Geophysics and Seismology Commons^™

Paleoseismic Investigation Of Rupture On The Dead Coyote Fault In The Kittitas Valley, Washington, Garet Huddleston

All Master's Theses

Recently discovered fault scarps along the Dead Coyote Fault (DCF) in the northern Kittitas Valley (KV) of central Washington suggests active faulting in the late Quaternary, but constraints on the timing and potential magnitude of earthquakes along the fault zone are limited. The KV lies at the northwestern edge of the Yakima Fold and Thrust Belt (YFTB), a low-strain region where individual structures are capable of producing M~7 earthquakes.

This investigation uses surficial geologic mapping and topographic analysis of the DCF scarps, ground penetrating radar transects, and paleoseismic trenching to determine the rupture history of the DCF. The trench was …

Approaches To Model Non-Uniqueness And Site Complexity For Non-Invasive Shear-Wave Depth Profiling, Christopher Boucher

Electronic Thesis and Dissertation Repository

Shear-wave velocity (VS) depth profiling and associated seismic site classifications were performed at 15 sites across Metro Vancouver, British Columbia using passive seismic and surface wave methods. Inversion model parameters are constrained at each site using nearby geodata in combination with developing regression models of shear-wave velocity with depth for three primary stratigraphic units. Statistical methods such as a Bayesian Information Criterion are applied post-inversion to evaluate models between and within varying parameterizations. Data evaluation metrics, including the use of microtremor horizontal-to-vertical spectral ratios (MHVSRs), are applied to identify two common deviations from the simple case of normally dispersive laterally …

Considering A Seismically Active Leech River Valley Fault Zone In Southwestern British Columbia, Jacob J. Kukovica

Electronic Thesis and Dissertation Repository

The transpressional reverse Leech River fault (LRF) extends across the southern tip of Vancouver Island and beneath the city of Victoria, British Columbia, Canada. New paleoseismic studies suggest at least three surface-rupturing earthquakes have exceeded a moment magnitude (M) of 6 within a proposed Leech River Valley Fault Zone (LRVFZ) within the last 9,000 years. We examine the impact of an active LRVFZ to predicted earthquake ground motions for Victoria. In a probabilistic formulation considering the likelihood of all earthquake sources, LRVFZ earthquakes will contribute the most to high-frequency ground motions (≥ 10 Hz) in Victoria. The Canadian …

Defining Historical Earthquake Rupture Parameters And Proposed Slip Distributions Through Tsunami Modeling In South-Central Chile, Alexander Dolcimascolo

All Master's Theses

Reliable tsunami early warning forecasts rely on accurate initial modeling conditions and interpretations of subduction zone behavior in a multi-century perspective. GPS and seismologic data were introduced this past century to study rupture dynamics in detail, however limited information is known about ruptures that pre-date the 20^th century. I propose a methodology that uses statistics to better understand these pre-20^th century ruptures. This methodology applies the historical and geologic tsunami record as a means to select a suite of tsunami simulations from earthquake source solutions. I chose south-central Chile (46°S to 30°S) to test this new methodology; it …

Investigating The 2016 Jackson, Wyoming Earthquake Sequence Using Waveform Cross-Correlation And Seismic Array Methods, Emily Jo Graves

Open Access Theses & Dissertations

During a visual inspection of PDAR data extracted for the catalog events, I observed additional, unreported events, which is to be expected during an energetic swarm or seismic sequence. The casual observation of missed events strongly implied that more such missed events could be found in the data, which could improve the completeness of the earthquake catalog for the Jackson, Wyoming area. Catalog completeness improves our assessment of a region's tectonic behavior and earthquake exposure. To search for recurring swarm or earthquake sequence behavior, I applied waveform correlation methods to scan nearly two decades of continuous PDAR waveforms, comparing to …

The First Earthquake Site Assessments In Alberta, Canada, Joseph J. Farrugia

Electronic Thesis and Dissertation Repository

A thorough characterization of the site conditions at Alberta seismic stations is a vital component in assessing seismic hazard in the province. This thesis provides the first earthquake site characterizations in Alberta, including shear-wave velocity (V_S) depth profiles, estimates of the average shear-wave velocity in the upper 30 m (V_S30) and peak frequency (f_peak), and their validation for prediction of earthquake site amplification. National Building Code of Canada site classes are limited to C and D based on V_S30 estimates, with D being the predominant site class. Three …

Development Of A Semi-Automated Methodology For Discriminating Between Natural And Manmade Seismic Events Using The Oiink Seismic Array, Paul Rodriguez Asihama

