Post News Network
Bhubaneswar, Oct 2: A part of Dhenkanal district was rocked by mild tremors over the last five days, spreading panic among the people though the tremors measured only 2 to 3 on Richter scale.
People have been living in fear of being struck by earthquakes of bigger magnitude with the district experiencing tremors more than eight times in the last five days.
The entire coastal Orissa and other parts were shaken by an earthquake that had its epicenter in Nepal April 15, 2014. Various parts of the state including Cuttack and Bhubaneswar felt a series of mild tremors May 21. It was then learnt that the earthquake had its epicenter in the Bay of Bengal, 320 km away from Bhubaneswar.
The country has been split into four seismic zones: Zone-2 (which can experience tremors measuring 6 on Richter scale); Zone-3(7 on Richter scale); Zone-4 (8 on Richter scale) and Zone-5 (more than 9 on Richter scale).
According to geologists, the southern part of the state, Keonjhar and Mayurbhanj come under Zone-2 while areas from Chilika to Bhitarkanika; Jharsuguda, Sundargarh, Bhubaneswar, Cuttack, Sambalpur, Hirakud, Dhenkanal and Balasore fall under Zone-3. However, the state has no areas coming under the high seismic zone.
The areas lying under Zone-3 are likely to have extensive destruction if earthquakes happen. As a matter of fact, the state has so far not experienced bigger earthquakes. Only mild tremors have been felt till date with negligible damage. However, the possibility of the state suffering a major earthquake cannot be ruled out. Geologists and seismologists are of the view that quakes originating in the Bay of Bengal may have ripple impact on the state.
Nabakrushna Mishra, joint director of geological survey office under the steel and mines department at Mahisapat in Dhenkanal, said as the district comes under Zone-3 it is likely to experience tremors having magnitude of 3 to 5 on Richter scale. Chances of the district being rocked by tremors are high as coal is being extracted extensively in Talcher in neighbouring Angul while adequate fillings are not being carried out in vacuums, Mishra said. Besides, other mining and stone quarrying activities are taking place in the district.
Moreover, the existence of rivers Brahmani and Mahanadi has also put the district in the weak zone, he said adding people have to remain alert about earthquakes.
Forecasting quakes not possible yet
Predicting the time of an earthquake and its location has not been made possible as yet. Scientists have not achieved any major breakthrough on earthquake prediction despite years of research on seismological activities. However, alertness about a quake can minimise the damage to some extent.
Causes of earthquake
Earthquakes are vibrations caused by tectonic plates breaking under stress. The underground surface along which the plates break and move is called a fault plane.
Earthquakes are usually caused by movements along the faults as a result of compression in the earth’s crust.
According to geologists, the earth’s surface is formed by six big and 14 small tectonic plates. Sometimes, such plates collide with each other during movement, creating intensive vibrations.
To measure the magnitude of the earthquake, American geologist Charles Francis Richter developed the Richter scale in 1935. The size or magnitude of earthquakes is determined by measuring the amplitude of the seismic waves recorded on a seismograph and the distance of the seismograph from the epicenter of the earthquake.
These are put into a formula which converts them to a magnitude, which is a measure of the energy released
by the earthquake. For every unit increase in magnitude, there is roughly a thirty-fold increase in the energy released. A 8.6 magnitude earthquake releases energy equivalent to about 10, 000 atomic bombs of the type used in World War II. Fortunately, smaller earthquakes occur much more frequently than larger ones.
