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Articles 1381 - 1410 of 2452

Full-Text Articles in Geophysics and Seismology

The Formation Of Distal Impact Ejecta, Brandon C. Johnson Oct 2013

The Formation Of Distal Impact Ejecta, Brandon C. Johnson

Open Access Dissertations

Here we present two models for the dynamics of ejection and formation of distal impact ejecta. The first model focuses on the most highly shocked material that forms a massive expanding vapor plume or fireball. In this model molten droplets or spherules condense from the vapor. We model the expanding vapor plume using a one dimensional Lagrangian hydrocode. The condensation of droplets is treated by directly coupling the equations for homogeneous nucleation and growth with our hydrocode. The second model is focused on less energetic material ejected as part of the excavation flow. Using the iSALE hydrocode, we determine the …


Holocene Fire Occurrence And Alluvial Responses At The Leading Edge Of Pinyon–Juniper Migration In The Northern Great Basin, Usa, Kerrie N. Weppner, Jennifer L. Pierce, Julio L. Betancourt Sep 2013

Holocene Fire Occurrence And Alluvial Responses At The Leading Edge Of Pinyon–Juniper Migration In The Northern Great Basin, Usa, Kerrie N. Weppner, Jennifer L. Pierce, Julio L. Betancourt

Geosciences Faculty Publications and Presentations

Fire and vegetation records at the City of Rocks National Reserve (CIRO), south-central Idaho, display the interaction of changing climate, fire and vegetation along the migrating front of single-leaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma). Radiocarbon dating of alluvial charcoal reconstructed local fire occurrence and geomorphic response, and fossil woodrat (Neotoma) middens revealed pinyon and juniper arrivals. Fire peaks occurred ~10,700–9500, 7200–6700, 2400–2000, 850–700, and 550–400 cal yr BP, whereas ~9500–7200, 6700–4700 and ~1500–1000 cal yr BP are fire-free. Wetter climates and denser vegetation fueled episodic fires and debris flows during the …


Using Svd For Improved Interferometric Green's Function Retrieval, Gabriela Melo, Alison Malcolm, Dylan Mikesell, Kasper Van Wijk Sep 2013

Using Svd For Improved Interferometric Green's Function Retrieval, Gabriela Melo, Alison Malcolm, Dylan Mikesell, Kasper Van Wijk

CGISS Publications and Presentations

Seismic interferometry (SI) is a technique used to estimate the Green’s function (GF) between two receiver locations, as if there were a source at one of the receiver locations. However, in many applications, the requirements to recover the exact GF are not satisfied and SI yields a poor estimate of the GF. For these non-ideal cases, we improve the interferometric GFs, by applying singular value decomposition (SVD) to the cross-correlations before stacking. The SVD approach preserves energy that is stationary in the cross-correlations, which is the energy that contributes most to the GF recovery, and attenuates non-stationary energy, which leads …


Aquifer Heterogeneity Characterization With Oscillatory Pumping: Sensitivity Analysis And Imaging Potential, M. Cardiff, T. Bakhos, P. K. Kitanidis, W. Barrash Sep 2013

Aquifer Heterogeneity Characterization With Oscillatory Pumping: Sensitivity Analysis And Imaging Potential, M. Cardiff, T. Bakhos, P. K. Kitanidis, W. Barrash

CGISS Publications and Presentations

[1] Periodic pumping tests, in which a fluid is extracted during half a period, then reinjected, have been used historically to estimate effective aquifer properties. In this work, we suggest a modified approach to periodic pumping test analysis in which one uses several periodic pumping signals of different frequencies as stimulation, and responses are analyzed through inverse modeling using a “steady-periodic” model formulation. We refer to this strategy as multifrequency oscillatory hydraulic imaging. Oscillating pumping tests have several advantages that have been noted, including no net water extraction during testing and robust signal measurement through signal processing. Through numerical experiments, …


Integrated Geophysical Investigation Of The St. James Fault Complex: A Case Study, Robert W. Jacob, Jeremy B. Byler, Mary Beth Gray Sep 2013

Integrated Geophysical Investigation Of The St. James Fault Complex: A Case Study, Robert W. Jacob, Jeremy B. Byler, Mary Beth Gray

