IISEE Newsletter Special Edition
November 2022

Foreword
Our institution, International Institute of Seismology and Earthquake Engineering (IISEE), mainly conducts threefollowing one-year training courses named (S) Seismology Course, (E) Earthquake Engineering Course and(T) Tsunami Disaster Mitigation Course.
This booklet is a collection of abstracts of individual study reports from the trainees of the 2021-2022 course.
Regarding the trainees from S course and T course, only trainees who have volunteered wrote their abstracts.
Therefore, please kindly note that not all the abstracts are posted in this booklet.
Their further detailed synopsis can be found on the following website.
https://iisee.kenken.go.jp/jp/information/syndb/
Also, the final presentation from nine trainees will be released on IISEE E-learning website. (Coming soon)
https://iisee.kenken.go.jp/jp/information/el/
We hope this booklet will help you.
Haruhiko Suwada, Hiroto Nakagawa, Mai Ito (E Course leader)
Tatsuhiko Hara
(S Course leader)
Yushiro Fujii(T Course leader)International Institute of Seismology and Earthquake Engineering,
Building Research Institute1 Tachihara, Tsukuba, Ibaraki 305-0802, JAPAN.
E-mail: iisee@kenken.go.jp

Table of Contents
Seismology Course
2.
3.
4.
5.
6.
7.

Source Modeling of the 2018 Lombok Earthquake Sequence Estimated from the
Empirical Green’s Function Method
Development of an Earthquake Early Warning System in the Western Part of Java Usinga Strong Motion Network
S-Wave Velocities Estimation Using Seismic Ambient Noise Analysis at San MiguelVolcano, El Salvador
Determination of Moment Tensor Solution in the Fiji Region Using the Waveform
Inversion Technique
Strong Ground Motion Simulation of the 2020 Masbate, Philippines Earthquake (Mw6.6)
Using Empirical Green’s Function Method
Stress Field Orientation Obtained from Earthquake Focal Mechanism in Indonesia
RegionEngineering Course
8.
9.
10.
11.
12.
13.
14.
15.
16.

Comparison of Retrofitting Methods on an Existing Residential RC Building in Algeria,
Heavily Damaged by The 2003 Boumerdes Earthquake
Estimation of the Equivalent Damping Ratio for Low Energy Dissipation Systems Under
Mainshock-Aftershock Sequences To Determine the Damage Level
Probabilistic Seismic Hazard Assessment of Timor-Leste
Seismic Evaluation of Reinforced Concrete Buildings in San Salvador, El Salvador;
Considering the Latest Seismic Hazard Analysis
Microzonation Map of Seismic Site Condition and Amplification of Greater Accra Region,
Ghana
Dynamic Behavior Of Traditional Composite Masonry Buildings In Bhutan
Structural Performance Evaluation of Cyclone Resilient Houses Damaged Due to
Tsunami After the January 2022 Hunga Tonga-Hunga Ha’apai Volcanic Eruption
Fragility Evaluation of Building Structures Based on Damage Survey Results of Tsunami
Disaster From Hunga Tonga – Hunga Ha’apai Volcano Eruption on 15 January 2022
Seismic Performance Evaluation of Typical Residential RC Buildings at Different Soil
Types With Seismic Zones in Bangladesh

Tsunami Course
17. Rapid Magnitude Estimation Using Local Earthquake Waveform Data and the Application
to Earthquakes in Indonesia Including the 2010 Mentawai Tsunami Earthquake
18. Solving the Puzzle of the 1996 Biak Indonesia, Tsunami
19. Slip Distribution of the 2006 West Java Earthquake by Inversion of Tide Gauge Data
Using Phase-Corrected Green’s Functions

1

Citation: Ratri, A., H. Miyake, S. Kita (2022), Source modeling of the 2018 Lombok earthquake sequence estimated from the empiricalGreen’s function method, Abstract of IISEE-GRIPS Master's Thesis.

Source Modeling of the 2018 Lombok Earthquake Sequence
Estimated from the Empirical Green’s Function Method
Aldilla Damayanti Purnama RATRI
Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG), INDONESIA
E-mail : aldilla.damayanti16@gmail.com

Hiroe MIYAKE (Supervisor)
Earthquake Research Institute, University of Tokyo, JAPAN

Saeko KITA (Supervisor)
International Institute of Seismology and Earthquake Engineering (IISEE), JAPAN

Conducting source modeling using empirical Green’s function (EGF) can beused to capture the rupture and aftershock direction.
In 2018, a series of earthquakes in Lombok, Indonesia, occurred close together, causing a lot of casualties andproperty damage. In this study, we conducted source modeling for these earthquakes by simulating the target
event with strong motion data of the smaller event in the surrounding area, which have the closest hypocenter andsimilarity of focal mechanism to the target event using empirical Green’s function method. Then, we determined
the source model parameters, including source dimension ratio (N) and stress drop ratio (C) to conduct
broadband ground motion simulation. After that, we did a grid search calculation to get the best-fit value for thestrong motion generation area (SMGA) parameters. We obtained the best-fit of SMGA size and rupture starting
point from the grid search to conduct source modeling. The SMGA size (Figure 1) indicated that the western part(green line) of Lombok was lower stress drops than the eastern part (purple line) of Lombok. The relative SMGA
location (Figure 2) indicated the rupture direction extends radially toward the bottom right-hand direction.
Furthermore, there is a relationship among the foreshock, the mainshock, and the largest aftershock that may
have triggered each other and have similar source characteristics with rupture directions.

