Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references (leaves 166-173). Also available in an electronic version.

Thesis (M.S.)--University of Montana, 2007. / Title from title screen. Description based on contents viewed July 31, 2007. Includes bibliographical references (p. 95-97).

Horizons responsible for the reflection of seismic waves within deep-sea sediments are shown to be less reliable for the purposes of correlation than their counter-parts in shallow margin sequences. Similar surfaces, such as abrupt lithological changes and unconformities, in the two different realms are not neccessarily produced by the same processes. It is the nature of these processes which control the chronostratigraphic significance of a reflector. Thus reflectors may be correlated with reference to their genetic process. Horizons caused by time-restricted physical processes have enhanced chronostratigraphic significance. In the deep-sea, layers in which the physical properties change slowly with depth (transition layers) are also important for reflector formation. In as much as these transitions can be affected by temperature, pressure and sediment geochemistry, as well as time, the equation of an horizon at two different localities does not neccessarily imply correlation in time (i.e. the horizon is not neccessarily a chronostratigraphic time line). The two most important factors affecting impedance are the primary sedimentary geochemical composition and the nature of the grain to grain contacts within the sediment. Impedance increases with increasing grain density and increased rigidity of the sedimentary frame. The inter-dependance of all sediment physical properties greatly complicates the study of the relationships between them. Modelling can be used to demonstrate the affects of variation of individual properties. Synthetic seismograms can be generated using either physical properties data measured from discrete samples or from wire-line data. While quality is a limiting factor to the performance of .-. physical properties modelling, the latter is of value in that it enables modelling at many more localities than is possible with wire-line techniques alone. Abrupt impedance contrasts that produce reflectors important in deep-sea seismic stratigraphy may be grouped into a) Compaction horizons produced by gradual increase in over-burden pressure, b) Cementation horizons produced by variation in diagenesis with depth c) Calcite compensation depth (CCD) controlled horizons characterised by marked variation in primary sedimentary content and d) Unconformities produced by bottom current action.

This PhD. thesis focuses on the vibrational communication of subterranean mammals, in particular, vocal communication of bathyergids (Heliophobius argenteocinereus, Fukomys mechowii, Fukomys darlingi) and seismic communication of Tachyoryctes. We recorded and analyzed the vocalization of three species and discussed the physical parameters of their vocalization in relationship to the special underground acoustic environment. Moreover, social systems of African mole-rats range from solitary to eusocial and thus our results enabled us to discuss the influence of sociality on vocal repertoire richness and its composition. Long distance communication possesses many challenges in underground environments; the only effective mean is seismic communication. We described for the first time seismic signaling in Tachyoryctes and proposed its function.

A 20 X 30 km2, 15 station, seismic network operated for 3 months in 1985, near Lake Bogoria in the Kenya Rift. The array provided both continuous and triggered seismic data. This thesis is concerned with the local earthquakes which occurred within 30 km of the network, in a 50 X 80 km2 study area including parts of the Rift shoulder and the central trough. 572 small events (ML < 2.7) could be located accurately (+2 km) in 3 dimensions. Unexpectedly, most of the seismic activity is associated with the major faults of the Rift shoulder, rather than the younger, minor faults in the central trough. A linear group of events in the central trough do not correspond to any surface feature, and seem to indicate a buried fault. The depth distribution of the seismicity peaks at 9 km and diminishes below 12 km, and the "brittle-ductile" transition is inferrred to occur within a 12 - 16 km depth range. This distribution is similar to those in other young intracontinental regions, suggesting a normal crustal rheology. Only a few events provided well-constrained focal mechanisms. Normal, steeply dipping, N-S striking fault plane solutions could be fitted to almost all events in the central trough. 12 of the best solutions were used to determine the stress orientation, the results indicated near-horizontal E-W extension, but this direction was poorly constrained. Suitable seismograms displayed shear wave polarisation and splitting compatible with the predictions of Extensive Dilatancy Anisotropy (EDA) theory. Instrinsic anisotropy, due to the basement fabric, is probably present, but the EDA should dominate the observations, thus allowing a determination of present-day stress orientation. Suprisingly, two dominent polarisation directions were seen in different parts of the array, indicating a change from E-W to NW-SE "tension" within the network.

