Tsunami News
Asian Marine Disaster ( k u n Bapat, Research Seismologist, Pune; Extracted from an article in
Indian Express dated 28 Dec. 2004)
The Asian Marine Disaster (AMD) on December 26 has no parallel in recent history. The Sumatra earthquake, with a magnitude of 8.9, is the fifth largest since 1900. When an earthquake of the magnitude of 7.5 or more occurs in the sea, it generates a sudden drop of water mass of huge proportions. The size of sudden drop of water volume in the present Indonesian earthquake could be about 100 km long and 70 km wide and about 1.5 krn deep. The sudden drop in seawater level at the epicenter is in the range of one to two meters.
When such a huge volume of water drops, it creates waves and they spread radially. These are known by their Japanese name of 'tsunami'. As long as they are confined to water, the amplitude of the waves is small, less than 50 cm. But as the waves approach land, the amplitude increases exponentially. The highest tsunami recorded in Japan was of about 28
m.
This time, apart from the Asian countries, even African states like Seychelles and Somalia - the latter 6,500km
away from the epicenter - were affected. It is fortunate Bangladesh was spared. If the sea enters it, there is great havoc since the land is just one meter above sea level for about 100 km from the sea.A few major tsunamis have hit the Indian coastal region. The first available record is from Madras Port Trust. The eruption of the Krakatoa volcano in Indonesia in August 1883 had its impact on the region with the height of the tsunami estimated at about 2 m. Earthquakes on January 4, 1907, in Indonesia and on June 26, 194 1, in the Andarnans, also gave rise to tsunamis of about one meter in height. An earthquake on November 27, 1945, located about 100
km
south of Karachi in the Arabian Sea, also generated a tsunami.Given this, it is clear that the phenomenon of the tsunami is not newlo India. During the geo-technical investigation period for the Koodarnkulam Nuclear Power Plant, this writer was the only person to have observed that the site at Kanyakumari is vulnerable to tsunami damage. Some found it difficult to accept the observations. But Sunday's tsunami was rare from the seismological point of view. Within four hours there were ten earthquakes: four in Sumatra, six in Nicobar.
In 1996 when I was in Australia, an earthquake in China generated tsunamis. The Tidal Facility Center at Adelaide immediately studied the event. After computer modeling, it was found that the height of the tsunami on the Australian coast would be negligible.
India needs to prepare itself better for every contingency. First, the IMD should issue a forewarning about the possible tsunami. Second, satellite should be upgraded with suitable equipment to track tsunamis. Our embassies in affected countries should be instructed to react to such developments. Further, joint or inter-country collaboration with neighbouring countries on tsunami-genic earthquake should be undertaken.
Earthquake in Andaman-Nicobar Islands of 13th September 2002 (C.P. Rajendran, Tiruvananthapurarn, Currelzt Science, 10 April, 2003, y.9 19)
The 13 September 2002 North Andaman earthquake (Ms 6.8) that caused moderate damage in the onshore region, appears to be a significant event in the chain of ongoing seismicity of this region. Epicentral location, relatively shallow focus and the faulting mechanism of this earthquake are suggestive of its association with the down-dip extension of the subduction interface. Our evaluation of the regional seismicity indicates that the recent spurt of activity may represent a peak in the progressive strike-slip deformation in the Andaman arc. Perhaps, this region has entered into a renewed phase of stress build-up, after decades of post-seismic relaxation subsequent to the 1941 (M>8) earthquake. Another intriguing question is whether the increased volcanic activity of early nineties in the nearby Barren Island was a consequence of post-1941 stress diffusion. The global data suggest a 50 year correlation between very large earthquakes and volcanic el-uptions, which seems feasible for this region. The Andaman arc offers a perfect setting to validate many assumptions on earthquakes, volcanoes and tsunamis.
Asia's Devastation (The Ecanolnist, 1 Jan. 2005, p.9)
The Indian Ocean tsunami has been caIled the world's worst ever natural disaster. In terms of cold statistics, that is wrong, even as the estimated death toll climbs well past 50,000. Other earthquakes have killed more, especially in poor and populous countries such as China: probably 600,000 or more in Tangshan in 1976, and 200,000 or so on two occasions in the 1920s. Iran lost an estimated 50,000 people to a quake in 1990 and a further 26,000 in Barn exactly a year ago to the day, on December 26th 2003. It is not even the Indian Ocean's deadliest disaster, for cyclones have often brought worse, most notoriously in 1970 when the then new state of Bangladesh lost about 500,000 people.
