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Gondwana Research, V. 8, No. 2, 2005

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SPECIAL CORRESPONDENCE

Destructive Earthquake and Disastrous Tsunami in the IndianOcean, What Next?

T. Harinarayana1,3 and Naoshi Hirata2

1 Present address: Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan,E-mail: [email protected]

2 Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan, E-mail: [email protected] National Geophysical Research Institute, Hyderabad, India

(Manuscript received: January 26, 2005; accepted January 31, 2005)

Abstract

A major earthquake event and a disastrous tsunami struck on December 26, 2004 in the Indian Ocean which led tothe death of nearly 250,000 people within a short period of time. This has given a major jolt not only to the scientists,but also to the authorities, planners and various national and international organizations. Discussions regarding ‘whatto do and how to cope with such situations’ are taking place and also on various plans and programmes for the future.We have analyzed the available scientific data related to the Sumatra earthquake and tsunami and also the earlierdisastrous events of the tsunami. This includes seismicity of the region, numerical modeling studies and crustaldeformation studies. Based on earlier reports of disastrous events, warning systems related to earthquakes and tsunamis,we suggest scientific studies that need to be taken up in the near future in the region. Our study will provide somedirection for the ongoing discussions to prepare better plans and programmes in the Indian Ocean by various South EastAsian countries.

Key words: Tsunami, earthquake, Indian Ocean, natural hazard, East Asia.

Introduction

It is now well known to the world that a ‘‘tsunami’’ canbe dangerous, destructive and cause extensive damage.When the first news came that an earthquake with a largemagnitude of 7 or 8 on the Richter scale, occurred nearSumatra in Indonesia on December 26, 2004, all theneighboring countries were of the view that the dangerwas far away from their location and hence took no action.Scientists, officials of the government and otherorganizations, and also the members of expert disastermanagement groups in South East Asian countries,although aware of the event within minutes after theoccurrence of the large earthquake, did not realize at thattime, the extent of damage that it could cause in otherregions several hundred kilometers away. The human lossfrom the Asian tsunami now stands at nearly 250,000,with a belated recognition that this great loss could havebeen avoided (Kerr, 2005; Bhattacharjee, 2005).

The tsunami came, caused tremendous damage to

human life and property and then retreated. What next?Will the tsunami strike again? How did the tsunamioriginate? What is to be done in the future?

The Sumatra Earthquake

The earthquake that created the tsunami is the world’sfifth largest with a magnitude of 9.0 on the Richter scaleand occurred at 00:58:50 (GMT) on Sunday, December26, 2004, off the west coast of Northern Sumatra,Indonesia. Table 1 (Yamanaka, 2004) provides the detailsof the main shock. The slip distribution of the earthquakeis presented in figure 1 (http://www.eri.u-tokyo.ac.jp/index.html, Yamanaka, 2004). The contour interval of theslip distribution is 2 meters and a maximum slip of13.9 meters is estimated from the data. This is a very largeslip compared to great earthquakes. For example, theImperial Valley earthquake of M 7.1 showed 1.4 mmaximum slip and for the Kobe earthquake (M 7.3), themaximum slip is 2.6 m (Kikuchi and Kanamori, 1996).

Gondwana Research (Gondwana Newsletter Section) V. 8, No. 2, pp. 246-257.© 2005 International Association for Gondwana Research, Japan. GNL


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Table 2 shows the details of the past largest earthquakeswith a magnitude greater than 8.5 (USGS, 2005a). Ascan be seen from the table, this is the world’s largestearthquake in the last 40 years. Certainly, it is a rareearthquake event in the history of the Indian Ocean.

