Influence of seasonal surface load variations and interseismic stress build-up on Himalayan seismicity, implications for earthquake triggering (Invited)

The spatial correlation between geodetic strain and microseismicity is a prominent feature along the Himalayan front. This correlation demonstrates that background seismicity is driven by quasistatic stress/strain build up in the interseismic period. In this context there is also evidence for a correlation between seasonal variations of seismicity, monitored form a local seismic network, and of geodetic deformation, which are known to be induced by seasonal fluctuations of surface loading (as estimated from GRACE measurements). By contrast we don’t observe any effect of earthtides on seismicity in the Himalaya. Altogether these observations bring quantitative constraints on the earthquake nucleation process, triggering mechanisms in a context where loading is quasistatic. This analysis helps assessing the influence of dynamic stress variations and reloading by afterslip in aftershocks sequence.