HR: 17:30h
AN: S42I-07    [PDF]
TI: Morphology of Submarine Landslides in Puget Sound
AU: * Smith, S B
EM: sbsmith@unr.nevada.edu
AF: Department of Geological Sciences, University of Nevada, Reno, Reno, NV 89557 United States
AU: Karlin, R
EM: karlin@mines.unr.edu
AF: Department of Geological Sciences, University of Nevada, Reno, Reno, NV 89557 United States
AB: Submarine landslides, probably triggered by large earthquakes, disturb Holocene sediments in Puget Sound. High-resolution seismic reflection profiling and sidescan swath surveys were conducted over large submarine landslides and debris flows. These large slides are in close proximity to the South Whidbey Island fault zone at Possession Point, Mukilteo, and Edgewater; near the Seattle fault off Alki Point; and near the Tacoma fault at Maury Island. The boundaries of the slides were mapped using sidescan swath surveys. Preliminary slide morphologies were determined from the seismic cross-sections. Three large slide complexes with multiple block slides and debris flows are found off Possession Point; the largest of which is 1.5 km x 1.0 km with a maximum thickness of approximately 50 meters. Large sand flows with maximum thicknesses of 30 to 40 meters occur off Mukilteo and Edgewater. An approximately 3.3 km x 2.2 km, 30 meter thick flow off Alki Point was deposited on top of folded sediments within the deformation zone of the Seattle Fault zone. Three large block slides are present off Maury Island; the largest of which is 2.75 km x 1.0 km, with a maximum thickness of approximately 100 meters. The volumes of these landslides are more than an order of magnitude larger than subaerial landslides in the region. Tsunamis generated by landsliding potentially constitute a major seismic hazard in coastal areas of the Puget Lowland.
DE: 3022 Marine sediments--processes and transport
DE: 3025 Marine seismics (0935)
DE: 7223 Seismic hazard assessment and prediction
SC: Seismology [S]
MN: 2003 Fall Meeting