The German Contribution to theTsunami Early Warning Systemfor the Indian Ocean

GITEWSGerman-Indonesian Tsunami Early Warning System

The extreme natural disasters ofrecent years such as earth-

quakes, volcanic eruptions, flood-ing, and last but not least, thetsunami in the Indian Ocean haveshown us that modern societies arebecoming increasingly vulnera-ble. Prevention against all types ofnatural hazards is now more im-portant than ever before. Earlywarning is therefore a top priorityfor science and research. It helpsus to protect human lives andavoid major damage to the econo-my and society.

German research institutions havedeveloped within a very short pe-riod of time a modern tsunami ear-ly warning system which is to be

realized within three years. It is based on tried andtested cutting-edge technologies. Less than twelvemonths after the disaster, it was possible to install thefirst measuring facilities such as seismometers, tidegauges, GPS buoys and ocean floor equipment forthe early warning system in Indonesia. Our good sci-entific relations with Indonesia are based on manyyears of trusting cooperation within the frameworkof the STC Agreement signed in 1979.

Acting quickly after the tsunami disaster in Decem-ber 2004, Germany was able to assist the people inIndonesia and the Indian Ocean rim countries andprovided hope and confidence. German reconstruc-tion activities in the tsunami region are supportedwith ¤500 million, of which ¤45 million are spent onthe establishment of a tsunami early warning system.

The international community has commissioned theIntergovernmental Oceanographic Commission ofUNESCO to coordinate the establishment of a tsuna-mi early warning system for the entire Indian Ocean.Germany and Indonesia are making substantial con-tributions to this system, which will also benefit allother countries bordering on the Indian Ocean. Thedata generated by the German-Indonesian earlywarning system will be available to all countries, foruse in issuing their own national warnings. All coun-tries in the region are therefore invited to contributeto an early warning system covering the entire Indi-an Ocean.

In the future we will need more advanced earlywarning systems to warn against other natural haz-ards and reduce the risk for those affected. The Ger-man Government will initiate the necessary steps.

P R E F A C E

Dr. Annette SchavanFederal Minister of Education and Research

Preface 3A CLEAR SIGNALThe Way to a German-Indonesian Tsunami Early Warning System in the Indian Ocean 4WAVE OF TERRORSunday 26 December 2004 - Disaster Log 6THE SUMATRA FAULT ZONEOne of the Earth's Most Turbulent Regions:the Sunda Arc off Indonesia 8A RACE AGAINST TIMEOverview of the Early Warning System 10ALARMING READINGSThe Land-Supported Observation Network 12WATCHER OF THE SEASThe Marine Monitoring Network 14A COMPLEX BASINModelling Wave Propagation 16IN CONSTANT READINESSThe National Warning Centre in Jakarta 18THE LAST MILEAlerting the Inhabitants, Education and Organisation 20THE EYE IN THE SKYContinuous Tsunami Monitoring with Satellites 22A VIEW OF THE ENTIRE EARTH The Tsunami Early Warning System as a Part of a Global Earth Observation Network 24WE HAVE BEEN WARNEDIncreasing International Cooperation in Disaster Prevention Masthead 26

GITEWS Consortium and Partners/Picture Credits 27

C O N T E N D S

Page 4

Page 6

Page 26

4

The Way to a German-IndonesianTsunami Early WarningSystem in the IndianOcean

After the severe earthquake offSumatra on 26 December

2004, a tsunami hit the coastsaround the Indian Ocean. Morethan 230,000 people lost theirlives. Waves, many metres inheight, destroyed 600,000 houses,and around 1.8 million peoplewere made homeless.

Germany was quick to agree aidfor rebuilding in the region. In ad-dition, everything was to be doneto ensure that such a disaster doesnot happen again. A consortium ofGerman research institutes devel-oped a concept for a tsunami earlywarning system in the IndianOcean. In a joint declaration of 14March 2005, Indonesia and Ger-many agreed to set up such a sys-

To be able to quickly assess thesituation, a national warning cen-tre is being set up in Jakarta. In anemergency, it falls back on thecomputer simulations that havepreviously been calculated forconceivable tsunami events.These generate the possible con-sequences for individual sectionsof the coastline. The aim is to beable to transmit a warning after

5

A CLEAR SIGNAL

...from recording the earthquake of 26 De-cember 2004 with the GEOFON networkand building the first seismic station on theisland of Nias (June 2005), to handover ofthe first tsunami buoys to Indonesia inHamburg in August 2005, and deployingthem into the water off the coast of Suma-tra in November 2005.

The First Steps

tem to be coordinated by the UNESCO IntergovernmentalOceanographic Commission (IOC).

Most tsunamis are preceded bya clear signal in the form of a ma-jor earthquake. Thus the warningsystem is based on a dense net-work of seismometers. The instru-ments are distributed in such away that in the Sunda Arc, thepoint of origin for the greatest riskof a tsunami in the Indian Ocean,

any earthquake can be recordedwithin two minutes at a minimumof three instrument locations. Thefirst German measuring stationswere installed on land as early as2005.

Also in 2005, the German researchvessel "Sonne" deployed the firstoceanographic measuring devicesin the Indian Ocean to carry out re-lated tests. Their purpose is to pro-vide early detection of a tsunami.

Pressure sensors, anchored on theocean floor along the Sunda Arc,indicate the passage of a tsunamiwave, where it is not just the seasurface that rises and falls, but theentire column of water right downto the seabed. The sensors sendtheir data to buoys on the surface.These buoys also detect currentsea levels using a second, indepen-dent method - the Global Position-ing System (GPS).

around ten minutes via clearly de-fined communications pathways.

