— Seismologists have identified potentially active faults near Olympia, Washington State, adding to the number of faults that may be active in the area.
Researchers from the University of Washington and the U.S. Geological Survey collected marine seismic reflection data to explore shallow structures associated with inferred faults in the Tacoma and Olympia areas of Washington State. Seismic reflection profiling, which uses sound waves to look into the Earth in the same way that sonograms do in medical imaging, is a valuable tool for examining faults beneath the surface.
Layers of glacial deposits formed beneath Puget Sound during the last glacial advance and retreat in the past 16,000 years provide a record of recent faulting in the region. This study documents two apparent faults cutting young deposits near Olympia. Because the faults cut through strata that may have been deposited during or after the glacial retreat, the faults appear to have had recent activity and therefore could pose an earthquake hazard to the population of the southern Puget Sound region.
High-Resolution Seismic Reflection Imaging of Growth Folding and Shallow Faults beneath the Southern Puget Lowland, Washington State.
Curtis R. Clement, Thomas L. Pratt, Mark L. Holmes, Brian L. Sherrod
Bulletin of the Seismological Society of America, 2010; 100 (4): 1710 DOI: 10.1785/0120080306
Link to BSSA abstract