People's Democracy

Tsunami Devastation

Raghu

THE toll of death and destruction caused by the tsunami waves on December 25 and 26, mostly in south and south-east Asia but also in far-off Indian ocean islands and even on the east African coast, continues to rise. As we go to press, more than 30,000 people are believed to have lost their lives, over 15,000 in Indonesia, 7500 in India, 5000 in Sri Lanka, 1500 in Thailand, many hundreds in Malaysia and the Maldives and several fatalities reported from Myanmar, Bangladesh, Mauritius, the Seychelles, Kenya and Somalia. The death toll is expected to climb further as search and rescue teams reach the more remote islands and other parts of Indonesia and the Andaman & Nicobar group of islands in India. In India, the worst hit areas have the Nicobar islands and vast stretches of coastal Tamil Nadu while some coastal areas in Andhra Pradesh and Orissa have also been affected. The human tragedy in all these countries and regions has been devastating and the coming days and weeks will reveal not only the extent of the havoc caused but also the need for relief and rehabilitation.

Whereas these aspects are clearly the most pressing, and call for immediate attention, this article attempts to explain the phenomena of tsunamis, examine possible measures for advance warning so as to minimise loss of life and damage to property, and look at disaster management in India in the light of past and present experience.

WHAT ARE TSUNAMIS’

Tsunamis or series of huge waves are caused by oceanic earthquakes and related volcanic eruptions, massive landslides in islands or other coastal landmass, meteorites striking the sea or by massive undersea explosions.  The term itself is of Japanese origin, literally meaning harbour waves because they strike along the coast, Japan being the most frequent victim of this natural phenomenon. Tsunamis are most common in the Pacific ocean which is the planet’s most earthquake-prone region rimmed by what is termed the “ring of fire” of active volcanoes.

In contrast, tsunamis are very rare in the Bay of Bengal and Indian Ocean regions. The present tsunamis were caused by the most massive earthquake in 40 years and among the four worst quakes in the previous century, registering 9.0 on the Richter scale, with its epicentre near the northern Indonesian island of Sumatra. Geologists believe that this megathrust, the highest grade of shift in the earth’s crust, was so large that the entire planet must have wobbled slightly in its orbit! Sumatra is located at a place where several of the planet’s tectonic plates (huge “sheets” of the earth’s solid crust or upper layer either on land or beneath the ocean floor) overlap and grind against each other, accumulating energy over several decades which is then released suddenly in the form of earthquakes. This particular deep-sea earthquake released energy equivalent to 1 million Hiroshima-size nuclear bombs and resulted in the massive tsunami waves. 

Not all earthquakes result in tsunamis nor can one deduce the possibility of a tsunami from the magnitude of a quake. Earthquakes also originate from different kinds of tectonic movement. For example, earthquakes along the famous San Andreas fault running north-south down California in the USA are caused by tectonic plates slip-striking against each other horizontally. On the other hand, the earthquake off Sumatra was caused by the Australian and Indian tectonic plates colliding almost head-on with each other and causing a massive vertical displacement relative to each other of over 60 feet. This seismic event took place under 9 km of ocean and along a fault over 1000 km long running north-south, so the sheer volume of water thrown up can be imagined. It is this kind of seismic phenomenon that typically results in a tsunami, in this case a series of massive waves travelling east-west.

A tsunami is a not a single wave but a series of waves, like the ordinary waves one sees on a beach. But unlike ordinary waves, which have relatively short wavelengths (distance between the crests of successive waves) of about 100 metres, tsunamis have wavelengths typically over 500 km and there could be as much as 2 hours’ gap between waves. Tsunamis travel across the deep sea at very high speeds of around 1000 kmph, the speed being a factor of the depth of the point of origin and the period (time between successive waves). The energy lost by tsunami waves is inversely proportional to the wavelength i.e. the greater the wavelength, the less the loss of energy. Therefore, in the deep open sea, tsunamis lose very little energy and keep travelling at almost constant high speeds. In deep waters, a tsunami would appear similar to and scarcely distinguishable from a ‘normal’ surge in water level. But as they approach a shoreline, their speed decreases sharply and the shallow depth forces the huge travelling volume of water upwards into massive waves. The height of these waves, their speed and ferocity depend a great deal on the contours of the particular shoreline or continental shelf, and therefore it is quite possible that some parts of the coast are hit harder while others suffer less damage.

This particular tsunami was an extremely fast-moving and huge volume of water, the waves being several hundreds of kilometres wide and travelling at over 1000 kmph. The tsunami would have hit Aceh in northern Sumatra within minutes of the earthquake which probably struck Car Nicobar not long afterwards. While Sumatra is about 1000 km from Port Blair in the Andaman Islands, this is a long chain of over a thousand islands with the farthest-east Indira Point being just 100 km from the last Indonesian island. The tsunami must have hit Chennai and the Sri Lankan coast about 2-3 hours after the quake.

Could some sort of warning have been given? Could the tsunami have been predicted or at least suspected? Would a warning or alert have prevented or at least minimised the massive loss of life in India and other countries in Asia?