FigureFig. 1. Scaling relationship between
strong motion generation area andseismic moment.

Fig. 2. Combination of three source models for the2018 Lombok earthquake sequence. The star andrectangle respectively show the hypocenter and the
SMGA for the foreshock (blue), the mainshock (red),and the largest aftershock (black).

Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG)
Indonesia Agency for Meteorology, Climatology, and Geophysics(BMKG) is an Indonesian non-departmental government institution thatcarries out government tasks in Meteorology, Climatology, Air Quality,
and Geophysics following the provisions of the applicable laws andregulations. BMKG also plays an essential role at the International levelby providing earthquake information and tsunami early warning tonational, ASEAN, and countries around the Indian Ocean.

2Citation: Wijaya, A., M. Yamada (2022), Development of an earthquake early warning system in the western part of Java using a strong
motion network, Abstract of IISEE-GRIPS Master's Thesis.

Development of an Earthquake Early Warning System in theWestern Part of Java Using a Strong Motion Network
Angga Wijaya
Geophysics Department, Indonesian Agency for Meteorological, Climatological and Geophysics(BMKG), INDONESIA
E-mail : angga.wijaya@bmkg.go.id

Masumi YAMADA (Supervisor)
Assistant Professor, Disaster Prevention Research Institute, Kyoto University, JAPANThe IPFx method has the potential as an EEWS for Indonesia with highaccuracy and faster in providing earthquake warnings.
The development of an earthquake early warning system (EEWS) has been done in this study by applying theextended integrated particle filter (IPFx) method using a strong ground motion network in the western part of Java,
Indonesia. The method was applied to continuous waveforms including 95 earthquakes (M > 4 and seismic
intensity ≥ II MMI) and to the one-day waveforms including the 2022 Banten earthquake sequences. We used 190
stations divided into 99 conventional force-balanced accelerometer sensors (FBA) and 91 Micro-ElectroMechanical System (MEMS) sensors. Early warning criteria were given when the number of picks was more than
five and the maximum seismic intensity was ≥ 3.5 (IV MMI) based on the seismic attenuation equation. Thissystem has successfully detected 95 earthquakes and provided warnings to 46 from 49 events with observed
seismic intensity ≥ 3.5 MMI. The IPFx method shows good accuracy to estimate earthquake source locations withmedian errors of 12 km, 22.7 km, 0.27, and 0.62 for the epicenter, depth, magnitude, and seismic intensity,
respectively, relative to the Indonesia Agency for Meteorology, climatology, and Geophysics (BMKG) catalog asshow in Fig. 1. The IPFx method was also more accurate and 12 seconds faster in source estimation of theMainshock of the 2022 Banten Earthquake than The Earthworm Based Earthquake Alarm Reporting System(eBEAR) that BMKG has tested, as shown in Fig. 2. Based on the good accuracy and speed in estimating
earthquake sources, the IPFx method has the potential to be developed into an earthquake early warning system
in Indonesia in the future.

FigureFig. 1. Histograms of epicenter, depth, magnitude, and SI
errors in first warning catalog for earthquake with SI ≥ 3.5(a) and final catalog (b). Red
histogram in (b) shows the parameters error for earthquakewith SI ≥ 3.5. The top-right numbers in each histogramshow the median error for IPFx method compared withBMKG catalog.

Fig. 2. Result of the Banten Mainshock on January 14,
2020, with magnitude 6.7 and SI 7.5 (VIII MMI). a)
Estimated source location at converged time. The
colored and white triangles, respectively, indicates thetriggered and non-triggered stations in estimationgroup. (b)-(d) Time history of estimated earthquakes
parameters after origin time. The vertical black lines
indicate time of earthquake warning.

Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG)The Indonesia Agency for Meteorology, Climatology, and Geophysics(BMKG) is a non-departmental government agency established in 1947
and carries out government duties in Meteorology, Climatology, Air
Quality, and Geophysics. BMKG conveys information about natural
phenomena, early warnings, and natural disasters such as earthquakes,
climate change, weather, etc.

3

Citation: Pineda, K., T. Hayashida (2022), S-wave velocities estimation using seismic ambient noise analysis at San Miguel volcano, El
Salvador, Abstract of IISEE-GRIPS Master's Thesis.

S-Wave Velocities Estimation Using Seismic Ambient
Noise Analysis at San Miguel Volcano, El Salvador
Kevyn Enrique PINEDA ORTIZ
Ministry of Environment and Natural Resources, EL SALVADOR
E-mail : kevyn.pineda@marn.gob.sv

