Stress orientation determined from fault slip data in Hampel Wash area, Nevada, and its relation to contemporary regional stress field ( USA).

Fault-slip data were collected from an area of relatively young faulting in a seismically active part of the Nevada Test Site 12 km NW of Mercury, Nevada. The data come primarily from intensely faulted Miocene tuffaceous sedimentary rocks in Hampel Wash, which is bounded on the north by the Quaternary ENE trending Rock Valley fault and on the south by a parallel unnamed fault. Analysis of the data using a least squares iterative inversion to determine a mean deviatoric principal stress tensor indicates a normal-faulting stress regime (S1 vertical) with principal stress axes in approximately horizontal and vertical directions (S1, trend = N19oE and plunge = 82oN; S2,, N30oE and 8oS; and S3, N60oW and 2oE). The N60oW least horizontal principal stress orientation obtained from the fault-slip inversion agrees with our geometric analysis of the data and is consistent with a modern least horizontal principal stress orientation of N50o-70oW inferred from earthquake focal mechanisms, well bore breakouts, and hydraulic fracturing measurements in the vicinity of the Nevada Test Site. -from Authors