Holocene Earthquakes on the Wassuk Range Fault Zone: Paleoseismic Observations from the Rose Creek Fan and Regional Geodetic Observations, Hawthorne, Nevada, USA

摘要

The Wassuk Range fault zone is an east-dipping, high-angle normal fault that flanks the eastern margin of the Wassuk Range near the town of Hawthorne in central Nevada. We present new paleoseismic observations bearing on the displacement and recurrence characteristics of surface rupturing earthquakes along the Wassuk Range fault zone that result from investigating fault scarps at the head of the Rose Creek alluvial fan, located approximately 8 mi (13 km) northwest of Hawthorne. We examine the fault's recent slip history in two fault trenches and through detailed surficial mapping of the fan. Preliminary results from the Rose Creek trenches indicate;(a) at least two surface rupturing earthquakes between approx9400+-95 calendar years B.P. and approx600-2000 ~(14)C years B.P. on the intermediate age surface at the apex of the fan, and (b) at least 2 surface rupturing events prior to approx600-2000 ~(14)C years B.P. on the younger fan surface. Offset of stratigraphic units provides evidence for a large penultimate event followed by a smaller most recent event, and we estimate a Holocene recurrence interval of approx3650-4450 years for surface rupturing earthquakes on the Wassuk Range fault zone. Additionally, GPS observation indicates that the Wassuk Range lies in a zone of transtensional strain accumulation. A marked increase in westward velocity between GPS sites WALK and EWLK suggests a geodetically estimated extension rate for the WRFZ on the order of 0.5-1mm/yr. These results highlight the WRFZ as a likely target for geothermal productivity.