Earthquake refers to the sudden shaking of the Earth’s surface, while earthquake hazard encompasses all the elements associated with an earthquake that can impact people’s daily lives. These hazards include ground shaking, surface rupture, landslides, liquefaction, tectonic deformation, and tsunamis, among others.
Vulnerability of India to Earthquake-related hazards:
- As per the Bureau of Indian Standards (BIS), over 58.6 percent of India’s landmass is susceptible to earthquakes ranging from moderate to very high intensity. The occurrence of the Killari earthquake in 1993 led to a revision of seismic zoning in India, with the low hazard zone, Seismic Zone I, being merged with Seismic Zone II.
- The risks associated with earthquake hazards have increased due to densely populated areas, extensive unscientific constructions, and unplanned urbanization.
- The Andaman & Nicobar Islands frequently experience destructive earthquakes due to their location on an inter-plate boundary.
- The growing use of high-technology equipment, which is susceptible to even slight vibrations, in industries, academia, and underground utilities for electricity and internet, has heightened the susceptibility to disruptions caused by moderate ground shaking.
- Regions in the foothills of the Himalayas are prone to liquefaction and landslides triggered by earthquakes.
Key features of major earthquake disasters in the past three decades:
- Latur 1993: A 6.2 magnitude earthquake with relatively shallow depth resulted in significant surface damage. The exact causes of the earthquake remain debatable due to the absence of plate boundaries in the region.
- Chamoli 1999: Caused by a thrust fault, this earthquake led to landslides, changes in surface water flow, surface rupture, and disconnected valleys.
- Bhuj 2001: Associated with a previously unknown reactivated fault, this earthquake resulted in extensive loss of life and property due to careless construction practices.
- Indian Ocean Tsunami 2004: Triggered by underwater seismic activity, this catastrophe generated massive waves that inundated coastal areas and islands, causing long-term changes.
- Kashmir 2005: A 7.6 magnitude earthquake caused by a severe upthrust of the Indian plate against the Eurasian plate, resulting in multiple aftershocks. Infrastructure and communication were severely disrupted.
India’s vulnerability to various earthquake hazards necessitates careful management and long-term planning. The reconstruction efforts in Bhuj following the 2001 earthquake serve as an instructive example.