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Articles 31 - 60 of 109
Full-Text Articles in Geophysics and Seismology
Plate Boundary Observatory And Related Networks: Gps Data Analysis Methods And Geodetic Products, Thomas A. Herring, Timothy I. Melbourne, Mark H. Murray, Michael A. Floyd, Walter M. Szeliga, Robert W. King, David A. Phillips, Christine M. Puskas, Marcelo Santillan, Lei Wang
Plate Boundary Observatory And Related Networks: Gps Data Analysis Methods And Geodetic Products, Thomas A. Herring, Timothy I. Melbourne, Mark H. Murray, Michael A. Floyd, Walter M. Szeliga, Robert W. King, David A. Phillips, Christine M. Puskas, Marcelo Santillan, Lei Wang
All Faculty Scholarship for the College of the Sciences
The Geodesy Advancing Geosciences and EarthScope (GAGE) Facility Global Positioning System (GPS) Data Analysis Centers produce position time series, velocities, and other parameters for approximately 2000 continuously operating GPS receivers spanning a quadrant of Earth’s surface encompassing the high Arctic, North America, and Caribbean. The purpose of this review is to document the methodology for generating station positions and their evolution over time and to describe the requisite trade-offs involved with combination of results. GAGE GPS analysis involves formal merging within a Kalman filter of two independent, loosely constrained solutions: one is based on precise point positioning produced with the …
2015 Gsa International Distinguished Lecturer Tours Key Locations In Central And South America, Lisa L. Ely
2015 Gsa International Distinguished Lecturer Tours Key Locations In Central And South America, Lisa L. Ely
Geological Sciences Faculty Scholarship
As the International Lecturer from North America, I visited 11 destinations in Ecuador, Peru, Chile, Costa Rica, Mexico, and Puerto Rico. The tour was designed to include locations where the topic of my presentation, “Following in the Footsteps of Darwin:
Combining Geological and Historical Evidence to Assess Earthquakes and Tsunami Hazards,” would have direct relevance.
Basal Characteristics Of The Main Sticky Spot On The Ice Plain Of Whillans Ice Stream, Antarctica, Tarun Luthra, Sridhar Anandakrishnan, J. Paul Winberry, Richard B. Alley, Nicholas Holschuh
Basal Characteristics Of The Main Sticky Spot On The Ice Plain Of Whillans Ice Stream, Antarctica, Tarun Luthra, Sridhar Anandakrishnan, J. Paul Winberry, Richard B. Alley, Nicholas Holschuh
Geological Sciences Faculty Scholarship
Understanding the processes that affect streaming ice flow and the mass balance of glaciers and ice sheets requires sound knowledge of their subglacial environments. Previous studies have shown that an extensive deformable subglacial sediment layer favors fast ice-stream flow. However, areas of high basal drag, termed sticky spots, are of particular interest because they inhibit the fast flow of the overriding ice. The stick-slip behavior of Whillans Ice Stream (WIS) is perhaps the most conspicuous manifestation of a subglacial sticky spot. We present new ice-thickness and seismic-reflection measurements collected over the main sticky spot in the ice plain of WIS, …
Gps Constraints On Interplate Locking Within The Makran Subduction Zone, Elyse Frohling, Walter Szeliga
Gps Constraints On Interplate Locking Within The Makran Subduction Zone, Elyse Frohling, Walter Szeliga
All Faculty Scholarship for the College of the Sciences
The Makran subduction zone is one of the last convergent margins to be investigated using space-based geodesy. While there is a lack of historical and modern instrumentation in the region, a sparse sampling of continuous and campaign measurements over the past decade has allowed us to make the first estimates of convergence rates. We combine GPS measurements from 20 stations located in Iran, Pakistan and Oman along with hypocentral locations from the International Seismological Centre to create a preliminary 3-D estimate of the geometry of the megathrust, along with a preliminary fault-coupling model for the Makran subduction zone. Using a …
