Dynamic Stresses, Coulomb Failure, and Remote Triggering-Corrected

Dynamic stresses associated with crustal surface waves with 15-30 s periods and peak amplitudes < 1 MPa are capable of triggering seismicity at sites remote from the generating mainshock under appropriate conditions. Coulomb failure models based on a frictional strength threshold offer one explanation for instances of rapid-onset triggered seismicity that develop during the surface-wave peak dynamic stressing. Evaluation of the triggering potential of surface-wave dynamic stresses acting on critically stressed faults using a Mohr's circle representation together with the Coulomb failure criteria indicates that Love waves should have a higher triggering potential than Rayleigh waves for most fault orientations and wave incidence angles. That (1) the onset of triggered seismicity often appears to begin during the Rayleigh wave rather than the earlier arriving Love wave, and (2) Love-wave amplitudes typically exceed those for Rayleigh waves suggests that the explanation for rapid-onset dynamic triggering may not reside solely with a simple static-threshold friction mode. The results also indicate that normal faults should be more susceptible to dynamic triggering by 20-s Rayleigh-wave stresses than thrust faults in the shallow seismogenic crust (< 10 km) while the advantage tips in favor of reverse faults greater depths. This transition depth scales with wavelength and coincides roughly with the transition from retrograde-to-prograde particle motion. Locally elevated pore pressures may have a role in the observed prevalence of dynamic triggering in extensional regimes and geothermal/volcanic systems. The result is consistent with the apparent elevated susceptibility of extensional or transtensional tectonic regimes to remote triggering by Rayleigh-wave dynamic stresses than compressional or transpressional regimes.