Synopses of Master Papers

Bulletin of IISEE, 47, 121-126, 2013

VALIDATION OF TSUNAMI INUNDATIONMODELING FOR THE 2004 SUMATRA-ANDAMANEARTHQUAKE FOR MAKING HAZARD MAPS IN
PENANG AND LANGKAWI, MALAYSIANoor Azam Shaari ∗MEE11622

Supervisor: Yushiro FUJII ∗∗Hideaki YANAGISAWA ∗∗∗ABSTRACT
We adopted three heterogeneous slip models estimated by inversion method from satellite altimetrydata, tsunami waveform data at tide gauges and the joint data as tsunami source models. Non-LinearShallow Water Equations (NSWE) by considering the effects of the earth’s curvature were applied in
the numerical simulation to evaluate the tsunami propagation and runup at the target areas in Penang
and Langkawi, Malaysia. We applied a nesting grid system with four layers in the numerical modeling.
The result shows that the locations in the study region, Pantai Acheh, Pantai Tengah,
Pantai Chenang, Kuala Triang and Pantai Kok, are prone to the tsunamis, where the tsunami heights ofabout 2.5 m were calculated. The calculated tsunami waves from the all source models almost
reproduce the observed ones at two tide gauges. Tsunami source models with larger slip amount overNicobar and Andaman Islands contribute to the maximum tsunami runup as high as 4.0 m in Pantai
Tengah and Pantai Chenang. These results are almost agreeable to the runup-height data by the fieldsurvey.
Keywords: 2004 Sumatra-Andaman earthquake, Tsunami Propagation, Runup, Inundation, Langkawi,Penang.
1. INTRODUCTION
An earthquake that occurred at 00:58:49 (UTC) on December 26, 2004 along the Sumatra Island andAndaman Islands has created a big impact after the giant tsunami waves and struck the world andMalaysia especially in the coastal areas. The 2004 Sumatra-Andaman earthquake with a magnitude ofM9.1 at epicenter 3.316 0 N/ 95.8540 E (USGS) has generated the giant tsunami waves propagated tofew states in the northwest of Peninsular Malaysia. It is recorded that about 68 people died, left 6
missing and 300 injured. The Northern States of the west coast of Peninsular Malaysia have been
badly affected by tsunami. Among the state affected were Kedah, Penang, Perlis, Perak and Selangor.
Tsunami simulations from three source models will be used to validate the tsunami
propagation in whole inundated areas in Langkawi, Penang and Kedah. This study is also aimed toanalyze the tsunami inundation to the target locations in Batu Feringghi (P1), Pantai Chenang (K2)and Kuala Triang (K3). Neighboring location such as P2, P4, K1 and K4 will also be analyzed as theyare located inside the same computational domain.

∗Malaysian Meteorological Department.
International Institute of Seismology and Earthquake Engineering (IISEE), Building Research Institute (BRI),
Japan.
∗∗∗Tohoku-Gakuin University, Japan.
∗∗2. DATA
2.1 Bathymetry and topography data
We used the bathymetry data from General Bathymetric Chart of the Ocean (GEBCO) with spatial
grid size at 30 arc-sec. Generic Mapping Tools (Wessel and Smith, 2007) is used to process and draw
the bathymetry data in the target area lies within 0°N to 15°N and 90°E to 105°E. For the calculationof the inundation, the topography data from Shuttle Radar Topography Mission (SRTM) is applied.
2.2 Computational regions and settings to evaluate tsunami propagations
In order to perform the numerical modelingto evaluate the tsunami wave propagation
towards the target area the computational
area is divided into three regions (Figure 1).
The bathymetry and topography data for all
the regions are interpolated from GEBCO
30 arc-sec. The calculation time for thecomputation is 28,800 s (8 hours) withcomputation time step (∆t) of 3 s. The ∆t isderived from the stability criterion∆xformula ∆t ≤. Maximum sea
2ghmaxdepth (h max ) of the computation region 1 is5,514 m and gravitational acceleration at
9.81 ms-2. Numerical simulation with thenesting grid system is carried out for theevaluation of the tsunami propagations fromsource area.
Figure 1. Location and boundary of eachcomputational region.
2.3 Computational regions and settings to evaluate tsunami inundations
In order to evaluate the tsunami inundation at each target locations, the computational area is divided
into four regions. The same computational regions as those in section 2.2 are applied to the regions 1and 2, but slight changes are made to region 3 to avoid the numerical instability during thecomputation. The same calculation time for the computation at 28,800 s (8 hours) is used at ∆t of 3 s.
The computation region 3 at the target area in Penang (Figure 2) and Langkawi (Figure 3) is divided
into smaller region 4. Target locations of P1, K2 and K3 are located at their smaller region 4 toanalyze the coastal wave amplification.
The bathymetry and topography grids in inundation area are merged for getting finer sea
bottom surface and elevation data. The bathymetry for the region 4 is interpolated from GEBCO 30
arc-sec, whereas the topography is from SRTM 3 arc-sec. Three different sets of numericalsimulations are performed to analyze the coastal amplification over the respective target locations.

