Reconciling geologic and geodetic fault-slip-rate discrepancies in southern California: consideration of non-steady mantle flow and lower crustal fault creep

Yun-Ruei Y. Chuang, & Kaj M. Johnson

Published 2011, SCEC Contribution #1455

In southern California, slip rates derived from geodesy-constrained elastic models are lower than geologic rates along the Mojave and San Bernardino segments of the San Andreas fault and the Garlock fault.; Iin contrast, the summed geodetic rate across the Mojave eastern California shear zone (ECSZ) is significantly higher than the summed geologic rate. We show that geodetic and geologic slip rates in southern California can be reconciled using a viscoelastic earthquake cycle model that explicitly incorporates time-dependent deformation due to non-steady interseismic fault creep in the lower crust and viscous flow in the upper mantle. To reconcile geologic and geodetic rates, our model requires that the southern San Andreas Fault and the Garlock Fault are in the late stages of the earthquake cycle resulting in lower current deformation rates than the cycle-averaged rate. Our model implies that the ECSZ and the San Jacinto faults are in the early stages of the earthquake cycle resulting in high current deformation rates.

Citation
Chuang, Y. Y., & Johnson, K. M. (2011). Reconciling geologic and geodetic fault-slip-rate discrepancies in southern California: consideration of non-steady mantle flow and lower crustal fault creep. Geology,.