Geophysics and Seismology Commons^™

Seismicity And Pn Velocity Structure Of Central West Antarctica, Erica M. Lucas, Andrew A. Nyblade, Andrew J. Lloyd, Richard C. Aster, Douglas A. Wiens, John Paul O'Donnell, Graham W. Stuart, Terry J. Wilson, Ian W. D. Dalziel, J. Paul Winberry, Audrey D. Huerta

Geological Sciences Faculty Scholarship

We have located 117 previously undetected seismic events mainly occurring between 2015 and 2017 that originated from glacial, tectonic, and volcanic processes in central West Antarctica using data recorded on Polar Earth Observing Network (POLENET/ANET) and UK Antarctic Network (UKANET) seismic stations. The seismic events, with local magnitudes (M_L) ranging from 1.1 to 3.5, are predominantly clustered in four geographic regions; the Ellsworth Mountains, Thwaites Glacier, Pine Island Glacier, and Mount Takahe. Eighteen of the events are in the Ellsworth Mountains and can be attributed to a mixture of glacial and tectonic processes. The largest event noted …

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 …

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 …

Surface Wave Inversion Of The Upper Mantle Velocity Structure In The Ross Sea Region, Western Antarctica, James D. Rinke

All Master's Theses

The Ross Sea in Western Antarctica is the locale of several extensional basins formed during Cretaceous to Paleogene rifting. Several seismic studies along the Transantarctic Mountains and Victoria Land Basin’s Terror Rift have shown a general pattern of fast seismic velocities in East Antarctica and slow seismic velocities in West Antarctica. This study focuses on the mantle seismic velocity structure of the West Antarctic Rift System in the Ross Embayment and adjacent craton and Transantarctic Mountains to further refine details of the velocity structure.

Teleseismic events were selected to satisfy the two-station great-circle-path method between 5 Polar Earth Observing Network …

Fluid Budget Of Metasedimentary Rocks From A Tertiary Accretionary Prism And Connections To Seismicity, Olympic Peninsula, Northwest Washington State, Holly Makena Macfadden Rotman

All Master's Theses

Metamorphic dehydration reactions and fluid movement in accretionary prisms have been linked to the recently discovered episodic tremor and slip (ETS) earthquake events along subduction zones, but prior studies lack the detail to effectively test the hypothesis that fluid flow triggers ETS events. I conducted field work along a 52.5 km transect on the Olympic Peninsula metasedimentary accretionary prism of the Cascadia subduction zone, and collected approximately 40 representative samples of sandstone and mudrock that were buried to 6–15 km. This depth range intersects the 10–50 km depth range of ETS events. My objectives are to quantify the water flow …

Energy Budget Analysis Of Slow-Slip Tremor Events Along The Cascadia Subduction Zone Using Continuous Gps Array Data, James Steven Chapman

All Master's Theses

Seismic hazards poised to cities by subduction zones are strongly controlled by fault slip along the deeper extent of the two plate interaction closest to population densities. In Cascadia, where Mw=9 size events are known to occur from a variety of sources, modeling of leveling data has suggested that the region of maximum slip lies well offshore and diminishes rapidly inland. However, over two dozen slow slip distributions have been imaged using Global Positioning System (GPS) along the lower reaches of the northern Cascadia locked zone between 30 and 40 km in depth. Averaged over many episodic tremor and slip …

The 2004 And 1861 Tsunami Deposits On Simeulue Island, Western Sumatra, Katherine Frances Whitlow

All Master's Theses

Megathrust earthquakes and associated tsunamis along the subduction zone along western Sumatra represent a significant seismic hazard that is not well understood. I present the results of mapping, paleoseimologic, and geochronologic studies of tsunami deposits exposed on Simeulue Island, western Sumatra, to document the timing of past tsunamis. Three field sites were targeted to conduct these studies: Inor, Busong Bay, and Langi Bay. Stratigraphic relationships, geochronologic data, and grain size analyses from these field sites show evidence of a tsunami that occurred in 1861 following a Mw ~8.5 earthquake. A wood fragment collected from an excavation at Inor yielded an …

Seismic Constraints On Slow Slip Events Within The Cascadia Subduction Zone, Ana Cristina Aguiar

All Master's Theses

Reanalysis of geodetic GPS time series from the Cascadia subduction zone have revealed at least 30 resolvable slow slip events along the megathrust, ranging from northern California to southern British Columbia, since 1997. Many of the smaller and more recent events are barely resolvable with GPS, but stand out clearly as tremor sequences. Since tremor bursts lasting less than 10-seconds are often visible across multiple stations, they offer the highest resolution for studying moment release through time. To test the hypothesis that tremor and transient deformation are two manifestations of the same faulting process, and to quantify the relative contribution …