Wenatchee Valley Erratics Zoom Program
When: December 14, 2021 at 7:00PM, when Stephen J. Angster, Research Scientist with the USGS Earthquake Science Center, Seattle Field Office, will present:
“Paleoseismic history and hazards associated with the Wallula fault zone: A new look at clastic dike features in southeast Washington”
In an effort to better understand seismic hazards within the Tri-cities region of SE Washington and NE Oregon, the USGS is leading an effort to characterize the paleoseismic and rupture history along the Wallula fault zone. In this talk, Steve will share recent field observations and new geochronologic data collected from a paleoseismic trench and roadcut exposure that display Holocene age liquefaction features (e.g. clastic dikes). These features appear within late Pleistocene slackwater deposits of the Missoula Floods (aka. Touchet Beds); and cap Holocene loess. Stratigraphic and sedimentologic relationships along with luminesces ages of the liquefied sediment suggest up to four seismically-induced liquefaction events during the Holocene, any of which were likely triggered by earthquakes sourced from either the Wallula fault zone and/or faults of the Yakima fold and thrust belt. Additional observations and analysis along a newly discovered late Holocene scarp indicate that the scarp is most-likely tectonic in origin and plausibly the surface rupture trace of the 1936 Milton-Freewater earthquake.
Here’s our Zoom link: https://us02web.zoom.us/j/82730527571 Sign in at 7:00 PM, Tuesday December 14.