Faculty Journal Articles

We noninvasively detected the characteristics and location of a regional fault in an area of poor bedrock exposure complicated by karst weathering features in the subsurface. Because this regional fault is associated with sinkhole formation, its location is important for hazard avoidance. The bedrock lithologies on either side of the fault trace are similar; hence, we chose an approach that capitalized on the complementary strengths of very low frequency (VLF) electromagnetic, resistivity, and gravity methods. VLF proved most useful as a first-order reconnaissance tool, allowing us to define a narrow target area for further geophysical exploration. Fault-related epikarst was delineated …


Faulty Measurements And Shaky Tools: An Exploration Into Hazus And The Seismic Vulnerabilities Of Portland, Or, Brittany Ann Brannon Aug 2013

Faulty Measurements And Shaky Tools: An Exploration Into Hazus And The Seismic Vulnerabilities Of Portland, Or, Brittany Ann Brannon

Dissertations and Theses

Events or forces of nature with catastrophic consequences, or "natural disasters," have increased in both frequency and force due to climate change and increased urbanization in climate-sensitive areas. To create capacity to face these dangers, an entity must first quantify the threat and translate scientific knowledge on nature into comprehensible estimates of cost and loss. These estimates equip those at risk with knowledge to enact policy, formulate mitigation plans, raise awareness, and promote preparedness in light of potential destruction. Hazards-United States, or Hazus, is one such tool created by the federal government to estimate loss from a variety of threats, …


Depth To Bedrock Estimations Using The H/V Spectral Ratio In The San Joaquin Valley, Tyler A. Morelli Aug 2013

Depth To Bedrock Estimations Using The H/V Spectral Ratio In The San Joaquin Valley, Tyler A. Morelli

Natural Resources Management and Environmental Sciences

Basin depth is a fundamental parameter in many types of geologic studies such as resource exploration and regional tectonic mapping. The Horizontal-to-Vertical Spectral Ratio (“H/V”) method has been successfully applied to estimating of basin depths up to several hundred meters. In this study the H/V method is applied to the deep basins on the western side of the San Joaquin Valley to determine the thickness of the sedimentary layers and depth to bedrock. Microtremor data from Earthscope Seismic Array stations are ideal to test the accuracy of the H/V method on deeper basins because the data is of high-quality and …


High-Resolution Δ13CCarb Chemostratigraphy From Latest Guadalupian Through Earliest Triassic In South China And Iran, Vladimir Davydov Aug 2013

High-Resolution Δ13CCarb Chemostratigraphy From Latest Guadalupian Through Earliest Triassic In South China And Iran, Vladimir Davydov

Geosciences Faculty Publications and Presentations

Large carbon cycle perturbations are associated with the end-Permian mass extinction and subsequent recovery, but Late Permian (Lopingian) carbon cycle dynamics prior to the mass extinction event remain poorly documented. Here we present a high-resolution δ13Ccarb chemostratigraphic framework from latest Guadalupian to earliest Triassic time, calibrated with high-resolution conodont biostratigraphy and high-precision geochronology. We observe two large negative excursions in δ13Ccarb, the first in uppermost Guadalupian strata and the second at the end of the Changhsingian stage, and between these events distinctive excursions from the middle Wuchiapingian to the early Changhsingian. The end-Changhsingian …


Changes In Elastic Wave Velocity And Rock Microstructure Due To Basalt-Co2-Water Reactions, Ludmila Adam, Kasper Van Wijk, Thomas Otheim, Michael Batzle Aug 2013

Changes In Elastic Wave Velocity And Rock Microstructure Due To Basalt-Co2-Water Reactions, Ludmila Adam, Kasper Van Wijk, Thomas Otheim, Michael Batzle

CGISS Publications and Presentations

The chemical interaction between carbon dioxide, water, and basalt is a common process in the earth, which results in the dissolution of primary minerals that later precipitate as alteration minerals. This occurs naturally in volcanic settings, but more recently basalts have been suggested as reservoirs for sequestration of anthropogenic CO2. In both the natural and man-made cases, rock-fluid reactions lead to the precipitation of carbonates. Here, we quantify changes in ultrasonic wave speeds, associated with changes in the frame of whole-rock basalts, as CO2 and basalt react. After 30weeks of reactions and carbonate precipitation, the ultrasonic wave …


Anticipating Stream Ecosystem Responses To Climate Change: Toward Predictions That Incorporate Effects Via Land–Water Linkages, J. M. Davis, C. V. Baxter, E. J. Rosi-Marshall, J. L. Pierce, B. T. Crosby Aug 2013

Anticipating Stream Ecosystem Responses To Climate Change: Toward Predictions That Incorporate Effects Via Land–Water Linkages, J. M. Davis, C. V. Baxter, E. J. Rosi-Marshall, J. L. Pierce, B. T. Crosby