But let not everything about this terrible event feel bad. For in that very geographical challenge lies also an opportunity, one that comes in three main forms. The first is that the involvement in the disaster of so many resorts favoured by tourists from rich countries in the West and the richer parts of northeast Asia has given it even more prominence in those countries than the sheer horror of the fatalities would have produced. Such selfish distortions are regrettable in theory-who noticed while millions welee dying in Congo's wars?
That sense of mutual vulnerability brings us back to the question of warning systems and to the third way in which this disaster could be turned into an opportunity. Money and complacency are two reasons why no tsunami warning system exists for the Indian Ocean. But the region also suffers from a political fear of co-operation. Suspicions and mistrust between many of the countries bordering the ocean, and between those in the seismically turbulent region beyond, in Pakistan, Afghanistan, Iran and elsewhere, mean that habits of cross-border cooperation are weak. Even the exchange of seismic data is
meagre, to say the least, let alone interchange on more politically and economically charged topics.
Natural Disaster Management (A.P.J. Abdul Kaiam, The Week, 9 Jan. 2005, p.3)
Nationally, we must have an Empowered National Disaster Management Authority, which can swiftly go into action to rninimise the damage level and ensure early restoration of normal life. This authority should be able to draw support from any group or facilities of ministries and departments of both the State and the Centre. The authority should also help in rehabilitation of affected people and help them overcome the trauma in a quick and' effective way. In this regard, the authority could also involve local volunteers, the civil administration and NGOs. A common complaint in many relief measures of the government is that they are slow and often do not get delivered fully to the intended people. From the kind of reports I receive now, I find that government agencies are performing round-the- clock operations and providing relief to unreachable areas. The armed forces are providing support in a big way. The authority must be given executive and legal,powe~-s to ensure that unscrupulous elements do not exploit well-meaning governmental initiatives.
We should prepare the dossier of all affected persons, institutions and systems and make them publicly available. Then every well-to-do Indian family should adopt one of the affected individuals and guide them financially and otherwise to help them start a normal life. This way, we can create a 'People's Movement'-a movement of the people, by the people and for the people. This should act as a forerunner for many other nations for overcoming natural calamities and enabling victims to lead a happy and prosperous life even in the midst of natural aberrations.
A Warning in Time (Tlze Week, 9 Jan. 2005, p.36-37)
India's weather scientists, geologists and oceanographers knew when earth shook off Sumatra on the morning of 26 December. But they thought there was nothing to worry because undersea earthquakes were too common in the region. What they didn't know was that the quake had happened not on the side facing the Pacific.
Two and half hours after the first quake of Sumatra, the tsunami struck India's east coast and crushed everything on its almost 2 krn invasion of the mainland in Andhra Pradesh, Tamil Nadu and Kerala. Admitted Science and Technology Secretary Dr. V.S.Ramarnurthy: "By around 7 am we knew that an earthquake had happened in Sumatra. But we had no idea about the tsunami till it hit Chennai and was reported on TV".
India has all the equipment to monitor earthquakes but none to spot tsunamis. There are acoustic satellite gauges and a marine satellite information system but all of them watch out.for cyclones, tide variations and other surface phenomenon.
But what happened after 9 am on December gives hardly any credit to the government. Even after the waves hit Chennai, (he disaster management cell under the home ministry did not contact the relief commissioners of coastal states like Andhra Pradesh or Kerala (which were hit) and Orissa or West Bengal (which were not hit) to initiate evacuation.
,
de he
?ext 90 minutes made al1,the difference - between saving lives and being unableto. The home . ministry's , assessment of the affected areas shows how manageable the situation
act;ally was, had timely action beenotake?. sa;ing lives would have meant only pulling
back within 2'km extent of thk invasion from thk sea. . J
Warning Centre (David Oppenheimer, Seismologist, The Week, 9 Jan, 2005, p.40)
. . ..
