Dr G K Panda *

Earthquakes are one of the most frightening and destructive of natural hazards with terrible after effects. An earthquake is a sudden movement of the Earth’s crust, caused by an abrupt release of strain that has accumulated over a long time. Earthquakes occur due to sudden transient motion of the ground as a result of release of elastic energy in a matter of few seconds.
The shifting masses send out shock waves which are often powerful enough to alter the surface of the Earth, thrusting up cliffs, opening great cracks in the ground, collapse of buildings and other man-made structures. They not only destroy villages, towns and cities but the aftermath leads to destabilize the economic and social structure of the nation.

More than 1.5 lakh tremors strong enough to be felt by humans occur each year worldwide. Most earthquakes are produced along faults, tectonic plate boundary zones, or along the mid-oceanic ridges (Figures 1).

The impacts of these events are most traumatic because it affects large area, occurs all of a sudden and is unpredictable. Sometime after the main shock wave, aftershocks can occur because of the continued release of frictional stress. Most aftershocks are smaller than the main earthquake, but they can still cause considerable damage to already weakened natural and man-made features. Earthquakes that occur under the seas and oceans or near bodies of water often give rise to tsunamis. The Sumatra-Andaman Island earthquake which occurred in the Indian Ocean along the Sunda trench in December 26, 2004 resulted in far greater destruction and loss of life.

• Zone I & II (Low damage risk zone) – This zone experiences seismic disturbances upto magnitude 9. These two zones are contiguous, covering parts of Karnataka, Andhra Pradesh, Odisha, Madhya Pradesh, and Rajasthan, known as low risk earthquake zones.
• Zone III is a moderate damage risk zone –This zone extends over a large part of the country stretching from the north including some parts of Rajasthan to the South through the Konkan coast, and also the Eastern parts of the country. Odisha also comes under this zone. It passes over the five mojor towns across the Mahanadi valley i.e Sambalpur, Burla, Hirakud, Bhubaneswar and Cuttack.
• Zone – IV is a high risk zone with earthquakes occurring in the magnitude of 9. The states coming under this zone are parts of the Northern belt starting from Jammu and Kashmir to Himachal Pradesh. This zone also includes Delhi and parts of Haryana; the Koyna region of Maharashtra is also in this zone.

(8) Zone – 5 is the high to Very High Risk zone with earthquakes occurring in the range of 8 in the Ritcher’s scale. The entire North-east, including the entire seven sister states, the Kutch district, parts of Himachal and Jammu & Kashmir, and the Andaman and Nicobar islands. Other Urban areas such as Ganhidham, Morvi, Rajkot and Jamnagar have also suffered damage to major structures, infrastructure and industrial facilities. Ahmedabad the capital was also severely affected. Gujarat Earthquake is very significant from the point of view of earthquake disaster mitigation in India. The problems observed in this disaster are no different from other major recent earthquakes in the world.

Earthquakes in Odisha

Odisha has also experienced a number of earthquakes in the past. But however, those have not created any kind of major devastation.  The districts which have experienced the occurrence the largest number of earthquakes during last fourty years are Sundargarh, Angul, Gajapati and Koraput. Other districts where earthquakes occurred are Jharsuguda, Cuttack, Balasore and Kalahandi.  The districts close to the Mahanadi valley in the north and Vansadhara in the south are most vulnerable as evidenced from spatial distribution of the epicenters. The map showing the distribution of Earthquake epicenters in and around Odisha during the last fourty years are shown in the Odisha map given below.

Earthquake education and preparedness plans can help significantly reduce death and injury caused by earthquakes. People can take several preventative measures within their homes and at the office to reduce risk. Supports and bracing for shelves reduce the likelihood of items falling and potentially causing harm. Maintaining an earthquake survival kit at home and at the office is also an important part of being prepared. At home, earthquake preparedness includes maintaining an earthquake kit and making sure that the house is structurally stable. During an earthquake, people indoors should protect themselves from falling objects and flying glass by taking refuge under a heavy table.

After an earthquake, people should move outside of buildings, assemble in open spaces, and prepare themselves for aftershocks. They should also listen for emergency bulletins on the radio, stay out of severely damaged buildings, and avoid coastal areas and shores to prevent from the tidal surges and tsunami.

* Dr. G. K. Panda is Professtor of Geography, Utkal University, Bhubaneswar