Rupture models for the A.D. 900–930 Seattle fault earthquake from uplifted shorelines
- 1U.S. Geological Survey, Woods Hole, Massachusetts 02543, USA
- 2U.S. Geological Survey, Golden, Colorado 80225, USA
Abstract
A major earthquake on the Seattle fault, Washington, ca. A.D. 900–930 was first inferred from uplifted shorelines and tsunami deposits. Despite follow-up geophysical and geological investigations, the rupture parameters of the earthquake and the geometry of the fault are uncertain. Here we estimate the fault geometry, slip direction, and magnitude of the earthquake by modeling shoreline elevation change. The best fitting model geometry is a reverse fault with a shallow roof ramp consisting of at least two back thrusts. The best fitting rupture is a SW-NE oblique reverse slip with horizontal shortening of 15 m, rupture depth of 12.5 km, and magnitude Mw = 7.5.
Footnotes
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↵GSA Data Repository item 2006110, alternative models, sensitivity tests, and a table of observations, is available online at www.geosociety.org/pubs/ ft2006.htm, or on request from editing{at}geosociety.org or Documents Secretary, GSA, P.O. Box 9140, Boulder, CO 80301, USA.
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- Accepted 14 February 2006.
- Received 28 August 2005.
- Revision received 4 January 2006.
- The Geological Society of America, Inc.