Theses and Dissertations--Earth and Environmental Sciences

Broadband waveforms from the Ozark, Indiana, Illinois, Kentucky temporary seismic array OIINK, a Flexible Array in the EarthScope project, were used to develop routines to identify and remove mine blast events from a database of local events and preserve the infrequent, small, natural earthquakes. The approach taken was to first create a database of all seismic events that were detected by the OIINK Seismic Array. False-detections, events detected from outside of the project area (approx. 302 thousand square km), and known (i.e. cataloged) local earthquake were also removed. The remaining in the database were local unknown events. During the Phase …

Earthquake Relocation And Focal Mechanism Analysis In The Area Of Rupture Following The Mw = 7.6 September 5 2012 Nicoya Earthquake Costa Rica, Gregory Brenn

Honors Theses

As part of a Keck Geology Consortium project on the Nicoya Peninsula, Costa Rica, a dense broadband seismic array was installed directly above the rupture zone of the long-anticipated Nicoya September 5th, 2012, Mw= 7.6 earthquake. 5 Nanometrics Trillium compact seismometers and Taurus digitizers were installed, defining a ~200km triangular area with one triangular side oriented parallel to the trench and the apex located ~15km inland from the coast. This seismic network was operating from July 2nd to July 18th, and with this data combined with the permanent stations of the Nicoya broadband network, 254 events were initially located. Comparison …

Relationships Between Earthquake Ground Motions And Modified Mercalli Intensity, Andrea Sweny

Electronic Thesis and Dissertation Repository

With widespread Internet use, web-based earthquake reports are a valuable source of felt intensitydata with broad geographical coverage. Paired with ground motion data, Internet surveys like theUSGS Did You Feel It? (DYFI) website can be used to derive relationships between ground motionparameters and Modified Mercalli Intensity (MMI). These are particularly important for regionswith sparse seismographic coverage where the quality and density of intensity data may be superiorto ground motion data. MMI-ground motion relationships are also needed to infer ground motionsof historical earthquakes.

Using well-documented earthquakes in across North America, we analyze correlations betweenfelt intensity and ground motions, including peak ground …

Seismic Microzonation Of Great Toronto Area And Influence Of Building Resonances On Measured Soil Responses, Dimitar Genchev Mihaylov

Electronic Thesis and Dissertation Repository

A pilot seismic microzonation of the Greater Toronto Area (GTA) is used to establish the conditions and limitations of geophysical methods for site response investigations in city conditions. Maps of fundamental soil resonant frequencies, amplifications at these frequencies and interpolated average shear wave velocity of top 30 m of soil profile (VS- 30) used in soil classification were compared to the maps of drift thickness and surficial geology for the GTA. The non-applicability of the interpolated VS-30 map for site classification between measured test points is indicated. It is also shown that the soil response cannot be estimated properly using …

Probabilistic Fault Displacement Hazard Analysis For Reverse Faults And Surface Rupture Scale Invariance, Zachary E. Ross

Master's Theses

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A methodology is presented for evaluating the potential surface fault displacement on reverse faults in a probabilistic manner. This methodology follows the procedures put forth for Probabilistic Fault Displacement Hazard Analysis (PFDHA). Empirical probability distributions that are central to performing a PFDHA are derived from field investigations of reverse faulting events. Statistical analyses are used to test previously assumed properties of scale invariance with respect to magnitude for normalized displacement. It is found that normalized displacement is statistically invariant with respect to magnitude and focal mechanism, allowing for the …

Analysis Of Shallow Seismicity And Stress Fields In Southeastern Alaska, Hugo Rodriguez

Open Access Theses & Dissertations

Southeastern Alaska is dominated by strike-slip motion along the Queen Charlotte-southern Fairweather fault system (QCFS) in the south and transitions to oblique convergent motion partitioned between strike-slip motion along the Denali and northern Fairweather fault systems and thrusting along faults of the St. Elias region. Geologic complications are further increased by the subduction of the Yakutat microplate beneath North America and glacial processes. By studying regional background seismicity we intend to better determine the current state of stress of southeastern Alaska from the Dixon Entrance to Yakutat Bay. Phase data was gathered for over 4000 earthquakes of depths <20 km and magnitude <5 that occurred from 1973-2005 from Alaskan and Canadian databases. We relocated these earthquakes using the Double-Difference joint hypocenter method. Two areas of interest were identified with high concentrations of seismicity after relocation calculations for the entire southeast Alaska region; Glacier Bay through Yakutat (GBY) and the area surrounding Mt. Ogden (MOG). Earthquake locations in GBY are diffuse with some isolated clusters. The MOG subregion is dominated by a large northeast to southwest trending cluster that trends along the Speel River. We used these relocations and first motion data to estimate the stress fields for earthquake clusters that formed. Only a few of the calculated stress tensors were successful in representing the region's overall tectonic signature. We combined the calculated stress information with GPS, magnetic and gravity data in order determine how plate motion is partitioned in this region and to identify other potentially active faults.