Crustal And Upper-Mantle Structure Beneath Ice-Covered Regions In Antarctica From S-Wave Receiver Functions And Implications For Heat Flow, C. Ramirez, Andrew A. Nyblade, S. E. Hansen, Douglas A. Wiens, Sridhar Anandakrishnan, Richard C. Aster, Audrey D. Huerta, Partick Shore, Terry Wilson
Crustal And Upper-Mantle Structure Beneath Ice-Covered Regions In Antarctica From S-Wave Receiver Functions And Implications For Heat Flow, C. Ramirez, Andrew A. Nyblade, S. E. Hansen, Douglas A. Wiens, Sridhar Anandakrishnan, Richard C. Aster, Audrey D. Huerta, Partick Shore, Terry Wilson
Geological Sciences Faculty Scholarship
S-wave receiver functions (SRFs) are used to investigate crustal and upper-mantle structure beneath several ice-covered areas of Antarctica. Moho S-to-P (Sp) arrivals are observed at ~6–8 s in SRF stacks for stations in the Gamburtsev Mountains (GAM) and Vostok Highlands (VHIG), ~5–6 s for stations in the Transantarctic Mountains (TAM) and the Wilkes Basin (WILK), and ~3–4 s for stations in the West Antarctic Rift System (WARS) and the Marie Byrd Land Dome (MBLD). A grid search is used to model the Moho Sp conversion time with Rayleigh wave phase velocities from 18 to 30 s period to estimate crustal …
Upper Mantle Structure Of Central And West Antarctica From Array Analysis Of Rayleigh Wave Phase Velocities, David S. Heeszel, Douglas A. Wiens, Sridhar Anandakrishnan, Richard C. Aster, Ian W.D. Dalziel, Audrey D. Huerta, Andrew A. Nyblade, Terry J. Wilson, J. Paul Winberry
Upper Mantle Structure Of Central And West Antarctica From Array Analysis Of Rayleigh Wave Phase Velocities, David S. Heeszel, Douglas A. Wiens, Sridhar Anandakrishnan, Richard C. Aster, Ian W.D. Dalziel, Audrey D. Huerta, Andrew A. Nyblade, Terry J. Wilson, J. Paul Winberry
Geological Sciences Faculty Scholarship
The seismic velocity structure of Antarctica is important, both as a constraint on the tectonic history of the continent and for understanding solid Earth interactions with the ice sheet. We use Rayleigh wave array analysis methods applied to teleseismic data from recent temporary broadband seismograph deployments to image the upper mantle structure of central and West Antarctica. Phase velocity maps are determined using a two–plane wave tomography method and are inverted for shear velocity using a Monte Carlo approach to estimate three-dimensional velocity structure. Results illuminate the structural dichotomy between the East Antarctic Craton and West Antarctica, with West Antarctica …
Spatiotemporal Slip Rate Variations Along Surprise Valley Fault In Relation To Pleistocene Pluvial Lakes, Brian N. Marion
Spatiotemporal Slip Rate Variations Along Surprise Valley Fault In Relation To Pleistocene Pluvial Lakes, Brian N. Marion
All Master's Theses
Using mapped paleoshoreline features with high-resolution topographic data and obtained radiocarbon dates on paleoshoreline tufas, I documented precise fault offsets of dated features over the last 25 ka along the Surprise Valley Fault (SVF). Fault offset measured in three lake sections within Surprise Valley ranged from 3.6 m in the southern section to 14.4 m in the central section. The offset paleoshorelines are dated to the late Pleistocene (<22 >ka) and were formed during the latest impoundment of pluvial Lake Surprise since the last glacial maximum. Slip rates vary along strike, assuming a fault dip of 68° with 0.25 ± …
A Seismic Transect Across West Antarctica: Evidence For Mantle Thermal Anomalies Beneath The Bentley Subglacial Trench And The Marie Byrd Land Dome, Andrew J. Lloyd, Douglas A. Wiens, Andrew A. Nyblade, Sridhar Anandakrishnan, Richard C. Aster, Audrey D. Huerta, Terry J. Wilson, Ian W. D. Dalziel, Patrick J. Shore, Dapeng Zhao
A Seismic Transect Across West Antarctica: Evidence For Mantle Thermal Anomalies Beneath The Bentley Subglacial Trench And The Marie Byrd Land Dome, Andrew J. Lloyd, Douglas A. Wiens, Andrew A. Nyblade, Sridhar Anandakrishnan, Richard C. Aster, Audrey D. Huerta, Terry J. Wilson, Ian W. D. Dalziel, Patrick J. Shore, Dapeng Zhao
All Faculty Scholarship for the College of the Sciences
