10:30 AM - 10:45 AM
[S02-4-01] Borehole seismological studies at Koyna-Warna: A unique example of the study of Reservoir Triggered Seismicity (RTS)
invited
The Koyna-Warna region located close to the west coast of India is an outstanding example of Reservoir Triggered Seismicity (RTS), where earthquakes have been occurring in a restricted area of 30x20 sq km since the impoundment of Koyna reservoir in 1962 and the Warna reservoir in late 1980's. So far the region experienced 22 earthquakes of M>5 including the largest triggered earthquake of M~6.3 on Dec 10 1967, about 200 earthquakes of M~4, and several thousand smaller earthquakes. The continued seismicity at shallow depths of 4-7 km in the Koyna-Warna region for the past 49 years was monitored through surface seismograph networks installed from time to time and the location accuracies were improved by enhancing the seismic network capabilities by various upgradations.
Recently under a deep drilling program initiated jointly by Ministry of Earth Sciences and CSIR-National Geophysical Research Institute to understand the earthquake mechanism at Koyna-Warna a very dense network of 22 surface broadband seismographs and six borehole seismographs up to depths of 1500m was installed forming a unique example to study the Reservior Triggered Seismicity (RTS) of Koyna-Warna. With the installation of this unique hybrid seismic network the detection capabilities and the accuracies of the hypo central parameters and the clear recording of the micro-seismic clusters have improved. There has been a significant improvement in the location of earthquakes and the absolute errors of location have come down to ± 300 m. All earthquakes of ML ≥ 0.5 are now located, compared to ML ≥1.0 earlier. The details of the seismic network along with the improvements will be presented here.
Key Words: RTS, Koyna-warna, Borehole Seismographs
Recently under a deep drilling program initiated jointly by Ministry of Earth Sciences and CSIR-National Geophysical Research Institute to understand the earthquake mechanism at Koyna-Warna a very dense network of 22 surface broadband seismographs and six borehole seismographs up to depths of 1500m was installed forming a unique example to study the Reservior Triggered Seismicity (RTS) of Koyna-Warna. With the installation of this unique hybrid seismic network the detection capabilities and the accuracies of the hypo central parameters and the clear recording of the micro-seismic clusters have improved. There has been a significant improvement in the location of earthquakes and the absolute errors of location have come down to ± 300 m. All earthquakes of ML ≥ 0.5 are now located, compared to ML ≥1.0 earlier. The details of the seismic network along with the improvements will be presented here.
Key Words: RTS, Koyna-warna, Borehole Seismographs