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Defining Crustal Fault Systems and Strain Accumulation Models in the Puget Lowlands of Western Washington: Katie Keranen
Project Title: Defining Crustal Fault Systems and Strain Accumulation Models in the Puget Lowlands of Western Washington
Mendenhall Fellow: Katie Keranen, kkeranen@usgs.gov
Duty Station: Seattle, WA
Start Date: October 13, 2008
Education: Ph.D. Geophysics, Stanford University, 2008
Research Advisor: Joan Gomberg, (206) 616-5581, gomberg@usgs.gov; Tom Pratt, (206) 543-7358, tpratt@usgs.gov; Brian Sherrod, (206) 553-0153, bsherrod@usgs.gov; John Vidale (University of Washington), (206) 543-6790, john_vidale@mac.com; Art Frankel, (303) 273-8556, afrankel@usgs.gov

Project Description: The crustal architecture of the Puget Sound basin of western Washington consists of a series of subparallel east-west to northwest-southeast striking fault zones that typically bound large crustal basins. The faults, including the Olympia, Tacoma, Seattle (SFZ), and South Whidbey Island (SWIF), are thought to accommodate north-south directed compression of ~4 mm/year across the region. Each of these fault zones has been active in the Holocene, with offset documented in trenches at one or multiple locations. Several of these fault zones have evidence for offset at ~900 AD, including the SFZ that had a ~M7+ event at that time. This event raised shorelines by up to 7 meters and caused a local tsunami in the Puget Sound. Current models infer that these active faults zones formed the regional pattern of large basins and uplifts, including the Tacoma, Seattle, and Everett basins, but the strain accumulated by each fault, subsurface fault geometry, and the spatial extent of the fault systems are poorly constrained. For example, vastly different geometries of the SFZ have been proposed. In addition, proposed upper crustal fault systems do not correlate well with local seismicity. These fault systems have the potential to directly impact the region extending from Olympia to Bellingham, Wash., including the densely populated urban areas of Tacoma and Seattle. Understanding the structure and activity of these fault systems is critical for regional hazards studies and to understand the regional tectonics of the Pacific Northwest.

This project seeks to (1) define crustal fault geometries in the Puget Lowlands; (2) constrain strain accumulation models in the brittle crust, and (3) understand the evolution and deformation history of the Puget Lowlands from the Eocene through present day. Primary datasets used in this work include multiple seismic reflection surveys, local seismicity, and GPS data. Data from geologic mapping and potential field surveys will also be integrated.   
 
 
 

 


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Last modified: 16:08:29 Thu 13 Dec 2012