geometry, drop-off in resolution with depth, and the effects of source-receiver geometry and velocity structure on resolution. Parameter weighting is important in removing streaking effects (caused by inhomogeneous ray coverage) from the solution. For the purposes of ray tracing, the model is parameterized in terms of constant gradient (velocity and attenuation) cells, which allow use of analytic expressions for kinematic and dynamic ray properties, attenuation and inversion quantities. This parameterization causes scatter in the amplitudes calculated using zero-order asymptotic ray theory, a problem which is remedied by smoothing the velocity models before amplitude calculation. Application of this 2[sup D] tomographic inversion scheme to first arrival travel times and amplitudes for the cross-ridge refraction line produced a 4-layer model for the shallow crust. Layer 1 is 250 — 650 m thick, with v₁ = 2.5 km/s and [Nabla, sub z]v₁ = 0.5 s⁻¹. Layer 2 is ~800 m thick, v₂ = 4.8 km/s and [Nabla, sub z]v₂ — 1.0 s⁻¹. Layer 1 and layer 2 likely represent the sequence of extrusives whereas layer 3 (~800 m thick, v₃=5.8 km/s, [Nabla, sub z]v₃=0.5 s-1) and layer 4 (v₄=6.3 km/s, [Nabla, sub z]v₄=0.3 s⁻¹) are associated with the dike complex and massive gabbro sequence, respectively. An abrupt velocity transition between layer 1 and layer 2 may be a metamorphic front within the pillow basalts. A low velocity-high attenuation anomaly (velocities decreased by < 0.4 km/s and Q ~20-100), which is interpreted as a zone of increased fracture porosity and/or permeability associated with axial hydrothermal circulation, exists beneath the ridge in layer 2 and upper layer 3. Smaller low velocity-attenuative zones in layer 2, located 8 km to either side of the ridge may be loci of off-axis hydrothermal circulation. No evidence is found for the existence of a crustal magma chamber in the depth range of 1.5 — 3.0 km below the seafloor. Tests indicate that a 1 X 1 km zone of partial melt represents the minimum dimension of such a feature that would be clearly detected by this refraction experiment. These results suggest that Endeavour Ridge may be experiencing a period of diminished magma supply with the magma chamber reduced or eliminated by hydrothermal circulation. Asymmetry of the velocity anomalies observed in layer 3 and layer 4 suggest that crustal temperatures are elevated by 125 — 200° C beneath the ridge and to the east relative to temperatures west of the ridge, indicating that a deep crustal or upper mantle melting anomaly may exist east of the ridge.
Science, Faculty of
Earth, Ocean and Atmospheric Sciences, Department of
Graduate
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Van, Avendonk Hermanus Josephus Antonius. "An investigation of the crustal structure of the Clipperton transform fault area using 3D seismic tomography /." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9823314.

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Delph, Jonathan, and Jonathan Delph. "Crustal and Upper Mantle Structure of the Anatolian Plate: Imaging the Effects of Subduction Termination and Continental Collision with Seismic Techniques." Diss., The University of Arizona, 2016. http://hdl.handle.net/10150/622908.

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The neotectonic evolution of the eastern Mediterranean is intimately tied to interactions between the underthrusting/subducting slab along the southern margin of Anatolia and the overriding plate. The lateral variations in the subduction zone can be viewed as a temporal analogue of the transition between continuous subduction and subduction termination by continent-continent collision. By investigating the lateral variations along this subduction zone in the overriding plate, we can gain insight into the processes that precede continent collision. This dissertation summarizes the results of three studies that focus on different parts of the subduction margin: 1) In the west, where the development of a slab tear represents the transition between continuous and enigmatic subduction, 2) In the east, where continent-continent collision between the Arabian and Eurasian Plate is leading to the development of the third largest orogenic plateau on earth after complete slab detachment, and 3) In central Anatolia, where the subducting slab is thought to be in the processes of breaking up, which is affecting the flow of mantle material leading to volcanism and uplift along the margin. In the first study, we interpret that variations in the composition of material in the downgoing plate (i.e. a change from the subduction of oceanic material to continental material) may have led to the development of a slab tear in the eastern Aegean. This underthrusting, buoyant continental fragment is controlling overriding plate deformation, separating the highly extensional strains of western Anatolia from the much lower extensional strains of central Anatolia. Based on intermediate depth seismicity, it appears that the oceanic portion of the slab is still attached to this underthrusting continental fragment. In the second study, we interpret that the introduction of continental lithosphere into the north-dipping subduction zone at the Arabian-Eurasian margin led to the rollback and eventual detachment of the downgoing oceanic lithosphere attached to the Arabian Plate. After detachment, high rates of exhumation in the overriding plate are recorded due to the removal of the oceanic lithosphere and accompanying rebound of the Arabian continental lithosphere. In the third study, we image a transitional stage between the complete slab breakoff of the second study and the continuous subduction slab of the first study. We interpret that trench-perpendicular volcanism and ~2 km of uplift of flat-lying carbonate rocks along the southern margin of Turkey can be attributed to the rollback and ongoing segmentation of the downgoing slab as attenuated continental material is introduced into the subduction zone. Combining these three studies allows us to understand the terminal processes of a long-lived subduction zone as continental material is introduced.
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Kashubin, Artem. "Seismic Studies of Paleozoic Orogens in SW Iberia and the Middle Urals." Doctoral thesis, Uppsala universitet, Geofysik, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-9405.