The sensors are to be installedand the data centre ready for oper-ation by the end of 2008. A two-year operating phase with Germansupport is then envisaged. A com-prehensive training and in-servicetraining programme for scientists,technicians and managers shall en-sure efficient operation, mainte-

nance and ongoing developmentof the system.

In 2010 the tsunami earlywarning system will be handedover in its entirety to the Indone-sian government. Its purpose is toprovide rapid and reliable infor-mation to the population at risk.Here the greatest challenges arerapid transmission of a warningin the event of a disaster. For this

reason, the German-Indonesianjoint project involves extensivemeasures to help regional and localorganisations develop evacuation

plans and educate thepopulation about thedangers of tsunamis,as well as escape op-tions.

The tsunami earlywarning system forthe Indian Oceanshould be seen as partof a warning systemwhose purpose is todetect other naturaldisasters such asearthquakes, volcaniceruptions and storms.The data acquired isto be made availableto all littoral states.

As part of the project, there will befurther development of new tech-nologies, particularly with respectto continuous sea level monitoringfrom satellites. Interlinked withother global Earth observation sys-tems, in the future they could makean important contribution to warn-ing coastal inhabitants well in ad-vance of disasters, and improvingour understanding of the environ-ment in terms of climate change.

6

Sunday26 December2004 - Disaster Log

At 01:59 hours CET (07:59hours local time), 150 kilo-

metres off the island of Sumatrathe earth opens up deep under-neath the sea. The second largestearthquake ever recorded sendstremors through Indonesia and thecoastal region around the Bay ofBengal. It reaches 9.3 on theRichter scale. No less than 10,000kilometres away in Europe, earthmovements of one and a half cen-timetres are recorded. But it is notthe immediate effect of the quake -the destruction of houses andbridges - that turn it into one of theworst natural disasters in the histo-ry of mankind, but the tsunamiwhich it triggers. In the hours thatfollow, waves several metres highcrash over the beaches of the Indi-an Ocean as far as East Africa.They are even recorded in the At-lantic and the Pacific.

02:14 hours: Indonesia is hit thehardest by the tsunami. The break-ing waves lay waste to the north-ern coasts of the island of Sumatra,even tearing down reinforced con-

strikes the population of India af-ter previously inundating the An-daman and Nicobar islands. Morethan 18,000 people drown in thetsunami waves, which rise toheights of up to six metres in themost severely devastated districtof Nagapattinam. As a result of thetsunami, more than 600,000 Indi-ans are made homeless.

05:00 hours: The tsunamimoves on across the low-lying is-lands of the Maldives. Two thirdsof the economic base of a countryliving from tourism and fishing isdestroyed, and more than 11,000people become homeless.

Around 09:00 hours: By nowthe tsunami has also left the Sey-chelles in its wake and reachesEast Africa. Whereas in Kenyamost beaches have been able to beevacuated in time, in Somaliaaround 300 people lose their lives -seven hours after the quake.

crete buildings that meet modernbuilding standards. In Banda Acehthe waves drag 30,000 people totheir deaths, and in the outlyingdistrict of Meuraxa only 10,000 ofits former 40,000 inhabitants sur-vive. According to official esti-mates, the tsunami claims 170,000dead in Indonesia alone, and more

than 550,000 are rendered home-less.

03:45 hours: The tsunamireaches Sri Lanka. In the east andsouth of the island the waves de-stroy 100,000 houses; 35,000 peo-ple die, and more than half a mil-lion lose their homes and all theirworldly possessions. Around the

same time, South West Thailand isalso inundated, particularly theprovince of Phang Nga and thetourist regions around Phuket.Among the 8,000 dead and miss-

ing are 2,500 foreign nationalsfrom 30 countries.

04:45 hours: Although almostthree hours have passed since theearthquake, the tsunami also

WAVE OF TERROR

7

The term "tsunami" (Japanesefor harbour wave; from

"tsu" - harbour, and "nami" -wave) was coined by Japanesefishermen who would returnfrom a fishing expedition to findtheir harbours devastated by thesea, even though they had notnoticed any unusual wave passthem out at sea. The reason forthis is Japan's steep coast,which falls away into deep wa-ter. The gigantic waves more orless only start to build up shortlybefore the shore, and then breakover the harbour walls, destroy-ing everything in their path.

The Big Wave in theHarbour

to oscillate violently. The wavesthat arose along the rift spread outin all directions and ran towardsthe surrounding coasts.

Unlike in the case of a storm,during a tsunami it is not just thewater surface that oscillates. If theocean floor rises or drops, it is theentire ocean lying above it that al-so moves in harmony - in the caseof the Sumatra quake, a column of

8 9

THE SUMATRA FAULT ZONE

One of theEarth's MostTurbulent Regions:the Sunda Arcoff Indonesia

There can hardly be a regionwhere the forces which shape

our planet make themselves feltmore greatly than in Indonesia.Two great tectonic plates meet justoff Sumatra, and the tensions be-tween them repeatedly result inviolent earthquakes. On the faultline between these plates, a vol-canic archipelago and an oceantrench have developed.

