Search the Internet          Tips

Bombay, parts of Maharashtra prone to moderate quakes

Is the country's commercial capital, Bombay, safe from earthquakes?

This is the question being asked by residents of the metropolis following the Republic Day earthquake that devastated several parts of Gujarat.

The Republic Day earthquake measured 5.1 on the Richter Scale in Bombay. And since then the city has experienced 108 aftershocks.

The risk assessment and vulnerability analysis in Maharashtra following the Latur-Osmanabad earthquake of September 30, 1993, had classified Bombay as a district of maximum risk.

The 11 other districts of Maharashtra that face maximum risk are Thane, which is adjoining Bombay, Latur, Beed, Parbhani, Nanded, Nagpur, Nasik, Satara, Pune, Sangli and Ratnagiri.

The background paper prepared by the Maharashtra Disaster Management Plan says Bombay's vulnerability is high. The impact of a major earthquake could be devastating as the city is an important business centre.

While most of the skyscrapers in the city are claimed to be earthquake-resistant, they may not escape damage in a massive earthquake like the one at Bhuj.

Hence the comprehensive disaster management plan, which is one of the best in the country, at least on paper, aims to educate people about the do's and don'ts in a crisis.

The Latur earthquake measuring 6.4 on the Richter Scale (with its epicentre at Killari) and the December 11, 1967, earthquake at Koyna measuring 6.3 prompted the Maharashtra government to come out with the plan and put a full-fledged system of disaster relief in place.

According to experts and geophysicists, Maharashtra occupies the central-western portion of peninsular India, technically an intra-plate continental area. Extensive research by various agencies has shown that the state is covered by Deccan traps -- a sequence of basalt flows formed over 65 million years ago. The area was thought to be seismically stable. But this belief was shattered by Koyna and Latur.

This led to a review of the region's seismic history and stability and as many as 12 districts were found to be quake-prone.

The tectonic stability of the Deccan plateau may appear to be inconsistent with this observed level of seismicity. But this apparent contradiction reflects the primitive knowledge of seismogenesis in a stable continental region and is the root of the problem of risk assessment of an earthquake, according to the paper on risk analysis prepared as part of the Maharashtra Emergency Earthquake Rehabilitation Programme of the MDMP.

According to the research paper, Maharashtra and its adjoining regions are prone to earthquakes of moderate magnitude, as can be seen from the experience of several years.

Koyna experiences the most number of tremors. During the 35 years from 1963 through 1997, records indicate that the region has faced 102,715 tremors, of which 79 were of magnitude four or more on the Richter Scale and seven were above five. Even last year, in March, there was an earthquake in the region which was measured at over 5 on the Richter Scale.

Apart from the Koyna region and Killari, Khardi (Bhatsa) and Medhi (Surya) have also been hit by tremors. The Deuskar Committee of 1995, which had studied the pattern of seismicity in Maharashtra, has shown a major alignment along the West Coast in the Western Ghats region.

Seismic activity can be seen near Ratnagiri as well. The north-south trend continues further into Gujarat. The striking characteristic of this narrow region is its alignment with the hot-spring belt. It appears that the off-coast activity is associated with submerged faults along the western coast of Maharashtra.

In north Maharashtra, the seismic activity near Dhule, Akola, Jalgaon and Amrawati could be due to the movements in the faults present in the area associated with the complex systems of the Narmada-Tapi and Purna lineaments.

In the northeast corner of Maharashtra, seismic activity in Nagpur and Bhandara districts may be associated with the Deolapur thrust or sheared and faulted zones of Ramtek and Sakoli basins.

Isolated activity has also been witnessed near Beed, Nanded, Ujjani and Solapur in eastern Maharashtra.

The West Coast-Western Ghat seismogenic region is the most active area in Maharashtra. The Koyna-Warna and Bhatsa areas are located in this region.

Earthquake risk assessment is the most difficult in Maharashtra because of the lack of seismic instrumentation in large parts of the state. In view of the increased seismic activity, the need for more seismic instrumentation and research in this field has been stressed.

Dr V Subramanian, retired professor of earth sciences at the Indian Institute of Technology, Bombay, who was appointed by the state government after the Latur quake to study the occurrence of earthquakes in Maharashtra, has pointed out several fault zones.

The Indian Institute of Geomagnetism in Bombay and the Bhabha Atomic Research Centre have also made references to several seismic faults in and around the metropolis.

According to a study, three major faults pass through Thane creek, Panvel creek and the Amba river or Dharamtar creek. Other faults lie in the Ulhas river, Manori creek, Malad creek and the three lakes -- Powai, Vihar and Tulsi. Another fault stretches northward of Colaba, touching Malabar Hill.

UNI

The Complete Coverage | List of earthquake sites

Back to top

Tell us what you think of this report