Geosciences Faculty Publications and Presentations

Climate change (CC) is projected to increase the frequency and severity of natural disturbances (wildfires, insect outbreaks, and debris flows) and shift distributions of terrestrial ecosystems on a global basis. Although such terrestrial changes may affect stream ecosystems, they have not been incorporated into predictions of stream responses to CC. Here, we introduce a conceptual framework to evaluate to what extent responses of streams to CC will be driven by not only changes in thermal and hydrologic regimes, but also alterations of terrestrial processes. We focused on forested water-sheds of western North America because this region is projected to experience …


A Solution To The Problem Of Interpreting Very Long Time Series Of Ambient Noise As Measured At Very Sparse Networks, Kathryn Teresa Decker Aug 2013

A Solution To The Problem Of Interpreting Very Long Time Series Of Ambient Noise As Measured At Very Sparse Networks, Kathryn Teresa Decker

Boise State University Theses and Dissertations

No abstract provided.


Breaking Peroxy Bonds In H20 Ice Doped With H202 To Create Positive Hole Charge Carriers., Corey C. Stockburger Aug 2013

Breaking Peroxy Bonds In H20 Ice Doped With H202 To Create Positive Hole Charge Carriers., Corey C. Stockburger

STAR Program Research Presentations

Using stress-activated electric conductivity in water ice doped with hydrogen peroxide as a model for stress-activated electric conductivity of igneous and high-grade metamorphic rocks due to the presence of peroxy defects, which when broken, createpositive-hole charge carriers. Blocks of pure H2O ice and H2O2–doped H2O ices, frozen at –20°C, will be stressed with piezo electric transducers(pzt) at one end to generate stress-activated electric currents flowing down the stress gradient. Pure H2O ice should produce no current or a small insignificant amount during rapid deformation or fracture. Stressing H2O2-doped H2O ices, however, should lead to 100-1000 times higher currents. These stress-activated …


A Geomechanical Study Of The Mississippian Boone Formation, Karen Nicole Mason Buckland Aug 2013

A Geomechanical Study Of The Mississippian Boone Formation, Karen Nicole Mason Buckland

Graduate Theses and Dissertations

The Boone Formation in northwest Arkansas is a chert-limestone sequence analogous to the subsurface Mississippi Lime reservoir in parts of Oklahoma and Kansas. It has low permeability and produces via horizontal drilling and hydraulic fracturing. The response to stimulation by fracturing is dependent on the quantity of chert in the area. Chert nodules and laterally extensive chert layers in the sequence are variable. Locally, cm- to dm-scale chert bedding is continuous and comprises up to 50% of the outcrop. Elsewhere, the chert is nodular and intermittent.

Samples collected from representative outcrops spanning the thickness and aerial extent of the formation …


Plains Co2 Reduction (Pcor) Partnership Atlas, Wesley D. Peck, Tera D. Buckley, Earl P. Battle, Megan M. Grove, Joyce M. Riske, Charles D. Gorecki, Edward N. Steadman, John A. Harju Jul 2013

Plains Co2 Reduction (Pcor) Partnership Atlas, Wesley D. Peck, Tera D. Buckley, Earl P. Battle, Megan M. Grove, Joyce M. Riske, Charles D. Gorecki, Edward N. Steadman, John A. Harju

EERC Maps and Infographics

The Plains CO2 Reduction (PCOR) Partnership Atlas provides a regional profile of CO2 sources and potential CO2 storage locations across the PCOR Partnership region. The revised fourth edition provides an update-to-date look at PCOR Partnership activities, including regional characterization and full-scale demonstration activities. Additional background information on carbon capture, utilization, and storage (CCUS) is included to give a better understanding of how CCUS addresses concerns about climate change while allowing future energy needs to be met.


The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock Jul 2013

The Need To Adapt The Exploration Model From The Oil Patch To Contaminated-Site Characterization: A Case From Hill Afb, Utah, Usa, John H. Bradford, Esther Babcock

CGISS Publications and Presentations

For decades, the oil industry has employed a working model for hydrocarbon exploration in which large-scale geophysical surveys are undertaken prior to a second phase of intensive, targeted drilling. This latter phase may be conducted in conjunction with further focused geophysical studies. The geophysical surveys provide lateral coverage and continuity that are used to drive placement of drilling locations. The reason for this approach is simple: wells are expensive relative to geophysical surveys. Also, practical limits on lateral coverage preclude optimization of exploration targets based on well information alone.


