eprintid: 1306 rev_number: 17 eprint_status: archive userid: 2 dir: disk0/00/00/13/06 datestamp: 2015-02-10 14:01:07 lastmod: 2017-02-08 12:21:33 status_changed: 2015-04-27 12:10:39 type: article metadata_visibility: show creators_name: Durá-Gómez, Inmaculada creators_name: Talwani, Pradeep corp_creators: Department of Geological Sciences, University of South Carolina, Columbia, SC, 29208, USA title: Hydromechanics of the Koyna–Warna Region, India ispublished: pub subjects: RI1 subjects: SR subjects: SS divisions: EPOS-P full_text_status: none keywords: Reservoir-induced seismicity, Koyna reservoir, pore pressure diffusion, stress memory, strain hardening abstract: Continuous reservoir-induced seismicity has been observed in the Koyna–Warna region in western India following the beginning of impoundment of Koyna and Warna Reservoirs in 1961 and 1985, respectively. This seismicity includes 19 events with M ≥ 5.0 which occurred in 7 episodes (I–VII) between 1967 and 2005 at non-repeating hypocentral locations. In this study, we examined the first six episodes. The seismicity occurs by diffusion of pore pressures from the reservoirs to hypocentral locations along a saturated, critically stressed network of NE trending faults and NW trending fractures. We used the daily lake levels in the two reservoirs, from impoundment to 2000, to calculate the time history of the diffused pore pressures and their daily rate of change at the hypocentral locations. The results of our analysis indicate that Episodes I and IV are primarily associated with the initial filling of the two reservoirs. The diffused pore pressures are generated by the large (20–45 m) annual fluctuations of lake levels. We interpret that critical excess pore pressures >~300 kPa and >~600 kPa were needed to induce Episodes I–III and Episodes IV–VI, respectively, suggesting the presence of stronger faults in the region. The exceedance of the previous water level maxima (stress memory) was found to be the most important, although not determining factor in inducing the episodes. The annual rise of 40 m or more, rapid filling rates and elevated dp/dt values over a filling cycle, contributed to the rapid increase in pore pressure. date: 2010 date_type: published publication: Pure and Applied Geophysics volume: 167 number: 1-2 publisher: Springer Verlag pagerange: 183-213 id_number: doi:10.1007/s00024-009-0012-5 refereed: TRUE issn: 0033-4553 official_url: http://dx.doi.org/10.1007/s00024-009-0012-5 access_IS-EPOS: limited owner: Publisher citation: Durá-Gómez, Inmaculada and Talwani, Pradeep (2010) Hydromechanics of the Koyna–Warna Region, India. Pure and Applied Geophysics, 167 (1-2). pp. 183-213. DOI: https://doi.org/10.1007/s00024-009-0012-5