koyna-sea floor
Quakes in Koyna is because of sea-floor spreading: Expert
MUMBAI, Sept 6/2000: The sea floor in the Arabian Sea is expanding by five cm a year leading to increasing seismic activity in the Koyna region of western Maharashtra which has seen more than a lakh tremors in the past 35 years.
According to a leading seismologist, the Koyna region is prone to the effects of sea-floor expansion along the carsburg ridge in the arabian sea-Indian ocean.
Dr J G Negi, scientist-Emeritus at the Hyderabad-based National Geological Research Institute (NGRI) says "the energy emanating from the sea-floor spreading is distributed to the rift zones in the Koyna-Warna region and the Himalayan area".
The region was hit by an earthquake measuring more than five cm on the richter scale yesterday. The first major earthquake in the region was on December 11, 1967, which claimed more than 100 lives and rendered several thousands homeless.
"There is a cyclic burst of seismic activity in the region," says Dr Negi referring to the frequency of earthquakes in the region. "Because of fault zones in the region this has become a highly seismic place."
During the past 35 years, the Koyna region was hit by 1,02,715 tremors, of which about 80 had an intensity of more than four cm and ten of them above five cm. This makes the western ghats the most seismogenic region of the state.
Yesterday’s quake is a clear indication of the rising seismic activity in the region, says Dr Negi, a recepient of the coveted Shantiswaroop Bhatnagar Award for excellence in science. The state capital, Mumbai is merely 250 kms away from this seismic zone.
According to experts and geophysicists, Maharashtra occupies the central-western portion of peninsular India, technically an intraplate continental area. Research carried out by various agencies reveal that most of the state is covered by deccan traps —as sequence of basalt flows formed 65 million years ago.
Though the area was earlier known to be seismically stable, it was shattered by the frequent earthquakes and the worst-ever Latur earthquake of September 30, 1993. This led to the review of seismic history which found that more that 12 districts are earthquake prone.
Thus, tectonic stability in the Deccan plateau may appear to be inconsistent with observed level of seismicity — this apparent contradiction reflects the primitive knowledge of seismogenesis in stable continental region and is at the root of problem of risk assessment of an earthquake, according to a paper on risk analysis prepared as part of the maharashtra earthquake rehabilitation programme under the Maharashtra disaster management plan.
In 1973, Dr Negi along with Dr M Krishnabrahmam carried out a study and concluded increase in seismic and geo-thermal activities in the region. An alarming factor found out during the study was the proximity of several dams to the epicentre.
The Deouskar Committee report of 1995, which studied the pattern of seismicity in the state said that the earthquakes in Maharashtra show a minor alignment along the west coast of western ghat region.
Seismic activity has also been noticed near Ratnagiri, Bhatsa and the Surya areas of Thane district as well as Mumbai.
The striking characteristic of this narrow region is its alignment with the hot-spring belt. "It appears that off coast activity is associated with submerged faults along the western coast of Maharashtra," the report had said.
This report and the observations made by Dr Negi matches that the frequent earthquakes in the region is because of sea-floor spreading, making further studies essential. (UNI)
MUMBAI, Sept 6/2000: The sea floor in the Arabian Sea is expanding by five cm a year leading to increasing seismic activity in the Koyna region of western Maharashtra which has seen more than a lakh tremors in the past 35 years.
According to a leading seismologist, the Koyna region is prone to the effects of sea-floor expansion along the carsburg ridge in the arabian sea-Indian ocean.
Dr J G Negi, scientist-Emeritus at the Hyderabad-based National Geological Research Institute (NGRI) says "the energy emanating from the sea-floor spreading is distributed to the rift zones in the Koyna-Warna region and the Himalayan area".
The region was hit by an earthquake measuring more than five cm on the richter scale yesterday. The first major earthquake in the region was on December 11, 1967, which claimed more than 100 lives and rendered several thousands homeless.
"There is a cyclic burst of seismic activity in the region," says Dr Negi referring to the frequency of earthquakes in the region. "Because of fault zones in the region this has become a highly seismic place."
During the past 35 years, the Koyna region was hit by 1,02,715 tremors, of which about 80 had an intensity of more than four cm and ten of them above five cm. This makes the western ghats the most seismogenic region of the state.
Yesterday’s quake is a clear indication of the rising seismic activity in the region, says Dr Negi, a recepient of the coveted Shantiswaroop Bhatnagar Award for excellence in science. The state capital, Mumbai is merely 250 kms away from this seismic zone.
According to experts and geophysicists, Maharashtra occupies the central-western portion of peninsular India, technically an intraplate continental area. Research carried out by various agencies reveal that most of the state is covered by deccan traps —as sequence of basalt flows formed 65 million years ago.
Though the area was earlier known to be seismically stable, it was shattered by the frequent earthquakes and the worst-ever Latur earthquake of September 30, 1993. This led to the review of seismic history which found that more that 12 districts are earthquake prone.
Thus, tectonic stability in the Deccan plateau may appear to be inconsistent with observed level of seismicity — this apparent contradiction reflects the primitive knowledge of seismogenesis in stable continental region and is at the root of problem of risk assessment of an earthquake, according to a paper on risk analysis prepared as part of the maharashtra earthquake rehabilitation programme under the Maharashtra disaster management plan.
In 1973, Dr Negi along with Dr M Krishnabrahmam carried out a study and concluded increase in seismic and geo-thermal activities in the region. An alarming factor found out during the study was the proximity of several dams to the epicentre.
The Deouskar Committee report of 1995, which studied the pattern of seismicity in the state said that the earthquakes in Maharashtra show a minor alignment along the west coast of western ghat region.
Seismic activity has also been noticed near Ratnagiri, Bhatsa and the Surya areas of Thane district as well as Mumbai.
The striking characteristic of this narrow region is its alignment with the hot-spring belt. "It appears that off coast activity is associated with submerged faults along the western coast of Maharashtra," the report had said.
This report and the observations made by Dr Negi matches that the frequent earthquakes in the region is because of sea-floor spreading, making further studies essential. (UNI)
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