Mechanism of triggered seismicity at Koyna: An evaluation based on relocated earthquakes

摘要

Seismicity associated with the Koyna Reservoir, western Maharashtra, is unique because it is one of the few sites in the world where earthquakes of M greater than or equal to 5.0 continue to occur three decades after the initial spurt of activity. This contrasts with most other seismogenic reservoirs where temporal patterns of seismicity are characterized by one or two peaks that taper-off with time. Persistence of moderate seismicity at Koyna is enigmatic, considering also the low seismic productivity of the peninsular shield. Temporal association of major earthquakes with annual reservoir loading has been observed for long. In this paper, we report a discernible difference between the spatial pattern of earthquakes associated with the reservoir loading and unloading. A conceptual model is proposed to explain the continued occurrence of earthquakes. [References: 37]