Essay: Earthquake forecasting

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  • Earthquake forecasting
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The Indian subcontinent situated on the boundaries of two continental plates is very prone to earthquakes. All five SAARC nations India, Pakistan, Nepal, Bhutan, Bangladesh who have the himalayan range as their boundary or are in close proximity to it, have a long history of seismic tremors. In Maldives and Srilanka there is no record of any disastrous earthquakes though some incidents of seismic activity have been noted in the records of the former’s National Centre for Historical and Linguistic Research. However, these two countries are generally considered earthquake free.

Massive earthquakes generally occur near the junction of two crustal plates. For example along the Himalayan range where the Indian plate goes below the Eurasian plate. This is the commonest form of earthquakes known as tectonic earthquakes. The other forms being volcanic earthquakes, impact earthquakes (due to the impact of meteorites), reservoir induced earthquakes and collapse earthquakes. Some of these have also been found in the SAARC region.

Earthquakes are responsible for the loss of about 50,000 lives every year in the world. Loss of property in a single earthquake is some times enough to upset a whole national economy. The intensity of an earthquake is measured on a 10 point scale originally defined by Richter in 1958. Earthquakes over 5.5 are progressively damaging to property and human life.

Pakistan occasionally falls victim to earthquakes. Quetta city was completely destroyed by an earthquake in 1935 and 30,000 persons were killed. The epicentre of the earthquake was very near Quetta and its intensity was 7.2 on the Richter scale. As regards the history of earthquakes in the country no reliable information about their (occurrence before 1933 is available. The only historical evidence is about Debal city that was destroyed in an earthquake in 893

A.D. Sayuti in Tehrikh-e-Khulfa has given complete details of the calamity. Another tremor which caused extensive fuanges in the land surface took place in the Rann of Kutch in 1819. During 1845-1861, not less than seven shocks of low intensity were recorded in the Karachi region. In 1931, parts of Baluchistan and Sindh experienced a shock of the magnitude of 8.3 on the Richter scale which lasted for about 30 seconds. The Makran earthquake of 1945 also caused widespread damage. During I955-1970, shocks of varied intensity were recorded in different parts of the Pakistan.

The recent 191 earthquake which ravaged the northern parts of the North West Frontier Province (NWFP) was less disastrous than the 1973 Besham earthquake which claimed 5,000lives in Kohistan district. Though the intensity of Besham earthquake was only 5.6 on the Richter scale as compared to 6.8 of the 199L earthquake, the damages and casualties was far less.

The cause of large-scale destruction on 1973 was because the area of Besham is rocky and mountainous and because jolts are usually more intense in mountainous regions as compared to the plains.ln 1973, many villages and houses in Besham were ranged to the ground as big rocks rolled down from the nearby mountains and landslides destroyed the villages.

Approximately 10,000 earthquakes have been accurately recorded within a 400 sq k- by 500 sq km area in northern Pakistan. The data collected by Water and Power Development Authority and Pakistan Atomic Energy Commission include earthquakes of magnitudes 6 to 2. They reflect the high seismicity of the region which includes the north western of the Indian plate, the Salt range, Potwar plateau” Hazara range, Peshawar basin and the lower and higher ranges of Indus Kohistan. Seismic activity in the Hazara range is between moderate to high and earthquakes here have caused offensive damage.

The Salt range has no known history of moderate or large earthquakes but, at low levels, the entire salt range is active especially along the long transverse fault. The other regions of major seismic activity in Pakistan are the Mir-Karakoram region, the Gardez, Kumar and Safed Koh fault zones, the Chaman fault zone, the Ornach-Nal fault zone, the Sulaitan range, the Quetta transverse zone, the northern and southern Kirthar ranges, the coaptal region southeast of Karachi” the Murray Ridge, the Makran region and the Indus basin.

According to the Meteorological Upper Atmosphere Research Station in Peshawar, 100,(m earthquakes of low and high intensity occur every year in the Hindukush area. The Hindukush range is about 1,613 km miles long and about 323 km wide running northeast to’ southeast. The range through Pakistan before entering Afghanistan and fragmenting into minor ranges. These ranges are the main source of earthquakes that jolt the NWFP and other parts of Pakistan at regular intervals. During the recent earthquake, Malakand Agency and Division, which are very close to the Hindukush mountains, suffered heavy losses as compared to other parts of the country.

