Evolution of seismicity near the southernmost terminus of the San Andreas Fault: Implications of recent earthquake clusters for earthquake risk in southern California

Egill Hauksson, Men-Andrin Meier, Zachary E. Ross, & Lucile M. Jones

Under Review January 16, 2017, SCEC Contribution #7176

Three earthquake clusters that occurred in the direct vicinity of the southern terminus of the San Andreas fault (SAF) in 2001, 2009, and 2016 raised significant concern regarding possible triggering of a major earthquake on the southern SAF, which has not ruptured in more than 320 years. These clusters of small and moderate earthquakes with M≤4.8 added to an increase in seismicity rate in the Brawley seismic zone that began after the 1979 Mw6.5 Imperial Valley earthquake, in contrast to the quiet from 1932 to 1979. The swarms so far triggered neither small nor large events on the SAF. The mostly negative Coulomb stress changes they imparted on the SAF may have reduced the likelihood that the events would initiate rupture on the SAF, although large magnitude earthquake triggering is poorly understood. The relatively rapid spatial and temporal migration rates within the clusters imply aseismic creep as a possible driver rather than fluid migration.

Key Words
seismicity, seismotectonics

Citation
Hauksson, E., Meier, M., Ross, Z. E., & Jones, L. M. (2017). Evolution of seismicity near the southernmost terminus of the San Andreas Fault: Implications of recent earthquake clusters for earthquake risk in southern California. Geophysical Research Letters, (under review). doi: 10.1002/2016GL072026.


Related Projects & Working Groups
Seismology