STRAIN ACCUMULATION NEAR YUCCA MOUNTAIN, NEVADA, 1983-1993

Over the decade 1983-1993 the U.S. Geological Survey has measured the deformation of a 50-km-aperture trilateration network centered on Yucc a Mountain the proposed disposal site for high-level nuclear waste in the United States. The network was surveyed in 1983, 1984, and 1993. T he average annual principal strain rates are 0.010 +/- 0.020 mu strain /yr N90 degrees W +/- 24 degrees and -0.009 +/- 0.021 mu strain/yr N00 degrees E +/- 24 degrees, indicating no significant strain accumulati on. The southeast corner of the network was disturbed on June 29, 1992 , by the Little Skull Mountain earthquake (M(s) = 5.4), the epicenter of which is about 20 km southeast of the Yucca Mountain site. Using th e seismically determined fault plane (dip 54 degrees S55 degrees E), w e find that 0.580 +/- 0.075 m of normal slip on a 5-km square rupture surface at a depth of about 8 km provides a good fit to the observed d eformation in the southeast corner of the network. The inferred seismi c moment is (4.4 +/- 0.6) x 10(17) N m, which compares well with the o bserved seismic moment of 4.1 x 10(17) N m.