The details of the aftershock activity with magnitudegreater than 6 in the epicentral zone have been compiledbased on the site maintained by the Research Group on“The December 26, 2004 Earthquake Tsunami Disaster ofIndian Ocean”, Japan and provided in table 3 websiteteam, 2005; http://www.drs.dpri.kyoto-u.ac.jp/sumatra/index-e.html. Figure 2 is updated information (up toJanuary 11, 2005) of aftershock activity provided by USGS(2005b) (see http://earthquake.usgs.gov/eqinthenews/2004/usslav/tect_lg.gif) considering the events withmagnitude 4 or greater. Major thrust, normal and strikeslip faults are also shown in the figure. The aftershockactivity concentrated more towards the north of the mainshock and very little or nil towards the south. This indicatesthat the rupture process progressed towards north andthe events are related to a major geological structure –

the Sunda Trench. The co-seismic rupture initially extendsto 500 km along the trench and extends further towardsnorth; however, some more data are required from GPSand other geodetic measurements. The Ocean HemisphereProject Network, operated by Earthquake ResearchInstitute, has a broadband seismic station which is veryclose to the epicenter of Mw = 9.0 off the west coast ofnorthern Sumatra. The distance is 3.2 degrees, and stationPSI is closer than any IRIS GSN or GEOSCOPE station.The distribution of the seismic stations around the mainevent is shown in figure 3. The station PSI is equippedwith instruments that can record 3-component broadbandsignals. Figure 4 shows the recorded events of threecomponents (NS, EW and vertical, Z) of the main eventearthquake on December 26. The large offset in verticalcomponent is dominant as compared to the horizontalcomponents. Both the horizontal components have shownlarge displacement. This is one of the possible reasons forgeneration of a large tsunami in the Indian Ocean. Theground motion in the epicenter zone continued for aperiod of about 2000 seconds (nearly 33 minutes).

Fig. 1. The slip distribution of Off the West Coast of Northern Sumatra Earthquake on December 26, 2004 with a contour interval of 2 m.A maximum slip of 13.9 m is deduced for the main event. (After Yamanaka, 2004).


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About Tsunamis

Apart from American scientists, the characteristics oftsunami are well studied by Japanese scientists. In factthe word “tsunami” originated from Japanese meaning“harbor wave”. The meanings of the word tsunami foundin the literature include seismic sea wave, Flutwellen,vloedgolven, raz de mare, vagues sismique, maremoto.The term “tidal wave” was also used earlier in a generalsense but now is considered as incorrect.

In simple terms, the tsunami can be understood as acomplex oscillating seismic sea wave generated due tolarge scale disturbance of land under the sea in a relativelyshort time duration. It is well known to the Circum-Pacificnations that a tsunami is one of the destructive naturaldisasters that need to be monitored with a warning systemto the people in a way that human loss and property canbe kept to the minimum. A well-organized Pacific TsunamiWarning Centre (PTWC), Hawaii, is in place and provideswarning messages regularly about the possible onset of atsunami. The people of Circum-Pacific nations have beencoping with tsunamis for centuries. The American peopleknew about tsunami events as early as the sixteenth century(Landers and Lockridge, 1989). The Japanese were themost affected by the tsunamis earlier, but not any more.

With an international warning system as well as the JapanTsunami Warning System, death and damage to theproperty is now minimum.

With the past experience of tsunamis, their pattern ismore or less clearly understood by the people in this partof the globe. A tsunami wave can divide at the shore orbreak and sometimes appear as flooding with waterrushing inside the land more violently and with great forcetowards a river or stream course. From the visualobservation it is also seen, in several cases, that when itfirst arrives the water level of the sea may dropsignificantly as if the sea water is receding to largedistance; however, it comes back more violently withfaster speed than a person can run. Secondly, it mayrepeat within a gap of minutes or even an hour andsometimes the later events may cause more severe damage(e.g., Bryant, 2001).

Tsunamis are generated mainly due to suddendisplacement of the sea bottom surface that generatesnear vertical disruption of the water column. Such aphenomena can occur usually due to the onset ofearthquakes under the sea. But in some cases, tsunamiscan also occur without earthquakes. For example, volcaniceruptions, displacement of marine sediments, landslidesnear the coast, manmade nuclear explosions in the seaand meteor impact from space can also generatedestructive tsunamis. It is known that large tsunamigenicearthquakes in an area as large as 100,000 squarekilometers may displace suddenly to several meters oreven more. The velocity of tsunamis varies and dependson many parameters such as the bathymetry, height ofthe originating wave, initial pressure changes in thesea, etc. and can travel with a velocity of more than1000 km/hour. Since the velocity is proportionate to thedepth of the water column at the location, near the shorethe velocity reduces to a few tens of kilometers. However,the wave height can reach tens of meters and run upincreases to as large as 100 m in extreme cases (Tinti,1991, IOC Report, 2002). The Sumatra tsunami movedwith a speed of about 800 km/hour and the giant wavewith a curved path traveled to about 4500 km within7 hours touching far away countries like Somalia. Basedon the available bathymetry data, a numerical modelinghas been carried out by DCRC group of Tohoku Universityand their results are presented in figures 5, 6 and 7. Basedon the numerical modeling studies, the initial expectedheight of the tsunami is about 2 to 3 m trough, then risingto a maximum height of 4 m. The shape of the waveformhas been estimated near the earthquake location and thisappears to assume a crescent shape almost parallel to theSunda Trench structure. The initial wavelength of the waveis more than 100 km. The propagation of the wave ismodeled assuming two types of fault strike. Both the