Three hours of warning between the tsunami setting off near Sumatra and arriving at coastal India is too little time. Even in Hawaii, where tsunami evacuation drills are performed to military precision, it takes three hours for the islanders to get their act together. But if education has been imparted, an early warning is ideal....
Deep ocean pressure gauges accurately measure tsunami waves as they are formed. The-advanced technology then sends a signal back inreal
time to the buoys anchored to the ocean floor which in turn send signals to the satellites that beam the information back to the monitoring stations.The key here is 'real time' transfer of the signals. This system can be set up between India, Sumatra, across the expanse of the Indian Ocean.
Asian Death Toll ( "The Hindu ", 5 Jan. 2005)
Number of dead will exceed 1,50,000. Death toll by country is: Indonesia 94,08 1 ; Sri Lanka - 30,196; India
-
957 1; Thailand - 5240, Somalia - 200; Myanmar - 90; Maldives - 62; Malaysia - 68; Tanzania - 10; Bangladesh -2 and Kenya - 1.Understanding What Precisely Happens (Erne, 10 Jan. 2005, p.39)
...
The earthquake reminded us-had we been foolish enough to forget it-that there are primal forces of nature that no amount of our wizard technology is able to confine. Yet technology can help. For decades, a sophisticated early warning system has helped limit catastrophic damage from tsunamis in the Pacific. So, in the aftermath of the Sumatran earthquake, it was natural to ask whether anything could have been done to mitigate the disaster. And that is a question whose answer requires an understanding of what, precisely, happened on the morning of 26 December.Geologists describe the tectonics-the almost imperceptibly slow movement of massive plates-of the southern Indian Ocean as complex, because a number of plates converge there. The floor of the Indian Ocean-the Indian plate-is moving north at around 6.5 cm a year, about twice the rate that your fingernails grow. As it moves, it is forced under the Burma plate to the east. Eighteen miles below the surface of the ocean, stresses that had been gradually accumulating forced the Burma plate to snap upward. That was a huge geological event, eventually measured as a 9.0 on the Richter scale. Indeed, the dislocation of the boundary between the Indian and
Burma
plates took place over a length of 2000 krn and within three days had set off 68 aftershocks.How Science can Save Lives (Tirne, 10 Jan. 2005, p.45)
...
We scientists find it dificult to convince people that they should be wo~ried about big, powerful geologic processes that may happen in their neighbourhood tomorrow-or in 10 generations time. It is hard to cajole people into worrying about what might happen a hundred years hence, when they have a tough job finding time to get their daily chores done. In poor countries, living is so hand-to-mouth that there is scant time to think about the distant future..... Whether or not forecasts become possible, could such an expanded effort be used to service an early warning system? If we had been able and willing to set up a warning system just after the great Sumatran quakes of 19th century, would we have had the persistence of vision to keep it running until last week?
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...
One test of whether humanity acts differently in the next millennium is this: Can .we marshal the visionary persistence needed to take charge of our future? Or will we carry on as we did throughout most of the past-simply reacting to tragedies as they happen? If the answer is the second, then there will continue to be more tragedies like that of last week.
Sumatra Earthquake of December 2004 (K.S. Subramanian, Geologist stationed at Chennai)
The arcuate Java trench lies to the south of Sumatra and the crust generated by the Indian Ocean Ridge in this part of the Earth is considered to be subducted in the trench. It is possible that the process of subduction may be marked by tectonic events related to features of subducting oceanic crust. In this context, the relevance of seamounts some of them rising to two or three kilometres from the ocean-floor may be considered. Seamounts are conical features composed of volcanic rocks and are rooted in the oceanic crust. Along with the crust they inevitably move towards subduction zones. If they are enveloped with sediments, they may glide down subduction zones. On the contrary, bare and rugged seamounts may offer resistance to smooth subduction and may be decapitated violently on entering a subduction zone or at some depth in the subduction zone. The shattering of colossal rock masses may well release stresses and give rise to seismic waves. One such event in the Java trench might have triggered a submarine earthquake.
An Eyewitness Account from Visakhapatnam (G. Gaitan Vaz, Geological Survey of India, Visakhapatnam)
An earth tremor occurred at-Visakhapatnam around 06-30 hrs on 26- 12-2004. Enquiries proved that the persons who were in horizontal position felt more the effect of tremor than those who were in vertical position. Movement of cots, chairs and mild window rattling were commonly experienced by the residents.
