10 quakes in 18 years in J'khand, claims geologist

Jharkhand has experienced more than 10 tremors in 18 years though their intensity was mild to medium, geologist Nitish Priyadarshi today claimed and suggested that newly constructed buildings in the state should be earthquake-resistant.
"Back-to-back tremors occurred for the first time in Jharkhand. The state has never experienced aftershocks," Priyadarshi, a member of the Geological Society of India, said here.
He said the Chhotanagpur Plateau in Jharkhand represents a part of the Indian Peninsular field that is "stable cratonic block of the earth crust".
Craton is the stable interior portion of a continent characteristically composed of ancient crystalline basement rock and there is a belief that land above a cratonic block is generally shielded from earthquakes.

"The cause for concern is that there had been more than 10 mild to medium tremors occurred in the area since 1997," said Priyadarshi.
"So, all the new buildings coming up in Chhotanagpur Plateau should be earthquake resistant," he said and suggested that with the consent of owners dilapidated buildings should be demolished to pave way for earth-quake resistant buildings.

"Two types of effects occur in the Chhotanagpur plateau. The first is sympathiser (the effect following tremors happening outside the region) and the second is localised following stress and strain in the rocks.
"Tremors in this plateau are shallow, usually shaking between a magnitude between one and 5 on the Richter scale and happening in less than 15 miles deep. These tremors happen randomly and are unpredictable," he added.

Quoting a 2002 report from the Bureau of Indian Standards, he said Jamshedpur and Chaibasa come in Seismic zone-2, Ranchi and Hazaribagh Zone 3 and the Santhal Pargana in Zone-4.