The earth's crust consists ofabout a dozen such plates. Theyare in constant motion againsteach other. The continents are onaverage 40 kilometres thick, theirrocks being over two billion yearsold. The ocean floor, on the otherhand, is at least ten times more re-cent and considerably thinner. Itsrocks are formed at the mid-oceanic ridges and are movedaway to the plate edges as if on agreat conveyor belt. If an oceanic

plate meets a continental plate atits edges, then its relatively heavyrocks are submerged under the lat-ter. They are swallowed up, andtheir component materials are re-cycled within the Earth.

In the Sunda trench off Indone-sia, the Indian-Australian Plate ismoving at a speed of six centime-tres a year (hardly faster than ittakes for a fingernail to grow),sliding under an appendage of theEurasian Plate. But this is not hap-pening without resistance. Theconveyor belt is shaking. Betweenthe interlinked rocks, stresses de-velop, and after the passage ofmany decades these may suddenlybe discharged.

On 26 December 2004, theEurasian Plate suddenly made aquick advance, causing thestrongest earthquake ever record-ed in this region. In the seabed acrevice yawned open, which with-in eight minutes, extended for1,200 kilometres northwards - afault more or less the same as thedistance between Berlin andRome. Along this fault line theearth's crust was thrown upwardsby up to fifteen metres.

The worst consequences werenot however produced by the earthtremors themselves, but the tidalwaves they triggered - the tsuna-mi. As the quake happened, theocean floor was lifted in someparts by a few metres, and in oth-ers it dropped. This jolting move-ment made the Indian Ocean start

The sudden release of the upper plate due to an earth-quake can result in a tsunami. The illustration on theright shows an underwater shot of the ocean floor offSumatra after the large quake of 26 December 2004.

Powerful Forces

water around 5,000 metresin height. This is what ac-counts for the powerful ener-gy in the gigantic waves andwhich can be carried overmany thousands of kilome-tres to the surroundingcoasts.

On the open seas, thewaves that formed off the is-land of Sumatra were initial-ly only 60 centimetres inheight, and with a wave-length of around 250 kilo-metres they were barely de-tectable by ships' crews. Itwas only near the coasts that

the tsunami showed its true face.In the shallow coastal waters, theocean floor acted as a brake on thewaves, making them tower up androll on towards the land. In someareas, the tsunami forced the wa-ter many kilometres inland. InBanda Aceh, for instance, 500 me-tres of coast were simply carriedoff, washed away, whereas lateron a large salt lake developed inthe hinterland.

10

Overview ofthe EarlyWarning System

You do not have to wait longfor the first warning signal.

During an earthquake, the shock-waves radiate out through the sub-surface at breakneck speeds, someof them at 30,000 kilometres anhour. This means that in Indone-sia, with the help of a dense net-work of seismometer stations, youcan determine within a couple ofminutes whether an earthquakehas happened along the SundaArc.

Such rapid measurements openup the possibility of giving ad-vance warning of what in certaincircumstances is the still greaterdanger - a tsunami. In comparisonto seismic waves, the tidal wavestriggered by an earthquake areslow. In December 2004, it tookup to one and three quarter hoursafter the quake until the coasts ofSri Lanka and Thailand were inun-dated; with proper preparationsthis gives a lot of time in which toalert the population.

It only took a quarter of an hour,on the other hand, for the tsunamito break over the coast of Sumatra.

This is where the great challengelies when it comes to constructingan early warning system in the In-dian Ocean. How to give a reliabletsunami warning within just tenminutes so that it also reaches theinhabitants of the endangered re-gions of Indonesia in good time?

On the other hand, not everyviolent earthquake triggers atsunami. On 28 March 2005, forinstance, the ocean floor onceagain split open off Sumatra dur-ing a quake of 8.7. This time afracture of more than 300 kilome-tres developed; but contrary tofears, this time it was not followedby the kind of devastating tsunamiof three months previously. Itwould appear that during thisearthquake the vertical displace-ment was only very small.

To be able to alert the popula-tion quickly and reliably, the earlywarning system in the IndianOcean is therefore based on a com-bination of several components:

1) The land-supported observa-tion network

Fully automated seismometersmonitor the region constantly andare able to detect and locate anearthquake in a very short time, aswell as determine its strength.They also trace the faultingprocess, which may last for min-utes. For this, the measuring sta-tions are also equipped with Glob-al Positioning System (GPS) re-ceivers. These give precise deter-

A RACE AGAINST TIME

11

mination of the displacement ofthe Earth's crust (pages 12 and 13).

2) The marine measuring net-work

Only measurements in theocean itself can determinewhether a tsunami has actuallybeen triggered. This requires a se-ries of buoys along the Sunda Arc.These link up with pressure mea-suring devices on the ocean floorand also detect the mean sea levelvia GPS sensors. If waves nowrun against the coast, their heightis once again measured on the off-shore islands using tide gauges(pages 14 and 15).

3) Modelling wave propagation As soon as the measuring in-

struments have detected a possi-ble tsunami, the next step is to es-timate what part of the coastmight see the tsunami piling up toa dangerous height and what theestimated time of arrival of thewaves might be there. Model cal-culations of this kind take a lot oftime. This is why conceivablescenarios must be generated inadvance for the entire region, sothat in an emergency the mostlikely scenario based on the cur-rent data is to hand in a very shorttime (pages 16 and 17).

4) The national warning centreAll the data from the measuring

stations converge via satellite onan incident centre in Jakarta.

Those responsible at national lev-el analyse the risk and send out awarning if there are signs that atsunami might follow a largeearthquake. This warning is dis-seminated via predeterminedcommunication channels. It con-tains details of the likely loss anddamage in terms of the populationand infrastructure (pages 18 and19).

