Project Title: Hydrology and Ecology of Sag Ponds as Recorders of Prehistoric Earthquakes
Mendenhall Fellow: Jonathan F. Hughes, (206) 553-0686, firstname.lastname@example.org
Duty Station: Seattle, WA
Start Date: October 2, 2003
Education: Ph.D. (Biological Sciences), Simon Fraser University, 2002
Research Advisors: Brian Sherrod, (206) 553-0153, email@example.com; Alan Nelson (303) 273-8592, firstname.lastname@example.org; Brian Atwater (206) 553-2927, email@example.com
Project Description: The main focus of this project is the documentation of the earthquake history of Price Lake fault, southeastern Olympic Peninsula, Washington (index maps below). Deposits beneath the lake and adjacent wetlands are being used to identify hydrologic changes that accompanied two ancient earthquakes—or one complete recurrence interval thousands of years long. The Price Lake site includes stands of tree trunks in growth position submerged beneath the lake, buried soils in bog deposits, and possibly earthquake-uplifted stream terraces. An 8-m tall scarp near the lake outlet makes Price Lake fault one of the most striking visual displays of fault slip in the region. The use of sag-pond deposits to document earthquake history is a new and innovative approach in the Puget Sound area and has been used only to a limited extent in other seismic regions.
Price Lake drains across a fault scarp that stands out on air photos and LIDAR images. It is fringed by bogs that, along with the lake, cover 50 hectares. As much as six meters of peat underlie the bog. Previously published evidence for past earthquakes includes reverse dip-slip offset in Vashon till exposed in trenches across local faults, drowned trees in the lake, and radiocarbon ages from drowned stumps and charcoal in scarp-derived colluvium (Wilson and others,1979. Geology 7: 235-239). Radiocarbon ages place the youngest event in the same era as the Seattle fault earthquake of AD 900-930. Using stumps rooted in the upper buried soil at Price Lake, the triggering hypothesis will be tested by means of tree-ring dating.
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Last modified: 16:08:28 Thu 13 Dec 2012