Guidance Statement On Undertaking Seismic Surveys In Western Australian Waters, Department Of Fisheries Jun 2013

Guidance Statement On Undertaking Seismic Surveys In Western Australian Waters, Department Of Fisheries

Fisheries Occasional Publications

No abstract provided.


Microbially Mediated Carbonate Precipitation Within Microbial Mat In Hyper-Saline Lakes Of The Bahamas, Shane Cone May 2013

Microbially Mediated Carbonate Precipitation Within Microbial Mat In Hyper-Saline Lakes Of The Bahamas, Shane Cone

Honors Capstones

No abstract provided.


Noncontacting Benchtop Measurements Of The Elastic Properties Of Shales, Thomas E. Blum, Ludmila Adam, Kasper Van Wijk May 2013

Noncontacting Benchtop Measurements Of The Elastic Properties Of Shales, Thomas E. Blum, Ludmila Adam, Kasper Van Wijk

CGISS Publications and Presentations

We evaluated a laser-based noncontacting method to measure the elastic anisotropy of horizontal shale cores. Whereas conventional transducer data contained an ambiguity between phase and group velocity measurements, small laser source and receiver footprints on typical core samples ensured group velocity information in our laboratory measurements. With a single dense acquisition of group velocity versus group angle on a horizontal core, we estimated the elastic constants C11, C33, and C55 directly from ultrasonic waveforms, and C13 from a least-squares fit of modeled to measured group velocities. The observed significant P-wave velocity and attenuation anisotropy …


Characterization Of Heterogeneous Media With Multicomponent Laser Ultrasonics, Thomas E. Blum May 2013

Characterization Of Heterogeneous Media With Multicomponent Laser Ultrasonics, Thomas E. Blum

Boise State University Theses and Dissertations

Wave propagation in scattering media is a complicated topic, but scattered elastic waves carry important information about the internal structure of the medium. It is a current topic of research and for the foreseeable future. Advances in theory and applications described in this manuscript benefit from new ways to collect more densely sampled, multicomponent, true-amplitude data.

Thus far, most fracture characterization experiments in the laboratory involve contacting transducers as elastic wave sources and receivers. Similarly, rock properties such as anisotropy and attenuation are also measured with contacting techniques. These type of measurements are well-suited for time-of-flight measurements, but for scattering …


Pattern Recognition In Earthquake Swarms From The 2009 Eruption Of Redoubt Volcano, Alaska, Catherine Jeanne Carlisle May 2013

Pattern Recognition In Earthquake Swarms From The 2009 Eruption Of Redoubt Volcano, Alaska, Catherine Jeanne Carlisle

Boise State University Theses and Dissertations

Earthquake swarms at volcanoes are common indicators of unrest and can be used to predict eruptions. However, not all earthquake swarms lead to an eruption but may die off instead. Variabilities in characteristics of swarms can lead to false predictions of an eruption. During the 2009 eruption of Redoubt Volcano in Alaska, there were five earthquake swarms, three of which preceded explosive eruptions and two that did not. These data were used to explore the variable characteristics that may be diagnostic of whether or not an eruption is imminent.

Data were recorded by the Alaska Volcano Observatory throughout the eruption. …


Geophysical Surveys And Archaeological Insights At Fort Pierre Chouteau A Frontier Trading Post On The Middle Missouri, Margaret Maurine Patton May 2013

Geophysical Surveys And Archaeological Insights At Fort Pierre Chouteau A Frontier Trading Post On The Middle Missouri, Margaret Maurine Patton

Graduate Theses and Dissertations

Fort Pierre Chouteau in present day South Dakota was the most important fur trading post of the American Fur Company in the 1830s, serving as a regional hub for the fur trade. The Fort was sold to the U.S. Military in 1855 for use as a base in the Sioux Wars but was abandoned in 1856. Geophysical surveys and previous excavations indicate evidence of both occupations. Geophysics is an important tool for determining the extent of archaeological sites, yet the relationships between geophysical anomalies and excavation features may not be readily evident. Initial geophysical surveys (Kvamme 2007) were completed to …


Assessing The Impact Of Additional Seismic Sources On The Probabilistic Seismic Hazard Assessment For The Las Vegas Valley, Nevada, Suchan Lamichhane, Barbara Luke, Wanda Taylor, William Savage Apr 2013

