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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

HIGH RESOLUTION GEOPHYSICAL INVESTIGATION OF LATE QUATERNARY DEFORMATION IN THE LOWER WABASH VALLEY FAULT SYSTEM

Rutledge III, Frederick Alexander 01 January 2004 (has links)
Seven and a half kilometers of high-resolution SH-wave seismic reflection profiles were collected across the Mt. Vernon graben, a 35 km by 3 km graben (bounded by the Wabash Island (WIF) and Hovey Lake faults (HLF)) in the southern Wabash Valley fault system (WVFS) of southern Indiana. Forty-six discrete faults were imaged that displaced Quaternary horizons in the vicinity of the WIF and HLF. The structural styles associated with faults include: 1) normal displacement, 2) reverse displacement and other compressional features, 3) varying magnitudes of slip along fault planes, and 4) different senses of slip along individual fault planes. Carbon 14 dating of displaced horizons suggests movement between approximately 26,000 and 42,000 YBP. The style and timing of Quaternary deformation within the WVFS, the close association of soil faults to documented post-Pennsylvanian bedrock faults (HLF and WIF), and focal mechanism studies of current seismicity in the Wabash Valley seismic zone are all direct evidence that the extensionally-formed faults of the WVFS are being transpressionally reactivated: a manner consistent with the current east-northeast westsouthwest regional compressive stress field.
32

Crosshole seismic tomography incorporating later arrivals / by Thomas Gruber.

Gruber, Thomas, 1967- January 1998 (has links)
Bibliography: leaves 238-257. / ix, 257 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Develops a tomographic seismic inversion scheme that makes use of first arrivals and later arrivals simultaneously ; is easier to analyse in terms of convergence, stability and uniqueness of solutions; and is a proper non-linear inversion scheme. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1998?
33

Applications of global seismic tomography and analysis of variational methods for the solution of the linearly attenuating frequency domain wave equation /

Johnson, Stuart G., January 1997 (has links)
Thesis (Ph. D.)--University of California, San Diego, 1997. / Vita. Includes bibliographical references.
34

Seismic velocity structure of the Puget Sound Region from 3-D non-linear tomography /

Symons, Neill. January 1998 (has links)
Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [148]-158).
35

Combined travel-time and amplitude interpretation of two seismic refraction studies in Europe

Deichmann, Nicholas, January 1984 (has links)
Thesis (Ph. D.)--Swiss Federal Institute of Technology Zürich, 1984. / Vitae. Abstract also in German. Includes bibliographical references (p. 103-112).
36

Studies of the crust-mantle system beneath Southern California

Humphreys, Eugene Drake. January 1985 (has links)
Thesis (Ph. D.)--California Institute of Technology, 1985. / Typescript (photocopy). Includes bibliographical references (leaves 183-189).
37

Seismic refraction and reflection in the Caribbean Sea

Edgar, Norman Terence, January 1968 (has links)
Thesis (Ph. D.)--Columbia University, 1968. / Includes bibliographical references (leaves 151-159).
38

High-Resolution Imaging of Earth's Lowermost Mantle

January 2019 (has links)
abstract: This research investigates the fine scale structure in Earth's mantle, especially for the lowermost mantle, where strong heterogeneity exists. Recent seismic tomography models have resolved large-scale features in the lower mantle, such as the large low shear velocity provinces (LLSVPs). However, differences are present between different models, especially at shorter length scales. Fine scale structures both within and outside LLSVPs are still poorly constrained. The drastic growth of global seismic networks presents densely sampled seismic data in unprecedented quality and quantity. In this work, the Empirical Wavelet construction method has been developed to document seismic travel time and waveform information for a global shear wave seismic dataset. A dataset of 250K high-quality seismic records with comprehensive measurements is documented and made publicly available. To more accurately classify high quality seismic signal from the noise, 1.4 million manually labeled seismic records have been used to train a supervised classification model. The constructed model performed better than the empirical model deployed in the Empirical Wavelet method, with 87% in precision and 83% in recall. To utilize lower amplitude phases such as higher multiples of S and ScS waves, we have developed a geographic bin stacking method to improve signal-to-noise ratio. It is then applied to Sn waves up to n=6 and ScSn wave up to n=5 for both minor and major arc phases. The virtual stations constructed provide unique path sampling and coverage, vastly improving sampling in the Southern Hemisphere. With the high-quality dataset we have gathered, ray-based layer stripping iterative forward tomography is implemented to update a starting tomography model by mapping the travel time residuals along the ray from the surface down to the core mantle boundary. Final updated models with different starting tomography models show consistent updates, suggesting a convergent solution. The final updated models show higher resolution results than the starting tomography models, especially on intermediate-scale structures. The combined analyses and results in this work provide new tools and new datasets to image the fine-scale heterogeneous structures in the lower mantle, which advances our understanding of the dynamics and evolution of the Earth's mantle. / Dissertation/Thesis / Doctoral Dissertation Geological Sciences 2019
39

Transient seismic velocities beneath active volcanoes

Cody Adam Kupres (18418983) 22 April 2024 (has links)
<p dir="ltr">Studying changes in seismic velocities beneath two separate volcanic systems in the Aleutian arc. Focusing on eruptive behavior, this research delineates subsurface changes through the lens of changes in seismic velocity.</p>
40

Investigations of the analysis and modelling of magnetotelluric data

Travassos, Jandyr de Menezes January 1987 (has links)
No description available.

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