Takumi HAYASHIDA (Supervisor)
International Institute of Seismology and Earthquake Engineering, Building Research Institute,
JAPANTransforming noise into signal to understand San Miguel volcano
San Miguel volcano is considered one of the most active volcanoes in El Salvador due to its multiple eruptions;however, its structural properties are not fully understood. Four broadband seismometers were deployed fromFebruary 2014 to April 2014. We analyzed ambient noise data (>0.2 Hz) using the spatial autocorrelation (SPAC)
method and seismic interferometry technique. The spatial autocorrelation technique enabled us to calculate thephase velocity of the surface waves from 0.2 to 1.0 Hz. We also calculated Rayleigh-wave group velocities withseismic interferometry, which exploits Green’s function from the cross-correlation of ambient noise recordings.
The combined use of the two methods offered ways to gain information about the subsurface seismic velocity
structure from the same dataset. Seismic interferometry retrieved the shallow soil structure, while the SPAC
method yielded deeper structures. Our results made it possible to perform a joint inversion of phase and groupvelocities to obtain the S-wave velocity (Vs) structure of the volcano (Fig. 1),
We located 15 volcano-tectonic earthquakes using the velocity model. The earthquakes were located with a root
minimum square lower than 0.5. The hypocenter locations show a focus distribution, beneath the volcanic building
with a shallow depth (Fig 2). The locations of the earthquakes are consistent with a deformation zone, known as
the San Miguel Zone Fault, on the volcano's northern flank.

FigureFig. 2. Located seismicity around the San
Miguel volcano. Inverted triangles represent
seismic stations.

Fig. 1. P-wave and S-wave velocity modelcomputed for the San Miguel volcano.

Ministry of Environment and Natural Resources (MARN)
The Ministry of Environment and Natural Resources (MARN) is anorganization established in 1997 to protect natural resources, as wellas the diversity and integrity of the environment to guarantee
sustainable development.

4

Citation: Mule, S., D. Suetsugu, T. Hara (2022), Determination of moment tensor solution in the Fiji region using the Waveform inversion
technique, Abstract of IISEE-GRIPS Master's Thesis.

Determination of Moment Tensor Solution in the Fiji
Region Using the Waveform Inversion Technique
Saula MULE
Fiji Seismology, Mineral Resources Department, Fiji
E-mail : mule.saul@gmail.com

Daisuke SUESTSUGU (Supervisor)
Japan Agency for Marine-Earth Science and Technology (JAMSTEC)

Tatsuhiko HARA (Supervisor)
International Institute for Seismology and Earthquake Engineering (IISEE)

Moment Tensor determination in the North Fiji basin
We conducted moment tensor determination for 27 events that occurred in the North Fiji Basin from 2015 – 2022with a magnitude of Mw > 4.0 and depths less than 350 km. We used seismograms from seismograph stations inFiji and the neighboring countries. We used a regional velocity model with a 10-km thick crust by Xu and Wiens(1997) to compute Green’s functions. Among 27 solutions, 12 solutions shown in Fig. 1 were then validated inreference to the Global Centroid Moment Tensor (GCMT) solutions. We found that the solutions obtained by thepresent study are generally consistent with the GCMT solutions in terms of focal mechanism and moment
magnitude. Stress axes of the focal mechanisms are consistent with the tectonic process reported by previous
studies. Focal depths were shallower than the GCMT centroid depths by 1.4 km on average. We also evaluatedthe effect of the velocity model on focal mechanism solutions by comparing waveform fitting and similarity to
GCMT. We performed the moment tensor inversion for events with Mw > 5.0 using the original regional model, its
modified model with a 20-km thick crust, and a global standard model. For most of the events used forcomparison, the waveform fitting is best for the original regional model with a 10-km thick crust than the other two
velocity models (Fig. 2). We compared focal mechanisms determined from data including and excluding stations
from the neighboring countries. The comparison shows that the mechanisms are closer to the GCMT by including
data from neighboring countries, suggesting the importance of international data exchange.

Figure.

Fig. 1. Focal mechanism solutions obtained in thisstudy which are consistent with the GCMT
solutions.

Fig. 2. Effects of the velocity model. Comparison ofvariance reductions for three velocity models of Xu andWiens (1997) with a 10km-thick crust (green circle), Xu
and Wiens (1997) with crustal thickness modified to 20 km(red triangle), and the iasp91 model (blue square) are
shown.

Minerals Resources Department Fiji
Mineral Resources provides geoscientific information about Fiji, develops
policies on mining and provides information and assistance to investors
on mining sectors, facilitates exploration, and provides information on the
non-living resources of the country. The Seismology unit’s primary role isto provide information on geohazards assessment and timely
dissemination of information at the time of any local or felt regional event.

5

Citation: Simborio, T., T. Yokoi, T. Hara (2022), Strong ground motion simulation of the 2020 Masbate, Philippines earthquake (Mw6.6) using
Empirical Green’s Function method, Abstract of IISEE-GRIPS Master's Thesis.

Strong Ground Motion Simulation of the 2020 Masbate,
Philippines Earthquake (Mw6.6) Using Empirical Green’s
Function Method
Tom Carlo Enriquez SIMBORIO
Department of Science and Technology–Philippine Institute of Volcanology and Seismology, Philippines
E-mail : tom.simborio@phivolcs.dost.gov.ph

