The coseismic geodetic signature of the 1999 Hector Mine Earthquake

The M=7.1 Hector Mine earthquake ruptured the Lavic Lake fault near Twentynine Palms, CA at 09:46 UTC October 16, 1999. Because it occurred near the eastern edge of the Southern California Integrated GPS Network (SCIGN), a network of permanent, continuously recording GPS receivers for measuring the crustal deformation field around Los Angeles, CA, it was possible to determine the deformation associated with the earthquake with unprecedented speed and reliability. Thirty-four stations recorded displacements over the 3-sigma level. The displacements measured with GPS can be modeled by a fault 46.2 +/- 2.6 km long, 8.2 +/- 1.0 km wide, striking 330 degrees, dipping 84 degrees east, with 301 +/- 36 cm right lateral strike-slip, and 145 +/- 36 cm of east-up dip-slip, yielding a potency of 1.3 km(3) and geodetic moment of 3.8 x 10(26) dyne-cm. The trace and dip of the model fault is consistent with the observed ground rupture and seismic focal mechanisms.