Himalayas more vulnerable to tremors: IISc study

BANGALORE: Two academicians from the Indian Institute of Science, Bangalore, based on their studies as well as those by researchers in the past, call for a critical reevaluation of the current understanding of past earthquakes in the Himalayas. K Rajendran and C P Rajendran of the Centre for Earth Sciences, IISc, have, in a yet-to-be published paper, titled, 'Revisiting the earthquake sources in the Himalaya: Perspectives on past seismicity (2011),' stated that the last major earthquake in the Central Himalaya may have occurred at least 1,000 years ago and that the gap in its seismicity is real. They base their findings on an analysis of the geological, historical and archaeological evidence at the sites of the past earthquakes. The understanding about Himalayan earthquakes in the 18th century and before is not clear. Despite the tradition of documenting earthquakes for nearly 4,000 years in the country, records of ancient earthquakes are incomplete, say the researchers. They contend that the region may have experienced more earthquakes in the past. Says K Rajendran: "Evidence of past earthquakes in the Himalayas gets concealed with layers of soil deposits, which when analysed offer a better understanding of seismic activity." The academicians had conducted investigations in Uttarakhand, where they found sand-filled, fissure-like structures, which usually result from forceful ejection of water during an earthquake shaking. The 1803 earthquake, their research points out, was not severe enough to damage stone structures located near Almora, although structures located as far as in Delhi, such as the Qutab Minar, were damaged.Instability Thy Name? Geologists from across the world have in their studies predicted that a great earthquake could occur in the Himalayas; a fact that gets accentuated when we take into consideration that the region has such an event has not occurred here since 1950. In 2001, a research paper published in Science magazine stated that several great earthquakes are overdue in this region but that recent low activity has focused attention away from the Himalayan arc.