THE REVIEW OF THE STRONG GROUND MOTIONOBSERVATION IN MALAYSIA AND PROPOSING
IMPROVEMENT BASED ON THE IMPORTANCE OFTHE LONG PERIOD GROUND MOTION
Elsie Benedict Jaimin∗
MEE09179

Supervisor: Toshiaki YOKOI∗∗

ABSTRACTDue to recent increase in human felt tremors in Malaysia, this study aims at proposal of an appropriate
setting of strong motion observation, highlighting the importance of long period ground motion. Twoways are taken to emphasize the long period ground motion (LPGM) for the strong motion
observation in Malaysia that is in the deterministic way and statistical way. Recorded Sumatra eventon September 29, 2009 at IPM broadband station in Malaysia were selected and in Japan, threeKik-net stations recording four events, coded as S1, S2, S3 and S4, occupied with borehole andsurface sensors, with depth ranging from shallow, intermediate and very deep were selected.
In deterministic way, the product of the transfer function, namely Fourier spectra ratio,
obtained from S2 event with IPM true ground motion, will produce the synthetic waveform at eachground model. Next, from the synthetic waveform deterministic estimate of acceleration (Sa) andvelocity (Sv) response spectra were calculated. For the statistical way, mean Sa ratio of four eventswere calculated. Then the product of mean Sa ratio with the estimated bedrock motion using theattenuation relation of Yuzawa and Kudo (2006) were obtained at each ground model.
Results show small amplitude of acceleration with long duration of motions about 20 minutes.
The obtained deterministic estimate of Sa and Sv shows predominant periods around 0.7 to 0.8 second
and 9 seconds respectively, which can still be observed with the appearance of other peaks that seems
to be controlled by the thickness of the sediments or soil layers at each ground models. Statisticalestimate of Sa shows three times higher than the deterministic estimate of Sa and might be due to theregionality in the attenuation characteristic of Malaysia and Japan. However, the trend is similar andthus the results are acceptable.
Considerable attention is paid to the long duration of motion about 20 minutes and somepossible ways to set up strong motion are proposed. For the necessity of assisting a structural design
and for hazard assessment, the measure should start with the data recording in all of the current
installed strong motion stations in Malaysia.
Keywords: Long period ground motion, Kuala Lumpur, deterministic estimate, statistical estimate,
Acceleration Response Spectra (Sa), Velocity Response Spectra (Sv).
1. INTRODUCTION
Malaysia is divided into two regions, separated by the South China Sea. West Malaysia consists of
Malaysian Peninsula and east Malaysia consists of Sabah and Sarawak. It lies on the stable Sunda
platform of the Eurasian plate and is bounded by two major seismically active plate boundaries, theIndo-Australian plate and the Philippine Sea plate. Kuala Lumpur, main capital city of Malaysia,
where most of the high rise building is situated had experience tremors especially by the people in∗

Malaysian Meteorological Department, Sabah Regional Forecast Office, Malaysia.
Chief Research Scientist, International Institute of Seismology and Earthquake Engineering, Building
Research Institute, Japan∗∗− 13 −

high rise building due to large events originating from the Sumatra region, the needs to study structure
response, ground motion and risk analysis had becomes vital.
Malaysian Meteorological Department (MMD) has increased its seismic observation stations
including ten strong ground motion observation networks placed in and around the Klang Valley area.
However, there has been no recorded strong motion data obtained from this strong motion stations andground motion on the surface of sediments at approximately 500 km to 600 km from the Sunda trenchis still unknown and it is a necessary information in setting up the strong motion observation networkin and around Klang Valley area.
This study aim to propose an appropriate setting of strong ground motion observation and toachieve this, examples of the estimated strong ground motion are shown, emphasizing the LPGM, 1 to
10 seconds or more in assisting the building and hazard risk study in Malaysia.

