Intraplate Seasonal Seismicity in the Northern Rocky Mountains of Montana and Idaho

Abstract:

Hydrologic processes have been shown to influence seismic productivity in many regions around the world, especially on active plate boundaries. To examine the influence of hydrologic cycles on seismicity in intraplate regions, we investigate temporal patterns of seismic productivity in the northern Rocky Mountains of Montana and Idaho. Seasonal variations are statistically significant, with peaks in productivity in the winter months of December and January, and reduced productivity in the summer months of June and July. Using a combination of SNOTEL and GPS data, we find that seismicity is most correlated with hydrologic loading rates rather than peak load, as predicted by rate and state models of fault behavior. However, we cannot distinguish between triggering by increases in stress rate from hydrologic loading, or a lagged response to pore pressure increases ~6 months after peak snowmelt and infiltration during early summer.