The Ministry of Earth Sciences (MoES) said the impact of high-intensity earthquakes can be greatly reduced through seismic hazard microzonation of vulnerable areas and putting in place adequate mitigation measures.
- An ambitious project of the ministry is aimed at seismic hazard microzonation of major Indian cities and areas falling under high-seismic Zones IV and V.
- Such areas vulnerable to earthquakes include all north-eastern states, Delhi, the Kutch region in Gujarat and Andaman and Nicobar Islands.
- Ministry plans for phased seismic hazard microzonation of important cities with a population of at least half a million.
- So far, micro-seismic mapping of Sikkim and eight cities Bengaluru, Delhi, Kolkata, Guwahati, Jabalpur, Ahmedabad, Dehra Dun and Gandhidham has been completed.
Seismic microzonation is defined as the process of subdividing a potential seismic or earthquake-prone area into zones with respect to some geological and geophysical characteristics of the sites such as ground shaking, liquefaction susceptibility, landslide and rockfall hazard, earthquake-related flooding so that seismic hazards at different locations within the area can correctly be identified.
- Microzonation of a region generates detailed maps that predict the hazard at much smaller scales.
The need for microzonation:
- Better understanding and planning: This will help authorities to better understand the areas which are more prone to seismic hazards and adopt mitigation measures accordingly.
- The earthquake effects depend on ground geomorphological attributes consisting of geological, geomorphology and geotechnical information. Hence, to mitigate, it is required to understand the impact of different geomorphological attributes.
- Absence of Prediction model: There is no reliable prediction model for earthquakes, in that case, it becomes very important to adopt preventive measures and have a well-planned mitigation measure put in place.
- Focus on mitigation and resilience: Japan is the best example of how effective and well-implemented mitigation measures helped its citizens. Citizens of Japan live in peace despite Japan falling in the high seismic zone and vulnerable to frequent earthquakes.
- Seismic by-laws: Civil engineers in Japan are completely aware of seismic laws and more focus is given to aggressive retrofitting of vulnerable structures and new structures are designed with seismic resilience.
For having a successful mitigating measure in place, it is necessary to religiously adhere to building by-laws and retrofitting of structures should be aggressively taken up, particularly high rise buildings, bridges, hospitals, schools, and other major infrastructure.