5) Alerting the inhabitants, edu-cation and organisation

Only well trained staff can usethe warning system to its fullestand improve it. The staff can en-hance their specialist and organi-sational skills in training units andworkshops, and scientists andPhD students have the opportunityto spend time researching in Ger-many. As part of this "CapacityBuilding", the inhabitants are alsoeducated on the dangers oftsunamis and the proper proce-dures, a process that begins atschool and finishes with evacua-tion exercises (pages 20 and 21).

System (GPS) allows very preciselocation detection of any point onthe Earth. This procedure there-fore also allows us to determinewhether the position of islands andsections of coast in the fault zonehas changed significantly. In thecase of the December 2004 earth-quake, for instance, some of theAndaman and Nicobar islandswere moved laterally by up to sixmetres and lifted by a maximum oftwo metres, whereas in otherplaces they dropped by up to onemetre.

An early warning system needsto be able to acquire a rapid pictureof shifts of this kind. And so, in fu-ture, GPS will constantly recordthe movements of the earth in thefault zone. The receivers for thesatellite signals are being installedon the offshore islands in the Sun-da Arc. This combination of twointerlinked GPS stations allowsminimisation of any potential er-rors on position calculation.

Along with the equivalent refer-ence stations on the mainland,they provide detailed informationon lateral movements and rates oflift and sinkage.

12 13

The Land-SupportedObservationNetwork

An earthquake is a violent joltwhere millions of tons of rockmove against each other in a veryshort time. Part of this energy isdistributed into the Earth's centreand in the form of waves acrossthe Earth's surface. These seismicwaves may travel around the en-tire globe a number of times.

Eleven minutes after the De-cember 2004 earthquake, theshock waves emanating from theSunda Arc reached Europe. TheGEOFON earthquake measuringnetwork, developed in Potsdam,automatically recorded the quakeand evaluated the data. Only twominutes later - also without anyhuman intervention - an earth-quake message was broadcast onthe Internet, and e-mails and SMStexts were sent to linked users.

So far, the stations of this net-work have mainly been concen-trated in Europe and linked withmeasuring networks of othercountries. For tsunami early warn-ing, the GEOFON network is be-ing extended in the region aroundthe Indian Ocean. The first four

German stations have alreadybeen installed in 2005, with 30 to40 new stations planned, half ofwhich are to be located in Indone-sia. In addition, Indonesia, Japanand China are extending theirearthquake monitoring system,and measuring locations alreadyin existence are being updated toinclude automatic operation andsatellite communication. The fullmonitoring system in the region isto comprise more than 100 sta-tions in total.

At the various locations, seis-mometers constantly measureearth movements over broad fre-quency ranges, especially alongthe Sunda Arc, which extends formore than 5,000 kilometres. Manystations are being built parallel tothe cost and on the offshore is-lands. However to obtain the mostaccurate picture possible of futurequakes, distribution by area is alsorequired. Basically, the nearer thestations are to the epicentre, thequicker they record the quake; butequally the harder it is to filter outthe relevant information. At moreremote stations, the seismic wavesdo indeed arrive rather later, but itis only these measurements thatenable the location and strength ofthe tremors to be precisely delim-ited.

It should not take more than oneor two minutes to automaticallydetect and evaluate an earthquakeoff Indonesia at three or four loca-tions, given the density of measur-

ing devicesenvisaged. Af-ter anothertwo or threeminutes amore accurateestimation ofthe location ofthe epicentreand of earth-quake magni-tude becomespossible. Thelocation andstrength of anearthquakeprovide thefirst indica-tions to sug-gest the possi-ble occur-rence of atsunami wave.What is nowvital for themodel calcu-lations is that

additional information be provid-ed as quickly as possible as to thedirection the rupture in the Earth'scrust takes and how long it is.

Seismometers distributedacross a wide area can follow thefaulting process throughout theentire earthquake. A supplemen-tary picture of where the greatestdisplacements in the Earth's crusthave occurred will also resultfrom highly accurate GPS mea-surements. Today, satellite navi-gation with the Global Positioning

ALARMING READINGS

The earthquake stations set up so far (the illus-trations on the left) deliver their data via satel-lite links more or less in real time to the centre inJakarta. There the information is collected via agreat satellite antenna from the whole of thecountry. The intention is to provide all measuringlocations with realtime communication.

Realtime Signals

14

The MarineMonitoringNetwork

When in November 2005the German research ves-

sel "Sonne" deployed an almostseven metres long buoy onto theopen seas, an important milestonein the construction of the earlywarning system was achieved.The yellow buoy and its counter-part deep down on the ocean floorare prototypes of the measuringinstruments that are to be able todetect a tsunami even when out atsea, i.e. during the formationphase.

The alarm comes from depthsof up to 5,000 metres. The under-water unit records the passage ofthe wave. This is possible becauseduring a tsunami the entire volumeof water is set in motion - from thesea surface right down to theocean floor. Every 15 seconds asensor on the ocean floor mea-sures the pressure exerted by thecolumn of water above it.

There are good reasons for mea-suring the tsunami on the oceanfloor. A pressure sensor on theseabed can detect sea level fluctu-ations of a few millimetres. Theprocedure is elegant because a

measuring device at such a depthdoes not register short-term seamovements. It is blind to small,wind-driven surface waves andonly retains the mean water level.The pressure sensor is supple-mented by a seismometer, whichcan immediately detect a quakewhen it happens.