Toshiaki YOKOI (Supervisor)
Japan International Cooperation Agency, Japan

Tatsuhiko HARA (Supervisor)
International Institute of Seismology and Earthquake Engineering, Building Research Institute, JapanThe Empirical Green’s Function method is applicable to the current
Philippine strong motion network.
Strong ground motions of the August 18, 2020 Mw 6.6 Masbate, Philippines earthquake were simulated using theAugust 11, 2020 Mw 4.9 Masbate, Philippines earthquake records of the Philippine Strong Motion Network
through the Empirical Green’s Function (EGF) method. The fault dimensions and stress drop ratios were
calculated through the source spectral fitting method. A grid search was done to obtain a set of parameters for the
EGF method that explains the observed strong motion data well. These parameters include the rupture starting
point, rupture velocity, rise time, length, and width of the strong motion generation area (SMGA). The result
suggests the rupture started in the shallow southern segment of the fault plane (Fig. 1). The peak groundaccelerations (PGAs) from the simulated waveforms (Fig. 2) are consistent with the observed PGAs, and a
directivity effect was also simulated (Fig. 3). The PGAs calculated using a ground motion prediction equation used
for hazard estimations in the Philippines overestimates for three stations among the four stations analyzed in thisstudy. The peak ground displacements (PGDs) from the simulated waveforms are underestimates compared tothe observed PGDs. The ratio of the size of the SMGA to the moment magnitude and the ratio of the rise time tothe moment magnitude are smaller than those obtained in previous studies.

FigureFig.
1.
Schematic
illustration of the strong
motion generation areaof the August 18, 2020,
Masbate,Philippines
earthquake. The star
represents the rupture
starting point.

Fig. 2. Observed and synthetic
waveforms of LYKN station (N-S)
component.
Fig. 3. Comparison ofobserved
PGAs
and
calculated PGAs.

the
the

Department of Science and Technology-Philippine Institute of Volcanology andSeismology (DOST-PHIVOLCS)
The Department of Science and Technology-Philippine Institute ofVolcanology and Seismology is the mandated institute to raise awarenessand mitigate disasters from volcanic eruptions, earthquakes, tsunamis, andother geotectonic hazards in the Philippines.

6

Citation: Pratama, W., S. Kita (2022), Stress field orientation obtained from earthquake focal mechanisms in Indonesia region, Abstract of
IISEE-GRIPS Master's Thesis.

Stress Field Orientation Obtained from Earthquake
Focal Mechanism in Indonesia Region
Your
Photo

Wahyudi Nasrul PRATAMAThe Agency for Meteorology, Climatology, and Geophysics (BMKG), REPUBLIC OF INDONESIA
E-mail : wahyudi.nasrul@bmkg.go.id

Saeko KITA (Supervisor)
International Institute of Seismology and Earthquake Engineering, Building Research Institute,
JAPANFirst report of the spatial mean of stress orientation and fault type in entire
Indonesia region
Determination of the stress field is essential to understanding the stress source and earthquake mechanism.
However, the stress field study has been rarely conducted in the Indonesia region. We constructed the stress map
in Indonesia derived from the Global Centroid Moment Tensor (GCMT) and the National Research Institute for
Earth Science and Disaster Prevention (NIED) focal mechanism data from 1990 until 2021. Overall, we used
3,756 earthquake focal mechanism data with a depth of ≤30 km. We applied two methodologies in this study;
firstly, we created a mesh size of 75 km x 75 km of spatial mean of maximum horizontal compression stress(SHmax) and fault type. Then, we also performed the stress tensor inversion method to confirm the spatial meanof SHmax orientations. We got very declivous plunges of 𝜎1 in the northern North Maluku, southern North Maluku,
and Batu-Mentawai-Pagai subduction segments. Meanwhile, the West and Central Java, the East Java, and the
Sumba subduction segments have relatively steeper plunge angles than other regions. We found that the two
methodologies we used yielded the same results in general. In our stress map, the orientations of SHmax arecommonly perpendicular to the trench in the subduction zone and subparallel to the plate motion. This stress map
also revealed the fault type distribution, which is generally consistent with the tectonic setting and focal
mechanisms of large earthquakes. We confirmed that the normal faulting associated with SHmax parallel to thetrench is intense near the trench of Java and Sumba subduction segments, indicating this area as the uncouple
subduction zone.

FigureFig. 1. SHmax orientation. Spatial SHmax(colored rectangle) and SHmax from inversion(black rectangle)

Fig. 2. Comparison between spatial mean fault
type with earthquake focal mechanism M≥7

The Agency for Meteorology, Climatology, and Geophysics (BMKG)The Agency for Meteorology, Climatology, and Geophysics (BMKG) is agovernmental institution that has responsibility to observe and analyze inthe fields of Meteorology, Climatology, Air Quality and Geophysics. In
field of geophysics, BMKG provide information about earthquake,tsunami, engineering seismology, potential geophysics and time code.

7

Citation: AIT ALI SLIMANE, N., T. Saito (2022), Comparison of retrofitting methods on an existing residential RC building in Algeria, heavily
damaged by the 2003 Boumerdes earthquake, Abstract of IISEE-GRIPS Master's Thesis..

