Koyna earthquakes: a review of the mechanisms of reservoir triggered seismicity and slip tendency analysis of subsurface faults

Koyna region in western India experienced more than 1,00,000 earthquakes of diferent magnitudes (M ~ 1.0–6.3) in the past fve decades. Earthquakes in this region are believed to be triggered by a change in fuid pressure due to the percolation of the reservoir (Koyna and Warna reservoir) water into the subsurface. A drilling program was set up by the Ministry of Earth Sciences, India and International Continental Scientifc Drilling Program (ICDP) to study the deep subsurface lithol ogy, structure, thermal attributes, etc. as the area is covered by~950 m of thick Deccan basalts. This paper reviews all the hypotheses proposed by earlier workers to explain the mechanism of reservoir trigger causing earthquakes and summarizes such theories to a simple generic model. Slip tendency analysis was further carried out based on the proposed model to explain the dependence of fault slip on fault geometry, rock mechanical properties, stress and fuid gradients. Finally, faults at various depths were characterized (favourably oriented, unfavourably oriented and severely misoriented) based on their potential to go into failure.

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Opracowanie rekordu ze środków MNiSW, umowa Nr 461252 w ramach programu "Społeczna odpowiedzialność nauki" - moduł: Popularyzacja nauki i promocja sportu (2021)