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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.
21

Marine seismic refraction study between Cape Simpson and Prudhoe Bay, Alaska

Bee, Michel 12 January 1979 (has links)
A marine seismic refraction study, conducted in August 1976 by personnel from Oregon State University and the University of Connecticut between Cape Simpson and Prudhoe Bay, Alaska, provides data for analysis which yields a subsurface structural and geological cross-section of the area. The results suggest that the structural homocline which dips to the east southeast on land extends to the offshore region as well. Correlation of geologic data from wells drilled on land with the refraction data permits tentative identification of geologic sequences on the basis of their seismic velocity. This study correlates 1.60 to 1.65 km/s layers to Quaternary sediments, 1.82 to 2.51 km/s layers to Tertiary strata, 2.91 to 3.40 km/s layers to Mesozoic formations to the east and 2.99 to 4.43 km/s to Early Mesozoic formations to the west. Velocities of 5.28 to 6.08 km/s are associated with probable argillite and phyllite of the Pre-Mississippian basement. At greater depths, refractors with velocities of 6.40 to 7.07 km/s are related to crystalline material which may be silicic or mafic. No seismic velocities typical of the upper mantle are present on the record sections, but a minimum depth calculation places the Mohorovicic discontinuity deeper than 20 km. Although the observed crustal velocities are ambiguous towards theories of the origin of the Canada Basin and the tectonic history of the northern Alaska margin, they tend to favor the orocline-Rift theory of Carey (1955) over a subduction margin. / Graduation date: 1979
22

Improved teleseismic Green's functions and western Canada mantle structure and evolution

Mercier, Jean-Philippe 05 1900 (has links)
The present thesis is divided into three distinct parts and focuses both on the improvement of deconvolution technique in a teleseismic context for crustal and upper-mantle studies and on the understanding of western Canada structure and evolution through seismic imaging. The first part presents estimates of the P-component of the teleseismic-P Green's functions for three stations of the Canadian National Seismic Network (CNSN) obtained using a new deconvolution technique. Our results show evidence of the principal, first-order scattered Moho phases and, in particular, the Pp_Mp. The second part presents teleseismic receiver functions from 20 broadband three-component seismometers deployed along the MacKenzie-Liard Highway in Canada's Northwest Territories as part of the joint Lithoprobe-IRIS CAnadian NOrthwest Experiment (CANOE). These stations traverse a Paleoproterozoic suture and subduction zone that has been previously documented in detail to mantle depths using seismic reflection profiling. Our results reveal the response of the ~1.8 Ga subduction zone on both the radial and transverse component. The identification of this structure and its comparison with fine-scale mantle layering below the adjacent Slave province and from a range of Precambrian terranes provides an unambiguous connection between fossil subduction and fine-scale, anisotropic mantle layering found beneath cratons. Previous documentation of similar layering below the adjacent Slave province provides strong support for the thesis that early cratonic blocks were stabilized through processes of shallow subduction. The last part presents P- and S wave velocity models for western Canada. In this part, we focus our attention on two distinct features: 1) the transition from Phanerozoic to cratonic mantle in northwestern Canada and 2) the complex tectonic environment at the northern terminus of the Cascadia subduction zone where the plate boundary changes from convergent to transform. We find that the main transition from Phanerozoic to cratonic mantle in northwestern Canada occurs at the Cordilleran deformation front. In northern Cascadia, we have imaged and characterized the signature of the subducting Juan de Fuca plate and observed evidence of subduction beyond the northern edge of the slab. Our result show that the Anahim hotspot track is underlain by a -2% low-velocity zone.
23

Improved teleseismic Green's functions and western Canada mantle structure and evolution