West Antarctica consists of several tectonically diverse terranes, including the West Antarctic Rift System, a topographic low region of extended continental crust. In contrast, the adjacent Marie Byrd Land and Ellsworth-Whitmore mountains crustal blocks are on average over 1km higher, with the former dominated by polygenetic shield and stratovolcanoes protruding through the West Antarctic ice sheet and the latter having a Precambrian basement. The upper mantle structure of these regions is important for inferring the geologic history and tectonic processes, as well as the influence of the solid earth on ice sheet dynamics. Yet this structure is poorly constrained due …
Hidden Intrabasin Extension: Evidence For Dike-Fault Interaction From Magnetic, Gravity, And Seismic Reflection Data In Surprise Valley, Northeastern California, Noah D. Athens, Jonathan M.G. Glen, Simon L. Klemperer, Anne E. Egger, Valentina C. Fontiveros
Hidden Intrabasin Extension: Evidence For Dike-Fault Interaction From Magnetic, Gravity, And Seismic Reflection Data In Surprise Valley, Northeastern California, Noah D. Athens, Jonathan M.G. Glen, Simon L. Klemperer, Anne E. Egger, Valentina C. Fontiveros
All Faculty Scholarship for the College of the Sciences
The relative contributions of tectonic and magmatic processes to continental rifting are highly variable. Magnetic, gravity, and seismic reflection data from Surprise Valley, California, in the northwest Basin and Range, reveal an intrabasin, fault-controlled, ~10-m-thick dike at a depth of ~150 m, providing an excellent example of the interplay between faulting and dike intrusion. The dike, likely a composite structure representing multiple successive intrusions, is inferred from modeling a positive magnetic anomaly that extends ~35 km and parallels the basin-bounding Surprise Valley normal fault on the west side of the valley. A two-dimensional high-resolution seismic reflection profile acquired across the …
Slip Pulse And Resonance Of The Kathmandu Basin During The 2015 Gorkha Earthquake, Nepal, John Galetzka, Walter Szeliga
Slip Pulse And Resonance Of The Kathmandu Basin During The 2015 Gorkha Earthquake, Nepal, John Galetzka, Walter Szeliga
All Faculty Scholarship for the College of the Sciences
Detailed geodetic imaging of earthquake ruptures enhances our understanding of earthquake physics and associated ground shaking. The 25 April 2015 moment magnitude 7.8 earthquake in Gorkha, Nepal was the first large continental megathrust rupture to have occurred beneath a high-rate (5-hertz) Global Positioning System (GPS) network. We used GPS and interferometric synthetic aperture radar data to model the earthquake rupture as a slip pulse ~20 kilometers in width, ~6 seconds in duration, and with a peak sliding velocity of 1.1 meters per second, which propagated toward the Kathmandu basin at ~3.3 kilometers per second over ~140 kilometers. The smooth slip …
Twentieth Century Dust Lows And The Weakening Of The Westerly Winds Over The Tibetan Plateau, Bjorn Grigholm, P. A. Mayewski, S. Kang, Y. Zhang, U. Morgenstern, M. Schwikowski, Susan D. Kaspari, V. Aizen, E. Aizen, N. Takeuchi, K. A. Maasch, S. Birkel, M. Handley, S. Sneed
Twentieth Century Dust Lows And The Weakening Of The Westerly Winds Over The Tibetan Plateau, Bjorn Grigholm, P. A. Mayewski, S. Kang, Y. Zhang, U. Morgenstern, M. Schwikowski, Susan D. Kaspari, V. Aizen, E. Aizen, N. Takeuchi, K. A. Maasch, S. Birkel, M. Handley, S. Sneed
All Faculty Scholarship for the College of the Sciences
Understanding past atmospheric dust variability is necessary to put modern atmospheric dust into historical context and assess the impacts of dust on the climate. In Asia, meteorological data of atmospheric dust is temporally limited, beginning only in the 1950s. High‐resolution ice cores provide the ideal archive for reconstructing preinstrumental atmospheric dust concentrations. Using a ~500 year (1477–1982 A.D.) annually resolved calcium (Ca) dust proxy from a Tibetan Plateau (TP) ice core, we demonstrate the lowest atmospheric dust concentrations in the past ~500 years during the latter twentieth century. Declines in late nineteenth to twentieth century Ca concentrations significantly correspond with …
Real-Time Monitoring Of Tectonic Displacements In The Pacific Northwest Through An Array Of Gps Receivers, Răzvan Popovici, Răzvan Andonie, Walter M. Szeliga, Timothy I. Melbourne, Craig W. Scrivner