Comparison of Retrofitting Methods on an Existing Residential
RC Building in Algeria, Heavily Damaged by The 2003 Boumerdes
Earthquake
Nassim AIT ALI SLIMANE
Student, University of Science and Technology Houari Boumediene (USTHB),
Faculty of Civil Engineering, Bab Ezzouar, Algeria.
E-mail : Nassimoffic@gmail.com

Taiki SAITO (Supervisor)
Professor, Department of Architecture and Civil Engineering,
Toyohashi University of Technology, Japan

Comparison of retrofitting methods applicable in Algeria on a reinforced
concrete residential building
The 2003 Boumerdes earthquake caused a large amount of damage, particularly in the city of Boumerdes. Afterthe disaster, a revision of the Algerian code and the retrofitting of the 1,200 dwellings of Ibn Khaldoun city were
made. The retrofitting method at that time was based on an experimental approach without following a specificcode. In Japan, being especially advanced in seismic evaluation and rehabilitation of different structures, the
JBDPA method was used during this study to evaluate and retrofit a building of Boumerdes and compare 4
models of retrofitting under 3 different earthquakes. The comparison was based on the seismic index “Is”, thestory drift and shear at each floor, to find the most safely and economically effective result. During the study, theJapanese code and factor had to be adapted to Algerian seismic activity and ground proprieties. The use of
STERA-3D and the THA method was also necessary for the calculations. The final result in Figure 1. showed themodel (Both) from the after earthquake retrofit having higher safety, but the JBDPA method proposed retrofitting
model with lower capacity, which satisfy the minimum safety conditions and by following Figure 2. were more
economical than the retrofit proposed at that time. Therefore, it would be beneficial for Algeria to be inspired by
the JBDPA method for the future changes in the Algerian seismic code and add to it an evaluation andrehabilitation procedure adaptable to the different seismic zones of Algeria.

Figure

5
4
3
2
1
0.00

Both
JacketingVrc.add (m3)Floor

No Masonry
Infill Walls

5.00

10.00
15.00
sdx(cm)Fig. 1. Graphe of Story drift “sdx” of each floor
for the 4 models (without retrofitting, withjacketing, with infill walls, with both), obtainedby the THA on STERA-3D using the record of
Boumerdes 2003 Eq.

40.00
35.00
30.00
25.00
20.00
15.00
10.00
5.00
0.00

33.57
28.35
25.03

Jacketing Infill Walls

Both

Fig. 2. Volume in m3 of additional reinforced concrete,
added for each retrofitting method (Jacketing, infill
walls, Both).

University of Science and Technology Houari Boumediene, Faculty of Civil Engineering
Created in 1974, the Faculty of Civil Engineering has as its main
missions research and teaching. They offers theoretical lessons
supported by experiments in practical work laboratories, field trips andinternships which train each year nearly 1,282 undergraduate students
and more than 1,052 second-cycle master students in the Building
industry who will become the country's future engineers.

8Citation: Cueva, J., K. Kusunoki (2022), Estimation of the equivalent damping ratio for low energy dissipation systems under mainshockaftershock sequences to determine the damage level, Abstract of IISEE-GRIPS Master's Thesis.

Estimation of the Equivalent Damping Ratio for Low Energy
Dissipation Systems Under Mainshock-Aftershock Sequences To
Determine the Damage Level
Jean Cueva
Japan-Peru Center for Earthquake Engineering Research and Disaster Mitigation (CISMID), Peru
E-mail : jcuevar@uni.edu.pe

Koichi KUSUNOKI (Supervisor)
Professor, Tokyo University.

To estimate more accurately the equivalent damping ratio during
aftershocks and to determine the damage level in RC buildings.
The assessment of Reinforced Concrete (RC) buildings, considering mainshock-aftershock (MA) sequences, hasbeen addressed in previous studies in which the main objective is to predict the damage level after a maximum
expected aftershock and then judge if the building can continue operating or not. This study uses numericalsimulations to determine the equivalent damping ratio for structures with low energy dissipation and undermainshock-aftershock sequences and uses several Single Degree of Freedom (SDOF) systems with different
hysteresis models (Degrading trilinear, Origin-oriented, Takeda, and Takeda-slip), changing some parameters of
the Capacity Curve (Trilinear curve) and different initial periods (0.2 to 1.2s). Results indicate the variation of thedamping ratio for each hysteresis model, and the higher and lower values correspond to the Degrading trilinear
and Origin-oriented models, respectively. In addition, the parameter 𝑎2 , which is defined as the ratio of theyielding stiffness to the elastic stiffness of the capacity curve, presents a significant influence on the equivalent
damping ratio. For that reason, this study presented a new expression to determine the damping ratio, which
considered a new reduction factor values “𝛾” and a new coefficient to quantify the additional damping ratio due tothe damage before yielding point “b,” both were determined for specific values of the parameter 𝑎2 . Due to thehigh values and the uncertainty of coefficient “b,” the new expression was reduced for practical purposes during
the mainshock and aftershock. Additionally, the damage level (ductility) for the maximum expected aftershock,and using the new “𝛾” values, presented a lower error percentage than the previous studies, which considered 𝛾
equal to 0.06.

FiguresFig. 1. Ductility versus Damping ratio relationshipduring Aftershock for 𝑎2 = 0.25 (Takeda slip), andcurve fitting for the median and median minus
standard deviation (SD).

Fig. 2. Linear regression for the Takeda slip modeland during the aftershock to determine the damping
ratio for a specific to 𝑎2 value.

Japan-Peru Center for Earthquake Engineering Research and Disaster Mitigation(CISMID)
Japan Peru Center for Earthquake Engineering Research and Disaster
Mitigation (CISMID) was established in May 1986 by the Faculty of Civil
Engineering of the National University of Engineering (FIC-UNI) andfinanced thanks to the cooperation of the Government of Japan throughits International Cooperation Agency (JICA).

9

Citation: Da Costa Oliveira, V., T. Itoi (2022), Probabilistic seismic hazard assessment of Timor-Leste, Abstract of IISEE-GRIPS Master's
Thesis.