Assessing The Impact Of Additional Seismic Sources On The Probabilistic Seismic Hazard Assessment For The Las Vegas Valley, Nevada, Suchan Lamichhane, Barbara Luke, Wanda Taylor, William Savage

College of Engineering: Graduate Celebration Programs

  • The densely populated (~2M) Las Vegas Valley, Nevada (LVV) is underlain by sediments that are cut by six mapped, active normal faults that comprise the Las Vegas Valley Fault System (LVVFS). Recent research indicates that these faults have the potential to generate earthquakes up to a maximum magnitude of 6.8.
  • The current (2008) USGS national seismic hazard model (NSHM) explicitly considered only the Eglington fault of the LVVFS (the remaining 5 LVVFS sources were classified as "Class B" in the USGS fault and fold database and effectively given a weight of zero in the 2008 NSHM) and also did not …


Detecting Geyser Activity With Infrasound, Jeffrey B. Johnson, J. F. Anderson, R. E. Anthony, M. Sciotto Apr 2013

Detecting Geyser Activity With Infrasound, Jeffrey B. Johnson, J. F. Anderson, R. E. Anthony, M. Sciotto

Geosciences Faculty Publications and Presentations

We monitored geyser activity in the Lower Geyser Basin (LGB) of Yellowstone National Park with dual four-element microphone arrays separated by ~ 600 m. The arrays were independently used to identify incident coherent plane wave energy, then conjoint cross beam back-azimuths from the two arrays were used to precisely locate signal sources. During a week in August 2011 we located repeating infrasound events, peaked in energy between 1 and 10 Hz, originating from at least five independent geothermal features, including the episodically erupting Great Fountain, Fountain and Kaleidoscope Geysers, as well as periodic infrasound from nearby Botryoidal and persistent sound …


The First Second Of Volcanic Eruptions From The Erebus Volcano Lava Lake, Antarctica—Energies, Pressures, Seismology, And Infrasound, A. Gerst, M. Hort, R. C. Aster, J. B. Johnson, P. R. Kyle Apr 2013

The First Second Of Volcanic Eruptions From The Erebus Volcano Lava Lake, Antarctica—Energies, Pressures, Seismology, And Infrasound, A. Gerst, M. Hort, R. C. Aster, J. B. Johnson, P. R. Kyle

Geosciences Faculty Publications and Presentations

[1] We describe a multiparameter experiment at Erebus volcano, Antarctica, employing Doppler radar, video, acoustic, and seismic observations to estimate the detailed energy budget of large (up to 40 m-diameter) bubble bursts from a persistent phonolite lava lake. These explosions are readily studied from the crater rim at ranges of less than 500 m and present an ideal opportunity to constrain the dynamics and mechanism of magmatic bubble bursts that can drive Strombolian and Hawaiian eruptions. We estimate the energy budget of the first second of a typical Erebus explosion as a function of time and energy type. We constrain …


A Latest Carboniferous Warming Spike Recorded By A Fusulinid-Rich Bioherm In Timor Leste: Implications For East Gondwana Deglaciation, Vladimir I. Davydov, David W. Haig, Eujay Mccartain Apr 2013

A Latest Carboniferous Warming Spike Recorded By A Fusulinid-Rich Bioherm In Timor Leste: Implications For East Gondwana Deglaciation, Vladimir I. Davydov, David W. Haig, Eujay Mccartain

Geosciences Faculty Publications and Presentations

During the late Paleozoic and early Mesozoic Timor lay in the northern part of the north–south East Gondwana rift system along which the western margin of Australia later developed. Discovery of a latest Gzhelian bioherm in the central highlands of Timor Leste has implications for latest Carboniferous–earliest Permian climate history and deglaciation in basins further south in the rift system.

Limestone outcrop of the Maubisse Formation near the village of Kulau is recognized as a bioherm with a massive lower unit, including reef framework at the base, and a bedded grainstone upper unit. The bioherm developed on a basalt substrate …


Reinterpreting The Stratigraphy Of The Florissant Fossil Beds National Monument Through Correlation By Magnetic Susceptibility And Geochemical Comparison, Lindsay Prothro Apr 2013

Reinterpreting The Stratigraphy Of The Florissant Fossil Beds National Monument Through Correlation By Magnetic Susceptibility And Geochemical Comparison, Lindsay Prothro

Honors Capstones

No abstract provided.


