Earthquake Risk And Vulnerability In India

According to the latest seismic zone map of India, about 59 per cent of India’s land area is vulnerable to moderate or severe seismic hazard, i.e., prone to shaking of MSK intensity VII and above. In the recent past, most Indian cities have witnessed the phenomenal growth of multi-storied buildings, super malls, luxury apartments and social infrastructure as a part of the process of development. The rapid expansion of the built environment in moderate or high-risk cities makes it imperative to incorporate seismic risk reduction strategies in various aspects of urban planning and construction of new structures.

During the period 1990 to 2006, India has experienced 6 major earthquakes that have resulted in over 23,000 deaths and caused enormous damage to property, assets and infrastructure.

The entire Himalayan Region is considered to be vulnerable to high intensity earthquakes of a magnitude exceeding 8.0 on the Richter Scale, and in a relatively short span of about 50 years, four such earthquakes have occurred: Shillong, 1897 (M 8.7); Kangra, 1905 (M.8.0); Bihar–Nepal, 1934 (M 8.3); and Assam–Tibet, 1950 (M 8.6).

Scientific publications have warned that very severe earthquakes are likely to occur anytime in the Himalayan Region, which could adversely affect the lives of several million people in India.

The Bhuj earthquake of 2001 caused widespread damage and destruction not only to residential buildings but also to government buildings, public infrastructure and to buildings housing industrial enterprises in more than 7,900 villages in 21 districts of Gujarat. The severe economic losses caused by the Gujarat earthquake were not only restricted to the local economy but also influenced the savings and investment patterns and stock market behaviour.

Thus, the economic impact of an earthquake in a metropolitan city like Delhi or Mumbai etc., will have primary, secondary and tertiary effects.

Critical Areas of Concern in Earthquake Management

There is an increasing need being felt for a more systematic, holistic and integrated effort to address the critical areas of concern responsible for the weak seismic safety measures in India.

These Guidelines have been drawn up to address these critical areas of concern and to provide the foundation for seismic safety.

The regions away from the Himalayas and other inter-plate boundaries were previously considered to be relatively safe from the devastating impact of earthquakes. However, the Koyna earthquake of 1967 and the Latur earthquake of 1993 dispelled this widely held view and influenced the revisions of the seismic zoning map. This map, however, only indicates areas with low, moderate and high seismic hazards based on past trends.

There is an urgent need to revise the seismic zone map of India to reflect the return period related design accelerations. This work will be carried out in a phased manner covering the Himalayan ranges, the North-East and the western region in the first phase.

The critical areas of concern for the management of earthquakes in India include the:

• Lack of awareness among various stakeholders about the seismic risk
• Inadequate attention to structural mitigation measures in the engineering education syllabus
• Inadequate monitoring and enforcement of earthquake-resistant building codes and town planning bye-laws
• Absence of systems of licensing of engineers and masons
• Absence of earthquake-resistant features in non-engineered construction in suburban and rural areas
• Lack of formal training among professionals in earthquake-resistant construction practices
• Lack of adequate preparedness and response capacity among various stakeholder groups

Urgent Need: A More Realistic and Scientific Seismic Zonation Map

The Ministry of Environment And Science (MoES) will coordinate this task in collaboration with technical institutions like the IMD, the Earthquake Risk Evaluation Centre (EREC), the BIS and the Geological Survey of India (GSI), along with the concerned scientific and professional institutions.