Thesis (Ph.D.) - Carleton University, 2006. / Includes bibliographical references (p. 163-172). Also available in electronic format on the Internet.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1998. / "February 1998." "Doctoral dissertation." Includes bibliographical references (p. 189-198).

Thesis (M.S.)--University of Nevada, Reno, 2004. / "December 2004." Includes bibliographical references (leaves 70-72). Online version available on the World Wide Web.

Thesis (Ph. D.)--Columbia University, 1968. / Includes bibliographical references (leaves 151-159).

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abstract: The goal of this study is to gain a better understanding of earthquake distribution and regional tectonic structure across Arizona. To achieve this objective, I utilized seismic data from EarthScope's USArray Transportable Array (TA), which was deployed in Arizona from April 2006 to March 2009. With station spacing of approximately 70 km and ~3 years of continuous three-component broadband seismic data, the TA provided an unprecedented opportunity to develop the first seismicity catalog for Arizona without spatial sampling bias. In this study I developed a new data analysis workflow to detect smaller scale seismicity across a regional study area, which serves as a template for future regional analyses of TA data and similar datasets. The final event catalog produced for this study increased the total number of earthquakes documented in Arizona by more than 50% compared to the historical catalog, despite being generated from less than three years of continuous waveform data. I combined this new TA catalog with existing earthquake catalogs to construct a comprehensive historical earthquake catalog for Arizona. These results enabled the identification of several previously unidentified areas of seismic activity within the state, as well as two regions characterized by seismicity in the deeper (>20 km) crust. The catalog also includes 16 event clusters, 10 of which exhibited clear temporal clustering and swarm-like behavior. These swarms were distributed throughout all three physiographic provinces, suggesting that earthquake swarms occur regardless of tectonic or physiographic setting. I also conducted a case study for an earthquake swarm in June of 2007 near Theodore Roosevelt Lake, approximately 80 miles northeast of Phoenix. Families of events showed very similar character, suggesting a nearly identical source location and focal mechanism. We obtained focal mechanisms for the largest of these events, and found that they are consistent with normal faulting, expected in this area of the Arizona Transition Zone. Further, I observed no notable correlation between reservoir water level and seismicity. The occurrence of multiple historical earthquakes in the areas surrounding the reservoir indicates that this swarm was likely the result of tectonic strain release, and not reservoir induced seismicity. / Dissertation/Thesis / Appendix A: Earthquakes recorded by EarthScope USArray / Appendix B: Total Arizona earthquake catalog / Appendix B: Earthquake catalog references / Appendix D: Mine Blast data / Appendix D: Potential mine blasts / Appendix D: Arizona blasting sites / Appendix E: Earthquake clusters / Appendix F: Antelope tutorial and parameter files / Appendix C: Stations used in this study / M.S. Geological Sciences 2011

abstract: Stratification is a dominant feature of all planetary interiors. Fine-scale structure associated with layering, as well as heterogeneities hold important clues on a planet's compositional, thermal, and dynamical state, as well as its evolution. This research centers on using data from seismic arrays, networks of seismic sensors, and array processing methodologies to map the fine scale structure in the Earth's upper mantle and deep layering in the Moon - Earth and Moon are the only two planetary bodies with seismic available data for such analyses. Small-scale structure in the Earth's upper mantle can give rise to seismic wave scattering. I studied high frequency data from the Warramunga Array in Australia using array seismology. I developed and employed back-projection schemes to map the possible upper mantle scattering or reflection locations. Mapped scatterers show good correlation to strong lateral P-wave velocity gradients in tomography models and may be associated with the complex tectonic history beneath north of Australia. The minimum scale of scatterers relates to the seismic wavelength, which is roughly between 5 and 10 km in the upper mantle for the frequencies we study. The Apollo Passive Seismic Experiment (APSE) consisted of four 3-component seismometers deployed between 1969 and 1972 that continuously recorded lunar ground motion until late 1977. I studied the deep lunar interior with array methods applied to the legacy APSE dataset. The stack results suggest the presence of a solid inner and fluid outer core, overlain by a partially molten boundary layer, but their reflector impedance contrasts and reflector depths are not well constrained. With a rapidly increasing number of available modern broadband data, I developed a package, Discovery Using Ducttape Excessively (DUDE), to quickly generate plots for a comprehensive view of earthquake data. These plots facilitate discovery of unexpected phenomena. This dissertation identifies evidence for small-scale heterogeneities in Earth's upper mantle, and deeper lunar layering structure. Planetary interiors are complex with the heterogeneities on many scales, and discontinuities of variable character. This research demonstrates that seismic array methods are well-suited for interrogating heterogeneous phenomena, especially considering the recent rapid expansion of easily available dense network data. / Dissertation/Thesis / Ph.D. Geological Sciences 2011

