TSUNAMI EARLY WARNING SYSTEM IN MALAYSIA
Norhadizah Bte MOHD KHALID*
MEE06014

Supervisor:

Yohei Hasegawa**
Yosuke Igarashi**

ABSTRACTThis study is on how to make the database for tsunami forecast using the tsunami simulation, retrieve andapply it to the Tsunami Early Warning System messages. Firstly, we searched the seismicity around
Malaysia and found out the tsunamigenic earthquakes by comparing the earthquake event with thetsunami record. The earthquake events shallower than 100 km and trench area were considered thepotential tsunami source. The most appropriate forecast points were determined by setting up andexamining candidates along the coast of Malaysia, each of which has 4-minutes, 10-minutes, 20-minutes
distance from the coast and they were with the 10-minutes intervals along the coast. Later, magnitude anddepth interval are set up by considering the historical events. The magnitude intervals are 6.6, 7.2, 7.8,
and 8.4, and depth intervals are 30 km, 50 km, 70 km and 90 km. The tsunami simulation is run for all theset up tsunami source and the result of tsunami height and travel time for all the forecast points are input
into the database. The location of tsunami source is calculated using interpolation or extrapolation.
Keywords: Forecast point, Travel time, Tsunami height, tsunami simulation.

INTRODUCTION
After the 26 December 2004 tsunami disaster, Malaysian government has decided to set up the national
tsunami early warning system to provide early warning on tsunami that are generated from subduction
zone area such as Indian Ocean, South China Sea, Sulu Sea and Pacific Ocean. The tsunami warningsystem consists of sub-system that provides real-time monitoring, alert seismic and tsunami activities.

EARLY WARNING SYSTEM PROCEDURE
Tsunamigenic Earthquake Locations
Earthquake events can be searched through the internet. The earthquake event was searched through theGlobal CMT Catalog Search for the years from 1976 until 2007 (present) from the internet(http://www.globalcmt.org/CMTsearch.html). The magnitude was set up from 6.0 to 10 and the depth
from 0 to 100 km to determine the location of tsunamigenic earthquakes. The depth and magnitude wereset based on the historical event. Comparison is made with other search data from National GeophysicalData Center (NGDC) Tsunami Event Database (http://www.ngdc.noaa.gov/seg/hazard/tsu_db.shtml) andIntegrated Tsunami Database (WinITDB). The NGDC Tsunami Event Database and Integrated Tsunami* Malaysian Meteorological Department, Malaysia, ** Japan Meteorological Agency, Japan

Database have much wider data from the year -2000 until 2007 and from -1628 until 2005, respectively.
Thus, neither of the databases gave any information on the fault parameters.
Therefore, this source of data were compared in the time of event, location and also depth to Global CMT
Catalog Search that has given the fault parameters that match each other to determine the tsunamigenic
earthquake event around Malaysia (Figure 1).
Surface Deformation
The dislocation theory was introduced by
Steketee (1958) and also by Rongved andFrasier (1958). All the papers revealed that theeffect of earth curvature is negligible for theshallow events at distances of less than 20°,
but the vertical layering or lateral
inhomogeneity can sometimes cause effects on
the deformation fields Okada (1985).
Earthquake generates tsunamis when the sea
floor deforms and vertically displaces theunderlying water of the equilibrium position.
The factor which determines the initial size oftsunami is the amount of vertical seafloor
displacement determined by the magnitude ofearthquake, depth and fault plane mechanism.
In this case, length, width anddisplacement of fault plane were determined
Tsunamigenic earthquake eventfrom magnitude using empirical formula.
Figure 1 Location of tsunamigenic earthquake
Meanwhile, the strike is set to be parallel toevents.
the trench, considering that most of theearthquakes happen along the trench: the dip is45° and slip is 90°. The dip and slip were set at these values because it is the worst case scenario oftsunami. The location of the hypocenter and source rupture is assumed to be in the middle of the fault
plane.
Bathymetry data
In this study, the bathymetry and topography data of ETOPO2 (2-minute grid interval) were downloaded
from the internet (http://www.ndgc.noaa.gov/mgg/global/global.html). The ETOPO2 bathymetry data
grid was derived from the satellite altimetry observations and gravity data were combined with shipboard
echo-sounding measurements Smith and Sandwell (1997). Using the bathymetry data, the map from 10°S
to 25°N latitude and 90°E to 130°E longitude was drawn to determine the sea depth around Malaysia.
Forecast Point and Source Point
Forecast point is the point that is set up near the coast for estimation of tsunami height and arrival time.
The criteria are to set up as close to the coast and also considering the bathymetry of the coastal area.
Firstly, the forecast point were set up at 10-minute ≈ 18.5 km from the coast with 10-minute intervals. Inother cases, forecast points were set up as follows:21) Near the coast 4-minute ≈ 7.4 km;
2) Far from the coast 20-minute ≈ 37 km; and3) Between the original forecast points along
the coastal area.
The simulation is run for all the forecast points(Figure 2). The source point was set up near thetrench and along the coast of the Philippines.
The source concentrated in the middle area ofthe Philippines Islands and southern
Philippines (Mindanao) and also around theMoluca Sea, along the trench. It was set up
according to grid size. The strike was set
parallel to the trench in this area because itgives a great impact on the area east ofMalaysia (Sabah).

