Long-range and long-term fault interactions in Southern California

Abstract

Paleoseismological data suggest the occurrence of four bursts of seismic moment release in the Los Angeles region during the past 12,000 yr. The historic period appears to be part of an ongoing lull that has persisted for about the past 1000 yr. These periods of rapid seismic displacement in the Los Angeles region have occurred during the lulls between similar bursts of activity observed on the eastern California shear zone in the Mojave Desert, which is now seismically active. A kinematic model in which the faults of the greater San Andreas system suppress activity on faults in the eastern California shear zone, and vice versa, can explain the apparent switching of activity between the two fault networks. Combined with the observation that short-term geodetic and longer-term geologic rates co-vary on major southern California fault systems, this suggests that either (1) a temporal cluster of seismic displacements on upper-crustal faults increases ductile deformation on their downward extensions, or (2) rapid ductile slip in the lower crust beneath faults loads the upper crust, driving a seismic cluster. We suggest that alternating periods of rapid seismic displacement may be the expected mode of seismicity when two fault systems accommodate the same plate-boundary motion, and slip on one system suppresses slip on the other.

Structural Properties and Deformation Patterns of Evolving Strike-slip Faults: Numerical Simulations Incorporating Damage Rheology

“…13) or exhibit alternating deformation periods before the initial faults become inactive and the new fault configuration stabilizes. These results are consistent with existing multi-disciplinary knowledge of fault systems (BEN-ZION and SAMMIS, 2003 and references therein;DOLAN et al, 2007) and the related numerical results of LYAKHOVSKY and BEN-ZION (2009).…”

Interseismic Deformation of the Altyn Tagh Fault Determined by Interferometric Synthetic Aperture Radar (InSAR) Measurements

“…The discrepancy between these two methods could be due to the different time scales if both methods have no errors or slip rates vary with time like faults in Southern California [69]. Cowie et al reported earlier that fault slip rates can vary in time or along strike the fault, both due to clustering or quiescence periods of the fault activity or due to long term effects [70,71].…”

Recent behavior of the North Anatolian Fault: Insights from an integrated paleoseismological data set

“…For example, parallel fault strands may accommodate some shear stress during some seismic cycles (switching [e.g., Dolan et al, 2007]), stress triggering may significantly shorten some interevent times [e.g., Stein et al, 1997], or leakage (i.e., a small amount of slip on one segment caused by rupture of an adjacent segment) may cause apparent variations in the interevent time at a point on the fault [e.g., Sieh, 1996]. Stress triggering may be caused by fault ruptures on adjacent segments of the NAF or other faults.…”