Indian earth science scientists have deduced that tsunamis can hit the Indian coast only when a big earthquake occurs on the sea bed in the 4,000 km Java-Sumatra region of the Indian Ocean on the east coast and the Makran region in the north Arabian Sea on the west coast.
“Unlike the Pacific Ocean, where there are regular earthquakes on the sea bed with a magnitude of 7 or more on Richter Scale, big earthquakes are likely to occur in these two regions of the Indian Ocean and Arabian Sea, on either side of the Indian sea coasts, which could cause tsunamis,” said former secretary of the Department of Ocean Development and ex-director of National Geophysical Research Institute (NGRI) Harsh K. Gupta on Wednesday.
Addressing top scientists, technologists and researchers at the Eighth National Conference of Ocean Society of India (OSICON 23) under way at the Indian National Centre for Ocean Services Information (INCOIS) here till August 25, the top scientist said that the December 2004 tsunami, which hit the Indian coast due to an earthquake of the magnitude of 9.2, was way bigger than the Hiroshima atom bomb on the Sumatra-Andamans belt.
When do tsunamis occur?
Tsunamis occur when the earth’s tectonic plates shift up or down leading to oscillation of water which gets amplified closer to the shore in the form of high waves. Post the 2004 tsunami devastation (about 2.50 lakh deaths, including more than 10,000 in India), Indian scientists decided to focus on these two regions for fairly accurate warnings by placing deep ocean bottom recorders – five in the Indian Ocean and two in the north Arabian Sea.
“This was done to prevent any false alarms whenever there is a quake under the ocean, as it could make people complacent when the real one occurs. In the Pacific Ocean, quakes are usually of a magnitude of 7 on Richter Scale or more, so people are used to taking preventive measures like evacuation and returning once the danger is passed,” explained Dr. Gupta.
Tsunami warning system
The Centre had established the Indian Tsunami Early Warning System (ITEWS) at INCOIS at ₹120 crore in 2007. It has been issuing tsunami advisories for all under-sea earthquakes of ≥ 6.5 magnitude for the last 15 years within 15 minutes throughout the Indian Ocean region through a lot of computational models, real time monitoring of ocean data and so on, he said.
Former Ministry of Earth Sciences secretary Shailesh Nayak called for better forecasting and computational models to understand the climate change by studying the ocean sub-surface temperatures, bio-geo-chemical changes, carbon cycle, trace elements as well as impact of human activity for a more accurate data dissemination. Effective communication with the policy makers, stakeholders and people was vital like potential fish advisories.
Dr. Srinivasan Endowment Award was presented to A.D. Rao from IIT, Delhi, on the occasion. Ocean Society of India president N.P. Kurian, and INCOIS group director E. Pattabhi Rama Rao spoke.