Figure 2 Location of
4-type forecast point

Magnitude and Depth interval

Notation:
20-minute ≈ 37 km
10-minute ≈ 18.5 km
Between the 10-minute4-minute ≈ 7.4 km;

The magnitude and depth interval were set. From the historical events, there hasn’t been any
tsunamigenic earthquake at the depth below 10 km. The interval for magnitude was set considering thatminimal magnitude of the most destructive events is M6.3 and the maximum is M9.1. In this case theM9.0 was not set because the determination of Magnitude 9 would take longer time (3000 sec freeoscillations).
Tsunami Simulation (Application)
In this simulation, the JMA simulation program is applied and this consists of the fault parameter
calculation, seafloor deformation and simulation program. The simulation program was carried out
considering the bottom friction and using the non-linear term.
Firstly, the area of computation is determined by considering the continental effect and mount
bed area. The area is 25°N to 10°S and 90°E to 130°E. The grid size was set from this as dx = 1,200 m
and dy = 1,050 m. The grid size was set for each forecast point. The calculation time was set 8 hours forthe area near east of Sabah. This is because of considering the reflection of the wave between thePhilippines and east of Sabah and also surrounding area. The time step (dx) used by JMA is 3 second.
This time step is actually for Japan case with 1-minute interval but it can be used also for the 2-minuteinterval as it follows the CFL conditions.
Result of the forecast point
In the below graph (Figure 3), a comparison was made for neighbouring forecast points by distance fromthe coast (4-minute, 10-minute and 20-minute). The first wave amplitude shows that the green and redlines are higher than the black line. This is because the depths of green and red lines are almost the same,
while the depth of the black line. When near the coast depth becomes shallow the wave amplitude
becomes higher for the black line. The graph shows that the red and black lines are higher than the green
line in the second wave. Since both black and red lines (4-minute and 10-minute) were obtained from theforecast points near the coast the wave amplitude will be much higher than the other while the arrival time3

will be a little bit later than that of green line (20-minute) forecast
point . We can see a quite similar pattern between the 10-minute and4-minute forecast points.

Figure 3 Comparison the three locations offorecast point – epicenter at Mindanao.

Notation:
20-minute ≈ 37 km
10-minute ≈ 18.5 km
4-minute ≈ 7.4 km

Figure 4 Comparison the forecast points of 4minutes, 10-minutes and 20-minutes distance tothe coast.

Meanwhile in Figure 4, which is for another forecast point set, the first wave amplitude shows
almost the same height, and only the red and black lines are a little bit higher than the green line. Thecomparison shows a very clear difference of the wave amplitude in the second wave, where the black line
which indicates 4-minute point from the coast is the highest among the 3 forecast points. This is because
the wave amplitude becomes higher when it reaches near the coast, and the wave energy is converted towave height. We compare the result of Figure 3 and Figure 4 and it makes quite the same result, therefore,
the 4-minute to the coast was chosen.

