Himalayan Earthquakes and Developing an Earthquake Resilient Society

Abstract

Himalayan region is seismically one of the most active continental regions. It experienced at least 4 M ~ 8 earthquakes during an active phase from 1897 to 1952. However, no such earthquake has occurred since 1952. Detailed investigations have revealed that the region is currently in a seismic quiescence phase, and enough strains have been accumulated to source several M ~ 8 earthquakes. However, when and where such an earthquake would occur cannot be forecasted. Even if such an earthquake is forecasted to occur, can everyone leave to a safe place? That is not practical. It is therefore important to learn to live with earthquakes and develop an earthquake resilient society. Recent earthquakes have demonstrated the effectiveness of such an approach. One very effective way to develop earthquake resilient society is to create an earthquake scenario for the repeat of an earlier earthquake, estimate the losses, and then go through an exercise of imparting and sharing with public, state and central governance the ways and means of reducing the anticipated losses. The National Disaster Management Authority (NDMA), Government of India, in collaboration with other agencies, built earthquake scenarios for the repeat of the 1905 Kangra earthquake of M ~ 8 and 1897 Shillong earthquake of M 8.7. Appropriate ground motion prediction equation was used to generate earthquake intensities. The intensities of the hypothetical Mw 8 earthquake located at Mandi in Himachal Pradesh (close to the epicenter of 1905 Kangra earthquake) were compared with the 1905 Kangra earthquake's isoseismals and found to be satisfactory. For the 1897 Shillong earthquake, the isoseismals drawn by experts for the 1897 earthquake were used. Using the 2011 Census data for demography and building typology, it was estimated that if the hypothetical Mandi earthquake occurs in the middle of the night, the human lives lost would be ~ 959100 combining the states of Himachal Pradesh, Punjab, Haryana and the Union Territory of Chandigarh. It may be noted that the 1905 earthquake had claimed ~ 20,000 human lives. For the repeat of Shillong M 8.7 earthquake in the mid of the night, the number of lives lost estimated would be ~ 423000 in the 8 north-east states (Assam, Arunachal Pradesh, Meghalaya, Sikkim, Nagaland, Manipur, Tripura and Mizoram). NDMA took up detailed preparatory exercises involving the center and state bodies for Rapid Visual Screening (RVS) of lifeline buildings; school sensitization events; Incident Response System (IRS); and Awareness Generation programs involving local celebrities and a variety of news media. National Disaster Response Force (NDRF) and State Disaster Response Force(s) (SDRF) played a crucial role. To test the preparedness, mega-mock drills were held on 13 February 2013 for the 3 north-western states and UT Chandigarh; and on 10 and 13 March 2014 for the 8 north-eastern states. Performances of all the sectors were evaluated by independent observers. There was an excellent media coverage and the very purpose of generating awareness of the losses due to foreseeable earthquakes and how to reduce them was amply demonstrated. It is important to conduct similar exercises in other regions falling under Seismic Zones V and IV of the country. Of utmost importance is educating school students on an yearly basis, ways and means of developing earthquake resilience.