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Controlled source seismic methods were employed in this study to investigate the reflectivity and velocity structure of two Hercynian orogens – the Uralides and Variscides. Conventional common depth point (CDP) sections from five reflection seismic campaigns and a velocity model obtained from tomographic inversion of wide-angle observations were the main datasets studied from the Middle Urals. These were complemented with the near-vertical seismic sections and velocity models from the Southern Urals. In the Variscides, conventional CDP processing, along with non-standard processing and synthetic data modeling, were used to obtain and interpret reflection seismic images of the Southwestern Iberian crust. Although, the Uralian and Variscan belts were formed in Late Paleozoic time in apparently similar plate collisional settings, a comparison of the seismic results show that the crust of these two orogens looks quite different at depth. In the Urals, collision of Baltica with Asian terranes (Siberia and Kazakhstan) resulted in a highly diversely reflective crust of 40-45 km thickness. The axial zone of the orogen is characterized by a high velocity crustal root of diffuse reflectivity and an imbricated Moho, with a crustal thickness reaching 55-60 km. The Moho discontinuity is marked by a sharp decrease in reflectivity and is well imaged in most locations except in the crustal root zone. The Southwestern Iberian Variscan crust is 30-35 km thick and is characterized by a highly reflective two-layered structure that resulted from collision of Luarussia and Gondwana, including terranes in-between them. This type of crustal structure is very similar to those imaged in other regions of the Variscan belt in the Europe. The Moho discontinuity is flat and appears to be the deepest reflection. This thesis compares the deep structure of the two orogens and interprets mountain building processes related to late Paleozoic plate movements.
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Hardwick, Anthony James. "New insights into the crustal structure of the England, Wales and Irish Seas areas from local earthquake tomography and associated seismological studies." Thesis, University of Leicester, 2009. http://hdl.handle.net/2381/8615.

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For the past three decades, deep crustal studies of the British Isles have been restricted to the interpretation of 2-D seismic reflection and refraction profiles, mostly acquired offshore. During this period, the British Geological Survey (BGS) seismic monitoring network has developed to an unrivalled density for a region of low intraplate seismicity. In an average year, the modern network records approximately 40 earthquakes in the crust beneath the British Isles with local magnitudes > 2. Statistical tests show the modern and historical pattern is not random. Understanding of the tectonic processes behind the pattern are hindered by the sparseness of onshore deep crustal studies where the majority of earthquakes are concentrated. For the first time local earthquake tomography, a method more commonly applied to tectonically active regions, is used to produce high resolution 3-D images of seismic P-wave velocity (Vp) and the P- to S-wave velocity ratio (Vp/Vs) in the crust beneath England, Wales and the Irish Sea. To account for low seismicity, over 1,000 earthquakes are utilised from the past 25 years of monitoring. The existing BGS digital catalogue is enhanced by a two-fold increase in seismic arrival time picks, significantly reducing earthquake location errors in the input dataset. The tomographic models establish a strong and previously undemonstrated link between Palaeocene magmatism and more widespread earlier phases of Caledonian magmatism. A regional Vp anomaly (> 7.2 km/s) in the lower crust centred on the East Irish Sea Basin is inferred as Palaeocene magmatic underplate with seismicity concentrated around its eastern and southern margins. In the mid- and lower-crust earthquake clusters are evident around the edges of local Vp/Vs anomalies (> 1.80), most significantly beneath the Ordovician volcanic centre in Snowdonia. The models are supplemented by the inversion of 185 independently determined focal mechanisms to consider the influence of local variations in far-field intraplate stresses alongside lithostatic stress from overburden pressure.
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Books on the topic "Crustal tomography"

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J, Mezcua, and Carreño E, eds. Iberian lithosphere heterogeneity and anisotropy, ILIHA. Madrid: Instituto Geográfico Nacional, 1993.

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Weber, Michael, and Ute Münch, eds. Tomography of the Earth’s Crust: From Geophysical Sounding to Real-Time Monitoring. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04205-3.

