Abstract

The Mw 7.3 Landers earthquake produced approximately 80 km of surface faulting along a preexisting, integrated system of faults separated by complex intersection points. The earthquake was accompanied by distributed seismicity and triggered slip across a large area of the central Mojave desert known as the Mojave block. We synthesized surface mapping, geodetic, and seismicity data to develop a kinematic model for regional co-seismic deformation. We interpret that the earthquake simultaneously accommodated north-directed motion of blocks within the San Bernardino mountains, dextral shear on northwest-striking faults in the central Mojave block, and minor northwest-southeast extension of the eastern Mojave block. This pattern of distributed heterogeneous co-seismic deformation is similar to a kinematic model proposed for cumulative late Cenozoic deformation of the Mojave block in which dextral shear, north-south shortening, and northwest-southeast extension are partitioned into discrete domains bounded principally by strike-slip faults. Based on the similarity between the co-seismic deformation and patterns of cumulative late Cenozoic deformation, we propose that infrequent multiple fault-segment ruptures similar to those associated with the 1992 Landers earthquake are part of the process by which the Mojave block has changed size and shape during the late Cenozoic. This model suggests that combinations of multiple-fault or multiple-segment rupture may be assessed as relatively more or less likely, depending on whether a particular rupture scenario contributes proportionally to the cumulative regional deformation.

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