HR: 14:25h
AN: NS23A-04 INVITED    [Abstracts]
TI: HIGH-RESOLUTION SEISMIC REFLECTION STUDIES OF ACTIVE FAULTS: A CASE STUDY FROM WASHINGTON STATE
AU: * Liberty, L M
EM: lml@cgiss.boisestate.edu
AF: Boise State University, Department of Geosciences 1910 University Dr, Boise, ID 83725-1536, United States
AU: Pratt, T L
EM: tpratt@ocean.washington.edu
AF: U.S. Geological Survey, School of Oceanography Box 357940 University of Washington, Seattle, Wa 98195, United States
AB: In the past five years, new high-resolution seismic surveys have filled in gaps in our understanding of active structures beneath the Puget Lowland region of Washington State. The extensive forests have made recognition of active faults difficult, but new Light Distance and Ranging (LIDAR) detailed topographic data have made a major breakthrough in mapping active faults. Extensive regional and high-resolution marine seismic surveys have been fundamental to understanding the tectonic framework of the area. These marine profiles, however, lack coverage beneath water bodies that large ships cannot navigate and beneath city streets underlain by late Pleistocene glacial deposits that are missing from the waterways. Recent land surveys and profiles in restricted waterways can therefore bridge the gap between paleoseismic and marine geophysical studies, and test elements of models proposed by regional-scale geophysical studies. We have also been venturing into more congested areas to seismically image faults in key urban locations. Results from recent surveys have: 1) documented new faults that had long been suspected in the Olympia area; 2) clarified the relationship between the LIDAR scarps and observed structures across the Tacoma fault zone; 3) provided a window into structures beneath the north and eastern portions of the western Tacoma fault zone; 4) documented deformation along the Seattle fault near a paleoseismic trench; 5) mapped the eastern part the Seattle fault zone beyond its previously mapped limits; and 6) documented multiple fault strands in the Seattle fault zone in the cities of Bellevue and Seattle. The results better constrain interpretations of paleoseismic data collected on these faults, and provide targets for future paleoseismic studies.
DE: 7221 Paleoseismology (8036)
DE: 7230 Seismicity and tectonics (1207, 1217, 1240, 1242)
DE: 8108 Continental tectonics: compressional
DE: 8123 Dynamics: seismotectonics
SC: Near-Surface Geophysics [NS]
MN: 2007 Fall Meeting