Table 1. The basic earthquake parameters of the main shock.

Date 04/12/26 00:58:51 (UT)

Longitude 3.251NLatitude 95.799EDepth 10 kmMagnitude 9.0(Strike, Dip, Rake) (330, 8, 90)Mo 1.8 x 10**22 NmMw 8.8Source duration 200 sDepth 32 kmDmax 13.9 m

Source: After Yamanaka (2004).

Table 2. World’s largest earthquakes (>8.5) since 1900.

Location Date UTC Magni- Coordinatestude

Chile 1960 05 22 9.5 38.24 S 73.05 WPrince William Sound, Alaska 1964 03 28 9.2 61.02 N 147.65 WAndreanof Islands, Alaska 1957 03 09 9.1 51.56 N 175.39 WKamchatka 1952 11 04 9.0 52.76 N 160.06 EOff the West Coast ofNorthern Sumatra 2004 12 26 9.0 3.30 N 95.78 EOff the Coast of Ecuador 1906 01 31 8.8 1.0 N 81.5 WRat Islands, Alaska 1965 02 04 8.7 51.21 N 178.50 EAssam - Tibet 1950 08 15 8.6 28.5 N 96.5 EKamchatka 1923 02 03 8.5 54.0 N 161.0 EBanda Sea, Indonesia 1938 02 01 8.5 5.05 S 131.62 EKuril Islands 1963 10 13 8.5 44.9 N 149.6 E

Source: USGS (2005a), National Earthquakes Information Centre.


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Fig. 2. The main shock and after shock activity of the events with magnitude >4 recorded up to January 10, 2005 along with main thrust andnormal faults in the region. Increased after shock activity towards the north of the main event may be observed. The concentration of theaftershocks is at the margin of the Indian plate and Sunda plate. (Source: USGS, 2005b).

models showed a similar pattern. Two to three hours arerequired for the initial wave to reach the countries likeSri Lanka and India and as long as 8 to 9 hours to reachthe farther countries like Somalia. The expected waveformof the tsunami at eight different locations – Male,

Colombo, Yala, Banda Arch, Madras (Chennai), Nilas,Galle and Phuket - are also estimated and presented infigure 7. It is clear from this figure that Banda Arch musthave experienced maximum height of the wave and highfrequency waves must have been experienced near Male.

20°N

15°

10°

5°

95° 100°E90°

Main Shock

26 December 2004

EXPLANATION

Aftershocks through 10 Jan 2005

4.0 - 4.9

5.0 - 5.9

6.0 - 6.9

7.0 - 7.9

Volcanoes

Faults (after Pubellier and others, 2004)

Thrust

Normal

Strike-Slip

Other


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Table 3. Details of the after shock activity of major events (>6) near the Sumatra earthquake epicentral zone (updated up to January 5, 2005).

