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Articles 1 - 12 of 12
Full-Text Articles in Tectonics and Structure
Induced Seismicity In The Raton Basin And Global Variability Of The 410-Km Discontinuity, Margaret E. Glasgow
Induced Seismicity In The Raton Basin And Global Variability Of The 410-Km Discontinuity, Margaret E. Glasgow
Earth and Planetary Sciences ETDs
Natural processes like mantle convection and plate tectonics dominate Earth’s seismic structure. Recently human activities have increasingly influenced the deformation of the shallow crust. In this dissertation, passive source seismology was used to constrain seismic discontinuities in the mantle transition zone and seismogenic structures in induced earthquake settings. Using a novel sampling method and uniform processing approach, I found the 410-km discontinuity is thermally and compositionally variable. Using a machine- learning approach, I found the three main zones of seismicity in the Raton Basin consist of short faults or fault segments with variable orientations. The zone that hosted a Mw …
The Uppermost Mantle Seismic Velocity And Viscosity Structure Of Central West Antarctica, J. P. O'Donnell, K. Selway, A. A. Nyblade, R. A. Brazier, D. A. Wiens, S. Anandakrishnan, R. C. Aster, Audrey D. Huerta, T. Wilson, J. Paul Winberry
The Uppermost Mantle Seismic Velocity And Viscosity Structure Of Central West Antarctica, J. P. O'Donnell, K. Selway, A. A. Nyblade, R. A. Brazier, D. A. Wiens, S. Anandakrishnan, R. C. Aster, Audrey D. Huerta, T. Wilson, J. Paul Winberry
All Faculty Scholarship for the College of the Sciences
Accurately monitoring and predicting the evolution of the West Antarctic Ice Sheet via secular changes in the Earth's gravity field requires knowledge of the underlying upper mantle viscosity structure. Published seismic models show the West Antarctic lithosphere to be ∼70–100 km thick and underlain by a low velocity zone extending to at least ∼200 km. Mantle viscosity is dependent on factors including temperature, grain size, the hydrogen content of olivine, the presence of partial melt and applied stress. As seismic wave propagation is particularly sensitive to thermal variations, seismic velocity provides a means of gauging mantle temperature. In 2012, a …
Ground-Rupturing Earthquakes On The Northern Big Bend Of The San Andreas Fault, California, 800 A.D. To Present, Katherine Scharer, Ray J. Weldon Ii, Glenn Biasi, Ashley Streig, Thomas Fumal
Ground-Rupturing Earthquakes On The Northern Big Bend Of The San Andreas Fault, California, 800 A.D. To Present, Katherine Scharer, Ray J. Weldon Ii, Glenn Biasi, Ashley Streig, Thomas Fumal
Geology Faculty Publications and Presentations
Paleoseismic data on the timing of ground-rupturing earthquakes constrain the recurrence behavior of active faults and can provide insight on the rupture history of a fault if earthquakes dated at neighboring sites overlap in age and are considered correlative. This study presents the evidence and ages for 11 earthquakes that occurred along the Big Bend section of the southern San Andreas Fault at the Frazier Mountain paleoseismic site. The most recent earthquake to rupture the site was the Mw7.7–7.9 Fort Tejon earthquake of 1857. We use over 30 trench excavations to document the structural and sedimentological evolution of a small …
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 …
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 …
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 …
The Crustal Thickness Of West Antarctica, Julien A. Chaput, Richard C. Aster, Audrey D. Huerta, X. Sun, Andrew Lloyd, Douglas A. Wiens, Andrew Nyblade, Sridhar Anandakrishnan, J. Paul Winberry, Terry Wilson
The Crustal Thickness Of West Antarctica, Julien A. Chaput, Richard C. Aster, Audrey D. Huerta, X. Sun, Andrew Lloyd, Douglas A. Wiens, Andrew Nyblade, Sridhar Anandakrishnan, J. Paul Winberry, Terry Wilson
Geological Sciences Faculty Scholarship