India has also not escaped major earthquakes though accurate figures are not available about monetary loss caused by these earthquakes. India has been divided into five seismic zones according to the maximum intensity of earthquakes expected. Of these, Zone V is seismically the most active, while Zone I is the least active. Tnney comprises the whole of northeast India the northern portion of Bihar adjoining Nepal, west Uttar Pradesh hills, Hinachal Pradesh around Mandi, Rann of Kutch and Andaman and Nicobar Islands. Tnney includes Himachal Pradesh” Delhi, parts of Punjab, Uttar Pradesh and Bihar, Sikkim and adjoining West Bengat a small portion near Calcutt4 Maharashtra near Kolma (south of Bombay), and a part of Gujarat. Znnell comprises ls6eining portions of Punjab and a small part of Rajasthan,

Uttar Pradesh, Madhya Pradesh,Bihar and adjoining West Bengal, Gujarat and Maharashtra and a small portion parallel to the west coast of peninsular India, a very small portion of Karnataka and Andhra Pradesh, and lakshadweep. Tnne II includes Tamil Nadu, parts of Karnataka, Andhra Pradesh, parts of Maharashtra, Rajasthan,

Uttar Pradesh, Madhya Pradesh, Bihar, Orissa and West Bengal. Tnne I comprises parts of Karnataka.

Andhra Pradesh, Maharashtra, Orissa, Rajasthan, Madhya Pradesh and Uttar Pradesh.

Nepal lying on the southern slopes of the Himalaya is subject to high seismic activity. A chronology of earthquakes

Of magnitudes six and above on the Richter scale indicates that beween 1800 and 1975, 23 major earthquakes have occurred in Nepal. Earthquakes of lower intensity occur frequently especially during the rainy season.

Observations suggest that large earthquakes occur about once in 50 years. There have been three major earthquakes in the last 55 years. The 1934 earthquake which affected Bihar and Nepal destroyed 3,400 lives in Kathmandu valley alone. In 1980, the area of Bajhang in western Nepal was struck by a powerful earthquake in which many people died, and considerable property was lost. On August 21,1984, an earthquake of magnitude 6.6 on the Richter scale, with its epicentre at Udaipur in eastern Nepal, killed 7000 people and destroyed several thousand houses.

The principal fault lines in the Nepal Himalaya are the transverse Main Central Thrust and the Main Boundary.

Thrust however, aside from these there are many longitudinal faults which divide the Himalaya into “blocks” from east to west. The epicentre of major earthquakes are often located along these fault lines. Most of the earthquakes between 1964 and 1986 have been clustered in western Nepal.

Bhutan in the northeastern part of the Himalayan belt has a high seismicity rate. Earthquakes of magnitude 7 to 7.5 on the Richter scale have been recorded in the country. Areas adjoining Bhutan have experienced earthquakes more than 8. The seismic zoning map prepared by the Indian Standards Institution does not cover Bhutan but from the study of the seismic zoning
map of adjoining areas, the entire country can be taken to be within seismic zone V corresponding to the highest seismic zone of India.

Bhutan, however has not been hit by any major earthquake in the past. The most recent earthquake which affected the country in August 1988 caused only minor crack on the Tashigang Dzong. In view of the fact that the past few earthquakes which hit the country had not been major ones and had caused only slight damages to structures, earthquake disaster management has not been a priority for the government. No infrastructure specifically charged with earthquake management has been set up. Nevertheless, the government enforces strict building specifications which take into account the seismicity of the country.

Bangladesh, particularly the northeastern region, has in the past experienced earthquakes of moderate to high intensity. The great earthquake of 189, which had its epicentre in the Shillong plateau of India caused widespread damage. Two other major earthquakes, the Bengal earthquake of 1885 and Srimangal earthquake of 1918, caused severe damages in limited areas surrounding their epicentres.