Mag Date (yyyy/mm/dd) UTC-time Lat. Lon. Depth Region

6.2 2004/12/26 01:21:21 6.392 93.389 30.0 Nicobar Islands, India region6.0 2004/12/26 02:52:02 12.479 92.566 30.0 Andaman Islands, India region7.1 2004/12/26 04:21:29 6.893 92.901 36.9 Nicobar Islands, India region6.6 2004/12/26 09:20:01 8.911 92.346 10.3 Nicobar Islands, India region6.3 2004/12/26 10:19:29 13.470 92.779 5.8 Andaman Islands, India region6.3 2004/12/26 11:05:01 13.567 92.872 13.1 Andaman Islands, India region6.1 2004/12/26 15:06:35 3.663 94.013 30.0 off the west coast of N. Sumatra6.2 2004/12/26 19:19:56 2.776 94.171 30.0 off the west coast of N. sumatra6.0 2004/12/27 00:32:16 5.490 94.451 30.0 Northern Sumatra, Indonesia6.1 2004/12/27 00:49:28 12.996 92.430 18.5 Andaman Islands, India region6.1 2004/12/27 09:39:07 5.361 94.661 35.0 Northern Sumatra, Indonesia6.1 2004/12/29 01:50:56 9.076 93.795 24.9 Nicobar Islands, India region6.2 2004/12/29 05:56:51 8.781 93.218 30.0 Nicobar Islands, India region6.3 2004/12/31 02:24:01 7.127 92.556 11.9 Nicobar Islands, India region6.0 2004/12/31 12:04:57 6.217 92.913 4.6 Nicobar Islands, India region6.5 2005/01/01 06:25:45 5.046 92.276 10.0 off the west coast of N. Sumatra6.2 2005/01/02 15:35:56 6.332 92.799 30.0 Nicobar Islands, India region6.1 2005/01/04 09:13:12 10.656 92.368 20.0 Andaman Islands, India region

Source: USGS (2005b).

Fig. 3. The network of seismic stations around the epicentral zone in the Indian Ocean. The green star indicates the stations belonging toIRIS/USGS/IDA/IRIS/CDSN, GEOSCOPE. The red star (PSI) indicates the seismic station belonging to Ocean Hemisphere Group, Earthquake ResearchInstitute, University of Tokyo, which is closer to the main shock (shown in red square) than any other seismic station around the region.

As a thumb rule, the velocity (V) of a tsunami in theopen ocean can be expressed as the product of the squareroot of the depth of the water (d) and the acceleration ofthe force of gravity (g).

V = (dg)1/2

Similar to the magnitude of an earthquake, tsunamimagnitude (Mt) can also be estimated based on the

observations of locations around its origin. Accordingly,Mt value for the Indian Ocean tsunami of December 26,2004 has been estimated (Abe (http://www.eri.u-tokyo.ac.jp/topics/SUMATRA2004/abe.html, 2005)based on the data from nine station locations. Table 4 showsthe maximum height (H2) of the wave experienced atvarious locations and the epicentral distance (x) from the


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Table 4. The tsunami parameters observed in Indian Ocean at differentlocations with maximum height and the distance from theepicentre (Abe, 2005).

Place H2 (Max. (X) Distance MtCrest-trough) from epicentre

Vishakapatnam, India 2.4 2070 9.3Tuticorin, India 2.1 2100 9.2Kochi, India 1.3 2400 9.0Cocos Is., Australia 0.5 1820 8.5Hillarys, Australia 0.9 4600 9.2Hanimaadhoo, Maldive 2.2 2500 9.3Male, Maldive 2.1 2500 9.3Gan, Maldive 1.4 2500 9.1Diego Garcia, Chagos A 0.8 2700 8.9

location. Based on the information available at theselocations and using the following formula (Abe, 1979, 1981),one can estimate the magnitude from tsunami parameters:

Mt = log H2 + log X + 5.55H2: Maximum crest-to-trough amplitude on tide gauge

record in meter X: Distance from epicenter to station alongthe shortest oceanic path in kilometers Abe (http://www.eri.u-tokyo.ac.jp/topics/SUMATRA2004/abe.html,2005) has computed the magnitude of the tsunami basedon the parameters (Table 4) observed at different locationsand obtained average value as Mt = 9.09. The computedvalue is close to the Mw = 9.0 of the Harvard solution.Such large tsunamis are very few during the last 170 years.The tsunami events with Mt = 9.0 and greater are givenin table 5.

Historical tsunami run-up data (http://www.ngdc.noaa.gov/seg/hazard/hazards.shtml) from 1500 to 2004 havebeen compiled and presented over a topographic map(Fig. 8). This shows that although tsunami events areconcentrated more near Japan and other Circum-Pacificcountries, it is not uncommon in the Indian Ocean, butthe frequency and its damaging effects may have beensmall in the past.

