The tremors felt in Idukki district on Sunday were a manifestation of the release of stress on the earth, which, however, did not originate in the Idukki reservoir, John Mathai, a senior official of the Centre for Earth Science Studies (CESS), Thiruvananthapuram, says.
The tremors felt at 4.06 a.m. and 6.29 a.m. had an intensity of 2.2 and 1.9, respectively, on the Richter scale.
Mr. Mathai told The Hindu on Tuesday that though the ground vibrations were less, people could hear a sound.
“Usually, there are stress-related tremors soon after a reservoir is built, but their intensity declines in the following years. After the reservoir has been in existence for 10 years, such tremors are not reported as the earth slowly adjusts to the stress. In the reservoir area in Idukki, the initial stress was less and no major tremors had been felt during that period,” he said.
The official said tremors were experienced in various States recently not as a result of stress caused by reservoirs. Reservoir-based stress was high during the rainy season as the water level would be high during the time.
The official said the tremors were unlikely to continue in the district, and studies were on to find out if a tremor of 3.8 intensity felt in Idukki and Kottayam districts on July 26 was related to Monday' tremors as their epicentres were close to each other.
