This project was an Indo-German research cooperation supported by the German DLR (Internationales Büro) and the Indian CSIR (Center of Scientific and Industrial Research) from 1994 to 2003. Project leaders: R.K. Chadha (NGRI, Hyderabad, India), H.-J. Kümpel (GGA-Institut, Hannover).
References
Gupta, H.K.; Radhakrishna, I.; Chadha, R.K.; Kümpel,
H.-J. & Grecksch, G. (2000): Pore pressure studies initiated in
area of reservoir-induced earthquakes in India. - EOS, Transactions,
American Geophysical Union, 81, No. 14, 145, 151.
Chadha, R.K., Pandey, A.P. & Kümpel, H.-J. (2003): Search for earthquake precursors in well water levels in a localized seismically active area of reservoir triggered earthquakes in India. - Geophys. Res. Lett., 30 (7), 1416.
Project summary and selected photos (photos by G. Grecksch):
The presence of fluids and pore pressure fluctuations are believed to
play a significant role in earthquake mechanics. This appears to be particulary
true for reservoir induced/triggered seismicity (RIS). We have set up a
collaborative project in the Koyna area, West-India, where RIS is ongoing
for more than 30 years and is highest in the world. Starting in 1995, an
array of observation wells has been drilled 130 to 250 m deep into the
stratified Deccan trap basalts around Koyna and equipped with digital pressure
transducers for quasi-continuous monitoring of well level changes (see
figures below). The overall objectives are
(a) to provide an extensive set of
high quality data on in-situ pore pressure/volume strain fluctuations in
a prominent RIS environment,
(b) through analysis of this data,
to make a substantial progress in understanding this extraordinary case
of RIS,
(c) to add to the knowledge of conditions
under which seismicity in stable continental regions may become critical,
and thereby
(d) to contribute to a better assessment
of seismic risk, in general.
The total array consists of 21 wells. It was completed in summer 1998. Recordings will be screened for (dis)similarities between anomalies in any of the well level signals and for coherences with changes in the reservoir level and local seismicity. The data collected from the first 13 wells indicate that the basalts are water saturated below some 10 m. Moreover, artesian conditions (2 wells) and tidal well level signals high above the noise level 10 wells reflect confined aquifer conditions at most sites. This gives evidence of remarkably tight formations at rather shallow depths, favourable for the detection of pore pressure anomalies induced by tectonic or reservoir related forces.
Seismicity in the Koyna Region 1995 with sites of seismic stations and of wells for continuous monitoring of in-situ pore pressure fluctuations (H.-J. Kümpel, after B.K. Rastogi, NGRI).
Koyna river near Shivaji Sagar reservoir, Maharashtra, India.
Basaltic Deccan traps near Koyna dam.
H.-J. Kümpel and I. Radhakrishna, hydraulic test at Ukalu well near Warna reservoir in Feb. 1997.