2. THEORY AND METHODOLOGY
Low frequency or long period waves are more robust to energy dissipation and hence can transmit
more energy over much longer distance (Balendra et al. 2002). Two examples due to the effect of longperiod wave in a great distance from large earthquake events. One is during the Michoacán earthquake(September 19, 1985, Ms = 8.1), causing 20,000 fatalities in Mexico City, 400 km away from theepicenter (Koketsu et al. 2005) and another is September 26, 2003 Tokachi-Oki earthquake (Mw 8.3)
250 km away from Tomakomai city which had caused two oil tanks to catch on fire.
For the estimation of ground motion at the bedrock, the following two ways are taken: One isthe deterministic way using the real earthquake and another is the statistical way using empiricalattenuation relation of the acceleration response spectra (Sa).
For the deterministic way, broadband seismological station IPM (4.48°N and 101.03°E)
recording the earthquake occurred at 10:16UTC September 30, 2009 with epicenter at 0.7°S 99.86°E
and at the depth of 81 km are used. Their geographical configuration is shown in Figure 1. Tan et al.
(2006) mentioned the similarity of geological condition for Ipoh and Klang Valley area, and it seems
that the path effect from the source event to Klang Valley can be replaced with that to IPM station.
IPM and Kuala Lumpur are located in almost similar azimuth from the epicenter of the event, whereastheir epicenter distance differs slightly. Klang Valley has an epicenter distance of around 500 km andfor IPM around 586 km. The data files of velocity waveform are downloaded from the Incorporated
Research Institutions for Seismology (IRIS) earthquake database. The sampling rate of theseismogram obtained at IPM is 20Hz and then the frequency components higher then 10Hz are notincluded. Therefore, a direct comparison with existing attenuation relation of PGA or PGV cannot
make sense. Next, the system correction and numerical differentiation to obtain the accelerograms areapplied using the Seismic Analysis Code (SAC). Figure 3(a) and 3(b) shows the acclerograms and thevelocity seismograms at IPM and Figure 4 shows the Sa and the velocity response spectra (Sv)respectively. Hereafter, these are called “observed Sa and Sv at IPM” respectively.
For the statistical modeling of the bedrock motion, the attenuation relationship of Sa
proposed by Yuzawa and Kudo (2008) is used that is obtained for the bedrock motion of LPGM
recorded at all around Japan by Kik-net. Any other formula cannot be found for LPGM at bedrock thatalso is applicable for the epicentral distance as far as about 500 km.
The site effect with a pair of three component sensors at the ground surface and another atthe bottom of borehole that reaches to hard rock are used and among them, AICH09, AICH20 and
AICH22 in Toyohashi Plain having different depths. Toyohashi Plain has the similar lateral extent andthe similar opening towards the subduction zone to those of Klang Valley and is not located on a deep
tectonic basin, same as Klang Valley. Depths range from shallow, intermediate to deep structure and itseems convenient to use all three different depths in discussion of amplification effect of Klang Valleyof which velocity structure is unknown.
The transfer function, namely, Fourier spectral ratio of the records obtained at the surface tothat at borehole are calculated for AICH09, AICH20 and AICH22 that are named as Ground Model 1(G1), Ground Model 2 (G2) and Ground Model 3 (G3) respectively. These are used in place of the− 14 −

local site effect for the deterministic estimation. Earthquake events are selected, shown in Figure 2, bytaking into account the recorded duration of waveform and the magnitude. The former is to consider
the possible long response time function due to basin induced surface waves and the latter for thecapacity of generating LPGM. Each event is named as S1, S2, S3 and S4 respectively. For
deterministic estimation, only S2 is used to calculate the transfer functions at three ground models.

Figure 1. The location of Kuala Lumpur, IPM
station, Sumatra earthquake event and thesubduction zone.

Figure 2. Map showing AICH09, AICH20and AICH22 and Four Seismic events alongthe trench.

