Deep structure of a fault discontinuity

Abstract

Relocated aftershocks at a fault discontinuity that ruptured in the 1992 Landers earthquake show that there is no simple connection between the Homestead Valley and Emerson faults at depth. Rather, faulting within the discontinuity is as complex as observed at the surface. Both aftershocks and mainshock slip on the far side of the discontinuity, that is on the Emerson fault, were confined primarily to depths above 10 km, whereas slip and after-shock activity on the near side of the discontinuity extended to 17 km. Similar behavior was also observed at a fault discontinuity in the 1979 Coyote Lake earthquake and may be attributable to the greater effectiveness of dynamic stress in inducing fault rupture at shallow depths. Copyright 1999 by the American Geophysical Union.