A number of times each day, theunderwater unit transmits the ac-cumulated data to the buoy via anacoustic signal. In an emergency,however, when the water level hasexceeded a threshold value, thedata is transmitted immediately.The buoy itself is the relay stationfor data transfer between the mea-suring device on the ocean floorand a satellite that then relayscommunication to the warningcentre. It also records meteorolog-ical factors, and registers for ex-ample air pressure and windspeed. Changes in air pressure inparticular could simulate a tsuna-mi. This has to be kept in mindwhen calculating the height of thewater, as is also the case with theregular tides.

The early warning system in-cludes ten such buoys and oceanfloor units. By the end of 2008they will form a chain along theSunda Arc keeping track on thewater level around the clock. Inaddition to the pressure sensors onthe seabed a second independentprocedure is employed so as to en-sure greater reliability of the sys-tem - namely GPS devices fitted to

15

WATCHER OF THE SEAS

In 2005 two buoys and pressure sen-sors were deployed into the water fromthe research vessel “Sonne”. The sen-sors record signals on the seabed thatare sent in the event of an alarm via thebuoys to the warning centre.

Alarm from the Depths

the buoys. These communicatewith navigation satellites of whichthere are now many in orbitaround the Earth. The distance tothe satellite can be calculated fromthe required runtime of the GPSsignals from the satellite to thebuoy, and, if the satellite path isknown, the mean sea level can al-so be calculated. The aim is toanalyse the data immediately onlocation at the buoy. In the firstphase, however, the desired accu-racy of measurement is to beachieved by the buoy interactingwith a land-based reference sta-tion.

On the open sea a tsunami is on-ly a few decimetres high, whereason the coast waves several metreshigh can build up. Here gauge sta-tions are to supply reliable data onthe current water level at the time.In the event of a disaster this is animportant requirement for target-ing rescue measures and givingadequate advance warning tomore remote areas. On the sea-ward side of the islands off thecoast of Sumatra, and along the In-donesian coast, the gauge networkis being modernised and extendedaccordingly. In addition, stationswith two pressure gauges and aradar gauge are planned, and theywill transmit the water level every15 seconds to the warning centre,as required.

16 17

ModellingWave Propagation

It was no single impact that setthe Indian Ocean in motion on

26 December 2004. The tsunamiwave emanated from a 1,200-kilo-meter long fault. Along this frac-ture, the waves piled up to form awide wall of water that ran towardsthe surrounding coasts and inundat-ed beaches, towns and villages. Incertain places the waves were re-flected, or else they passed aroundislands. After the devastatingfloods, the Indian Ocean carried onreverberating for a whole day.

To be able to predict tsunamis,you first need information on thequake. The sea level rises or fallsdepending on the extent to whichthe ocean floor rises or drops duringthe earthquake. The way in whichthe wave that develops then spreadsout and where it finally hits land de-pend however on the relief of theseabed and its transition to thecoast.

The Indian Ocean is contained ina narrow belt of shallow water - theshelf. Just off this shelf zone, theseabed falls away sharply; up to4,000 or 6,500 metres deep, de-pending on the region. The Sunda

trench is even deeper in parts.Archipelagos, underwater moun-tain ranges and ridges divide theocean into several basins.

The craggy mountain landscapeon the ocean bed is being surveyed,among other features, by the Ger-man research vessel "Sonne", to ob-tain reliable information on waterdepths. This is because the speed ofa tsunami depends exclusively onthe depth of water: the deeper thewater the faster the wave.

In an ocean of 7,000 metres indepth, the waves spreads out at aspeed of 950 kilometres per hour -the speed of a jumbo jet. On theopen seas the tsunami wave extendsover hundreds of kilometres. How-ever, it only attains the rather unas-suming height of a few decimetres.But as it approaches the coast, thespeed drops rapidly, alreadyamounting to less than 40 kilome-tres per hour in shallow water of 10metres deep. The wave height, onthe other hand, rises to severaldozen metres. Off Thailand theshallow water zone extends out along way. This is why in December2004 the tsunami needed a verylong time to reach the coast of Thai-land - just as long as the much moreremote coasts in East India and SriLanka.

There are particularly abruptchanges in the behaviour of a tsuna-mi at the edge of the shelf. The waveis suddenly subjected to a brakingeffect and more and more waterpiles up from behind. The tsunami

A COMPLEX BASIN can even split into two or threewaves. On the increasingly shallowshelf, the wave builds up to ever in-creasing heights, until it becomesunstable and breaks. Finally the wa-ter runs onto the beach in the formof a wall several metres high.

The extent to which the individ-ual sections of coast are at risk canonly be predicted if local circum-stances are taken into account.Where large islands off the coastform chains as they do off Sumatra,some areas are in the islands' sha-dow. Elsewhere, on the other hand,there are funnel shaped bays or riverestuaries that the water mass runsinto, increasing in speed and height.It is a similar story in the hinterland.Here, for instance, there are drainsin wide urban streets where thereare concrete buildings, and the wa-ter mass flows through, whereasdense mangrove forests can slowand stop the floodwater.

Because of the complex topogra-phy of the seabed and the coast, de-termining wave propagation andrisk potential with computer simu-lations is very time-consuming. Therelevant calculations approximat-ing to reality must already havebeen made before any potential dis-aster. And they must cover hun-dreds of potential earthquake focialong the Sunda Arc as well as a va-riety of earthquake intensities. Inthe event of an earthquake, the sim-ulation model that best matches thecurrent data can then be used.

