Role of flexure in earthquake triggering along the Western Ghat escarpment, India

Structure of the Koyna‐Warna Seismic Zone, Maharashtra, India: A possible model for large induced earthquakes elsewhere

“…The focal planes for events along our proposed NMFZ and SMFZ could represent strike‐slip motion on either NW or NE trending faults. However, as we discuss below, we suggest that the likely fault planes are oriented northwest on the main faults, as has been observed for much of the Western Ghats [ Catherine et al , ].…”

“…Although the fault step‐over model is consistent with the seismotectonics for the Koyna‐Warna area, the stress field that gives rise to the current seismicity is not well understood. An alternative model by Catherine et al [] suggests that the seismicity in the Koyna‐Warna area arises from E‐W‐oriented plate flexure, which results in a reduction in normal stresses on preexisting faults. This mechanism, combined with reservoir‐induced stresses, can account for the normal faulting observed in the region, but it is unclear how their model accounts for the strike‐slip faulting observed in western India and the Koyna‐Warna area.…”

“…However, there are numerous areas worldwide that have reservoirs or that experience large volumes of injected fluid without generating large‐magnitude earthquakes. For example, Catherine et al [] discussed several areas in western India that have experienced apparent reservoir‐induced earthquakes, but the earthquakes have not been particularly large, nor has the seismicity been persistent for decades. Because larger magnitude induced earthquakes are generated on critically stressed, preexisting fault structures [ Simpson , ], it is important to understand the fault structures in areas that might be susceptible to induced earthquakes, preferably before human activities enhance the possibility of large earthquakes.…”