Abstract

The 1992 Landers, California, earthquake sequence and its aftershocks delineate an active 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 Positioning System (GPS) network that was installed and occupied in May 1991, with uncertainties of less than 1 cm on interstation baseline vectors. Changes in absolute displacement vectors on the decimetre and centimetre level were determined for individual sites, providing more samples of the sparsely sampled Landers displacement field. Measured displacements result from secular strain across the Mojave Desert, coseismic elastic recovery, and postseismic deformation during the six weeks between the earthquake and the GPS experiment. Secular strain and postseismic displacement are relatively small. Thus, first-order modeling of these fields allows calculation and subtraction of their signals, leaving a coseismic residual field. The GPS-determined far-field coseismic displacements differ significantly from elastic half-space models, offering new insight on the role of regional-scale heterogeneity in crustal structure.

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