Some lessons from 1900

Print edition : September 15, 2001

THE earthquake of January 26, 2001 caused unprecedented damage in Gujarat. The neighbouring State of Rajasthan and the Sind province in Pakistan were also affected badly. The tragic seismic contingency has had another fallout. It instilled seismic awareness in the people and in the administrators. This is evident from actions taken by various State governments and other agencies for disaster management.

The Assam government has plans to establish a disaster mitigation cell. The Punjab and Himachal Pradesh governments have issued orders that seek to ensure that any new civil construction is carried out in accordance with the recommendations of the Bureau of Indian Standards. States like Uttaranchal are drawing up plans for disaster mitigation. The Disaster Mitigation Institute in Bhopal, which could not do any remarkable work when an earthquake rocked Jabalpur in May 1997, is preparing itself to face any such eventuality in the future. Parliament has appointed a committee to study issues related to disaster management, under the chairmanship of Sharad Pawar, who as the Chief Minister of Maharashtra did excellent work in disaster mitigation after the Latur earthquake in 1993.

Most disaster management plans concentrate on the post-disaster situation, which principally involves the three basic operations of rescue, evacuation and rehabilitation. Logically, any disaster mitigation plan must comprise measures that have to be taken before, during and after a disaster. Unfortunately, the first two stages are either given marginal importance or totally forgotten. This was clear from the experiences at Latur and Bhuj. The governments of Gujarat and Maharashtra have spent about Rs.2,000 crores each on rehabilitation during the post-seismic period. But they do not seem to have thought of establishing institutes to do research on earthquakes or disaster mitigation in the affected areas or in other locations. Establishing such an institute would cost hardly Rs.5 crores, which could have been easily set aside from the funds they received in the form of aid.

Until 1967, most of the engineers and scientists in the country were under the impression that peninsular India was free from seismic activity. But the earthquakes at Koyna (1967) and Latur (1993) changed their perception. Tamil Nadu is thought to be mostly free from seismic activity. But an earthquake rocked Coimbatore as far back as 1900. A study of the earthquake will help in understanding its nature and drawing lessons that would be of help in the event of its recurrence.

An earthquake of a moderate magnitude (6 on the Richter Scale) occurred near Coimbatore at 3-11 a.m. (Indian Standard Time) on February 8, 1900. Its maximum intensity was VII on the Modified Mercalli Intensity Scale. It caused the largest extent of damage at two locations - Coimbatore and Coonoor - and its impact was felt in the areas that lie between Udipi in the north and Thiruvananthapuram in the south and Kozhikode, Bangalore, Chennai, Nagapattinam and Madurai in the east-west direction. The epicentre of the earthquake was located at 10 45' North Latitude and at 76 45' East Longitude.

At Coimbatore (Intensity VII), several buildings were seriously damaged. Roof tiles collapsed. The jail building suffered the most. A Roman Catholic chapel near the railway station gave in. A boy who was trapped in a collapsed mud house was rescued. At Coonoor (Intensity VII), the railway refreshment room and the Commissioner's bungalow developed cracks. The Nilgiri Railway (Intensity VII) suffered losses owing to the fall of boulders on the track. The shock was felt at Kuppam (Intensity VI) and Perundurai (Intensity VI). Records from Mysore (Intensity VI) say that resting cattle stood up. The roof tiles of most houses were damaged and walls developed cracks.

A statistical analysis indicates that such seismological events might recur in 100 years, plus or minus about 30 years. Although such statistical forecasts are probabilistic and somewhat grotesque, they give a reasonable idea about the seismogenic potential of the region. It could be said that seismic activity in this region has been on the rise for the past 15 years. There were two earthquakes, each with a magnitude of around 5.0 on the Richter Scale, in Idukki and Coimbatore districts on the Kerala-Tamil Nadu border in December 2000 and January 2001 respectively. It could be said that seismic activity began sometime in 1988 when the Idukki area was shaken by an earthquake of a magnitude of 4.8 on the Richter Scale. Incidentally, the Idukki dam happens to be located in this seismically vulnerable area. The dam area has a seismic network.

Modern seismological instruments record earthquakes of a very low magnitude - up to -2.0 or so. As a result of the tremendous increase in their detection potential, they record thousands of seismic events of small magnitudes, known as micro-earthquakes or ultra-micro-earthquakes (of negative magnitudes of up to -3.0). Seismologically speaking, it is not correct to describe them as earthquakes. These are minor geological movements that occur routinely. However, activists have cited these data in support of their fight against the dam at Idukki. Actually, the construction in the 1960s of the Idukki dam and the reservoir has nothing to do with the seismic activity in the region.

The governments of Tamil Nadu and Kerala should use this historical information to protect the populations of the States from any seismic event in the future. Earthquakes do not kill people. It is the collapse of man-made structures that kills.

A two-point programme would help in mitigating the effects of seismic disasters. The first step is to measure geological and seismological parameters such as micro-earthquakes, the magnetic field, the gravity field, the sub-surface temperature and electrical resistivity. The second is to educate people about earthquakes. The Kerala Sastra Sahitya Parishad, which has done good work in popularising science, could undertake the work of creating seismic awareness. Government employees need to be trained in earthquake disaster mitigation. At present there is no disaster mitigation cell in Kerala. The one in Tamil Nadu concentrates on floods and cyclones.

A major feature of the earthquake of 1900 is that there was no casualty. This could be owing to the fact that most of the houses were made of thatch or had tiled roofs. Though present-day houses are built of better construction materials, they may prove to be more vulnerable because there is extensive use of glass, electrical fittings and instruments. The storage of cooking gas, petrol or diesel, which is inflammable, adds to the risk. A minor tilt may cause an electrical short circuit or a fire. Under such circumstances, most of the damage may be caused by the secondary effects of an earthquake, and not by the quake itself. There are records to show that secondary effects caused heavy damage during the Tokyo earthquake of 1923. The city was reduced to ashes by a fire that broke out after the earthquake.

Studies indicate that any seismic event in the Coimbatore region could reach a maximum magnitude of 5.5 to 5.75 on the Richter Scale. The attempt here is to awaken the people and the administration so that the people are trained and prepared to face any such eventuality. This is a probabilistic assessment, done with a view to increasing the people's preparedness.

Earthquakes are part of the dynamic movement of the earth. All the advancements in science and technology cannot prevent an earthquake. People should learn to live with this reality. Compared to other disasters, an earthquake lasts for the least duration and the possible response time is very low. Even if one gets only 10 seconds, one should come out of his or her house when an earthquake occurs.

The most important part of any disaster management plan is mitigation. An earthquake measuring 7.9 on the Richter Scale at Bhuj caused several thousand deaths. But an earthquake of a similar magnitude in Seattle in the U.S. did not result in a single death. India, with its large number of scientists and engineers, can make remarkable achievements in mitigation.

Arun Bapat is a research seismologist based in Pune.

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