Real-Time Monitoring Of Tectonic Displacements In The Pacific Northwest Through An Array Of Gps Receivers, Răzvan Popovici, Răzvan Andonie, Walter M. Szeliga, Timothy I. Melbourne, Craig W. Scrivner
All Faculty Scholarship for the College of the Sciences
The Pacific Northwest Geodesic Array at Central Washington University collects telemetered streaming data from 450 GPS stations. These real-time data are used to monitor and mitigate natural hazards arising from earthquakes, volcanic eruptions, landslides, and coastal sea-level hazards in the Pacific Northwest. The displacement measurements are performed at millimeter-scale, and require stringent analysis and parameter estimation techniques. Recent improvements in both accuracy of positioning measurements and latency of terrestrial data communication have led to the ability to collect data with higher sampling rates, of up to 1 Hz. For seismic monitoring applications, this means 1350 separate position streams from stations …
The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence For Hydration And Thermal Upwellings, E. L. Emry, A. A. Nyblade, J. Juliá, S. Anandakrishnan, R. C. Aster, D. A. Wiens, Audrey D. Huerta, T. J. Wilson
The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence For Hydration And Thermal Upwellings, E. L. Emry, A. A. Nyblade, J. Juliá, S. Anandakrishnan, R. C. Aster, D. A. Wiens, Audrey D. Huerta, T. J. Wilson
All Faculty Scholarship for the College of the Sciences
Although prior work suggests that a mantle plume is associated with Cenozoic rifting and volcanism in West Antarctica, the existence of a plume remains conjectural. Here we use P wave receiver functions (PRFs) from the Antarctic POLENET array to estimate mantle transition zone thickness, which is sensitive to temperature perturbations, throughout previously unstudied parts of West Antarctica. We obtain over 8000 high‐quality PRFs using an iterative, time domain deconvolution method filtered with a Gaussian width of 0.5 and 1.0, corresponding to frequencies less than ∼0.24 and ∼0.48 Hz, respectively. Single‐station and common conversion point stacks, migrated to depth using the …
The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence For Hydration And Thermal Upwellings, E. L. Emry, Andrew A. Nyblade, J. Julia, Sridhar Anandakrishnan, R. C. Aster, Douglas A. Wiens, Audrey D. Huerta, Terry J. Wilson
The Mantle Transition Zone Beneath West Antarctica: Seismic Evidence For Hydration And Thermal Upwellings, E. L. Emry, Andrew A. Nyblade, J. Julia, Sridhar Anandakrishnan, R. C. Aster, Douglas A. Wiens, Audrey D. Huerta, Terry J. Wilson
Geological Sciences Faculty Scholarship
Although prior work suggests that a mantle plume is associated with Cenozoic rifting and volcanism in West Antarctica, the existence of a plume remains conjectural. Here we use P wave receiver functions (PRFs) from the Antarctic POLENET array to estimate mantle transition zone thickness, which is sensitive to temperature perturbations, throughout previously unstudied parts of West Antarctica. We obtain over 8000 high-quality PRFs using an iterative, time domain deconvolution method filtered with a Gaussian width of 0.5 and 1.0, corresponding to frequencies less than ∼0.24 and ∼0.48 Hz, respectively. Single-station and common conversion point stacks, migrated to depth using the …
Estimation Of Offsets In Gps Time-Series And Application To The Detection Of Earthquake Deformation In The Far-Field, Jean-Philippe Montillet, S. D. P. Williams, A. Koulali, S. C. Mcclusky
Estimation Of Offsets In Gps Time-Series And Application To The Detection Of Earthquake Deformation In The Far-Field, Jean-Philippe Montillet, S. D. P. Williams, A. Koulali, S. C. Mcclusky
All Faculty Scholarship for the College of the Sciences
Extracting geophysical signals from Global Positioning System (GPS) coordinate time-series is a well-established practice that has led to great insights into how the Earth deforms. Often small discontinuities are found in such time-series and are traceable to either broad-scale deformation (i.e. earthquakes) or discontinuities due to equipment changes and/or failures. Estimating these offsets accurately enables the identification of coseismic deformation estimates in the former case, and the removal of unwanted signals in the latter case which then allows tectonic rates to be estimated more accurately. We develop a method to estimate accurately discontinuities in time series of GPS positions at …