Probabilistic Seismic Hazard Assessment of Timor-Leste
Vitoria Maria de Lillia da COSTA OLIVEIRA
Earthquake and Seismology/Geohazard and Geological Engineering Division.
E-mail : voliveira@ipg.tl

Dr. Tatsuya ITOI (Supervisor)
Associate Professor, Graduate School of Engineering, The University of Tokyo

Using the probabilistic seismic hazard approach to identify the seismic
hazard level for seismic building code of 10% and 2% exceedance in 50 years.
This dissertation examines the purpose of defining the seismic hazard level in Timor-Leste for seismic building
codes based on past earthquakes and tectonic settings. The historical earthquake occurrences from 1960 to 2021
were collected from the United States Geological Survey (USGS) and the Institute of Geology and Petroleum(IPG) with a magnitude between 2 and 8.1 Richter Scala. Earthquake source zoning was based on theoccurrences of historical earthquakes surrounding Timor-Leste, and the frequency magnitude distribution by using
the Gutenberg-Richter recurrence law was estimated. The kernel density function has been used to modulate theprobability distribution of hypocenter distance from different source zones. The simulation procedure was todetermine peak ground acceleration using the Ground Motion Prediction equation adapted from Si et al, 1999.
The result gave the seismic hazard curves, and a seismic hazard map plotted for the return period of 475 (Fig.
1)and 2500 years (Fig. 2) (10% and 2% exceedance in 50 years, respectively). The highest total hazard observedin the Atauro site was a very high hazard level with a PGA value of 440 gal and 209 gal, which was included inclass V and class III, corresponding to a 2% and 10% probability of exceedance in 50 years respectively.
However, the smallest total hazard observed in the Viqueque site for 2% probability of exceedance for 50 years
was a moderate hazard level with a PGA value of 171 gal, consisting of class II, and in RAEOA site was a low
hazard level with a PGA value of 80 gal, which corresponding to class I, for a 10% probability of exceedance for
50 years.

FigureFig. 1. Peak ground acceleration for 2% probability ofexceedance in 50 years.

Fig. 2. Peak ground acceleration for 10% probabilityof exceedance in 50 years.

Institute of Petroleum and Geology-Public Institute (IPG-IP)
The Institute of Petroleum and Geology (IPG), established in 2012 basedon Decree-Law nº 33/2012 of July 18, is a public institution of the TimorLeste Government, under the supervision of the Ministry of Petroleum
and Mineral (MPM) to develop geological studies of mineral resources,
including Timor-Leste’s oil and gas, and, Geo-hazard, using modern
technical and scientific basis, enabling the development of the country.

10

Citation: Campos, E., T. Azuhata, Y. Otsuka (2022), Seismic evaluation of reinforced concrete buildings in San Salvador, El Salvador;considering the latest seismic hazard analysis, Abstract of IISEE-GRIPS Master's Thesis.

Seismic Evaluation of Reinforced Concrete Buildings in San
Salvador, El Salvador; Considering the Latest Seismic Hazard
Analysis
Eugenia Guadalupe CAMPOS CARRANZAEngineers and architects, specialized services (INGENYARSE), El SALVADOR.
E-mail : camposcarranza.eu@gmail.com

Tatsuya AZUHATA1 and Yuri OTSUKA2 (Supervisors)
1Department of Structural Engineering, Building Research Institute2International Institute of Seismology and Earthquake Engineering, Building Research InstituteThe seismic performance of RC buildings in EL Salvador and Japan
designated by current seismic codes were compared based on theprobability of collapse. The results revealed problems with the seismic
performance of RC buildings in El Salvador.
This investigation focused on the seismic evaluation of low-midrise reinforced concrete buildings in San Salvador,considering the inelastic demand defined by the current seismic design code (NTDS-94). Moreover, the latest
Probabilistic Seismic Hazard Assessment (PSHA) for the country, which will be the base for the new seismic code,
was used. The implemented methodology was the Probabilistic Based Earthquake Engineering (PBEE)
framework, which involves a holistic overview of the performance integrating hazard, structural, and damage
analysis. Four simplified framed structures treated as a single degree of freedom (SDOF) systems were studied,
two are based on El Salvador seismic standard, and the others are based on Japanese seismic provisions. The
above with the intention to compare the influence of the hazard definition and the required capacity specified ineach building code on the building's performance. Two approaches were employed to give a solution to the PBEE
basic formulation; numerical integration and approximate analytical solution. Based on the results of the
Incremental dynamic Analysis using 40 Inland waves, we calculated the probabilities of limit state exceedance in
50 years in terms of inter-story drift ratios. The probabilities of exceeding the design limit drift imposed by El
Salvador's seismic code of 0.015 rad are more than 5% for both Salvadoran SDOF systems (6-story and 10-story
buildings) calculated using both approaches. We observed that El Salvador models have higher probabilities of
exceeding safety limits than Japanese models. Hence, the influence of the seismic hazard curve and the seismic
demand, which in the case of El Salvador depends on the response reduction factor R, was evident. The
approximate solution derived more conservative results in the performance of the models.

FigureFig. 1. Example of an SDOF model of the buildings in
the left and Mean IDA curves or 50% percentile curves
for the 4 model buildings to the right.

Fig. 2. Probability of exceedance limit
states in 50 years calculated by
Numerical Integration.