Knowledge of the structureof the ocean floor plays amajor role in simulating thewave runtimes and heights

Mountain Rangeson the Ocean Floor

18

The NationalWarning Centre in Jakarta

The decisive interface of thetsunami early warning system

is the national warning centre,which is manned around the clock.This is where all the data arrivesfrom earthquake and GPS mea-surements, as well as water levelheights from ocean buoys andcoast gauges. They have to beavailable to the staff on duty asquickly as possible. On the basis ofthis information, the assessment ismade whether, where and in whatstrength a tsunami might occur.In an emergency, the distributingcentre extracts the prepared cata-strophe scenarios from a database.These contain estimates on theruntime of the wave and the ex-pected wave height, as well as dataon the risk areas. This informationis sent with a warning to the gov-ernment, the provinces at risk, lo-cal authorities, aid organisationsand the general public, to deployrapid evacuation measures and sethumanitarian aid in motion.Indispensable preconditions forrapid warning are an adequatecommunications network, and

clear communication and com-mand structures. The seismic datais recorded around the clock. Oneach earthquake recorded, thestrength and position of its focuscan first be roughly estimated. If itturns out that this is an earthquakethat might trigger a tsunami, theentire early warning centre isplaced in an increased state ofreadiness.In the warning centre the situationis constantly assessed using thecurrent measurement results, withvarious databases being accessedin the search for a rapid decision.Here the model calculations are al-so stored. By the time the system iscommissioned, as many conceiv-able scenarios for tsunami eventsin the Indian Ocean as possibleshould have been enacted for theentire region. This is how thewarning centre will quickly havethe best matching scenario avail-able for the constant incomingstream of measuring parameters.From all of this it can be deducedwhen and at what height the waveswill arrive and on what sections ofthe coast.In particular, for decision makersit is important to be able to form anoverview as quickly as possible ofthe extent of a possible disaster.For them it is important to knowwhich area and which parts of atown are hit, how many people livethere, whether transport routessuch as bridges are at risk, andwhat industries are based in the re-

gion. The warning centre also hastopographical maps and currentdata sets on settlement structures,density of population, demograph-ic developments, transport net-

19

IN CONSTANT READINESS

The satellite pictures show a part ofthe north western coast of BandaAceh (Indonesia) before and afterthe devastating tsunami hit many lit-toral states of the Indian Ocean onBoxing Day 2004.The tidal wave swept away almostall of the densely populated spit andmany parts of the fields used foraquaculture. Banda Aceh was one ofthe most severely damaged towns.

A Picture of Desolation

works, infrastructure and industry.All the relevant information is in-put into preassembled documentsand forwarded to the relevant of-fices.In the event of a disaster the warn-ing centre obtains more detailedinformation on the current situa-tion. In particular, this includes da-ta from Earth observation satel-lites. This can help to assess thedamage caused and coordinateaid. It can also help in quicker ex-change of information with neigh-bouring countries. The national in-cident centre in Jakarta is integrat-ed in an international network ofwarning centres in the IndianOcean, whose construction is be-ing coordinated by UNESCO.

20 21

Alerting theInhabitants,Educationand Organisation

After the first tsunami wavewashed over Banda Aceh on

26 December 2004, taking every-thing in its wake, many survivorsreturned to the beaches to look fortheir missing family members orfriends. They were not aware that,with the delay typical for longtsunami waves, a second and thirdwave were still to come so they ranto their deaths.

Tsunamis are rare occurrences.The disaster in Indonesia has madeit clear in many respects how im-portant it is to make the populationpermanently aware of the dangersof such tsunamis. The people inthe areas at risk were not informedof the significance of the sea sud-denly receding after an earth-quake, or when a first tsunamiwave has already devastated thecoast.

The most important and mostdifficult stage of a tsunami earlywarning system is warning thoseliving in the coastal regions - thelast mile. Life-saving measures

will only work if the warningreaches the inhabitants quicklyand in a comprehensible form, andif as many as possible are alreadyaware of the potential danger.

Even a strong earthquakeshould result in increased alertnesson the part of the population. Toachieve this, awareness of the in-terconnections between earth-quakes and tsunamis must bebrought into the school curriculumand adult education. The alarm it-self can be broadcast on radio andtelevision; typically sirens andloudspeaker systems are used.Since there is no electricity insome rural areas of Indonesia,mosques and other institutions canalso be involved and equippedwith loudspeakers.

People in the regions at riskmust also know where they shouldescape to in the event of a disaster.Suitable safety zones should bedisplayed based on risk maps andescape plans; and evacuation-training exercises help to acquaintindividuals with disaster protec-tion measures.

For the institutions involved itis important to operate the earlywarning system efficiently andimprove it step by step. Above all,communication between the na-tional and regional institutions, aswell as the local decision makersshould be smooth and problem-free. For this, clearly agreed re-sponsibilities are needed, with lo-cal issues being involved at an ear-

ly stage in the early warning con-cept.

"Capacity Building" covers abroad programme of training andin service training. Training unitsare envisaged giving the staff theopportunity to extend their indi-vidual and organisational skills.The individual workshops dealwith the communications infra-structure, management duties, andthe specialist and technical aspectsof early warning. Scientists, engi-neers and technicians from the lit-toral states are therefore inductedon site in the functioning of thesystem, its maintenance and fur-ther development.

Established researchers can ac-quire further qualifications as partof an academic educational and

training programme. The possibil-ity of engaging in joint researchwork with German institutions ismade available to them. During afour year period, six scientists willbe invited to spend one or twomonths in Germany.