Tsunani Warning Systems

Well-established tsunami warning systems exist indifferent parts of the world, among which PTWC – PacificTsunami Warning Center, Hawaii is in place and beingoperated with the data from all the Circum-Pacific nations.This was established way back in 1949 in Ewa Beach,Hawaii. It provides warnings for teletsunamis to theparticipating countries. Apart from this there is WestCoast/Alaska Tsunami Warning Centre located in Palmer,Alaska for both local and regional tsunamis. Furtherstudies are being pressed in the region, realizing theimportance of the tsunamis and their disastrous effect onhumans and property (IOC report, 2002). The JapaneseTsunami Warning System is another important centre. The

Fig. 4. Displacement seismograms for the main shock of December26, 2004 from the station PSI. The horizontal axis is the timein seconds and the vertical axis is the displacement in centimeters.The sensor (STS-1) has a sensitivity of 10-2 m/s = 24 V,the digitizer (Q330) has a sensitivity of 20V = 223 counts andthe total sensitivity is 1m/s = 1.007X109 counts.

(A)

(B)

(C)


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Table 5. Ten largest tsunamis around the world since 1837 till date.

Year of origin Location Magnitude of Tsunami

1837 Valdivia, Chile 9.31841 Kamchatka 9.01868 Arica, Chile 91877 Iquique, Chile 91946 Aleutians 9.31952 Kamchatka 91957 Aleutians 91960 Chile 9.41964 Alaska 9.12004 Sumatra, Indonesia 9.0

Source: Abe (2005).

details of the Japanese Tsunami Warning System are asfollows:

The Japanese Tsunami Warning Center was establishedway back in 1952 and is being maintained by the JapanMeteorological Agency (JMA). The agency operates about180 seismic stations and 80 water level stations. Figure 9shows the details of locations of various stations and theirdistribution. In addition to this there are fuse-type tidegauges, water level gauges with ultrasonic detectors inharbors to monitor the large tsunamis and run-up. Themain centre is supported with information from six

regional centers located at Sapporo, Sendai, Tokyo, Osaka,Fukuoka, and Naha (Okinawa). The systems are fullyautomated to compute the seismic parameters and eachsystem is called Earthquake and Tsunami ObservationSystem (ETOS). With the onset of an earthquake, JMAestimates the location of the quake. If it is located underthe sea area with shallow depth, the expected onset oftsunami and the affected regions are estimated and basedon the information, warnings are issued to those locationswell in advance with the information about the expectedtsunami is minor (<2 m) or major. JMA is planning for athree-minute warning system to all the seashore areas.This will provide the information, within three minutes,to all the areas that expect hazardous events.

What Next?

Rehabilitation of the suffering, protection of thesurvivors and reduction of the related health hazards toavoid epidemics should be the topmost priority in the firstinstance and every country is doing its best in thatdirection, with some countries taking the help ofinternational agencies. Secondly, there is no guaranteethat the event cannot happen again, if not on the same

Fig. 5. Numerical modeling results based on the bathymetric data from etopo5. (a) A crescent shaped initial wave at the origin can be seen with anapproximate trough depression of 3 m towards east and about 4 m crest towards west indicating amplitude of 7 m for the initial wave generation.(b) The large wavelength of about 800 km and propagation direction can be observed. (Courtesy: Tohoku University, Japan; DCRC, 2005).

Initial Water SurfaceDCRC, Tohoku Univ.

Maximum Tsunami HeightDCRC, Tohoku Univ.

-4 -2 0 2 4 m 0.0 1.0 2.0 3.0 4 m


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parameters need to be observed by systematic scientificinvestigations in the Indian Ocean at the earliest.