Figure 2. Location and boundary forcomputational region 3 for Penang.

Figure 3. Location and boundary forcomputational region 3 for Langkawi.

2.4 Tide gauge stations and tsunami waveform data
There are four tide gauge systems that are now operated in the study area. Two of the systems areoperated by Department of Survey and Mapping (JUPEM); one located in Penang (5°25’N/100° 21’E)
and the other in Langkawi (6° 26’N/ 99° 46’E). The other two operated by Malaysian Meteorological
Meteorology (MMD) is located in Penang (5° 27’N/100° 10’E) and Langkawi (6° 15’N/ 99° 44’E).
Observed tsunami waveforms by JUPEM at sampling interval of 50 s will be used in the study.
Figures 4 and 5 show the locations of the tide gauge stations at Penang and Langkawi.

Figure 4. Location of tide gauge station atPenang.

Figure 5. Same as Figure 4, but forLangkawi.

2.5 Tsunami source region and source models
In this study three heterogeneous slip models from Model 1 by Hirata et al. (2006), Model 2 by Fujiiand Satake (2007), and Model 3 by Tanioka et al. (2006) will be used in the validation process. Initial
sea surface heights from the slip models shown in Figure 6 are calculated by the Okada formulation(Okada, 1985). The different variation of tsunami propagations is expected to be produced from thedifferent parameters and slip amount used in the simulation.

Figure 6. Seafloor deformations by Model 1 (left), Model 2 (center) andModel 3 (right). Red and blue lines indicate the uplift and subsidence area,
respectively, with the contour interval of 1.0 m.

3. THEORY AND METHODOLOGY
3.1 Non-linear shallow water and governing equations
The original Tohoku University’s Numerical Analysis Model for Investigation (TUNAMI-N2) model
neglects the earth’s curvature (Dao and Tkalich, 2007). To consider the effects of the earth’s curvature,
the NSWE model is reformulated in spherical coordinates (Yanagisawa, 2012). The continuity andmomentum equations are rewritten as follows;∂η1  ∂M∂++N (cos θ ) = 0

∂t R cos θ  ∂λ ∂θ(1)∂MgD ∂η∂MNgn 211∂  M 2 +M M2 + N2 = 0θ+++(cos)7/3
∂tR cos θ ∂λ R cos θ ∂λ  D  R cos θ ∂θDD(2)∂NgD ∂
1N 2 gn 21∂ MN∂ (cos θη ) +N M2 + N2 = 0+cos+()+θ
7/3∂t R cos θ ∂θR cos θ ∂λ D  R cos θ ∂λ D
D(3)Where η is wave amplitude, M is discharge fluxes in the λ (along a parallel of latitude) direction, N isdischarge fluxes in the θ (along a circle of longitude) direction, R is radius of the earth at 6378.137 km,
t is time and n is manning roughness coefficient (n = 0.025 in this study).
3.2 Runup and inundation height
The main objective of this study is to investigate the onshore effects of a tsunami or runup. Runup andinundation height are referring to the maximum vertical tsunami height onshore and elevation of local
watermark measured from the sea level at the time of tsunami attack.