For the deterministic way, accelerograms at each ground are derived by the convolution of
the acclerograms of IPM with the transfer function of each ground in the frequency domain and then
the waveforms are reconstructed using the reverse Fast Fourier Transform (FFT). Then Sa and Sv arecalculated from these synthetic ground motion in the time domain using the View Wave softwaredeveloped by Kashima (2009).
For the statistical way, at each station, the ratio of Sa at surface and borehole, for four eventsare calculated. Then, the mean Sa ratio is obtained by averaging out all the four Sa ratio at each groundthat will suppress the features of Sa ratio that are the properties of each event. Next, the product ofthese mean Sa ratio to the estimated Sa at bedrock using the attenuation relationship proposed by
Yuzawa and Kudo (2006) will provide us Sa estimated at ground surface. Hereafter, the Sa estimated at
ground surface is called statistical estimate of Sa.

3. RESULTS OF THE ANALYSIS
IPM waveforms as depicted in Figure 3(a) show small amplitude of acceleration, main part is about
300 seconds and at the end of the record amplitude is still bigger than the noise level observed before
P-onset. Figure 3(b) in velocity waveforms show the long duration obtained on this hard rock site
more clearly. The calculated Sa and Sv for IPM of both damping factor, 1% and 5% shows
predominant periods around 0.7 to 0.8 second in north-south (NS) component and 9 seconds in
up-down (UD) and east-west (EW) component respectively as shown in Figure 4.
Figure 5 show small peak acceleration at all ground model with long duration of groundmotion and clearly depicted in velocity seismograms. A comparison of Figure 12 and Figure 13 withFigure 6(a) and (b) shows that the long duration takes place in the absence of a deep tectonic basin andthat this LPGM is observed in the bedrock ground motion. The cause of LPGM may be due to theearth crust that is different from the cases of Tomakomai City and Mexico City where amplification in
deep basin occurred resulting in higher amplitude of acceleration at ground surface.
The deterministic estimate of Sa at each ground shows the predominant period of 0.7 to 0.8second. However, by comparing Figure 7, Figure 8 and Figure 9 to that of Figure 4, following− 15 −

observation can be noted where other peak also appears in the relatively short period at G1 and twopeaks in short period component for G3, whereas for G2, similar results were obtained with that of theobserved Sa at IPM. As for the deterministic estimate of Sv, long period peak at IPM around 9 seconds
can still be observed at each ground. However, at G1 and G3, other peaks also appear at short periodand relatively short period, while G2 shows nearly similar results with the obtained Sv at IPM. Thesepeaks seem to be controlled by the thickness of the sediments.
(a)

(b)

Figure 3. (a) Accelerogram and (b) velocity
seismogram of true ground motion at IPM
station bedrock.

Figure 4. Observed respond spectra at IPM. Top left)
Sa with h=5%, top right) Sa with h=1%, bottom left)
Sv with h=5% and bottom right) Sv with h=1%.

(a)

(a)

(b)

(b)

(c)

(c)

Figure 5. Three component of acceleration
waveform obtained at (a) G1, (b) G2 and (c)G3 ground surface.

Figure 6. Three component of velocity
waveform obtained at (a) G1, (b) G2 and(c) G3 ground surface.

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Figure 7. Three components of Sa and Sv atground surface of G1. They are made from the
bedrock motion observed at IPM and thetransfer function calculated for G1. Top leftpanel) Sa with h=5%, top right panel) Sa with
h=1%, bottom left panel) Sv with h=5% andbottom right panel) Sv with h=1%

Figure 8. Three components of Sa and Sv atground surface of G2. They are made from the
bedrock motion observed at IPM and the transfer
function calculated for G2. Top left panel) Sa with
h=5%, top right panel) Sa with h=1%, bottom leftpanel) Sv with h=5% and bottom right panel) Sv
with h=1%(a)(b)(c)(d)

Figure 9. Three components of Sa and Sv atground surface of G3. They are made from the
bedrock motion observed at IPM and thetransfer function calculated for G3. Top leftpanel) Sa with h=5%, top right panel) Sa with
h=1%, bottom left panel) Sv with h=5% andbottom right panel) Sv with h=1%.