Detailed marine bathymetric study

Detailed seafloor survey in and around the epicentralzone is a necessary requirement. This can be carried outusing a dedicated research vessel with high-resolutionseafloor mapping capability, possibly with ROV and otherseafloor direct access facility. Apart from this, seismicreflection/refraction can also be initiated to map theshallow (1 km) subsurface structure. For such a researchprogram, a group called POGO (Partners for Observationof the Global Oceans) has already been formed. They canbe requested to initiate experiments in the Indian Ocean.In Japan, the Japan Marine Science and Technology Center(JAMSTEC) has the capability to do so and may be

Fig. 6. Tsunami propagation in the Indian Ocean with time from numerical modeling computed for the 30° N-30° S and 60° E-120° E region witha spatial grid size of 10' X 10' and with a temporal grid size of 20 sec. (Courtesy: Tohoku University, Japan). For both the models theassumed fault parameters are Dip=13°, Slip=55°, Length=800 km, Width=85 km, Dislocation=11m, Depth=7 km. The strike direction formodel-1=350°, model-2= 330° (DCRC, 2005).

magnitude. Lower magnitude tsunamis do repeat due tosudden spurt of cluster of aftershock activity near theepicentral zone or as far away as even 1000 km. This isthe scenario experienced before by Pacific and Japanesewarning systems. There are systematic ‘do’ and ‘don’t’guidelines available to the people from the tsunamiwarning centers (see web http://www.prh.noaa.gov/ptwcfor details). Till a well established warning system is inplace in Indian Ocean, which may take a couple of yearsor more, the authorities need to be on high alert infollowing these guidelines. Secondly, short- and long-termscientific investigations are a necessary requirement tounderstand the present situation. This will form a basicguideline to initiate and establish effective tsunamiwarning systems and also help in the mitigation of suchcalamities in the future. Accordingly, the following

Model-I Model-2

Strike of fault = 350° Strike of fault = 330°

time (h) time (h)

0 5 10 15 20 0 5 10 15 20


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requested to take up such studies in the region. In fact,JAMSTEC is planning to take up a collaborative study withvarious organizations such as BPPT, BGR, GSI, Prince ofSongkhla University and LDEO during February–March,2005. Prof. Suyehiro Kiyoshi, JAMSTEC, is leading theteam. Three types of studies are being planned – sea floorsurvey including ocean bottom seismometer, crustaldeformation survey and tsunami engineering studies.

Aerial photograph analysis

Aerial photograph analysis is perhaps anotherimportant study that suits the present situation where alarge area is affected by the aftershock activity withwide-spread damage by the tsunami disaster. The recentlydeveloped digital photogrammetry technology enables usto visualize the tsunami damages clearly and to measureheights of the every point where the tsunami arrived. Bymeasuring the heights of the former beach-line, we cananalyze the uplift of the coast. It is important that theaerial photographs must be taken with InertialMeasurement Unit and Position and Orientation System.These systems can give the altitude information (position,pitch and roll) of an airplane, and therefore enable us to

orient photographs precisely in the digital photogrammetryworkstation system without survey on the ground. Evenhigh-resolution satellite images are not enough for suchdetailed observation, and such aerial photographs are sobasic that they can support much observation. TheEarthquake Research Institute (ERI), Japan, is regularlycarrying out such studies and they are fully coping withsuch equipment and data analysis.

Multiparametric geophysical studies

Marine gravity, magnetic, Marine EM studies on aregional basis for the Bay of Bengal region and moredetailed studies near the epicentral zone to map thesubsurface structures. The analysis of the subsurfacestructures will provide basic information about the totalscenario of the seismic processes related to the recentearthquake. Such studies have already been taken upearlier by NIO, Goa (Choubey et al., 1991; Gopalraoet al., 1994). Detailed bathymetric measurements are anecessary requirement to understand the complexity ofthe tsunami wave propagation as seen with numericalmodeling studies. The coastal land use details are anotherimportant parameter. This is mainly due to increased

Fig. 7. The numerical modeling simulation of waveform of the tsunami that must have experienced at different locations. The shape and frequencyof the wave strongly depends on the distance from the epicenter and also on the bathymetry (DCRC, 2005).

Source-DCRC; NumericalModeling Group; TohokuUniversity, Japan; Modeling atsunami generated by NorthernSumatra earthquake, 12/26/2004


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population in coastal regions in recent years for betteruse of marine life, fishing, etc. and also for national andinternational tourism. Deep crust and mantle structure isalso an important aspect in understanding the seismogenicprocesses in the long run. For this purpose, detailed marinegeophysical studies need to be initiated, which would helpto understand the various seismotectonic processes in this

complex region. The studies may include seismictomography, marine MT, marine magnetics and gravity.In fact some studies of marine magnetic and marine EMare reported for some parts of the Indian Ocean by IIG,Mumbai (Iyengar et al., 1992a, b), under a collaborativeprogram with the Ocean Hemisphere Group of ERI,University of Tokyo, Japan (John Joseph et al., 2000).