The flat dilatometer (DMT) and piezocone penetration (CPTU) tests are likely to be among the most widely used in situ testing methods for soil characterization and indirect determination of geotechnical design parameters such as: strength, stiffness, permeability and compressibility. The flat dilatometer has proved to be a reliable, robust and adaptable tool, and the data obtained with this instrument is very repeatable, and easy to reduce and process. Furthermore, the addition of a seismic module to the standard flat dilatometer (SDMT) to measure the shear wave velocity (Vs) significantly complements the set of data typically obtained with a standard DMT test. Nonetheless, the experience in interpreting the combination between Vs and DMT data is fairly limited due to the recent introduction of the SDMT for commercial applications. Additionally, the estimation of the coefficient of earth pressure at rest (K₀) has been the most important application of the DMT since its introduction. However, a potential weakness of the DMT is that the derivation of K₀ is based upon empirical correlations developed some time ago and neither improvement work nor upgrade of these approaches has been performed in the last 10 years. Throughout the years several additional sensors have been developed in order to supplement the data collected with the CPTU test. Among the wide variety of sensor developed, the lateral stress module mounted behind a piezocone represents a promising tool for estimation of in situ lateral stress conditions from the interpretation of lateral stress penetration data. However, the popularity of the so called lateral stress cone has declined over the years due to constraints in both the instrumentation and the interpretation of measured data. Also, the application of this instrument remains limited to specific soils conditions and specific projects. However, the valuable experience gained throughout the years in the development and application of several lateral stress cones in combination with developments in electronics and understanding of soil behaviour allow the improvement of this type of technology. This thesis presents the results of a comprehensive laboratory and field testing programs performed by the author at several research sites located in the Lower Mainland of BC, undertaken in order to assess the performance of the seismic flat dilatometer and lateral stress seismic piezocone (LSSCPTU), built and develop at UBC. Firstly, the analysis of field measurements with the SDMT collected at several sites have demonstrated the potential for an improved soil characterization through the combination of DMT parameters and the small strain shear modulus (G₀). Additionally the usefulness of the DMT-C closing pressure for soil identification is shown. On the basis of several relationships identified from this data, a new soil type behaviour system based upon SDMT measurements is proposed. Furthermore, empirical correlations based upon fairly large and updated databases have been developed to estimate K₀ and Vs values from DMT parameters. / Applied Science, Faculty of / Civil Engineering, Department of / Graduate

Wavefield reconstruction is a crucial step in the seismic processing flow. For instance, unsuccessful interpolation leads to erroneous multiple predictions that adversely affect the performance of multiple elimination, and to imaging artifacts. We present a new non-parametric transform-based reconstruction method that exploits the compression of seismic data b the recently developed curvelet transform. The elements of this transform, called curvelets, are multi-dimensional, multi-scale, and multi-directional. They locally resemble wavefronts present in the data, which leads to a compressible representation for seismic data. This compression enables us to formulate a new curvelet-based seismic data recovery algorithm through sparsity-promoting inversion (CRSI). The concept of sparsity-promoting inversion is in itself not new to geophysics. However, the recent insights from the field of "compressed sensing" are new since they clearly identify the three main ingredients that go into a successful formulation of a reconstruction problem, namely a sparsifying transform, a sub-Nyquist sampling strategy that subdues coherent aliases in the sparsifying domain, and a data-consistent sparsity-promoting program. After a brief overview of the curvelet transform and our seismic-oriented extension to the fast discrete curvelet transform, we detail the CRSI formulation and illustrate its performance on synthetic and read datasets. Then, we introduce a sub-Nyquist sampling scheme, termed jittered undersampling, and show that, for the same amount of data acquired, jittered data are best interpolated using CRSI compared to regular or random undersampled data. We also discuss the large-scale one-norm solver involved in CRSI. Finally, we extend CRSI formulation to other geophysical applications and present results on multiple removal and migration-amplitude recovery. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