Pressure-Temperature-Time Constraints For Exhumation Of Ultrahigh-Pressure Metamorphic Rocks, North Qaidam Terrane, Western China, Brittany Kristine Fagin
Pressure-Temperature-Time Constraints For Exhumation Of Ultrahigh-Pressure Metamorphic Rocks, North Qaidam Terrane, Western China, Brittany Kristine Fagin
All Master's Theses
Ultrahigh-pressure rocks of a Paleozoic continental suture zone are exposed in the southeastern North Qaidam terrane (Dulan region). Garnetite sample D119 contains minor Czo+Qtz+Chl+Ttn; rutile inclusions in titanite suggest that titanite replaced rutile during decompression. Pressure-temperature estimates of sample D119 are 16.1-18.4 kbar and 485-520 °C. Sample D130B is a mafic band in calc-silicate gneiss, with garnet porphyroblasts in a fine-grained Hbl-Cpx-Pl-Qtz symplectite that is interpreted as former omphacite. D130B symplectite pressure-temperature estimates are 7.7-9.4 kbar and 623-708 °C. Titanite U-Pb ages of 419.7±3.1 Ma and 415.9±4.2 Ma are interpreted to date retrogression of D119 and D130B, respectively. Average exhumation …
Clockwise Rotation Of The Brahmaputra Valley Relative To India: Tectonic Convergence In The Eastern Himalaya, Naga Hills, And Shillong Plateau, Philippe Vernant, R. Bilham, Walter Szeliga, D. Drupka, S. Kalita, A. K. Bhattacharyya, V. K. Gaur
Clockwise Rotation Of The Brahmaputra Valley Relative To India: Tectonic Convergence In The Eastern Himalaya, Naga Hills, And Shillong Plateau, Philippe Vernant, R. Bilham, Walter Szeliga, D. Drupka, S. Kalita, A. K. Bhattacharyya, V. K. Gaur
All Faculty Scholarship for the College of the Sciences
GPS data reveal that the Brahmaputra Valley has broken from the Indian Plate and rotates clockwise relative to India about a point a few hundred kilometers west of the Shillong Plateau. The GPS velocity vectors define two distinct blocks separated by the Kopili fault upon which 2–3 mm/yr of dextral slip is observed: the Shillong block between longitudes 89 and 93°E rotating clockwise at 1.15°/Myr and the Assam block from 93.5°E to 97°E rotating at ≈1.13°/Myr. These two blocks are more than 120 km wide in a north‐south sense, but they extend locally a similar distance beneath the Himalaya and …
Thermodynamic Model For Energy-Constrained Open-System Evolution Of Crustal Magma Bodies Undergoing Simultaneous Recharge, Assimilation And Crystallization: The Magma Chamber Simulator, Wendy A. Bohrson, Frank J. Spera, Mark S. Ghiorso, Guy Brown, Jeffrey Creamer, Aaron Mayfield
Thermodynamic Model For Energy-Constrained Open-System Evolution Of Crustal Magma Bodies Undergoing Simultaneous Recharge, Assimilation And Crystallization: The Magma Chamber Simulator, Wendy A. Bohrson, Frank J. Spera, Mark S. Ghiorso, Guy Brown, Jeffrey Creamer, Aaron Mayfield
All Faculty Scholarship for the College of the Sciences
The Magma Chamber Simulator quantifies the impact of simultaneous recharge, assimilation and crystallization through mass and enthalpy balance in a multicomponent–multiphase (melt + solids ± fluid) composite system. As a rigorous thermodynamic model, the Magma Chamber Simulator computes phase equilibria and geochemical evolution self-consistently in resident magma, recharge magma and wallrock, all of which are connected by specified thermodynamic boundaries, to model an evolving open-system magma body. In a simulation, magma cools from its liquidus temperature, and crystals ± fluid are incrementally fractionated to a separate cumulate reservoir. Enthalpy from cooling, crystallization, and possible magma recharge heats wallrock from its …
Upper Mantle Seismic Anisotropy Beneath The West Antarctic Rift System And Surrounding Region From Shear Wave Splitting Analysis, Natalie J. Accardo, Douglas A. Wiens, Stephen Hernandez, Richard C. Aster, Andrew Nyblade, Audrey D. Huerta, Sridhar Anandakrisnan, Terry Wilson, David S. Heeszel, Ian W.D. Dalziel