Fig. 8. World tsunami run-up data (1500-2004) (shown as black round symbol) overlaid on a topographic map with present-day plate boundaries.Concentration of the locations can be observed near Japan and also along the Circum-Pacific region. A few of them are also seen in theIndian Ocean. (Source: http://www.ig.utexas.edu/research/projects/plates/images/topo.pb.gif).

Fig. 9. Distribution of seismograph and observation system around the Japan and its islands that are being used for the tsunami warning system bythe Japan Meteorological Agency (JMA). The instruments used are seismographs=150, high magnification equipment=26. Apart from this,Ocean Bottom Seismometers and array stations also exist for the warning system.


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With international cooperation and collaborative projectsbetween all South East Asian countries and also with theUSA and Japan, results can be achieved within a relativelyshorter period of time.

Ocean network

A highly sensitive deep ocean network is an essentialcomponent in the Indian Ocean. It could detect tsunamisas small as 1 centimeter and instantly transmit the datavia satellite from buoys to nearby warning centers. Suchsystems were established in Pacific Ocean during 2001.“NOAA scientists believe that about 20 such detectorscould provide adequate coverage for coastal warningsaround the Pacific, and 50 would provide the basis of aglobal system,” says Eli Kintisch in his news report inScience (Kintisch, 2005). Figure 10 provides the detailsof the proposed locations around the globe for theestablishment of Deep Ocean Sensor Equipment.

Summary

Past events around the world certainly provide directionto the future. If we see the deaths due to tsunamis in theCircum-Pacific Ocean countries, USGS data gives the totalnumber as close to 53,500 from 1800 till date. Due to thehigh frequency of the onset of tsunamis in the PacificOcean, these countries have learned in their own way tolive with it since centuries. In recent years, a full-fledgedwarning system has also been established. This is anindication of how crucial and important the warningsystem is.

Fig. 10. Proposed locations in the Indian Ocean and around for theestablishment of deep ocean sensor equipment for co-ordinatedtsunami warning systems (from Eli Kintisch, 2005).

Another important aspect one should look at is howmuch preparation is necessary for a natural disaster. Forexample, if an earthquake of magnitude about 6 occursin a populated location in Japan, the number of humanlosses will probably be in single/double digit number,whereas we know the number in a thickly populatedcountry like India for a similar magnitude in Killari inMaharashtra and Bhuj in Gujarat. The number has crossed10,000. The reason for this is lack of attention to qualityconstruction in the well-known seismically active regionidentified in the Kutch region of Gujarat. Many countriesdo not realize the problem till it comes to their doorstep.The formula seems to be that the value of life decreaseswith increasing population.

Among the various known natural disasters such asearthquakes, floods, tsunamis, typhoons, landslides,volcanic eruptions, wild forest fires, etc., warning systemsexist for most, except earthquakes. Developed countrieslike the USA and Japan are fully equipped to cope witheven earthquakes. Many countries need to change theirmindset towards this direction. Modern technology canprevent or reduce the loss of human life and property, notonly in the context of tsunamis, but also other naturalhazards, provided we put it to the best possible use.

Acknowledgments

We would like to thank all the agencies that haveworked quickly to produce the scientific results of thisglobal event of the Sumatra earthquake and tsunami andprovided the information generously in various websites.Without access to such information the preparation of thisreport would not have been possible. We duly acknowledgeUSGS authorities and DCRC scientists of TohokuUniversity, Japan. We gratefully acknowledge the effortsand help rendered by the Chief Editor of GondwanaResearch, Prof. M. Santosh, for the quick review of thismanuscript. The first author had fruitful discussions withhim on the tsunami during a brief visit to Kochi Universityduring January 2005. We also like to thank Prof. H. Utada,Earthquake Research Institute (ERI), University of Tokyo,Japan for all his encouragement during the preparationof the manuscript. The work was carried out by the firstauthor as a visiting professor at Ocean Hemisphere NetworkProject, ERI, and he would like to thank the Institute forextending all the facilities and information for thecompletion of the work within a short period of time.

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