The Lena West property near Lac des Bois, NT, held by Diamondex Resources Ltd., is an area of interest for exploration for kimberlitic features. In 2005, Frontier Geosciences Inc. was contracted to carry out seismic reflection and time-domain transient electromagnetic (TEM) surveys to investigate the possibility of kimberlite pipes being the cause of total magnetic intensity (TMI) anomalies previously identified on the property. One small part of the property, Area 1915, was surveyed with two perpendicular seismic reflection lines 1550 m and 1790 m long and three TEM lines consisting of six or seven individual soundings each with a 200 m transmitter loop. The results generated by Frontier Geosciences did not indicate any obvious vertical features that correlated with the TMI anomaly. The purpose of this study is to reprocess the seismic reflection data using different approaches than those of Frontier Geosciences and to invert the TEM data using a 1-D inversion code, EM1DTM recently developed by the UBC Geophysical Inversion Facility, to improve upon previous results and enhance the interpretation. A secondary objective is to test the robustness of EM1DTM when applied to observed TEM data, since prior to this study it had only been applied to synthetic data. Selective bandpass filtering, refraction and residual statics and f-x deconvolution procedures contributed to improved seismic images to the recorded two-way traveltime of 511.5 ms (approximately 1100 m depth). The TEM data were successfully inverted and converted to pseudo 2-D recovered resistivity sections that showed similar results to those from Frontier Geosciences. On the final seismic reflection sections, several strong reflectors are identified and the base of the overlying sedimentary layers is interpreted at a depth of ~600 m. The TEM results show consistent vertical structure with minimum horizontal variation across all lines to a valid depth of ~150 m. However, neither TEM nor seismic reflection results provide any information that correlates well with the observed TMI anomaly. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

No description available.

Les phénomènes de ruptures dynamiques, incluant les tremblements de terre, peuventêtre observés de l’échelle atomique jusqu’à l’échelle des failles crustales sismogéniques.Les ruptures dynamiques sont généralement induites par une diminution de la résistancedes failles quand le glissement et la vitesse de glissement augmentent. Au coursde ce travail de thèse, nous avons utilisé des méthodes expérimentales novatrices permettantde reproduire des micro-tremblements de terre en laboratoire (Stick-Slip) dans desconditions de pression proche de la réalité. Les expériences utilisées nous ont permisd’explorer différents stades du cycle sismique, depuis l’activité précurseur des microséismes,la propagation de la rupture, jusqu’à l’endommagement cosismique au niveaude la zone de glissement. Les résultats expérimentaux ont été comparés avec des observationssismologiques et la théorie de la mécanique de la fracture élastique linéaire. Laplupart des résultats présentés ici suggèrent que le paramètre controllant la complexitédes mécanismes de rupture est l’état de contrainte initial. Pour résumer, une augmentationde la contrainte initiale induit (i) l’apparition de précurseurs pendant la phase denucléation, (ii) la transition entre des ruptures de type sub-Rayleigh et supershear, (iii)l’activation de mécanismes d’affaiblissement pendant les séismes, (iv) une augmentationde l’endommagement pendant le glissement sismique. / Dynamic rupture phenomena, including earthquakes, can be observed from the atomicscale up to the scale of seismogenic crustal faults. Dynamic ruptures are generatedbecause fault strength drops with increasing slip and slip-rate. During this PhD,we used experimental methods allowing reproduction of earthquakes at the scale of thelaboratory under crustal stress conditions. Experiments used allowed the study of differentstages of the seismic cycle, from the nucleation to the propagation of the seismicrupture, and to study the energy budget of laboratory earthquakes. Experimental resultswere compared to natural observations and to current theory. Most of the results presentedin this manuscript tend to show that the main parameter controlling the complexityof rupture processes is the stress acting on the fault plane. To summarize, increasingnormal stress leads to (i) the occurence of foreshocks during the onset of instability, (ii)the transition between sub-Rayleigh and supershear ruptures, (iii) the activation of weakeningmechanisms during faulting, (iv) the increase of damage along the fault duringearthquakes.