Near-prospective test of Coulomb stress triggering

Anne E. Strader, & David D. Jackson

Published April 4, 2014, SCEC Contribution #2104

Numerous studies retrospectively observed a strong association between earthquake location and increased static Coulomb stress. In addition to confirming these results for southern California seismicity, we observed prospective forecasting potential in static stress evolution. With 141 seismic and 98 aseismic stress sources, we considered alternate choices of stress components and receiver fault orientations, examined the effect of Coulomb triggering on earthquake magnitude, calculated stress histories for receiver quakes to see if some occurred after their stress had peaked, examined whether stress changes from the Hector Mine earthquake alone changed the earthquake rate as expected, and estimated the conditional distribution of earthquake occurrence given resolved Coulomb stress change. We found that with 95% confidence, M ≥ 2.8 receiver earthquakes nucleate in areas of shear or Coulomb stress change increase. On average, 59% of earthquakes occurred within stress-enhanced zones, regardless of the choice of rupture plane or type of stress change. The 1999 Hector Mine, California, earthquake increased the seismicity in regions of positive and negative stress change but more so in the positive regions. Earthquakes frequently occur after their calculated peak stress has occurred, indicating that elastic calculations do not tell the whole story. We found no significant evidence that stress change affects the magnitude of receiver quakes. Thus, instantaneous Coulomb and shear stress change apparently influence the locations but not the magnitudes of future earthquakes.

Key Words
seismology, Coulomb, stress, earthquake, triggering, forecasting

Citation
Strader, A. E., & Jackson, D. D. (2014). Near-prospective test of Coulomb stress triggering. Journal of Geophysical Research: Solid Earth, 119(4), 3064-3075. doi: 10.1002/2013JB010780.

Related Projects & Working Groups
Earthquake Forecasting and Predictability