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Tomography of the Earth's crust: From geophysical sounding to real-time monitoring : GEOTECHNOLOGIEN Science Report no. 21. Cham: Springer, 2014.

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Korenaga, Jun. Magmatism and dynamics of continental breakup in the presence of a mantle plume. Cambridge, Mass: Massachusetts Institute of Technology, 2000.

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Michael, Weber, and Ute Münch. Tomography of the Earth's Crust : from Geophysical Sounding to Real-Time Monitoring: GEOTECHNOLOGIEN Science Report No. 21. Springer London, Limited, 2014.

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Michael, Weber, and Ute Münch. Tomography of the Earth's Crust: From Geophysical Sounding to Real-Time Monitoring - Geotechnologien Science Report No. 21. Springer, 2016.

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Book chapters on the topic "Crustal tomography"

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Lin, Yu-Pin. "Crustal Velocity Variations in Taiwan Revealed by Active-Source Seismic Observations." In Isotropic and Anisotropic Seismic Tomography Using Active Source and Earthquake Records, 35–59. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-5068-8_3.

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Phillips, W. S., H. E. Hartse, S. R. Taylor, A. A. Velasco, and G. E. Randall. "Application of Regional Phase Amplitude Tomography to Seismic Verification." In Monitoring the Comprehensive Nuclear-Test-Ban Treaty: Regional Wave Propagation and Crustal Structure, 1189–206. Basel: Birkhäuser Basel, 2001. http://dx.doi.org/10.1007/978-3-0348-8262-0_5.

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Gobarenko, V., and T. Yegorova. "Seismicity and Crustal Structure of the Southern Crimea and Adjacent Northern Black Sea from Local Seismic Tomography." In Springer Proceedings in Earth and Environmental Sciences, 215–27. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-21788-4_18.

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Roure, François, Sami Khomsi, Dominique Frizon de Lamotte, and Rémi Lepretre. "Tethyan and Alpine Controls on the Crustal Architecture of the Tunisian and Algerian Atlas and Tell: Needs for Coupled Deep Seismic Soundings and Tomography." In The Structural Geology Contribution to the Africa-Eurasia Geology: Basement and Reservoir Structure, Ore Mineralisation and Tectonic Modelling, 11–14. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-030-01455-1_3.

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Sandvol, Eric, Khaled Al-Damegh, Alexander Calvert, Dogan Seber, Muawia Barazangi, Randa Mohamad, Rengin Gök, Niyazi Türkelli, and Cemil Gürbüz. "Tomographic Imaging of Lg and Sn Propagation in the Middle East." In Monitoring the Comprehensive Nuclear-Test-Ban Treaty: Regional Wave Propagation and Crustal Structure, 1121–63. Basel: Birkhäuser Basel, 2001. http://dx.doi.org/10.1007/978-3-0348-8262-0_3.

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Spakman, Wim, and Rinus Wortel. "A Tomographic View on Western Mediterranean Geodynamics." In The TRANSMED Atlas. The Mediterranean Region from Crust to Mantle, 31–52. Berlin, Heidelberg: Springer Berlin Heidelberg, 2004. http://dx.doi.org/10.1007/978-3-642-18919-7_2.

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Spakman, W. "Tomographic Mapping of the Upper Mantle Structure Beneath the Alpine Collision Belt." In Crust/Mantle Recycling at Convergence Zones, 163–72. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-0895-6_16.

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Fuchs, K., and P. Giese. "Geophysical Targets of the Continental Deep Drilling Program of the Federal Republic of Germany Tomography of the Crust and its Permeability A Window into the Lower Crust and an In-Vivo Deep Laboratory." In Exploration of the Deep Continental Crust, 120–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-45616-9_14.

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Cheng, Win-Bin, Chengsung Wang, Chuen-Tien Shyu, and Tzay-Chyn Shin. "Crustal structure of the convergent plate-boundary zone, eastern Taiwan, assessed by seismic tomography." In Geology and geophysics of an arc-continent collision, Taiwan. Geological Society of America, 2002. http://dx.doi.org/10.1130/0-8137-2358-2.161.

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Averill, Matthew G., G. Randy Keller, Kate C. Miller, Piotr Sroda, Tiffni Bond, and Aaron Velasco. "Data fusion in geophysics: Seismic tomography and crustal structure in Poland as an example." In Geoinformatics: Data to Knowledge. Geological Society of America, 2006. http://dx.doi.org/10.1130/2006.2397(11).