Upper Mantle Seismic Anisotropy Beneath The West Antarctic Rift System And Surrounding Region From Shear Wave Splitting Analysis, Natalie J. Accardo, Douglas A. Wiens, Stephen Hernandez, Richard C. Aster, Andrew Nyblade, Audrey D. Huerta, Sridhar Anandakrisnan, Terry Wilson, David S. Heeszel, Ian W.D. Dalziel
Geological Sciences Faculty Scholarship
We constrain azimuthal anisotropy in the West Antarctic upper mantle using shear wave splitting parameters obtained from teleseismic SKS, SKKS and PKS phases recorded at 37 broad-band seismometres deployed by the POLENET/ANET project. We use an eigenvalue technique to linearize the rotated and shifted shear wave horizontal particle motions and determine the fast direction and delay time for each arrival. High-quality measurements are stacked to determine the best fitting splitting parameters for each station. Overall, fast anisotropic directions are oriented at large angles to the direction of Antarctic absolute plate motion in both hotspot and no-net-rotation frameworks, showing that the …
Seismic And Geodetic Evidence For Grounding-Line Control Of Whillans Ice Stream Stick-Slip Events, Martin J. Pratt, J. Paul Winberry, Douglas A. Wiens, Sridhar Anandakrishnan, Richard B. Alley
Seismic And Geodetic Evidence For Grounding-Line Control Of Whillans Ice Stream Stick-Slip Events, Martin J. Pratt, J. Paul Winberry, Douglas A. Wiens, Sridhar Anandakrishnan, Richard B. Alley
All Faculty Scholarship for the College of the Sciences
The tidally modulated, stick‐slip events of Whillans Ice Stream in West Antarctica produce seismic energy from three locations near the grounding line. Using ice velocity records obtained by combining time series from colocated broadband seismometers and GPS receivers installed on the ice stream during the 2010–2011 and 2011–2012 austral summers, along with far‐field seismic recordings of elastic waves, we locate regions of high rupture velocity and stress drop. These regions, which are analogous to “asperities” in traditional seismic fault studies, are areas of elevated friction at the base of the ice stream. Slip events consistently initiate at one of two …
Tidal Pacing, Skipped Slips And The Slowdown Of Whillans Ice Stream, Antarctica, J. Paul Winberry, Sridhar Anandakrishnan, Richard B. Alley, Douglas A. Wiens, Martin J. Pratt
Tidal Pacing, Skipped Slips And The Slowdown Of Whillans Ice Stream, Antarctica, J. Paul Winberry, Sridhar Anandakrishnan, Richard B. Alley, Douglas A. Wiens, Martin J. Pratt
All Faculty Scholarship for the College of the Sciences
We summarize new observations of the deceleration and stick–slip motion of Whillans Ice Stream (WIS), Antarctica. We refine the location of the large sticky spots that resist motion between slip events, the locations of which are controlled by the patterns of subglacial water flow. Our examination of the long-term velocity time series for the ice stream reveals that the decadal-scale deceleration is not occurring at a steady rate, but varies at the sub-decadal timescale. This unsteady deceleration modulates the temporal evolution of a broad (~50 km across) surface-elevation bulge forming at the junction between the relatively narrow upstream portion of …
Controls On Fault Geometry During Early Stages Of Extension In The Larkspur Hills, Northwest Basin And Range, Diana Jean Strickley
Controls On Fault Geometry During Early Stages Of Extension In The Larkspur Hills, Northwest Basin And Range, Diana Jean Strickley
All Master's Theses
Detailed analyses of normal faults in the Larkspur Hills, CA-NV, northwest Basin and Range, offer insight into factors controlling normal fault initiation, growth, and distribution. N-trending faults in the southern portion of the study area share trends of major range-bounding structures and Pliocene linear volcanic vents; in contrast, NNW- and NNE- trending faults dominate further north and into south-central Oregon. Stress analyses and comparison with experimental and field data suggest that preexisting structures control faults in the northern Larkspur Hills, while faults form perpendicular to σ3 in the southern hills. The change in fault orientations is abrupt, occurring across a …