In addition, eight doctoral stu-dents from Indonesia and the ad-joining countries are on three-yearcourses in Germany. During thistime they are involved in the con-struction of the system and arecontinually in contact with the in-stitutions of their home country.Part of the plan is that they will re-turn each year for six to eightweeks. The entire programme oftraining and in-service training isagreed in close cooperation withUNESCO.

THE LAST MILE

... play a major role in educating thedecision makers.The evacuation of the inhabitantsmust be tested ready for the realthing. With illustrative training mate-rials in the language of the countryand regular alarm exercises, anawareness of the dangers can be de-veloped early on right now.

Information and Training

22 23

ContinuousTsunami Monitoringwith Satellites

Thanks to new technologies, inten or twenty years a tsunami

early warning system could differsignificantly from today. Insteadof measuring wave movementswith buoys and tide gauges at cer-tain points, it would be cleverer tomonitor the ocean from space andthus to obtain an overall picture ofthe tsunami as it develops andspreads.

Satellite observations of 26 De-cember 2004 provide some indica-tion that this should be possible. Inthe hours after the earthquake, theFranco-American satellite Jason1, the European satellite Envisat,and the American satellite Geosatall passed over the Indian Oceanand recorded the heights of thewaves in succession. Based on thisdata, scientists later reconstructedthe path that the tsunami had tak-en. They also found that the tsuna-mi waves on the open sea were nomore than 60 centimetres high.

These satellites work with anactive radar system. Their antenna

transmits radar waves in the formof short, consecutive signals.These waves are propagated at thespeed of light and reflect if theystrike the surface of the sea. Thesatellite antenna records the re-flected signal. The distance cov-ered can be determined from theruntime, and as a result the dis-tance of the satellite from the seasurface.

There are already a few satel-lites that measure mean sea levelin this way. However, such satel-lites are relatively large and ex-pensive. An alternative is to linktsunami observation from spacewith satellite systems already inexistence or currently under con-struction, such as the Global Posi-tioning System (GPS).

There are currently 24 Ameri-can GPS satellites orbiting theEarth. With the European Galileosystem, this figure will more thandouble by 2010. Even today, atany point on the Earth's surface,the signals from at least four suchsatellites can be received. In satel-lite navigation the runtimes ofthese various signals are used todetermine one’s location. They al-so allow measurement of mean sealevel.

It is true that the GPS satellitesignals are not as strong as thoseof the Earth monitoring satellitesdesigned for measuring heights.However, they are distributed overthe sea surface in the same way.Additional small satellites can re-

ceive these reflected GPS sig-nals in a low orbit and simulta-neously measure the distance tothe GPS satellite. The combina-tion of this data then gives themean sea level calculation (seechart).

The advantage of thismethod is that the receivingsatellites do not need an activeradar system, but only an activeGPS and communication sys-tem. Tsunami observation fromspace can make do to a large ex-tent with specialised smallsatellites involving low-levelorbits around the Earth. Overtime, all the oceans could thusbe monitored with just a fewcost-effective satellites. Thesesmall satellites could also carryout other types of work, such astasks related to climate model-ling. Initial tests for such a sys-tem are already being carriedout by the German georesearchsatellite CHAMP, among oth-ers.

THE EYE IN THE SKY

First attempts at observing the sea level by satel-lite have given promising results. It is conceivablethat in the future this technology could also beused for early warning.

New Technologies

24 25

physical observation network(GEOSS or Global Earth Observa-tion System of Systems) over thecoming years. The coordinationcommittee between the participat-ing states is based in Geneva, andEurope is making an importantcontribution in terms of the cre-ation of a set of earth observationsystems (GMES or Global Moni-toring for Environment and Secu-rity).

Nowadays navigation satellitesare seen as the lodestars for trans-port by road, air and sea. Earth ob-servation satellites could becomethe new lodestars for disaster pre-vention. They deliver more thanjust impressive pictures. For yearsthey have been playing an ever in-creasing role in warning of ex-treme world events and in diagnos-ing natural disasters such asstorms, tidal waves, or forestblazes, as well as the resultingdamage. Advancing desertifica-tion and the retreat of glaciers dueto climate change are also coveredby the Earth observation satellites.It will only be internationallylinked, ongoing data acquisitionon our environment that will allowus to see how the natural equilibri-um formed over millennia is beingchanged by human activities.

The TsunamiEarly WarningSystem asPart of a Global EarthObservationNetwork

The tsunami disaster of Decem-ber 2004 has renewed the dis-

cussion as to how people onoceanic coasts can in future bewarned of such dangers. The UNESCO IntergovernmentalOceanographic Commission(IOC) is pursuing the aim of set-ting up a worldwide tsunami earlywarning system. As early as 1960the IOC was coordinating a re-gional warning system in the Pa-cific. For decades it remained theonly one of its kind, although therewas repeated insistence on the im-portance of installing similar sys-tems in other regions.

In January 2005 the IOC wascommissioned by the United Na-tions to coordinate the measures ofthe littoral states in the construc-tion of a tsunami early warningsystem in the Indian Ocean. The

main aim of the German-Indone-sian initiative is to create reliablestructures, which are usable overthe long term, for such a warningsystem in the region most at riskfrom earthquakes, the Sunda Arc.The German and Indonesian re-search ministries signed a cooper-ation agreement relating to this on14 March 2005.

