Interseismic deformation associated with three-dimensional faults in the greater Los Angeles region, California

摘要

Existing interseismic models arc not well-suited to simulate deformation within the network of finite, intersecting, nonplanar faults observed in the greater Los Angeles region. Instead of applying fault slip rates to a model a priori, we allow three-dimensional fault surfaces to interact and accumulate mechanically viable slip distributions and then use the deep nonseismogenic portion of slip to calculate interseismic deformation. We apply this approach to the Los Angeles region and find that the geologic timescale model results match well geologic slip rate data and the interseismic timescale model results match well the heterogeneous GPS velocity pattern in the Los Angeles region. Model results suggest that localized geodetic convergence in the San Gabriel basin can be achieved with slip on multiple active fault surfaces in the Los Angeles region including relatively fast slip on the Sierra Madre fault and slow slip on the Puente Hills thrusts, in agreement with geologic data. The ability of the three-dimensional model to reproduce well both geologic slip rates and interseismic geodetic velocity patterns suggests that current day contraction rates in the greater Los Angeles region are compatible with long-term geologic deformation rates and disputes suggestions of significant temporal variations in fault slip rates inferred from existing investigations.