Scientists from the National Geophysical Research Institute (NGRI) in Hyderabad have forecast a very special type of shallow earthquake in the Koyna region of Maharashtra. It is being hailed as the first successful scientific prediction of an earthquake.

Details are published in the latest issue of the Journal of Geological Society India. It says a five-member team led by seismologist Harsh Gupta forecast on May 14 that an earthquake of magnitude 4 on the Richter Scale would occur in 10-km radius of Koyna within the next 15 days. He had circulated it to several leading science journals. The forecast came true on May 21 when a quake of 4.2 magnitude rattled the area.

‘‘I am very happy and satisfied that based on an empirical approach, we made a correct forecast,’’ says Gupta.

Working in the region for the last 44 years, Gupta and his team have put seven seismographs that record even minute movements of the earth. Once they noticed early signatures called ‘nucleation’ or an intense swarm of tiny earthquakes which started on May 12, they were able to make the prediction. ‘‘The prediction was correct,’’ says P.S. Goel, secretary of the newly formed Ministry of Earth Sciences (MES) and chairman of the Earth Commission of the Government.

But Goel adds that Koyna is a very special case. Earthquakes in the region, around 110 km from Pune, are of a unique nature since they are triggered by water pressure from the Koyna dam which is called reservoir-induced seismicity (RIS). Koyna’s worst quake measuring 6.3 was on December 11, 1967 and it claimed about 125 lives and injured over 1,500.