All activities within the Ger-man-Indonesian project for settingup an early warning system for theIndian Ocean have been agreedwith the IOC. The data for rapid

warning of the population is to bemade available to all the littoralstates of the Indian Ocean. Thesystem is of such flexible designthat integration of the seismic oroceanographic measuring net-works of other countries in the re-gion has proved to be possible.

Over the long term, this kind of

A VIEW OF THE ENTIRE EARTH

Natural dangers such as earth-quakes, tsunamis or volcaniceruptions are distributed more orless throughout the world.Some regions of the Earth, suchas Indonesia, however, are espe-cially at risk. To the right of thepicture Jakarta is highlighted;the volcanic craters on the islandof Java can easily be made out.

Many Different Dangers

system can be transposed to otherregions of the Earth. In view of therisk of earthquakes in theCaribbean or Mediterranean, theIOC is considering setting up atsunami early warning system inthese areas as well. Due to theshort distances and short advancedwarning times, these areas repre-

sent similar challenges in terms oftechnology and management tothose in the Indian Ocean.

The concept for the German-Indonesian early warning systemalso envisages later interlinkagewith another global monitoringsystem. The aim of internationalefforts is to build up a global geo-

26

Increasing InternationalCooperationin DisasterPreventionEarthquakes occur at points

where rigid blocks of theEarth's crust strike against eachother. If the tensions between suchplates suddenly discharge, and oneof them suddenly moves forward,it can lift up the entire ocean aboveit and trigger a powerful tsunamiwave. We may assume that in fu-ture Indonesia, given its immedia-cy to the seismically active SundaArc, will again be the country tobe hit most strongly and most fre-quently by such tsunami events inthe Indian Ocean.

The tsunami of December 2004devastated beaches and villages,swallowing up houses and vehi-cles. There was no reliable data onthe strong earthquake and no pos-sibility of warning people of theimpending disaster. The wavesalone, which reached Thailandand Sri Lanka after one and a halfhours' delay, and then India stilllater, took tens of thousands totheir deaths because informationwas not passed on, and because

there were no evacuation plans forsuch a disaster scenario.

The tsunami early warning sys-tem that is now being developedunder the auspices of German-In-donesian cooperation can make avital contribution to the region be-ing better equipped in future topredict the waves. It does thisthrough specially developed tech-nology, reliable information andrapid communication. It forms apart of the IntergovernmentalOceanographic Commission(IOC) of the UNESCO coordinat-ed warning system, and as suchrepresents a milestone of interna-tional cooperation in disaster pre-vention.

To a greater degree than everbefore, the extent of the tsunamidisaster in the Indian Ocean hasopened the eyes of the world to thefuture importance of developingearly warning systems and Earthobservation. They can do humani-ty an invaluable service in limitingthe effects of natural disasters suchas earthquakes and tsunamis, vol-canic eruptions and storms, and inextending our knowledge of glob-al and regional changes to the en-vironment.

WE HAVE BEEN WARNED

Published by:GeoForschungsZentrum PotsdamTelegrafenberg14473 Potsdam, Germany

Responsible: Dr. Jörn Lauterjung,Dr. Alexander Rudloff

Design and text: Thomas de Padova

Layout: Otto Grabe

Translation: JMCommunication,Vienna, Austria

Printed in Potsdam1st edition, May 2007

M A S T H E A D

Picture Credits:

All illustrations are by the GFZ Potsdam, except for:

Page 3: BMBFPages 6, 19 top: J. Borrero/

USC/TRC Page 7: UN/E. Schneider

Page 9 right: JAMSTECPage 10 top, 24 top, 25: ESAPages 15, 16 top, 17 top:

IFM-GEOMARPages 18/19: DLRPages 20/21: J. Sopaheluwakan/

LIPI

For further information please visit: http://www.gitews.org

The “German-Indonesian Tsunami Early Warning System”(GITEWS) is a contribution on the part of the German govern-ment to rebuilding the infrastructures in the region of the Indi-an Ocean. The project is funded by the German Federal Min-istry of Educational Research (BMBF).

GeoForschungsZentrum Potsdam (GFZ), Potsdam (Consortium Leader)

Alfred Wegener Institute for Polar and Marine Research (AWI),Bremerhaven

Federal Institute for Geosciences and Natural Resources(BGR), Hannover

German Aerospace Centre (DLR), Oberpfaffenhofen

Deutsche Gesellschaft fuer Technische Zusammenarbeit (GTZ)GmbH, Eschborn

GKSS Research Centre, Geesthacht

German Marine Research Consortium (KDM), Berlin

Leibniz Institute of Marine Sciences (IFM-GEOMAR), Kiel

United Nations University, Institute for Environment and Hu-man Security (UNU-EHS), Bonn

GITEWS - Consortium

Indonesian Partners

• State Ministry of Research and Technology (RISTEK), Jakarta

• Meteorological and Geophysical Agency of Indonesia (BMG), Jakarta

• National Coordinating Agency for Survey and Mapping (BAKOSURTANAL), Cibinong

• Agency for the Assessment and Application of Technology (BPPT)

• National Institute for Aeronautics and Space (LAPAN)

• Indonesian Institute of Sciences (LIPI), Bandung

• Ministry of Communication and Information Technology(DEPKOMINFO), Jakarta

• Secretariat of National Coordinating Board for Disaster Management and IDPs (BAKORNAS PBP), Jakarta

GFZ Potsdam, AWI, DLR and GKSS are members of theHelmholtz Association of German Research Centres