NUMERICAL SIMULATION OF TSUNAMIPROPAGATION AND INUNDATION ALONG THE
RAKHINE COAST AREAS IN MYANMARSu Hninn Htwe
MEE12619

Supervisor:

Bunichiro SHIBAZAKI 
Yushiro FUJII ABSTRACTThis study aimed to assess the tsunami hazard at the Rakhine coast in Myanmar by tsunami
propagation and inundation simulation considering a scenario earthquake along the Arakan Trench.
We selected the location of the 8 tide gauge stations as the output points located in the Rakhine coast.
Seven are assumed as tide gauge stations and one is an actual tide gauge station operated by theMyanmar government. To calculate the tsunami maximum wave heights and tsunami arrival times atthe output points, we performed numerical simulations using TUNAMI-N2. We assumed a scenario
earthquake (Mw 8.9) along the Burma subduction zone off the Rakhine coast. We used the 1
arc-minute and 30 arc-seconds GEBCO bathymetry data. The numerical modeling of tsunami
propagation is based on a uniform grid system in cartesian coordinates. The numerical modeling oftsunami inundation is based on a nested grid system in spherical coordinates using non-linear theory
with four different spatial grid sizes. The maximum tsunami height was around 1.4 m along theRakhine coast. We performed tsunami inundation modeling around Sittwe City, and found a littletsunami inundation occurred in this area.
Keywords: Numerical simulation, Tsunami height, Tsunami arrival time, Tsunami inundation,Assessment, Arakan Trench.
1. INTRODUCTION
Myanmar is one of earthquake prone countries, which is situated on the boundary of theAlpide-Himalayan Earthquake Belt where devastating earthquakes have occurred from time to time.
An active and long subduction (the Indo-Burma) zone lies near the Myanmar coastal areas. Thus, theMyanmar coastal areas are vulnerable to not only regionally but also distant tsunami. The earliest
earthquake on record which affected the western coast of Burma (Myanmar) took place on 2nd April
1762 (e.g. Cummins, 2007). It was violent and felt all over Bengal, Arakan etc., chiefly and more
severely in the northern part of the east of the Bengal Bay. The giant Sumatra earthquake on 26thDecember 2004, according to the information from tsunami surveys, the height of the wave arrived in
Myanmar was from 0.4 m to 2.9 m (Satake et al., 2005). Although Myanmar had less fatalities anddamages among the countries hit by the tsunamis of the 2004 Sumatra earthquake, it is clearly shownthat Myanmar coastal areas are vulnerable to tsunami. Cummins (2007) also suggested that there is ahigh possibility of occurrence of a tsunamigenic earthquake in the northern Bay of Bengal near
Rakhine coast which is a populated coastal area. A tsunami threat can significantly devastate thisregion. Therefore, numerical tsunami simulation is imperative to determine the travel time and heightof tsunami that may affect the region. By knowing the tsunami characteristics that is expected to attack
the region, a tsunami hazard planning can be made to mitigate its effect on the populated coastal areasof Myanmar.
Department of Meteorology and Hydrology (DMH) of Myanmar
International Institute of Seismology and Earthquake Engineering/Building Research Institute, Tsukuba, Japan1

2. THEORY AND METHOD
2.1 Governing Equation in Cartesian Coordinate SystemThe fundamental equations of the continuity and momentum in two dimensions for the cartesian
coordinate system are expressed below:
𝜂(1)

()

()

()

()

𝜂(2)

𝜂(3)

where, M and N are the components of discharge fluxes in the x and y directions, 𝜂 is the verticaldisplacement of water surface above the still water surface, t is the time, D is the total water depth, xand y are the horizontal axes, g is the gravitational acceleration, h is the sea depth,
are thebottom frictions in the x- and y- directions andis the density.
2.2 Governing Equation in Spherical Coordinate System
It is necessary to use the spherical coordinate system in performing the numerical simulation tocapture the globular shape of the earth. The continuity and momentum equations are expressed in theterms as follows:𝜂(4)()][𝜂((𝜂)

()
(()

√))

(5)
√(6)

where, 𝜂 is the wave amplitude, M is the discharge fluxes in the(along a parallel of latitude)
direction, N is the discharge fluxes in the (along a circle of longitude) direction, R is the radius of
the earth at 6378.137 km, t is the time, n is the manning roughness coefficient, g is the gravitational
acceleration, D is the water depth, andthe bottom friction term.

M √andN √are

3. TSUNAMI NUMERICAL SIMULATION
3.1 Tsunami Simulation
We used the TUNAMI-N2 (Tohoku University’s Numerical Analysis Model for Investigation of theNear-field tsunami No.2) code, which was developed by Disaster Control Research Center (DCRC)
Tohoku University, Japan (Koshimura 2013; Imamura et al., 2006), in order to simulate thegeneration and propagation of the tsunami wave considering a shallow water wave theory and bottomfriction. The propagation and inundation were calculated by using the TSUNAMI-N2 code based on
the cartesian coordinate and spherical coordinate systems.

