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Bombay, Pune, Nashik faces maximum earthquake risk: study

Bombay, Latur, Beed, Parbhani, Nanded, Nagpur, Nashik, Satara, Pune, Sangli and Ratnagiri have been identified as districts of maximum earthquake risk in the state as per the Maharashtra Disaster Management Plan.

The low intensity earthquake of the order of 3.6 on the Richter scale that rocked Bombay on May 30 shows the city does not lie in a no-earthquake zone. The earthquake was also felt at the Thane-Khargar belt, 35 kms north of the Colaba observatory, where the seismic activity was recorded.

Additional Chief Secretary (Home) K C Shrivastava, speaking at the three-day international workshop on disaster management plan for the state today, said several areas in the state are earthquake-prone. In the absence of a proper disaster management plan the damage to the society and mankind would be enormous.

According to a retired Indian Institute of Technology professor V Subramaniam, the city and its surrounding region is situated on more than ten fault planes. Three faults pass through the Thane creek, Panvel creek and Amba river or the Dharamtar creek. These three faults meet at a triple junction at Uran. An earthquake has rocked this place on April 23, 1996, causing cracks in some structures.

Prof Subramaniam, project advisor to a state government-funded programme, is working with geophysicists of the Indian Institute of Geomagnetism and seismologists at the Bhabha Atomic Research Centre. He is engaged in identifying earthquake-prone areas of Maharashtra.

Additional Municipal Commissioner Ratnakar Gaikwad pointed out that a disaster could compound problems in Bombay since it has numerous high rise buildings and over 19,000 old and dilapidated buildings. A macro- and micro-plan was needed to tackle such situations, he said.

A paper, on risk analysis, presented at the conference states that Maharashtra occupies the central-western portion of peninsular India, technically an intraplate continental area. Most of the state is occupied by the "Deccan traps", a sequence of basalt flows formed about 65 million years ago.

Though this area was known to be seismically stable with little chance of disastrous earthquakes, this belief was shattered by the Koyna earthquake of December 11, 1967, with a magnitude of 6.5 on the Richter scale. The recent Latur earthquake of September 30, 1993 having a magnitude of 6.4 on the Richter scale. It occurred on the central part of the shield, leading to a review of seismic activity in a stable-shield zone.

Maharashtra and the adjoining regions are prone to earthquakes of moderate magnitude as can be seen from the experience of several years. The Koyna region experiences the maximum number of tremors in the state. During the 35 years between 1963 and 1998, the Koyna region has endured 102,715 tremors, of which 79 registered above four on the Richter scale. Seven rose above five on the Richter scale. Excluding the Koyna region, and other regions of Killari, Khardi (Bhatsa) and Medhi (Surya), there has been 137 tremors up to 1996, the paper stated.

The Deouskar committee, which carried out a study on seismic plates and pattern of seismicity in Maharashtra, reported that earthquakes in the state are more along the west coast and the Western ghats. Seismic activity was also reported near Ratnagiri.

In north Maharashtra, the seismic activity near Dhule, Akola, Jalgaon and Amravati was due to the movements on faults present in the area associated with the complex Narmada-Tapi and Purna system. In the north-east corner of Maharashtra, earthquake activity in Nagpur and Bhandara districts may be associated with the Deolapar thrust or the sheared and faulted zones of the Ramtek and Sakoli regions.

Isolated activity is also seen near Beed, Nanded, Ujjani and Solapur in the eastern part of the state and Uran, Kolhapur and Sindhudurg in south-west Maharashtra. The Latur-Osmanabad region is already known for seismic activity, the committee study pointed out.

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