Dynamic triggering of small local earthquakes in the central Himalaya

We present the first observation of remote dynamic triggering of local microearthquakes in central Himalaya caused by the teleseismic waves from the 2007 M-w 8.5 Sumatra earthquake that occurs similar to 4500 km away. We find small local earthquakes in the Kumaon-Garhwal Himalaya triggered by teleseismic long-period surface waves. Interestingly, an elevated level of seismicity persists for a week or so after the arrival of the teleseismic waves. The teleseismic waves impart similar to 9 kPa of peak dynamic stresses, suggesting that the Himalayan faults in this area are sensitive to small stress changes. This heightened and protracted seismicity indicates that the transient dynamic stresses may have triggered secondary processes, such as slow slip, that may be responsible for the persistence of this earthquake sequence. The region is thought to be close to a large damaging earthquake in the near future. This study provides improved constraints on the factors controlling the earthquake cycle.