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According to them (fishermen), the water level within the fishing harbour raised approximately 3.0 m above msl around 9-30 hrs. :.. the trawlers and boats moved within the fishing harbour limit without any control.. I noticed the evidence of overflow of sea water above the jetty level. Fishes of various sizes were found strewn everywhere within the fishing harbour.I
entered into the fishing harbour and reached R. V Samudra Kaustubh (GSI Vessel) to enquire about the safety of the vessel and personnel. By this time I witnessed the second cycle of water level rise and it touched the jetty level but did not overflow like the first time. Within about ten minutes the water level reached the record lower level of about 2.5 m below rnsl. Consequently, R.V Samudra Kaustubh almost touched the ground at jetty no.5. The bridge of the vessel came to the level of jetty around 11-00 hrs. While observing this, about 1 m height wall of water gushed into the fishing harbour and raised the water level to about 2.5 m which made R.L!
Su17zudra Kaustubhto float. Similar rise and fall of water levels were observed three times till 11-30 hrs. Reportedly, after 14-30 hrs the magnitude of water fluctuation and frequency were reduced.
and minimum level of 2.90 rn at 12-15 hrs. The magnitude and frequency of fluctuation reduced after 15-00 hrs (Source: GSI Website).
Coral Reefs Escape Tsunami Fury (Tlre H I ' I I c ~ , 7 Jan. 2005)
A report from Tuticorin states the tsunami waves which hit the coast have not caused damage to coral reefs between Tuticorin and Rameswaram. Water near the COI-a1 reef collections was clear, without any turbidity.
Opening of Andarnan Sea: A New Tectonic Insight (Partha Psatim Chakraborty, lndian School of
Mines, Dhanbad)
I want to draw your attention to one o f o u ~ recent paper in Earth and Planetary Science Letters (EPSL; irz press) where we could identify the high strain zone in this region and identified the depths of plate flex i iig ill this region. Incidentally, the eartllquake has happened very close to our marked zone and its epicentral depth (28 kni) is very close to our estimated depth of plate flexing (i.e. 25-30 km).
Proposed Group Discussioli on Tsunamis at Hydcrabad (Prof. K.V. Subbar-ao, Hydel-abad
University)
The coastal districts of India took the brunt of the recent tsunami, with Nagapattinam in Tamil Nadu being the worst hit. Is these any geological stl-ucture that favoui.cd Tmnil Nadu? How about the role of submarine canyons off east coast reported by Professors C. Mahadevan and E.C. La Folid of the Andhrd University way back in late 1950s? There are also records of earthquakes and similar phenomena on the west coast. We should try and compare these records and identify the reasons and effects as well. The Andarnan and Nicobar Islands are badly hit, tather twice. The total death toll in Asia is said to be over
150,000 as per the latest estimates.
What next? What are the lessons to be learnt from this tsunami? Where do we stand in terms of warning systems? What is the role of science in eilrly warning systems? Are we ready with at least basic evacuation procedures in cases of disastei-s such as these? Should we not train our students at different levels and also the gcneral public on the problems and initiate follow up action in case of natural hazal-ds? Obviously we all now know the disastrous effects of tsunami and also earthquakes. It is time that we quickly put up an action plan for "preparedness", leave alone the awareness and early warning systems! Japan has done so well in all aspects relating to earthquakes and tsunamis and this can be used as a role model to be fol towed.
In order to focus attention on some of the issues relating to natural hazards, in particular the recent tsunami, the Geological Society of India and the University of Hydesabad are holding a Group Discussion of scientists, government organizations, doctors, engineers, lawyers, administrators, NGOs, students, and representatives of the citizens gl-oups
on
Sunday the lCiU1 January, 2005 at Hyderabad. The agenda includes: (1) Scope of the tragedy; (2) What causes a tsunami?; (3) Eastern Indian coastal zone and seismic activity; (4) Tsunami warning system; (5) Preparedness; .(6) How to handle these natural calamities; (7) How science can save lives.It is proposed to voice our opinion on the future course of action.