Mercier, Jean-Philippe 05 1900 (has links)
The present thesis is divided into three distinct parts and focuses both on the improvement of deconvolution technique in a teleseismic context for crustal and upper-mantle studies and on the understanding of western Canada structure and evolution through seismic imaging. The first part presents estimates of the P-component of the teleseismic-P Green's functions for three stations of the Canadian National Seismic Network (CNSN) obtained using a new deconvolution technique. Our results show evidence of the principal, first-order scattered Moho phases and, in particular, the Pp_Mp. The second part presents teleseismic receiver functions from 20 broadband three-component seismometers deployed along the MacKenzie-Liard Highway in Canada's Northwest Territories as part of the joint Lithoprobe-IRIS CAnadian NOrthwest Experiment (CANOE). These stations traverse a Paleoproterozoic suture and subduction zone that has been previously documented in detail to mantle depths using seismic reflection profiling. Our results reveal the response of the ~1.8 Ga subduction zone on both the radial and transverse component. The identification of this structure and its comparison with fine-scale mantle layering below the adjacent Slave province and from a range of Precambrian terranes provides an unambiguous connection between fossil subduction and fine-scale, anisotropic mantle layering found beneath cratons. Previous documentation of similar layering below the adjacent Slave province provides strong support for the thesis that early cratonic blocks were stabilized through processes of shallow subduction. The last part presents P- and S wave velocity models for western Canada. In this part, we focus our attention on two distinct features: 1) the transition from Phanerozoic to cratonic mantle in northwestern Canada and 2) the complex tectonic environment at the northern terminus of the Cascadia subduction zone where the plate boundary changes from convergent to transform. We find that the main transition from Phanerozoic to cratonic mantle in northwestern Canada occurs at the Cordilleran deformation front. In northern Cascadia, we have imaged and characterized the signature of the subducting Juan de Fuca plate and observed evidence of subduction beyond the northern edge of the slab. Our result show that the Anahim hotspot track is underlain by a -2% low-velocity zone.
24

Influence of focal depth on the displacement spectra of earthquakes

Wilson, Jeffrey Kent 12 1900 (has links)
No description available.
25

Spatial and temporal seismicity variations in the South Sandwich and Northwestern South American subduction

Billington, Edward Davis 12 1900 (has links)
No description available.
26

Seismicity of the Central Georgia Seismic Zone

Allison, Jerry Dewell 08 1900 (has links)
No description available.
27

Automatic P-wave Picking of Microseismic Events in Underground Mines

Johnson, Stephanie 01 May 2014 (has links)
This thesis investigates microseismic P-wave arrival time detection performance of automatic picking algorithms, as well as the handpicking performance of human experts. The data set used in this project was collected from Malmberget mine (LKAB, Sweden) and the handpicked P-wave arrivals were prepared by multiple expert analysts from the Institute of Mine Seismology (IMS). Characterization of the event records in the data set was completed including the magnitude distribution of the events, noise content of the traces, and frequency spectrum of the traces. Three promising automatic P-wave picking algorithms from previous seismological research were investigated: the short-term average to long-term average ratio detector (STA/LTA), the characteristic function detector (CF), and the autoregressive modelling detector (ARfpe). Several versions of each algorithm were implemented, and the most promising versions were tested on the full dataset of microseismic events. The STA/LTA algorithm and CF algorithm were superior to the ARfpe algorithm in terms of accuracy and percentage of false negatives (missed P-wave arrival time picks). The analyst P-wave arrival times were compared and statistical distributions of the analyst P-wave arrival time differences were studied. The analyst P-wave arrival time difference and algorithm P-wave arrival time difference were defined as the mean analyst P-wave arrival time minus the specific analyst P-wave arrival time pick or the specific algorithm P-wave arrival time pick. The analyst and algorithm P-wave arrival time differences were combined into separate statistical distributions and compared. The analyst P-wave arrival time distribution lengths varied by a factor of 5, and the percentage of outliers in the distribution varied between 12% and 32%. The STA/LTA algorithm had comparable distribution statistics to the worst analyst P-wave arrival in terms of median value, distribution length, and percentage of outliers. However when the number of traces with automatic P-wave picks within the analyst handpicking range was calculated the STA/LTA algorithm had only 32.0% of picks and the CF algorithm had only 11.6% of picks. / Thesis (Master, Mining Engineering) -- Queen's University, 2014-04-30 21:45:13.741
28

Microearthquakes and tectonics of South Australia /

Stewart, Ian Charles Ferguson. January 1972 (has links) (PDF)
Thesis (Ph.D.) from the Dept. of Physics, University of Adelaide, 1973. / 3 offprints in back pocket.
29

Crustal structure from seismic refraction in the Medicine Lake area of the Cascade Range and Modoc Plateau, Northern California

Catchings, Rufus. January 1983 (has links)
Thesis (M.S.)--University of Wisconsin--Madison, 1983. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 93-97).
30

An investigation and application of the crustal transfer ratio as a diagnostic for explosion seismology

McCamy, Keith, January 1967 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

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