Thermobarometry And Geochronology In The Dulan Region, North Qaidam Ultrahigh-Pressure Terrane: Resolving Spatial Variation Of Ages, Temperatures, And Pressures, Megan Eileen Regel
Thermobarometry And Geochronology In The Dulan Region, North Qaidam Ultrahigh-Pressure Terrane: Resolving Spatial Variation Of Ages, Temperatures, And Pressures, Megan Eileen Regel
All Master's Theses
The Dulan ultrahigh-pressure (UHP) terrane exposes 449-422 Ma eclogites in the east and 449-418 Ma high-pressure granulites to the west, but the relationship between the units is poorly understood. Zirconium-in-rutile temperatures show an east-west 3- 5°C/km gradient in four UHP eclogites: 662-716±10°C; garnet-omphacite-phengite thermobarometry of peak conditions yields 659-730±82°C, 25.3-27.1±3.2 kbars. Zircon U-Pb ages of four eclogites are the same within uncertainty, averaging 434±2.9 Ma. Tiin- zircon thermometry and rare earth element patterns indicate these ages represent eclogite facies metamorphism. One high-pressure/high-temperature (HP/HT) granulite yields a minimum rutile temperature of 773±4°C. Previous thermobarometry of highpressure granulites yields ≥800°C and 14-17 …
Spatial Relationship Between Gps Slip And Seismic Tremor During Cascadia Slow Slip Events, Hillary Lynn Goodner
Spatial Relationship Between Gps Slip And Seismic Tremor During Cascadia Slow Slip Events, Hillary Lynn Goodner
All Master's Theses
We model GPS deformation and timing of seismic tremor associated with transient deformation in Cascadia to test the hypothesis that tremor and slip occur synchronously but are spatially offset. For the period 2010–2013, we use seismic tremor data with a duration-moment relationship to predict GPS time series and compare them to observations. We find that observed GPS displacements are best predicted when tremor locations on the plate interface are shifted 15 km up-dip of their published epicenter. To test whether the spatial offset of tremor and slip is due to systematic mislocation of published epicenters, we attempt to identify individual …
Proxy-Based Reconstructions Of Earthquakes And Tsunamis At Quidico, South-Central Chile, Isabel J. Hong
Proxy-Based Reconstructions Of Earthquakes And Tsunamis At Quidico, South-Central Chile, Isabel J. Hong
All Master's Theses
We utilized geomorphic, microfossil, sedimentological, and stratigraphic methods to investigate the paleotsunami history at Quidico, Chile (38.1° S, 73.2° W). A combination of pits, cores, and riverbank exposures provide stratigraphic evidence of 8 sand layers at Quidico, including tsunami deposits from 2010 and 1960. The sands are laterally continuous but display landward thinning, disappearing completely from the stratigraphy 1.2 km inland from the coast. Intervening sediment layers consist of organicrich silts and peat. Grain size analysis shows the sand units are bimodal in distribution whereas the organic-rich silts and peat have a broader, bimodal distribution. Lithological analysis showed similarities among …
Glacier Slip And Seismicity Induced By Surface Melt, Peter L. Moore, J. Paul Winberry, Neal R. Iverson, Knut A. Christianson, Sridhar Anandakrishnan, Miriam Jackson, Mark E. Mathison, Denis Cohen
Glacier Slip And Seismicity Induced By Surface Melt, Peter L. Moore, J. Paul Winberry, Neal R. Iverson, Knut A. Christianson, Sridhar Anandakrishnan, Miriam Jackson, Mark E. Mathison, Denis Cohen
All Faculty Scholarship for the College of the Sciences
Many of the key processes governing fast glacier flow involve interaction between a glacier and its basal hydrological system, which is hidden from direct observation. Passive seismic monitoring has shown promise as a tool for remotely monitoring basal processes, but lack of glacier-bed access prevents clear understanding of the relationships between subglacial processes and corresponding seismic emissions. Here we describe direct measurements of basal hydrology, sliding, and broadband seismicity made in a unique subglacial facility in Norway during the onset of two summer melt seasons. In the most pronounced of these episodes, rapid delivery of surface meltwater to the bed …
2012 Haida Gwaii Quake: Insight Into Cascadia's Subduction Extent, Walter Szeliga
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.