4. RESULTS AND DISCUSSION
4.1 Tsunami wave propagations
The result of Model 1 shows that K1, K2,
K3 and K4 are facing large tsunami heightfrom 2.4 m up to 2.9 m but it is slightly
lower at P1, P2 and P4. Wave pattern ofModel 3 is slightly similar to that of theModel 1 but the tsunami height at K4 is only
1.5 m which is about half of 2.9 m in Model
1. The calculated tsunami height of Model 2
is relatively small compared with Models 1
and 3. The calculated tsunami height at P1,P2 and P4 from Model 1 is almost agreeable
to the computation result reported in Koh etal. (2009) by using an in-house Tsunami
Numerical Simulation Model (TUNA). The
pattern of maximum tsunami heights at allcoastal points show that P5, K1, K2, K3 andK4 have been hit by the high waves about
2.0 m from Model 1.
Figure 7 shows the calculated
tsunami waveforms at four tide gauge
stations in Penang and Langkawi and thecomparison with the observed waveforms at
TG1 and TG3. The calculated waveforms
and the observed data generally fit to eachother. The waveforms by Model 1 almost
reproduce the observed ones.

Figure 7. Comparison between the calculated tsunami
waveforms (blue lines) and the observe ones (redlines) at tide gauge stations by Model 1(left), Model2(center) and Model 3(right).

4.2 Tsunami inundation analysis
All the calculated runup heights in Penang are
underestimated compared with the observation data.
The observed maximum tsunami runup is at as highas 4.0 m at P2 (Figure 8). Maximum tsunami runup
estimated at K1 and K2 was between 3.2 and 4.0 mfor both Model 1 and 3, respectively (Figure 9). The
calculated result is almost agreeable to the observed
data which is recorded at the maximum height of 3.75m at K2. Tsunami runup at the target locations K3
and K4 seem to be overestimated, where thecalculated result from Model 1 shows the maximum
runup at 5.1 and 5.3 m, respectively (Figure 10). The
maximum runup from the observed data is only
between 2.25 and 3.09 m. The computed runup at K3
by Model 3 is almost agreeable to the observed data of
3.1 m.

Figure 8. Comparison between thecalculated maximum tsunami runup heights
and observed ones at the target locations in
Penang

Figure 9. Same as Figure 8, but in Pantai
Chenang, Langkawi.

Figure 10. Same as Figure 8, but in Kuala
Triang, Langkawi.

5. CONCLUSIONS
The result of the tsunami propagation analysis shows that about 2.5 m of tsunami waves approaching
the coastal locations P5, K1, K2, K3 and K4 may severely impact the area if there is no sufficient
protection given by the authority. The calculated maximum runup heights at K1 and K2 are as high as
4.0 m which is almost agreeable to the field observation data. The elevation profile also suggests thatthe location P1, P4 and K2 are exposed to the tsunami threat as they are located at low land. It wasalso found that the tsunami generated by the source Models 1 and 3 with higher slip distributions inNicobar and Andaman Islands contributed to the large tsunami heights and runups over the study
region. The source parameters from historical earthquakes and tsunamis in the northern Sumatra
especially at Nicobar and Andaman islands will be investigated in order to estimate the impact to thenorthwest Peninsular Malaysia. The inundation results from the numerical simulations will besuggested for making tsunami hazard maps in Penang and Langkawi.

ACKNOWLEDGEMENT
Special thanks to Mohd Yusof Bin Abu Bakar and Zulkifli Bin Mohamad, the officers at theDepartment of Survey and Mapping Malaysia (JUPEM) and Malaysian Meteorological Department(MMD) for their support to make this study successful.

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