Bangladesh on the eastern flank of the Himalayan foothills has been divided into four seismic zones. The north and northeastern part including Sylhet, Mymensingb and Rangpur towns are in Zone 1, which is the most active zone of the country. Dinajpur, Bogrc, Dhaka, Comilla and Chittagong Hill Tracts fall in Zone 2, where the shocks are moderate. Rajshahi, Pabna” Faridpur, Noakhali, Chittagong and Co:Cs Bazar, where minor shocks occur, are in Tnne 3. The southwestern part of Bangladesh, including Jessore, Khura, Barisal and Patuakhali, fall in Zone 4 where negligible shocks are observed.

When earthquakes occur major disasters take place. Buildings can collapse. Floods may occur due to collapse of dams and protective works on rivers, avalanches and landslides take place tidal waves on coastal belts can occur hazardous substances and gases can be released and essential services like water supply, electricity, sewage systems, communication lines, be disrupted. The major factor contributing to both economic and human loss is the collapse of buildings during earthquakes.

Earthquake forecasting is a relatively complex task. It aims at forecasting location, time and magnitude of an impending earthquake. A network of 56 seismographic stations has been set up in India and more are being planned under the jurisdiction or coordination of the India Meteorological Department (IMD) which measures daily seismic activity parameters, namely, velocity of primary and secondary waves and micro-earthquakes over the point where the instrument is set. Apart from these parameters, various other ground parameters are also taken into account for prediction purposes like crustal deformation, change in seismic wave velocity due to stresses in rocks.Large decrease in magnetic susceptibility of rocks just before earthquakes and change in electrical resistivity of rocks.

Sea level changes have been noticed prior to the occurrence of an earthquake and so has unusual behaviour of certain animals, particularly fishes and mammals. Dogs have been seen howling and chimpanzees have been seen to spend their nights on the ground rather than on trees a few days before the occurrence of an earthquake. The behaviour of these animals can probably be monitored for a rough estimate of the onset of an earthquake. These parameters are empirical and no constant factor has been found to predict accurately the occurrence of earthquakes.

Although no definite research finding is available on the most suitable engineering structure of buildings situated in active seismic zones the Government of India has issued guidelines regarding construction of buildings and other engineering structures for the states situated in seismic zones IV and V.

The salient points of these recommendations are that buildings and structures in earthquake zones should be strengthened and retrofitted against future earthquakes. For this purpose, appropriate technical guidance will be provided by the Earthquake Research Centre of the Roorkee University and by the Department of Agriculture and Cooperation. Rural buildings and structural designs should be built al p€r the existing rural housing scheme in Tnne V.

The Housing and Urban Development Corporation has been asked help in the evaluation of suitable designs. In north Bihar, special cells are to be created in Darbhanga, Madhubani, Monghyr and other districts to coordinate work on strengthening of building.An institute for the study of seismic phenomena in northeastern states is to be set up and the engineering departments of these states are being encouraged to develop earthquake resistant designs. Municipal by laws for building construction for cities in zones IV and V are being suitably arnended to incorporate earthquake resistant construction features.

A seismic code which is meant to outline the steps necessary in the event of earthquakes so as to minimise damage to life and property is to be drawn up. The basic responsibility for undertaking relief and rescue operations is of the state government. In case of a severe disaster, the Union Government provides financial and material support.

The Department of Agriculture and Cooperation is the nodal department. The relief commissioner functions as the nodal officer, who liaises with ministries and departments through the Crisis Management Group (CMG). The relief commissioner is responsible for sending central teems to the affected states for assessing damage. In the states, the state relief commissioner or in his absence, the secretary, revenue department is the nodal point for rescue and relief operations. In serious cases, the state government may also form a group of cabinet ministers to oversees relief and rescue operations.

However, it is at the district level that all relief and rescue operations are actually implemented. The district collector is overall in charge of relief and operations who is assisted by revenue officers as well as other departments and agencies at the district level. Every district is responsible for drawing up a district contingency plan for timely action in case of earthquakes, in seismically active zones. The contingency plan involves three types of actions preparedness, actual relief and rescue operations and rehabilitation. The preparedness phase involves coordination with IMD seismological observatories stations and All India Radio and Doordarshan for advance warning whenever possible.

Evacuation centres with strongly built structures are earned for people in areas likely to affected by earthquakes. However, in most cases, relief and rescue organisations have no prior intimation about impending earthquakes.