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Conference papers on the topic "Crustal tomography"

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Díaz, Daniel, Maximiliano Leiva, Emilio Vera, Andrei Maksymowicz, Luis Villegas, and Sergio Contreras. "SHALLOW EXPRESSION MAPPING OF CRUSTAL FAULT USING ELECTRICAL RESISTIVITY TOMOGRAPHY." In Symposium on the Application of Geophysics to Engineering and Environmental Problems 2015. Society of Exploration Geophysicists and Environment and Engineering Geophysical Society, 2016. http://dx.doi.org/10.4133/sageep.29-074.

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Zulfakriza, E. Saygin, P. Cummins, S. Widiyantoro, and Andri Dian Nugraha. "Upper crustal structures beneath Yogyakarta imaged by ambient seismic noise tomography." In PADJADJARAN INTERNATIONAL PHYSICS SYMPOSIUM 2013 (PIPS-2013): Contribution of Physics on Environmental and Energy Conservations. AIP, 2013. http://dx.doi.org/10.1063/1.4820337.

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P. Neptrochnov, Y., B. N. Grinko, and V. V. Bezverbnaya. "Crustal Structure of the East Mariana Basin Revealed by Seismic Tomography Experiment." In 60th EAGE Conference and Exhibition. European Association of Geoscientists & Engineers, 1998. http://dx.doi.org/10.3997/2214-4609.201408436.

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Operto, S., J. X. Dessa, and J. Virueux. "Crustal Seismic Imaging from Ocean Bottom Seismometer Data by Full Waveform Tomography." In 67th EAGE Conference & Exhibition. European Association of Geoscientists & Engineers, 2005. http://dx.doi.org/10.3997/2214-4609-pdb.1.p271.

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Bagherpur Mojaver, Omid, and Fiona Darbyshire. "CRUSTAL STRUCTURE OF EASTERN CANADA AND NE USA FROM AMBIENT NOISE TOMOGRAPHY." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-352845.

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Kamei, R., R. G. Pratt, and T. Tsuji. "Waveform Tomography Imaging of Deep Crustal Faults - Application to Nankai Subduction Zone." In 73rd EAGE Conference and Exhibition incorporating SPE EUROPEC 2011. Netherlands: EAGE Publications BV, 2011. http://dx.doi.org/10.3997/2214-4609.20149629.

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Martha, Agustya Adi, Sri Widiyantoro, Phil Cummins, Erdinc Saygin, and Masturyono. "Upper crustal structure beneath East Java from ambient noise tomography: A preliminary result." In NATIONAL PHYSICS CONFERENCE 2014 (PERFIK 2014). AIP Publishing LLC, 2015. http://dx.doi.org/10.1063/1.4915017.

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Ojo, A. O., S. Ni, and Z. Li. "Upper Crustal Structure of Cameroon (West Africa) from Ambient Noise Love Wave Tomography." In 78th EAGE Conference and Exhibition 2016. Netherlands: EAGE Publications BV, 2016. http://dx.doi.org/10.3997/2214-4609.201600910.

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E. Pawlak, A., and D. W. Eaton. "Crustal Structure Beneath Hudson Bay from Ambient-noise Tomography - Implications for basin formation." In 72nd EAGE Conference and Exhibition incorporating SPE EUROPEC 2010. European Association of Geoscientists & Engineers, 2010. http://dx.doi.org/10.3997/2214-4609.201401367.

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Merrill, Reid, Michael G. Bostock, Simon M. Peacock, A. J. Calvert, and Nikolas I. Christensen. "A DOUBLE DIFFERENCE TOMOGRAPHY STUDY OF THE WASHINGTON FOREARC: DOES SILETZIA CONTROL CRUSTAL SEISMICITY?" In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-353785.

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Reports on the topic "Crustal tomography"

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Conley, Andrea C., Patrick Hammond, Sanford Ballard, and Michael Begnaud. 3D Crustal Tomography Model of Utah. Office of Scientific and Technical Information (OSTI), June 2020. http://dx.doi.org/10.2172/1635753.

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Conley, Andrea, Patrick Hammond, Sanford Ballard, and Michael Begnaud. 3D Crustal Tomography Model of Utah - Contain of the Model File in GeoTess File Format. Office of Scientific and Technical Information (OSTI), June 2020. http://dx.doi.org/10.2172/1763579.

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Solomon, Sean C. 'Q Tomography in Oceanic Crust'. Fort Belvoir, VA: Defense Technical Information Center, February 1995. http://dx.doi.org/10.21236/ada300325.

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Toksoez, M. N., and Youshun Sun. P and S Wave Velocity Structure of the Crust and Upper Mantle Under China and Surrounding Areas From Body and Surface Wave Tomography. Fort Belvoir, VA: Defense Technical Information Center, March 2008. http://dx.doi.org/10.21236/ada486734.

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