Role of static stress transfer in earthquake occurrence in the Himalaya

Abstract

Coulomb failure hypothesis suggests that earthquake interaction can lead to earthquake sequences and clustering. This implies that the phenomenon should be considered a fundamental feature in any description of seismicity and evaluation of the seismic hazard and risk of a region. We translate this idea to the Himalaya and investigate how significantly the past earthquakes of the region may have influenced the present day seismicity and seismic hazard potential along its different segments. For this, we estimate separately the change in Coulomb failure stress at the source of the most recent moderate magnitude earthquake along the Kumaon Garhwal segment, the March 29, 1999 Chamoli earthquake, due to two possible major sources. These are (i) the process of subduction of the Indian plate beneath the Himalaya and (ii) some selected preceding moderate and small earthquakes in and around the region, during their post seismic phase. Our results indicate that the change due to the former source completely overshadows that due to the latter. The implication of our calculations is that the plate subduction processes in the Himalaya (i) actively promote large, moderate and small earthquake activity and (ii) also indirectly influence the regional seismicity through the occurrence of the past earthquakes.