The combined inversion of seismic and geodetic data for the source process of the 16 October 1999 Mw 7.1 Hector Mine, California, earthquake

We investigate the source process of the M-w 7.1 Hector Mine earthquake by inverting broadband regional and local seismic displacement waveforms combined with Global Positioning System (GPS) and synthetic aperture radar interferometry (InSAR) geodetic measurements. We find that the three data sets individually produce remarkably similar slip distributions over a multisegment fault. A simultaneous inversion of the three data sets is presented, and the sensitivity of the combined inversion to the weighting of the three independent data sets is examined. The results indicate that the overall length of the fault that slipped is 42 km with a peak slip of 5.50 in and total scalar seismic moment of 6.8 X 10(19) N m. The majority of slip is located on the western branch of the Lavic Lake fault to the northwest of the hypocenter, although the overall rupture is bilateral with appreciable slip on the Bullion fault to the southeast. Some slip is located on an eastern branch of the Lavic Lake fault, an apparent bifurcation, which is also evident from aftershock locations. The average slip and stress drops are 2.70, 1.62, 1.60 m and 78, 36 and 55 bars for the western Lavic Lake, the eastern Lavic Lake, and Bullion faults, respectively. The results also indicate that the overall rupture process is relatively slow, which is characterized by a several-second delay before the onset of significant slip, a 1.8 km/sec rupture velocity of the primary asperity, and long, spatially variable, dislocation rise times.