REGIONAL COSEISMIC DEFORMATION FROM THE JUNE 28, 1992, LANDERS, CALIFORNIA, EARTHQUAKE - RESULTS FROM THE MOJAVE GPS NETWORK

The 1992 Landers, California, earthquake sequence and its aftershocks defineate an a part of the Eastern California shear zone. The surface rupture lies within the Mojave Desert, providing a unique opportunity to characterize far-field deformation with a regional Global Positioni ng System (GPS) network that was installed and occupied in May 1991, w ith uncertainties of less than 1 cm on interstation baseline vectors. Changes in absolute displacement vectors on the decimetre and centimet re level were determined for individual sites, providing more samples of the sparsely sampled Landers displacement field. Measured displacem ents result from secular strain across the Mojave Desert, coseismic el astic recovery, and postseismic deformation during the six weeks betwe en the earthquake and the GPS experiment. Secular strain and postseism ic displacement are relatively small. Thus, first-order modeling of th ese fields allows calculation and subtraction of their signals, leavin g a coseismic residual field. The GPS-determined far-field coseismic d isplacements differ significantly from elastic half-space models, offe ring new insight on the role of regional-scale heterogeneity in crusta l structure.