TSUNAMI WARNING SYSTEMS

Soon after the magnitude of the disaster became apparent by Sunday on December 26 evening, the government announced that India would join the International Tsunami Warning Programme which she had not so far. 

An international Tsunami Warning System (TWS) was set up by the US National Oceanic and Atmospheric Administration (NOAA) in 1965 after the disastrous tsunamis triggered by 9.0 Richter magnitude quakes hit Alaska. The TWS was to cover the Pacific region and brought into partnership the Pacific rim nations in North and South America, China, Japan, Thailand and Philippines in Asia, the Pacific islands (including French islands thus bringing in France also) and Russia. The system has a Tsunami Warning Centre in Hawaii, located virtually in the middle of the Pacific and itself a frequent tsunami victim, and is based on 30 seismographic stations to monitor tremors and 70 tidal stations monitoring sea levels, all relaying readings to the Hawaii centre via satellite.

The system is triggered by seismic readings suggesting a large earthquake, which then alerts the system and operators to look for tell-tale tsunami indicators, particularly rise in sea-levels. However, since correlating these specifically to tsunamis rather than tidal flows is somewhat problematic, it can take about 1 hour for all the information to be assimilated and analysed, and for a tsunami warning to be issued (which is said to predict the arrival of the first tsunami wave to within 10 minutes). Such a time interval would enable evacuation of coastal areas at a distance of 750 km or more provided action is taken immediately on receipt of a warning.

In the present case, if a tsunami warning had been given soon after the quake or at least when it hit Aceh, there might barely have been time to start evacuating the Tamil Nadu and Sri Lankan coasts. However, since tsunamis are rare in the Indian ocean and Bay of Bengal, there were no tidal sensors in this region and even Thailand, which is a member of the Pacific TWS has no sensors off its western coast and there are no sensor buoys in the Indian ocean. The only sensor south of the quake’s epicentre registered only a 2 feet high wave heading towards Australia and the TWS Centre website issued only a statement to that effect emphasising that “no warning or watch [is] in effect!”

It may be argued that the sheer magnitude of the earthquake and its location should have at least led to some apprehension of a tsunami. But again the rareness of the phenomenon in this part of the world meant that leave alone India, no national, regional or global system responded in this manner. The previous tsunami in the region had been in 1883 when the famous Krakatoa volcano in Indonesia had a massive eruption.

For all its limitations and weaknesses, TWSs have over the years proved their usefulness in minimising fatalities and casualties. 

Over 51,000 people have died in 94 tsunamis during the previous century but the death toll has dropped sharply after the installation of the TWS in the Pacific region. In Japan for instance, while over 6000 people died in 14 tsunamis before the TWS took effect, only 215 fatalities have been recorded in 20 tsunamis since the mid-sixties.

For India to have a meaningful TWS, it would not be sufficient to merely join the existing Pacific-wide system or other regional systems such as the ones being operated by Japan or around Alaska. There requires to be a system quite similar to that in the Pacific, with several seismic and tidal sensors in different littoral nations around the Indian ocean and Bay of Bengal. This will not be easy and will involve considerable expenditure at the system level. On December 27, Indonesia said it could not afford the tidal sensors whereas the THRUST (Tsunami Hazard Reduction Utilising Systems Technologies) programme linked to the NOAA satellite systems have tried out a relatively low-cost option in Chile costing only $15,000 (Rs 7,00,000) per sensor. Most regional and lower-cost options rely more on seismic signals and interpretation of the same in tsunamigenic zones than on actual sea-level readings. Thus lower-cost options for the Indian ocean region should probably combine automated satellite-based systems with more conventional real-time communication systems using telephone, radio etc. Even after the 1964 Alaskan quake, before the TWS was set up, people in California, alerted by tsunami warnings through conventional means, were able to evacuate the coastal areas and move to higher ground saving countless lives.

RESCUE AND RELIEF

But all the talk in the past few days of TWSs and computerised date-bases of information linked through satellite and internet places too much reliance on high-tech solutions and somehow re-affirms the myth assiduously being propagated in India that, armed with science and technology, it will soon be a developed country. The harrowing live pictures on numerous television channels showing villagers helpless, recovering the dead and injured on their own with their bare hands, without shelter, food or drinking water even 36-48 hours after the tsunamis struck, should be enough to shatter that myth.

India needs --- desperately and urgently --- to get its act together in terms of simple rescue and relief operations. After the massive Latur and more recently the Gujarat earthquakes, after the Orissa super-cyclone, there was much talk of a national Disaster Management Plan. This seems to have evaporated into thin air as easily as the steel frame of Indian administration melts in the face of any calamity. Data-bases are all very well, as are digital diaries, but a simple phone book is also useful and ready to hand, earth-moving equipment, ambulances, fire-fighting systems all are essential pre-requisites for disaster management and need not wait for magical high-tech solutions.

All warning systems are only as good as the use to which this alert is put. Effectivity of early warnings depend hugely on the ability of the local authorities to appreciate danger, to effectively disseminate information to locals and, of course, on public awareness which needs to be consciously engendered. In all these areas, India clearly has a long way to go. We can at least begin by honestly learning from past mistakes and taking earnest measures to rectify them.