Preliminary Report on the 16 October 1999 M 7.1 Hector Mine, California, Earthquake

Abstract

The Hector Mine earthquake occurred within the Eastern California Shear Zone (ECSZ). By virtue of its remote location, the societal impact of the Hector Mine earthquake was, fortunately, minimal in spite of the event's appreciable size. The ECSZ is characterized by high seismicity, a high tectonic strain rate, and a broad, distributed zone of north-northwest-trending faults (ECSZ; Figure 1; Dokka and Travis, 1990; Sauber et al., 1986; Sauber et al., 1994; Sieh et al., 1993). Data regarding the slip rates of faults within the ECSZ suggest that on the order of 15% of the Pacific-North American plate motion occurs along this zone (Sauber et al., 1986; Wesnousky, 1986). Most of the faults in the ECSZ have low slip rates and long repeat times for major earthquakes, on the order of several thousands to tens of thousands of years. The occurrence of the Hector Mine earthquake within seven years and only about 30 km east of the 1992 M_w 7.3 Landers earthquake suggests that the closely spaced surface faults in the ECSZ are mechanically related.