Notation:
20-minute ≈ 37 km
10-minute ≈ 18.5 km
4-minute ≈ 7.4 km

Figure 5 Comparison among the location offorecast points with the 10-minutes interval alongthe coast.
In this case, we searched for the best forecast point location among the interval along the coast. The redand green lines indicate amplitude from two points with the interval of 10-minutes and the black lines isin the middle of them (Figure 5). The depth of these three forecast points is almost the same. Among theforecast points of each 10-minutes interval, the graphs (Figure 5) show quite similar pattern in the firstand second wave amplitudes. The similarity in wave height was observed between the green and red lines,
while the black line was much higher and not similar to the others for the rest of the wave amplitude.
Therefore, 10-minute interval was considered to be enough.
As a conclusion, the interval was set around 10-minutes from one forecast point to another andthe distance from the coast is 4-minutes. In this case, bay site is considered. It is because in the V-shapearea and also bay area they give a big impact on tsunami height.
Retrieve data method
SQL Database4MySQL command is used to make tables from the simulation result. The simulation result was divided
into (3) three tables under the name of “Tsunami” main table, that is, “FP” table, “Hyp” table and also
“Simudata” table. FP table contains the number of forecast points, depth (m), latitude and longitude,
meanwhile “Simudata” table contains the number of forecast points, arrival time(minutes), maximumheight (cm), minimum height (cm) and “Hyp” table contains parameters information on longitude,latitude, magnitude, depth, strike, total station, total time, length, width, Us component, Ud component,Ut component, dip, rake and filename.
Interpolation
Surrounding hypocenter and centroid data
Each latitude, longitude and strike must be searched before making hyp table. On each of the four corners
that have the same strike, centroid data are added as the grid data. The centroid data were not applied if
there is different strike at each point and also there are only three corners. Later, Hyp table is used to seek
the nearest centroid data by calculating distance. The magnitude and depth surrounding the input
hypocenter at each four epicenter were searched by using interpolation logarithm. The coefficient forhorizontal interpolation (location of latitude and longitude) is calculated by a linear method.
Database Search
There are two ways of database search that are “simple” database search and also “max risk method”
database search. These two methods of search are based on the simulation data. The “simple” databasesearch is used when there is not enough simulation data and too little to use interpolation method. Thismethod searches for the nearest simulation point data to the epicenter. In the case of searching for thedepth and magnitude, either way, it can use the interpolation method to get the database output or use thenearest element as a database output.
“Max risk method” database search is the other method used to calculate fault distance frommagnitude of the earthquake. In this method the target area is within half length of the earthquake’s fault
distance. The search for maximum data at each forecast point within half length of the earthquake’s fault
distance and the maximum data will be the output database.
Issuance of Tsunami Warning
Issuance of the warning is very important for disaster mitigation. The warning must be clear andunderstandable by everyone. It must not confuse the public. Therefore, the warning format has been
decided and it is divided into 3 stages of warning. The first message is for the information on the fastest
arrival time and the highest tsunami height in the state area, including name of the coastal area affected.
The second message gives more specification on each state coastal areas affected with arrival time andtsunami height. The third message is the downgrading and cancellation of state coastal areas.

DISCUSSION AND CONCLUSIONSFirstly, the seismicity at the surrounding areas of Malaysia was investigated. Then, the historicalearthquakes and tsunami events were searched. Locations of tsunamigenic earthquakes were determinedby combination of these two kinds of events. In this search, the locations of tsunamigenic area werelocated at west of Sumatera, Andaman Island, Sulawesi and southern Philippines. Tsunami from theseareas might propagate to Malaysian coast. Bathymetry data ETOPO2 are used to search the depth of thesurrounding sea. Near the coastal area of Malaysia, the sea depth is shallow, less than 50m. We compared5

the result from the wave form data to check if it gives a good result for each shape of the coastal areaaccording to the tsunami theory. The graph plotted shows that when the magnitude is larger the tsunami
height becomes higher. This is because of the energy conservation, namely, when the wave approachesthe coast, the depth becomes shallow and the kinetic energy of the wave is converted to height or
potential energy. Meanwhile, the graph of tsunami height versus depth where the magnitude is constantindicates that the depth of deformation gives less impact on tsunami height if it becomes deeper. This
result is consistent with the theory of tsunami.
Later, all the results of simulation were gathered and put in the database using MySQL in theform of table. In the program, interpolation and extrapolation method were used to determine location,
magnitude and depth from the simulation epicenter point. This method is easy to use but not so accurate
especially for extrapolation when the simulation epicenter point is far from the hypocenter. The result
then is used to issue the warning.

ACKNOWLEDGEMENT
I would like to express my sincere gratitude to K. Nakata, M. Kiyomoto of JMA and the advisers B.
Shibazaki and Y. Fujii for their continuous support, valuable suggestion and guidance during my study.
REFERENCES
Okada, Y., 1985, Bull. of the Seismo. Soc. of America, 75, 1135–1154.
Rongved, L., and Frasier, J. T., 1958, Journal of Applied Mechanics, 25, 25-128.
Smith, W. H. F. and Sandwell, D.T., 1997, Science, 277, 195-196.
Steketee, J.A., 1958, Can. J. Phys., 36, 192-205.

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