Earthquake precursory studies in India: Scenario and future perspectives

Earthquakes are the worst natural calamities that strike without any notice and cause immediate loss of life and property. Internationally, serious and scientifically acceptable earthquake prediction studies started in 1970s and short term prediction of the Heicheng earthquake of February 4, 1975 in China is a land mark. In India, a successful medium term prediction of August 6, 1988 earthquake, (M 7.5) in northeast Indian region encouraged to intensify such studies in the country. These predictions were based mainly on seismological precursors. Initially, the precursory studies were taken in isolated manner, but after validation of specific geophysical parameters, efforts were made to adopt an integrated approach involving collection, analysis and interpretation of various precursory observations in a comprehensive and coordinated manner. Accordingly, a few Multi-parametric Geophysical Observatories (MPGOs) have been established at the selected locations in seismically active areas in the country. This approach led to successful short term prediction of some moderate earthquakes (M ⩾ 4) in Koyna region (famous for Reservoir Triggered Seismicity) in western India. Simultaneously, efforts have been made to generate long term multi-parametric observations from these observatories, as a basic scientific input required for future earthquake prediction related studies. The real-time analysis of these data sets would help to understand the earthquake generation process and attaining the predictive capabilities by developing models for short term earthquake forecasting. To facilitate direct observations and test the hypothesis of Reservoir Triggered Seismicity (RTS) as well as to understand the earthquake generation processes, it is planned to undertake deep borehole (6–8 km) investigations in Koyna region of western India.The paper highlights the efforts made so far in India in the area of earthquake precursory studies as well as the future road map.