Why the May 12 Nepal quake is called an aftershock

The May 12, 2015 earthquake of 7.3 magnitude that struck 68 km west of Namche Bazar, close to Mount Everest is an aftershock of the April 25 Nepal quake of 7.9 magnitude that has till date killed over 8,000 people and injured many thousands and renderedseveral thousands more homeless. The magnitude of aftershocks will always … Continue reading Why the May 12 Nepal quake is called an aftershock

A shallow quake but high magnitude

Published in The Hindu on September 1, 2012 The 7.6-magnitude quake that occurred at a depth of nearly 34 km below the ocean floor was due to the Pacific plate subducting (sinking) under the Philippines plate on the eastern side of Philippines. “From the seismologic point of view the earthquake is a shallow one,” said … Continue reading A shallow quake but high magnitude

April 11 quake: Distance from epicentre protects Indian cities

Published in The Hindu on April 13, 2012 If the amount of energy released during an earthquake is measured in terms of magnitude, its effects on the earth's surface are expressed in terms of intensity. Unlike magnitude that is determined using an instrument, intensity is measured only by effects felt by people. The one widely … Continue reading April 11 quake: Distance from epicentre protects Indian cities

Why the April 11 quake was caused by a strike-slip fault

Published in The Hind on April 13, 2012 Besides the subduction zone (where the Indian plate dives under the Burmese plate) that lies to the west of Indonesia, the Indian Ocean has a diffused seismicity zone. This zone lies to the west of the subduction zone. The east-west trending zone extends from 80 degree East … Continue reading Why the April 11 quake was caused by a strike-slip fault

Sumatra quake: Why there was no tsunami

Published in The Hindu on April 12, 2012 The U.S. Geological Survey (USGS) initially estimated Wednesday's earthquake off the west coast of Northern Sumatra, at 8.9 magnitude. But it was subsequently lowered to 8.7 and then to 8.6. Similarly, the focus of the quake was first thought to be 33 km from the surface, but … Continue reading Sumatra quake: Why there was no tsunami

Tsunami: role of mega thrust confirmed

Published in The Hindu on December 22, 2005 One year after the killer waves struck havoc that killed hundreds of thousands of people, the answers for what actually caused the tsunami have been documented by Discovery Channel. The study proved conclusively that it was a mega thrust — a large-scale rupturing and vertical displacement of … Continue reading Tsunami: role of mega thrust confirmed