On The Lack Of Stratospheric Dynamical Variability In Low‐Top Versions Of The Cmip5 Models, Andrew J. Charlton-Perez, Mark P. Baldwin, Thomas Birner, Robert X. Black, Amy H. Butler, Natalia Calvo, Nicholas A. Davis, Edwin P. Gerber, Nathan Gillett, Steven Hardiman, Junsu Kim, Kirsten Krüger, Yun-Young Lee, Elisa Manzini, Brent A. Mcdaniel, Lorenzo Polvani, Thomas Reichler, Tiffany A. Shaw, Michael Sigmond, Seok-Woo Son, Matthew Toohey, Laura Wilcox, Shigeo Yoden, Bo Christiansen, François Lott, Drew Shindell, Seiji Yukimoto, Shingo Watanabe Mar 2013

On The Lack Of Stratospheric Dynamical Variability In Low‐Top Versions Of The Cmip5 Models, Andrew J. Charlton-Perez, Mark P. Baldwin, Thomas Birner, Robert X. Black, Amy H. Butler, Natalia Calvo, Nicholas A. Davis, Edwin P. Gerber, Nathan Gillett, Steven Hardiman, Junsu Kim, Kirsten Krüger, Yun-Young Lee, Elisa Manzini, Brent A. Mcdaniel, Lorenzo Polvani, Thomas Reichler, Tiffany A. Shaw, Michael Sigmond, Seok-Woo Son, Matthew Toohey, Laura Wilcox, Shigeo Yoden, Bo Christiansen, François Lott, Drew Shindell, Seiji Yukimoto, Shingo Watanabe

Faculty Articles

We describe the main differences in simulations of stratospheric climate and variability by models within the fifth Coupled Model Intercomparison Project (CMIP5) that have a model top above the stratopause and relatively fine stratospheric vertical resolution (high-top), and those that have a model top below the stratopause (low-top). Although the simulation of mean stratospheric climate by the two model ensembles is similar, the low-top model ensemble has very weak stratospheric variability on daily and interannual time scales. The frequency of major sudden stratospheric warming events is strongly underestimated by the low-top models with less than half the frequency of events …


Elastic Laboratory Measurements And Modeling Of Saturated Basalts, Ludmila Adam, Thomas Otheim Mar 2013

Elastic Laboratory Measurements And Modeling Of Saturated Basalts, Ludmila Adam, Thomas Otheim

Geosciences Faculty Publications and Presentations

Understanding the elastic behavior of basalt is important to seismically monitor volcanoes, subsea basalts, and carbon sequestration in basalt. We estimate the elastic properties of basalt samples from the Snake River Plain, Idaho, at ultrasonic (0.8 MHz) and seismic (2–300 Hz) frequencies. To test the sensitivity of seismic waves to the fluid content in the pore structure, measurements are performed at three saturation conditions: saturated with liquid CO2, water, and dry. When CO2 replaces water, the P-wave velocity drops, on average, by 10%. Vesicles and cracks, observed in the rock microstructure, control the relaxation of pore-fluid pressures …


Clustering Revisited: A Spectral Analysis Of Microseismic Events, Deborah Fagan, Kasper Van Wijk, James Rutledge Mar 2013

Clustering Revisited: A Spectral Analysis Of Microseismic Events, Deborah Fagan, Kasper Van Wijk, James Rutledge

CGISS Publications and Presentations

Identifying individual subsurface faults in a larger fault system is important to characterize and understand the relationship between microseismicity and subsurface processes. This information can potentially help drive reservoir management and mitigate the risks of natural or induced seismicity. We have evaluated a method of statistically clustering power spectra from microseismic events associated with an enhanced oil recovery operation in southeast Utah. Specifically, we were able to provide a clear distinction within a set of events originally designated in the time domain as a single cluster and to identify evidence of en echelon faulting. Subtle time-domain differences between events were …


2012 Haida Gwaii Quake: Insight Into Cascadia's Subduction Extent, Walter Szeliga Feb 2013

2012 Haida Gwaii Quake: Insight Into Cascadia's Subduction Extent, Walter Szeliga

Geological Sciences Faculty Scholarship

The limits of Cascadia were first defined to contain nearly the entire margin of the Pacific Northwest, from Cape Mendocino through the Alaska Panhandle [Schuchert, 1910; Schuchert and Barrell, 1914]. Since that time, the boundary of Cascadia has shrunk to become essentially synonymous with the region where the Juan de Fuca plate subducts beneath the North American plate. As a consequence, seismic hazard assessments in the Pacific Northwest have conventionally focused on the potential for large megathrust earthquakes along the interface of the Juan de Fuca and North American plates.