Figure 10. Comparison of Empirical Sa at (a) IPM
and the ground surface of (b) G1, (c) G2 and (d)G3 for the damping of 5%.

In Figure 10(a), the comparison of the statistical estimate of Sa given by the attenuation
relation of Yuzawa and Kudo (2006) with the observed Sa on IPM hard rock is shown. Figures 10(b),(c) and (d), show the comparison of the deterministic estimate of Sa to the statistical estimate of Sa ateach ground surface for the period of 1 to 10 second. In all of these four cases, the latter show theamplitude about three times higher than the former. Nevertheless, this difference, which is less than

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ten times, is still acceptable and comparatively good in estimating the ground motion compared to theestimation done by Miyake and Koketsu (2010). This difference can be due to the regionality ofattenuation characteristics of Japan and Malaysia that can have differences to big scale structure,
heterogeneity and then scattering characteristics. Moreover, neither radiation pattern of the event S2
nor local amplification of IPM is considered in this paper. Although this is a rough estimation, thedeterministic estimate of Sa falls in the same order with the statistical one and then is acceptable.
The distance between IPM station and Kuala Lumpur is approximately 180 km. The
epicentral distances to Kuala Lumpur and IPM are about 500 km and 586 km respectively. Therefore,
Kuala Lumpur will experience a larger amplitude of ground motion acceleration compared to IPM
station. The geometrical spreading factor of body waves 1 r and that of surface wave is 1 r givingthe estimation of the amplitude ratio of Kuala Lumpur to IPM about 1.2 and 1.1 respectively. The
difference between them is not considerable.

4. CONCLUSIONS
Based from the result obtained, Kuala Lumpur can experience ground motion that has long duration ofmotion with small amplitude. Considering the cost efficiency and to optimize the hardisk data storage,
setting up of the current strong motion observation into triggered base system is proposed. However,the small amplitude and long duration of motion is difficult to obtain using the usual setting of strong
motion triggering system. As an alternative, seismic signal received at MMD observatory center that issent from the Agency for Meteorology, Climatology and Geophysics (BMKG), Indonesia, via satellite
communication will then be used to launch a triggering signal to the strong motion sites in Malaysia.
Signal being transmitted via radio communication is faster than P-wave, which will takeapproximately two minutes to arrive at the station for 500 km of epicentral distance. After receiving
the triggered signal, the accelerograms will start recording for example one minute before the P-wave
arrival at the site. Configuring the recording duration about 20 minutes, based on the duration ofsimulated synthetic ground motions, is also necessary to acquire important information. The duration
should be from the time an earthquake occurs until it returns to the level of background noise.
However, it is best that more accurate and desirable value is to be decided from time to time
highlighting the characteristic of ground motion with small amplitude and long duration. An efficientseismic risk study and structural design shall start from the recorded data at the strong motion stationsin Malaysia.

AKNOWLEDGEMENT
Special thanks to Prof. K. Kudo, Nihon University and Dr. Y. Yuzawa, Tokyo Electric Power Service
Co. Ltd. for the permission to use their attenuation relation. I also would like to extend my thanks toDr. Tohishide Kashima for helping me in the data processing.

REFERENCES
Balendra, T., Lam, N.T.K., Wilson, J.L., Kong, K.H., 2002, Engineering Structure, Vol. 24, Issue 1,January 2002, 99-108.
Koketsu, K., Hatayama, K., Furumura, T., Ikegami, Y., and Akiyama, S., 2005, SeismologicalResearch Letter, Vol. 76, No. 1, January/February 2005, 67-73.
Kashima, T., 2009, ViewWave Software (version 1.56), http://smo.kenken.go.jp/~kashima/viewwave.
Yuzawa, Y., and Kudo, K., 2008, Proc. of 14th WCEE, S10-057.

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