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

摘要: The Koyna-Warna area of India is one the best worldwide examples reservoir-induced seismicity, with distinction having generated largest known induced earthquake (M6.3 on 10 December 1967) and persistent moderate-magnitude (>M5) events for nearly 50 years. Yet, fault structure tectonic setting that has accommodated seismicity poorly known, in part because seismic occur beneath a thick sequence basalt layers. On basis alignment epicenters over an ~50 year period, lateral variations focal mechanisms, upper-crustal tomographic velocity images, geophysical data (aeromagnetic, gravity, magnetotelluric), geomorphic data, correlation similar structures elsewhere, we suggest lies within right step between northwest trending, right-lateral faults. sub-basalt basement may form local structural depression (pull-apart basin) caused by extension step-over zone Our postulated model accounts observed pattern normal faulting region dominated north-south directed compression. faults extend well beyond immediate area, possibly suggesting more extensive hazards central area. Induced have been many places worldwide, but relatively large-magnitude are less common critically stressed, preexisting necessary component. We releasing bends step-overs like those postulate serve as ideal environment generating moderate- to large- magnitude (reservoir, injection, etc.) earthquakes.