The stress therefore is on actual relief and rescue operations, evacuation of people trapped in debris, establishment of alternate mens of mobile communications and construction of temporary bridges, culverts, provision of medical facilities, supply of food and other nutritional requirements.

Voluntary and charitable organisations also help in these operations. Rehabilitation of affected people is a time consuming press and involves strenuous rebuilding of the collapsed structures restoration of communications, provision of cash relief to the affected people, employment generation & and restoration of the ecosystem etc.

In Nepal, the seismological centre of the Department of Mines and Geology operates a network of five seismic stations clustered in the central development region. However, a network of 15 to 20 stations are required to accurately record quakes of lower intensity. Extensive time series data is indispensable for seismic zoning and for preparing vulnerability profiles.

According to a study of the consequences of earthquakes in Nepal the August 1,1988 (Udayapur) earthquake’ which was of a moderate category left 663 in
jured, of which 168 were serious. A total of 63,003 buildings were damaged, of which 21,832 were totally destroyed. A total of 1,483 heads of cattle were killed. The study pointed out that damage to ordinary buildings and structures were far more than to RCC structures which appeared to have withstood the shocks more effectively. Ground fissuring was prominent Iandslides in the Churia and Mahabharath Range affected an area of 0.62 million hectare. These had serious consequences for the stability of irrigation canals, and roads and trails.

In some portions of the Terai region, the earthquake caused liquefaction in subsurface ground layers and sand boils. This extensive damage caused by a relatively mild earthquake indicates an overall lack of preparedness for facing such existencies.

The Earthquake affected areas reconstruction and rehabilitation project (EAARRP) was launched after the earthquake of 1988. The Department of Housing and typical planning initiated a programme of rehabilitation which will also introduce fuenges in the design sf buildings and other infrastructures. However, the implementation of the programme has been obstructed by financial constraints. Under the Natural Calamities Relief Act of 1982 and the Soil and Watershed Conservation Act, eight long term plans and a Natural Calamities Assistance Fund have been established.

Considerable financial and technical aid has been received from external donor agencies. The major focus of the assistance has been on rehabilitation and reconstruction. Several donors have also been involved in integrated sectoral programs and income generation activities in the affected areas. UNDP has initiated a long term technical programme to formulate a national building code and to introduce improved building materials and construction techniques.

The agency is also aiding Nepal in enhancing its level of preparedness. One outcome of this assistance is going to be a national housing strategy. In Pakistan, identification of seismic zones is done by the Geological Survey of Pakistan. The GSP regularly undertakes survey and research to monitor changes in earthquake prone areas. In 1976, the Geological Survey of Pakistan and the National Science Foundation of USA, started the Geodpamics of Pakistan Project which has provided Pakistani earth scientists with an opportunity to expand their knowledge about the geodynamics of their land.

The project has led to a better understanding of the geodynamics of Baluchistan.

Building codes prepared by the Environment and Urban Affairs Division provide specifications for the design of earthquake resistant buildings. The building regulations formulated by urban development authorities are specific and safety measures are ensured in every building. There are special rules for high rise buildings. In rural areas however these specifications are rarely followed.

The government’s emphasis is on connecting far-flung areas with the national road network and modern communication systems. Relief work is often delayed because of the absence of a road and communication link with affected areas. Access to remote areas during heavy snowfall or bad weather becomes impossible.

Establishment of base camps in above areas for relief operation is an important work done by the government. No arrangements have so far been made for fire outbreaks. In urban areas, municipalities have arrangements for fire fighting. But in the remote mountain settlements where earthquakes cause devastating damage, evacuation, relief work, fire fighting and rehabilitation is done with the help of armed forces. Emergency plans are prepared both by provincial and local authorities.

Evacuation centres are established and with the help and assistance of other departments and agencies, supply of food and water and arrangements for prevention of epidemics are made. The armed forces play a crucial role in all these arrangements in pakistan.

On December 2, 1994, an earthquake of magnitude 6.0 occurred in the remote and barely accessible region of swat and Indus Kohistan, south of Hindukush and Karakoram range of mountains. Several thousand people died and some 60,000 to 100,000 were affected. The Karaftoran highway which was at that time under construction and renovation was very badly damaged and was unusable throughout most of the relief operation. Helicopters were used to Pattan, where a hospital camp was established even though the village was very badly damaged.

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