Nucleation And Seismic Tremor Associated With The Glacial Earthquakes Of Whillans Ice Stream, Antarctica, J. Paul Winberry, Sridhar Anandakrishnan, Douglas A. Wiens, Richard B. Alley
Nucleation And Seismic Tremor Associated With The Glacial Earthquakes Of Whillans Ice Stream, Antarctica, J. Paul Winberry, Sridhar Anandakrishnan, Douglas A. Wiens, Richard B. Alley
All Faculty Scholarship for the College of the Sciences
The ability to monitor transient motion along faults is critical to improving our ability to understand many natural phenomena such as landslides and earthquakes. Here, we usedata from a GPS and seismometer network that were deployed to monitor the regularly repeating glacial earthquakes of Whillans Ice Stream, West Antarctica to show that a unique pattern of precursory slip precedes complete rupture along the bed of the ice stream. Additionally, we show that rupture can be independently tracked by increased levels of microseismic activity, including harmonic tremor, that are coincident with the onset of slip at any location, thus providing a …
Comparison Of Earthquake Source Models For The 2011 Tohoku Event Using Tsunami Simulations And Near‐Field Observations, Breanyn T. Macinnes, Aditya Riadi Gusman, Randall J. Leveque, Yuichiro Tanioka
Comparison Of Earthquake Source Models For The 2011 Tohoku Event Using Tsunami Simulations And Near‐Field Observations, Breanyn T. Macinnes, Aditya Riadi Gusman, Randall J. Leveque, Yuichiro Tanioka
All Faculty Scholarship for the College of the Sciences
Selection of the earthquake source used in tsunami models of the 2011 Tohoku event affects the simulated tsunami waveform across the near field. Different earthquake sources, based on inversions of seismic waveforms, tsunami waveforms, and Global Positioning System (GPS) data, give distinguishable patterns of simulated tsunami heights in many locations in Tohoku and at near‐field Deep‐ocean Assessment and Reporting of Tsunamis (DART) buoys. We compared 10 sources proposed by different research groups using the GeoClaw code to simulate the resulting tsunami. Several simulations accurately reproduced observations at simulation sites with high grid resolution. Many earthquake sources produced results within 20% …
Feasibility Of Seismic Monitoring To Identify Avalanche Activity: Snoqualmie Pass, Wa, Kathryn Johnston
Feasibility Of Seismic Monitoring To Identify Avalanche Activity: Snoqualmie Pass, Wa, Kathryn Johnston
All Master's Theses
Avalanches across the Interstate-90 corridor over Snoqualmie Pass, in Washington State, are a concern for winter travelers and backcountry recreation. The temporary closure of the interstate for avalanche mitigation work also affects commerce by delaying transportation of merchandise. The study of seismic signals associated with snow avalanches could allow for greater understanding of avalanche properties, while remote sensing of avalanche activity could help established avalanche control programs and regional avalanche centers with forecasting and mitigation efforts. Two seismic stations were installed near the Alpental ski area on Snoqualmie Pass and recorded seismic activity throughout the winters of 2009-2010 and 2010-2011. …