P-to-S receiver functions (PRFs) from the Polar Earth Observing Network (POLENET) GPS and seismic leg of POLENET spanning West Antarctica and the Transantarctic Mountains deployment of seismographic stations provide new estimates of crustal thickness across West Antarctica, including the West Antarctic Rift System (WARS), Marie Byrd Land (MBL) dome, and the Transantarctic Mountains (TAM) margin. We show that complications arising from ice sheet multiples can be effectively managed and further information concerning low-velocity subglacial sediment thickness may be determined, via top-down utilization of synthetic receiver function models. We combine shallow structure constraints with the response of deeper layers using a …
Paleoseismologic Evidence For Holocene Activity On The Pinto Mountain Fault, Twentynine Palms, California, Ana Maria Cadena
Paleoseismologic Evidence For Holocene Activity On The Pinto Mountain Fault, Twentynine Palms, California, Ana Maria Cadena
All Master's Theses
Excavations across the Pinto Mountain fault in Twentynine Palms, California exposed faulted strata across a 32-m wide zone. Trench wall exposures revealed clear evidence for five ground-rupturing events during the Holocene, and two additional events in the late Pleistocene. Optically stimulated luminescence ages from alluvial sediments suggest that the most recent event occurred between 1.7-2.9 ka B.P. and the penultimate event between 2.7-4.2 ka B.P.. Prior to the penultimate event, there were five ground-rupturing earthquakes on the eastern Pinto Mountain fault between 3.5-13.6 ka B.P.. The average recurrence interval since 13.3-13.6 ka B.P. is 1510-1680 years, and 1200-1500 years in …
Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi
Interseismic Strain Accumulation Along The Western Boundary Of The Indian Subcontinent, Walter Szeliga, Roger Bilham, Din Mohammad Kakar, Sarosh H. Lodi
All Faculty Scholarship for the College of the Sciences
Despite an overall sinistral slip rate of ≈3 cm/yr, few major earthquakes have occurred in the past 200 years along the Chaman fault system, the western boundary of the India Plate with the Eurasia Plate. GPS and InSAR data reported here indicate sinistral shear velocities of 8–17 mm/yr across the westernmost branches of the fault system, suggesting that a significant fraction of the plate boundary slip is distributed in the fold and fault belt to the east. At its southernmost on‐land segment (≈26°N), near the triple junction between the Arabia, Eurasia, and India Plates, we find the velocity across the …
Surficial Slip Distribution On The Central Emerson Fault During The June 28, 1992, Landers Earthquake, California, Sally F. Mcgill, Charles M. Rubin
Surficial Slip Distribution On The Central Emerson Fault During The June 28, 1992, Landers Earthquake, California, Sally F. Mcgill, Charles M. Rubin
All Faculty Scholarship for the College of the Sciences
We present the results of our mapping of a 5.6‐km length of the central Emerson fault that ruptured during the 1992 Landers earthquake in the southwestern Mojave Desert, California. The right‐lateral slip along this portion of the rupture varied from about 150 to 530 cm along the main rupture zone. In some locations a total of up to 110 cm of additional right‐lateral slip occurred on secondary faults up to 1.7 km away from the main rupture zone. Other secondary faults carried up to several tens of centimeters of left‐lateral or thrust displacement. The maximum net vertical displacement was 175 …
Long Dormancy, Low Slip Rate, And Similar Slip‐Per‐Event For The Emerson Fault, Eastern California Shear Zone, Charles M. Rubin, Kerry Sieh
Long Dormancy, Low Slip Rate, And Similar Slip‐Per‐Event For The Emerson Fault, Eastern California Shear Zone, Charles M. Rubin, Kerry Sieh
All Faculty Scholarship for the College of the Sciences
Excavations in a playa along the 1992 rupture of the Emerson fault reveal evidence of two paleoseismic events, with only one large prehistoric rupture in the past 15 millennia. Accelerator mass spectrometer radiocarbon ages of charcoal from playa sediments and from fault‐scarp colluvium directly beneath the playa beds indicate that the last large prehistoric slip event occurred about 9000 ka. Trench‐wall exposures revealed clear evidence of at least one pre‐9 ka rupture at the playa site. The event horizon of this earthquake is between two pedogenic carbonate layers that have radiocarbon ages of 14.8 ka and 24.1 ka, implying that …