GPS Observations in the Yakima fold-thrust belt, Washington Abstract


  • The Yakima fold-thrust belt (YFTB) of south-central Washington absorbs the clockwise rotation of Oregon about a pole near the Idaho-Washington-Oregon border. Accordingly, shortening across the YFTB occurs in a fan-like manner, increasing in rate from east to west. In the west it impinges on the Cascade volcanic arc and likely into the forearc but through-going structures are far from clear. The rotation of Oregon requires some north-south shortening west of the Cascade arc which has hazard implications for the highly-populated Portland-Seattle corridor. We made new survey-mode GPS observations at about 60 sites within and around the YFTB in 2012 and 2013. These observations are being combined with earlier survey-mode data obtained by the USGS, University of Washington and Central Washington University and with continuous observations from PBO and PANGA networks to obtain an improved picture of surface velocities. The new velocity field and interpretations will be presented at the meeting. [This work was funded by the USGS National Earthquake Hazards Programs and field equipment was supplied by UNAVCO. Additional assistance came from Stan Liffmann, Ray Clayton, Walter Szeliga, Steve Reidel, Andrew Miner and many land-owners who allowed us access to the marks.]

publication date

  • 2014

presented at event