23.2 Study Area and Target Area
Myanmar experienced the tsunami effect of the M 9.2 earthquake on 26th December 2004 Sumatraearthquake. After the Sumatra earthquake, some researchers (Cummins, 2007) pointed out thepossibility of a potential tsunamigenic earthquake that may occur on the northern part of the Bengal
Bay. If this tsunamigenic earthquake occurs, it will mostly affect the Rakhine coast that faces theBengal Bay. Thus, a study of the characteristics of the tsunami that may devastate the Rakhine coast isimperative to the dense population of Sittwe City to mitigate the possible effect of tsunami wave. In
this study, the computational domain ranges from 9°N to 25°N in Latitude and from 86°E to 99°E inLongitude.
4. DATA
4.1 Bathymetry Data for Tsunami Simulation
For the tsunami simulations, we used the 1 arc-minute bathymetry data and 30 arc-seconds bathymetry
data from the General Bathymetry Chart of the Ocean (GEBCO) which can be downloaded from thewebsite (http://www.bodc.ac.uk/data/online_delivery/gebco/). Table 1 shows a summary of the data
and resolution used for the simulations.
Table1. Summary of bathymetry data and resolution used for simulation.
GEBCO
GEBCO _08
Bathymetry Data
1arc-min30 arc-secResolution
1 arc-min1 arc-min
Grid dimension
780 × 960
780 × 960
Temporal Grid Size(dt)3s3s

4.2 Bathymetry and Topography Data for Tsunami Inundation Modeling
In order to perform the tsunami numerical modeling, the computational area is divided into fourregions. The bathymetry data for four regions are interpolated from the General Bathymetry Chart ofthe Ocean (GEBCO) 30 arc-seconds grid data. For the calculation of inundation area, we obtained datafrom the Shuttle Radar Topography Mission (SRTM) retrieved from the Internet(http://dds.cr.usgs.gov/srtm/version2_1/SRTM3/Eurasia). The bathymetry and topography data for thefour domains were interpolated from large region to small region. The topography data for the first to
third domains were interpolated from the 30 arc-seconds GEBCO and for the fourth domain it wastaken from the Shuttle Radar Topography Mission (SRTM) 3 arc-second resolution data as shown inFigure1.

Region 1

Figure1. Location and boundary for each computational domain in inundation. Left figure
shows Region 1 and right figure shows Region 2 (green rectangle), Region 3 (blue rectangle)
and Region 4 (red rectangle).

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4.3Tide Gauge Stations
In this study, we set the location of the 8 tide gauge stations along
the west coast of Myanmar. Tsunami waveform was calculated at
the 8 tide gauge stations to obtain the tsunami wave height andarrival time at each location as shown in Figure 2. Among these 8tide gauge stations, we assumed the 7 tide gauge stations and set
them in the important places along the study area. One tidegaugestation (Sittwe) is an actual tide gauge station operated byMyanmar.

Figure 2. Location of thetide gauge stations.

5.

RESULT AND DISCUSSION

5.1 Computational Dimension and Source of Scenario Earthquake for Simulation
In this study, we used the computation region used for the earthquake scenario as shown in section 4.1
and Table 1. The spatial grid interval
was 1,774 m and ∆y was 1,844 m for the 1 arc-minute GEBCO
and 30 arc-seconds GEBCO data resolutions. In order to stabilize the numerical computation, thetemporal grid sizes (∆t) were set at 3.0 s for uniform grid computation in the 1 arc-minute bathymetry
data and 30 arc-seconds bathymetry data which satisfies the Courant-Friedrich- Lewy (CFL) condition.
The total duration of the calculation was 3 hours and had time steps of 3,600 for computational time inuniform grid simulations using the 1 arc-minute bathymetry data simulation and 30 arc-seconds
bathymetry data simulation. The maximum water depth () was 4,222.05 m in the 1 arc- minuteGEBCO andm in the 30 arc seconds GEBCO.
We used the source parameters for the scenario earthquake by Oo Than (2010). We assumed
the depth as 0 km (depth of the top edge corner of the fault).
Table 2. Source parameters of scenario earthquake at the Arakan Trench.
Lat(°N)Long(°E)

Length(km)Width(km)Strike(°)

Dip(°)

Rake(°)

Slip amount(m)Top depth(km)17.00

93.9375

358.794172.811

341

10127

7.67

05.2 Maximum Tsunami Heights
From the tsunami simulation, we obtained tsunami waveforms and the maximum tsunami wave
heights as well as the tsunami arrival times at 7 assumed and 1 actual (Sittwe) tide gauge stations.
Using the TUNAMI-N2 code, we estimated the tsunami wave heights in every time step for coastal
output points with the scenario. From the simulation using 1 arc-minute GEBCO, we obtained thehighest tsunami wave height of 1.48 m at TG07 and the second highest tsunami wave height of 1.45 mat TG06. The 3 tide gauge stations (TG03, TG04 and TG08) had the maximum tsunami wave heightsfrom 1 m to 1.3 m and TG 01, Sittwe and TG05 recorded waves of less than 1 m. From the simulation
using the 30 arc-seconds GEBCO, we obtained the highest tsunami wave height of 1.40 m at TG05
and the second highest tsunami wave height of 1.37 m recorded at TG07. The maximum tsunami wave
heights at 5 tide gauge stations (TG01, TG03, TG04, TG06 and TG08) were between 1 m and 1.4 m
and Sittwe tide gauge station recorded a maximum tsunami wave height of 0.57 m.