As the global demand for energy and natural resources continues to increase so does our interaction with Earth's near surface through resource extraction and waste injection. In monitoring these interaction, seismology plays a central role. The focus of this work is on improving the detection and localization of seismic sources, a fundamental problem in seismology. After discussing the strengths and limitations of existing methods for source detection and localization, I develop a solution based on a beamforming approach that uses cross-correlation functions in a maximum likelihood search for sources of seismic energy. I call this method InterLoc, short for `interferometric locator', and apply it to data recorded at two active underground mines to demonstrate its effectiveness in monitoring both impulsive sources and persistent sources. Next, I demonstrate how persistent seismic sources, typically seen as contaminants, can be used directly to measure small changes in the medium between a source and either source-station pairs. This method relies on the ability to locate and monitor source activity and then use this information to identify and select cross-correlation functions to isolate each source of interest. From the resulting cross-correlations, it is possible to measure small temporal changes in the waveforms. To demonstrate this method, I show how ore-crushers can be used to track the growth of a block cave by measuring changes in traveltimes due to ray paths having to circumvent the growing cave. In the final chapter I focus on the development of a processing framework for the detection and location of microseismic events recorded on dense (or large-N) surface arrays. The proposed framework involves: (1) data reduction; (2) dividing the array into smaller sub-arrays; (3) waveform processing within fixed time windows; (4) stacking of time windows selected based on each potential origin time and source location; and (6) combining the output from all sub-arrays to infer detections and locations of sources. This methodology is validated with synthetic data built to emulate a real dataset from a 10,050 node survey to evaluate the suitability of land for carbon sequestration. Based on the presence of very strong coherent contaminating sources and low rock quality, I am only able to detect sources with moment magnitude greater than -0.5. In the five hours of data processed there is no positive detections suggesting this could be a good site for carbon storage. More work is needed to improve the detection threshold and quantify risk based on event location and magnitude. In summary, my work demonstrates how the interference (via cross-correlation) and stacking of seismic waveforms can be combined in different ways to create effective solutions for problems faced by today's industries.

This thesis work was directed at aspects of two related problems: (1) sediment compaction and fluid expulsion processes in a subduction margin accretionary prism, and (2) the nature and concentration of gas hydrates that form bottom-simulating reflectors (BSRs) observed in the accretionary prism sediments of the northern Cascadia margin. The formation of the gas hydrate and the occurrence of BSRs in the study area are believed to be mainly a consequence of upward fluid expulsion in the accretionary prism. Therefore, the two study objectives are closely correlated. Most of this thesis work was carried out analyzing multichannel seismic data and incorporating available information including downhole and other geophysical measurements. Seismic techniques, such as velocity analysis, forward modelling, and waveform velocity inversion, were used in analyzing the data to advance our understanding of the tectonic and geophysical processes in a dynamic accretionary prism environment. The velocity structure and the inferred porosity variations across the frontal region of the accretionary prism have been quantitatively assessed by a detailed seismic velocity analysis. Within the Cascadia basin sediments approaching the deformation front, and within the frontal thrust zone of the accretionary prism, seismic velocities increase landward as a result of sediment consolidation. An important conclusion is that more than one third of the pore fluid content of the incoming sediment is lost by the time they are incorporated into the accretionary prism. In the lower slope region of the deformation front, a pronounced velocity decrease is evident. This low-velocity zone is explained by underconsolidation resulting from rapid horizontal shortening and vertical thickening of the sediment column, accommodated by displacements along thrust faults or by distributed deformation. A prominent BSR becomes visible immediately landward of the deformation front in the accreted sediment, and is developed over much of the low-to-mid continental slope. The upward pore-fluid migration is believed to play an important role in the formation of a gas hydrate BSR. From the estimated fluid loss of 35% over the 3-km-thick Cascadia Basin sediments with an average sediment porosity of 30%, the quantity of the expelled fluid reaches 315 m3/m2 over a distance of 12 km before the basin sediments are incorporated into the accretionary prism. Assuming that 100 mmol/L of methane is removed from the expelled fluid as it moves into the hydrate stability field, a 90-m-thick layer with an average hydrate saturation of 10% of the pore space can be formed by the rising fluids. A velocity-depth function in the lower slope region, representing a no-hydrate/no-gas reference profile, has been established from the detailed semblance velocity analyses and the ODP log data. The observed and measured sediment velocities near the ODP drill sites increase downward more rapidly than the reference profile above the BSR. Based on the reference profile, the velocity inversion results imply that the velocity increase due to hydrate above the BSR accounts for ~2/3 of the impedance contrast required to produce the BSR reflection amplitudes. The remainder of the impedance contrast appears to come from the velocity decrease associated with small concentrations of free gas below the BSR. The integrated analysis of the multichannel seismic and ODP downhole velocity data has allowed the velocity enhancement associated with the formation and concentration of gas hydrate to be estimated. If the BSR is overlain by a 100 m zone of sediment with a mean porosity of 50% in which the hydrate saturation increases linearly from zero at the top of the zone to 20% at the BSR, the estimated hydrate concentration-depth profiles indicate a total hydrate amount of about 5 m3/m2 of ocean floor or methane amount of 820 m3/m2 at STP. Throughout the Vancouver Island continental margin, where the clear BSR have been observed in an area of 30x200 km, the total methane gas estimated can amount to about 175 Tcf (trillion cubic feet) or 2.6 Gt of carbon. / Graduate