Engineers and Architects, specialized services INGENYARSEINGENYARSE S.A. de C.V. is a consulting and structural design
company in El Salvador that have carried out the design of many
important public infrastructure, mostly of them bridges. Moreover, thecompany is actively involved in the development of human talent offering
training courses in structural design topics to students and professionals
trough the civil engineering national associations.

11Citation: Fordjour, B., S. Nakai (2022), Microzonation map of seismic site condition and amplification of Greater Accra Region, Ghana,
Abstract of IISEE-GRIPS Master's Thesis.

Microzonation Map of Seismic Site Condition and
Amplification of Greater Accra Region, Ghana
Benjamin Osei FORDJOUR
Ghana Geological Survey Authority, GHANA.
E-mail : benjamin.fordjour8@gmail.com

Shoichi NAKAI (Supervisor)
Professor Emeritus, Chiba University, and Visiting Research Fellow, Building Research Institute,
JAPANThe Vs30 and site amplification map will serve as an improved first-orderapproximation and geotechnical base map for the capital region.
The capital city of Ghana, Accra, is located within the most seismically active region of the country. This study
seeks to assess the seismic site condition and amplification based on the shear wave velocity for the regional
capital by the topography as a proxy method. Point slope measurements are extracted and subjected to seismic
site condition correlation of the NEHRP for stable regions. The correlative seismic site condition within a limiting
slope boundary corresponding to a specific soil class is obtained using regression analysis. We first analyzed
available single-point microtremor measurements to know the fundamental subsurface ground frequencies for the
study area, after which some inversion parameters based on diffusion assumption were considered concerning
the soil frequencies to understand the terrain within the study area. The inversion outcome could not support theactual representation of soil layers since it did not include dispersion curves to aid in generating profiles withrelatable soil layers. The obtained Vs30 is then further subjected to the linear site amplification equation for stableregions by Stewart et al. (2017). Scaling ground condition for linear soil response over an average oscillator
period of 0.4 to 2 seconds. An interpolation using the inverse distance weight method was applied to thecalculated seismic site conditions and the site amplification data sets to generate a representative map at asquare kilometer area raster. A comparison will then be made between the global seismic site condition map tounderstand the changes and possible similarities. The newly generated map could serve as an improved firstorder approximation of Vs30 for the capital region.

FigureSoil
Class

Vs30 Range Slope range (m/m) Slope (M)(m/s)(stable continent)Intercept
(C)

E

<180

<2.0E-5

9000000

0D

180–240

2.0E-5–2.0E-3

30303

179

240–300

2.0E-3–4.0E-3

30000

180

300–360

4.0E-3–7.2E-3

18750

225

360–490

7.2E-3–0.013

22414

199

490–6200.013–0.018

26000

152

620–760

0.018–0.025

20000

260

>760

>0.025

30400

0

C

B

Fig. 1. Table Summary of slope
ranges for subdivided National
Earthquake
HazardReduction
Program (NEHRP) Vs30 categories

Fig. 2. Graph model designed
to estimate the intended
amplification for the study
area with corner velocities V1
and V2 at 239 and 945 m/s,
respectively, at an averageslope of -0.505

Fig. 3. Final Vs30 and Site
Amplification Map showing
clusters within geologicalunits

Ghana Geological Survey Authority, (GGSA)The Ghana Geological Survey Authority (GGSA) is an institution under
the Ministry of Lands and Natural Resources of Ghana, established in
1962. The institution under the GGSA Act 2016 (Act 928) is mandated toadvise, promote and research geoscientific issues concerning mineral
resources, groundwater, environment, geo-hazards and land use
planning to support sustainable economic development in Ghana.

12

Citation: Tenzin, K., M. Miyamoto, T. Aoki (2022), Dynamic behavior of traditional composite masonry buildings in Bhutan, Abstract of IISEEGRIPS Master's Thesis.

Dynamic Behavior Of Traditional Composite Masonry Buildings In
BhutanKunzang Tenzin
Division for Conservation of Heritage Sites, Department of Culture, Ministry of Home and Cultural
Affairs, Royal Government of Bhutan.
E-mail :kunzangt@mohca.gov.bt

Mitsuhiro MIYAMOTO and Takayoshi AOKI (Supervisor(s))
Kagawa University & Nagoya City University, JapanThe dynamic behavior of traditional composite masonry building in
Bhutan are studied by shaking table test and numerical analysis
In this study the seismic performance of the composite masonry buildings in Bhutan is evaluated by shaking table
test and numerical analysis. The shaking table test was executed on four 1/6 reduced scale models which
comprises of two rammed earth models (unreinforced and retrofitted) and two stone masonry models(unreinforced and retrofitted). The numerical analysis was carried by transforming the model specimen into the
lumped mass models of the two-degree freedom system. The linear and nonlinear time history analysis was
executed using the input motion from the experimental test. The experimental results show that natural frequencyof the specimens decreases with an increase in input ground motion, reflecting the degradation of stiffness due tooccurrence of damages. Comparing the natural frequencies, the retrofitted models showed a higher value thanunreinforced models. The proposed retrofitting measures improved the seismic performance of the structures by
preventing the occurrence of cracks and limiting the damage propagation. The comparative analysis was madebetween the numerical analysis and experimental test results in terms of the maximum acceleration response ateach floor level at each input ground motion. From the results we conclude the numerical simulation results are inclose range to the experimental test. Further, the good correlation between the damage occurrence and results oftime history analysis is observed in all the models.