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Figure 3. Comparison of the maximum tsunami
heights obtained through a numerical simulation
using TUNAMI-N2 code for coastal output
points with different bathymetry data the 1
arc-minute and 30arc-seconds.

Figure 4. Tsunami arrival time calculated ateach tide gauge station for the tsunami source
using the 1 arc-minute and 30 arc-seconds
bathymetry data.

5.3Tsunami Travel TimeWe derived the tsunami arrival times from the waveforms recorded at each tide gauge station as shownin Figure 4. Tsunami arrived in a few minutes at all tide gauge stations after occurrence of theearthquake as calculated using the GEBCO 1 arc-minutes and GEBCO 30 arc-seconds datasets becauseof its close proximity from the tsunami source. Two output points located in a subsidence area computeda negative tsunami waves using the 1 arc-minute GEBCO and 30 arc-seconds GEBCO. Positive waves
reached the 6 output points in different time depending on the distance of the output points from thetsunami source. Tsunami arrival time did not change much in the simulation with the grid resolution of
the 1 arc-minute and the grid resolution of 30 arc-seconds.
5.4Tsunami Inundation
The tsunami inundation is calculated on the fourth domain using the bathymetry of the 30 arc-seconds
uniform grid and topography grid data (seeFigure 1), and in this domain there were 780
and 960 grid points along the latitude andlongitude directions, respectively, for which
the computation time was 3 hours which hadtime steps of 10,800 for the nested grid
simulation. In order to stabilize thenumerical computation, temporal grid size(∆t) was set to 1.0 s for the nested gridcomputation, which satisfies the CFL
condition.
Figure 5 shows a result of tsunami
inundation modeling around Sittwe City.
Yellow and blue rectangle areas areFigure 5. Tsunami heights obtained from tsunami magnified in Figures 6 and 7. Inside of theinundation simulation for region 4.
blue rectangle, the maximum tsunami heightin inundation areas reached around 1 m (Figure 7). Populated area in Sittwe City is located in the yellow
rectangle. The highest tsunami wave height of 0.75m was calculated at the coast line (Sittwe City).
However, there was a little inundation in Sittwe City obtained from the simulation.

5Figure 6 . Magnified view around Sittwe City
shown in the yellow rectangle in Figure 5.

Figure 7. Magnified view southern part ofSittwe City shown in the blue rectangle inFigure 5.

6. CONCLUSION
We performed numerical simulation of tsunami propagation along the Rakhine coast in Myanmar byassuming a scenario earthquake (Mw 8.9) along the Burma subduction zone. The results show that themaximum tsunami height is around 1.4 m along the Rakhine coast. The maximum tsunami wave
height using the 30 arc-seconds bathymetry data except the tide gauges TG06 and TG07 was higher
than that using the 1 arc-minute bathymetry data. The patterns of the maximum tsunami wave height
were not similar in 1 arc-minute bathymetry data and 30 arc-seconds bathymetry data. This is probably
because of the characteristics of the ocean bottom topography and the tsunami energy directivity.
We calculated tsunami arrival time at each tide gauge stations. The tsunami wave arrived
within a few minutes at all tide gauge stations after occurrence of the earthquake as calculated usingthe GEBCO 1 arc-minutes and GEBCO 30 arc-seconds datasets because of its close proximity fromthe tsunami source.
We also performed tsunami inundation modeling around Sittwe City. The highest tsunami
wave of 0.75 m was calculated at the coast line of Sittwe City. There was a little inundation calculated
in the city obtained from the simulation.
According to the tsunami simulation results from this study, there is a threat of tsunami
to the Rakhine coast. In order to obtain more consistent and better results for the tsunami inundation
computation, the use of detailed and accurate bathymetry as well as topography data is essential in asmall grid size, which is much more effective in the numerical computation. The local communities
living in the areas with vulnerabilities should have the awareness about tsunami disaster.
My future work plans include formulation of a tsunami hazard map based on the result of
my study and to prepare tsunami evacuation plan for the coastal communities to protect them from thetsunami effects. I also would like to continue tsunami simulation and inundation modeling for othertsunami prone areas along the Myanmar coast.
ACKNOWLEDGEMENTS
I’m deeply grateful to respectable supervisors, Dr. Bun’ichiro SHIBAZAKI and Dr. Yushiro FUJII for
their comments, wise advice and guidance during this study. I extend my thanks to Dr. Toshiaki
YOKOI, director of IISEE and also to the BRI staff for their friendship and support at the requiredmoments.
REFERENCES
Cummins, P. R., 2007, Nature 449, 75-78 doi: 10.1038/nature06088.
Fujii, Y., IISEE Lecture Note 2013, IISEE/BRI.
Tun, P. P., 2008, IISEE/BRI, Tsukuba, Japan.
Oo Than, 2010, IISEE/BRI, Tsukuba, Japan.

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