Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 24 for “"low-velocity zone"”.
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Seismic tomography and surface deformation in Krýsuvík, SW Iceland
… 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 …
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A model of the crust and upper mantle structure of the Hellenic and Cyprus subduction zones constrained by gravity and seismic data
… tomography studies suggest the presence of a low-velocity zone in the upper mantle beneath southwestern Anatolia. The low-velocity zone is interpreted as asthenospheric material rising up through a slab window (slab-tear) in the subducting African plate. The slab-tear and possible detachment …
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The crust and upper mantle structure of eastern Anatolia, Turkey from gravity modeling constrained by seismic data
… region is part of a young continental collision zone between the Arabian and Eurasian plates. The lithosphere in Eastern Anatolia is underlain by a low-velocity zone associated with asthenospheric flow in the upper mantle. The asthenospheric flow might have been caused by lithospheric …
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ΣΕΙΣΜΙΚΗ ΤΟΜΟΓΡΑΦΙΑ "ΠΡΟΣΔΙΟΡΙΣΜΟΣ ΖΩΝΩΝ ΤΑΧΥΤΗΤΑΣ ΣΤΟΝ ΕΥΡΥΤΕΡΟ ΕΛΛΗΝΙΚΟ ΧΩΡΟ"
3-DIMENSIONAL VELOCITY STRUCTURE BENEATH GREECE AND SURRONDING REGIONS IS DETERMINED USING THE METHOD PROPOSED BY AKI AND LEE. THE DATA USED ARE ARRIVAL TIMESOF P-WAVES FROM 166 EARTHQUAKES WHICH OCCURRED SINCE 1972 TO 1986 AND RECORDEDAT 62 STATIONS IN THE AREA INCLUDED BETWEEN 33.0 N - 43.0 N AND …
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Double-Difference Tomography Applied to Monitoring of Geologic Carbon Sequestration in the Aneth Oil Field, Utah
… four time periods for time-lapse analysis. A low velocity zone spanning the lateral extents of the observable region, likely representing a CO2 plume, is detected when considering voxels containing the highest ray path coverage. A series of synthetic tomography tests simulating different CO2 …
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Full wavefield inversion methods for monitoring time-lapse subsurface velocity changes
Quantitative measurements of seismic velocity changes from time-lapse seismic experiments provide dynamic information about the subsurface that improves the understanding of the geology and reservoir properties. In this thesis, we propose to achieve the quantitative analysis using full wavefield …
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S-wave velocity structure beneath the Kaapvaal Craton from surface-wave inversions compared with estimates from mantle xenoliths
… to about 180km depth [James et al 2004]. Seismic velocity-depth and density-depth profiles calculated on the basis of these P-T data and the mineral modes of the xenoliths are used to produce theoretical surface-wave dispersion curves and to generate roughly the upper 200km of a starting/reference …
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Testing the Utility of S Receiver Function Analysis For Mapping Seismic Discontinuities In the Sierran Lithosphere
… findings and detecting the Sierran basal low velocity zone, which often characterizes the lithosphere-asthenosphere boundary. We observe discontinuities broadly consistent with P receiver function results and delamination structures, however resolution considerations and other limitations …
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Formation and evolution of the eastern Black Sea basin: constraints from wide-angle seismic data
… centre of the basin, and reveal a wide-spread low-velocity zone (LVZ) within the deep sediments. The depth of this LVZ coincides with the organic-rich mud layer identified as the Maikop, and indicates overpressure within this formation. From the seismic velocity model, excess pore pressures of …
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Surface Wave Inversion of the Upper Mantle Velocity Structure in the Ross Sea Region, Western Antarctica
… fast seismic velocities in East Antarctica and slow seismic velocities in West Antarctica. This study focuses on the mantle seismic velocity structure of the West Antarctic Rift System in the Ross Embayment and adjacent craton and Transantarctic Mountains to further refine details of the velocity …
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Imaging the crust and uppermost mantle of north central Alaska using the joint inversion of ambient seismic noise correlation and receiver function
Seismic velocity models obtained from the joint inversion of ambient seismic noise correlation and receiver function analysis show a representation of the crustal and uppermost mantle velocity structure in north central Alaska. Due to the lack of station coverage and inhospitable terrain, the …
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Seismic study of the crust and upper mantle structure in eastern Asia using ambient noise correlation and earthquake data
… are commonly applied to investigate the velocity structures of the crust and upper mantle. Among all these methods, seismic tomography is one of the most powerful tools to image the earth’s structure. Recent theoretical and experimental studies suggest that the media impulse response …
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Microseismic guided wave eigenfunction theory with application to event depth classification in the Eagle Ford shale
… of guided waves that propagate in deep low-velocity zones are investigated using eigenfunction theory, and a novel application for microseismic event depth constraint to an unconventional reservoir is developed. Eigenfunctions, historically used in the analysis of Rayleigh and Love …
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In Situ Compressional Wave Velocity Across An Exposed Brittle Fault Zone
The effects of lithology, fracturing, and gouge zone mineralization on the geophysical properties of fault zones are not very well understood. In situ seismic data collected over the exhumed San Gregorio Fault at Moss Beach, CA were used to relate in situ compressional wave velocity to internal …
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Local Earthquake Tomography at Mt. Pinatubo, Philippines
A new high-resolution 3-dimensional P-wave velocity model for Mt. Pinatubo volcano was developed by tomographic inversion of P-wave arrivals from 3,007 earthquakes recorded during a four month period from May to August, 1991. The arrivals were recorded by a network of seismic stations, consisting …
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Tectonics, cru[s]tal and upper mantle structures of Taiwan
… down to about 16 km in eastern Taiwan.</p> <p>Velocity structures for P-waves in the apparent mantle are derived from direct measurements of apparent velocities (dΔ/dT) and studies on later arrivals with the TSNT stations. Short-period P-waves from earthquakes between 3° and 30° are used. A …
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An Examination of Site Response in Columbia, South Carolina: Sensitivity of Site Response to "Rock" Input Motion and the Utility of Vs(30)
… code, particularly the use of average shear wave velocity in the upper 30 meters as an index for engineering design response spectra. Site specific subsurface models are developed for four sites in and near Columbia, South Carolina using shear wave velocity measurements from cone penetrometer …
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The structure and seismicity of Icelandic rifts
… and volcanic processes in the extensional rift zones. My analysis of persistent seismicity located in an intervening region between individual spreading segments, uniquely records the segmentation of plate spreading on the scale of individual volcanic systems. Precise location and …
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Seismic Imaging of the Global Asthenosphere using SS Precursors
… While this layer is often characterized by low seismic velocity and high seismic attenuation, the global structure of the asthenosphere remains poorly understood. In this dissertation, twelve years of SS precursors reflected off the top and bottom of the asthenosphere, namely, the LAB and …
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New Constraints on Fault-Zone Structure from Seismic Guided Waves
The structure of fault zones (FZs) plays an important role in understanding fault mechanics, earthquake rupture and seismic hazards. Fault zone seismic guided waves (GW) carry important information about internal structure of the low-velocity fault damage zone. Numerical modeling of observed FZGWs …
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