FigureFig. 1.Shaking table test on 1/6 models of
unreinforced and retrofitted rammed earth and stone
masonry. The natural frequency at each input motion
is presented.

Fig. 2. Results from numerical analysis performed byforming lumped mass system. The experimental
results is compared with the numerical in terms ofacceleration response at roof level for each specimen

Department of Culture, Ministry of Home and Cultural Affairs, Bhutan
The Department of Culture is central agency for realization of harmonious
and progressive society through preservation, protection, development
and promotion of the shared ideals & values and unique cultural identity
and its expression. The Department is responsible for carrying out
conservation and preservation of heritage structures and traditional
construction practices in the country.

13

Citation: Leger, V., T. Azuhata (2022), Structural performance evaluation of cyclone resilient houses damaged due to tsunami after theJanuary 2022 Hunga Tonga – Hunga Ha’apai volcanic eruption, Abstract of IISEE-GRIPS Master's Thesis.

Structural Performance Evaluation of Cyclone Resilient Houses
Damaged due to Tsunami after the January 2022 Hunga TongaHunga Ha’apai Volcanic Eruption
Victorina Stephanie Nodis Leger
Ministry of Infrastructure Tonga.
E-mail : legervictorina@gmail.com

Tatsuya AZUHATA
International Institute of Seismology and Earthquake Engineering, Building Research Institute,
JAPANThis method should be regularized as a first step towards identifying thebuilding’s risks for future disaster mitigation planning of housing in Tonga.
After the event of January 2022, it has been an eye opening for buildings located in the coastlines and specifically
our Cyclone Resilient Houses (CRH) that were damaged. The CRH that had been popularized in the past 40
years for housing reconstruction programs are now questionable after the January 2022 event. The study of thelateral forces impact by wind, earthquake and tsunami against re-evaluating the strength of the CRH timber shear
walls using the Australia Standard AS1684.2 – 2010 Capacity of Wall Bracings on timber framed structures. Thisis assessed against the demand lateral forces from tsunami in addition to wind and earthquakes based on theAustralia standard AS1170.2 and AS1170.5 - 2002 and tsunami force using the Japanese guideline because
Tonga have not adopted one. The result shows that the capacity of the shear walls is safe in the case of tropical
cyclones and earthquakes because of the adequate nailed connections. However, tsunami load is too big tocompare against the capacity of the CRH and therefore CRH can never withstand tsunami with inundation depth
over 1m. Shear wall capacity of CRH depends mainly on the nail-joint properties although not specificallyenforced in the construction of the CRH. The Cost review analysis of the CRH have been more expensive
recently to approximately 8 times more and there should be other alternatives to consider other type of structuresinstead of timber. This draws attention into enforcing structural performance evaluation of existing buildings
through updating the current Building Regulations to suggest future disaster mitigation planning of housing.

Figure𝜂 = 7𝑚𝜂 = 1𝑚Fig. 1. Damages to the CRH at different
inundation depths

CAPACITY
Direction
X (Longtidunal)
Y (Transverse)
DEMAND
Direction
X (Longitudinal)
Y (Transverse)

Timber Panel
114.48
66.13

Steel Strap
16.05
24.75

Total
130.53
90.88

Wind
29.72
61.52

Earthquake
73.08
73.08

Tsunami (h=1.0m) [*]52.92
105.84

Fig. 2. Types of Wall Bracings Considered for capacityof shear walls (AS 1684.2) and the Table of thecompared Capacity vs. Demand of CRH

The Ministry of Infrastructure Tonga
The Ministry of Infrastructure Tonga was established as a reform to
combine both the Ministry of Works and the Ministry of Transport in 2015.
We plan, build, regulate and facilitate construction and maintenance of
public infrastructure relating to housing, transportation on land, sea andair to achieve better quality, safer, affordable and readily available roads,
buildings and transport infrastructures and services that support
sustainable well-being and resilience of the people of Tonga.

14

Citation: Manu, M.S., T. YOKOI, T. AZUHATA (2022), Fragility evaluation of building structures based on damage survey results of tsunami
disaster from Hunga Tonga – Hunga Ha’apai volcano eruption on 15 January 2022, Abstract of IISEE-GRIPS Master's Thesis.

Fragility Evaluation of Building Structures Based on Damage
Survey Results of Tsunami Disaster From Hunga Tonga – Hunga
Ha’apai Volcano Eruption on 15 January 2022
Mele Siale MANU
Natural Resources Division, Ministry of Lands and Natural Resources, TONGA
E-mail : melesiale05@gmail.com

Tatsuya AZUHATA (Supervisor)
Department of Structural Engineering, Building Research Institute, JAPANToshiaki YOKOI (Supervisor)
Japan International Cooperation Agency, JAPAN

Tsunami fragility curves indicate that timber structures are the mostvulnerable structural system to a tsunami in Tonga.
On 15 January 2022, Tonga was hit by a tsunami caused by the eruption of the HUNGA TONGA – HUNGAHA'APAI (HT-HH) volcano. This study aims to detect the vulnerable structural systems from this disaster, usingfragility curves for future disaster mitigation planning. I gathered data on the inundation depth and structural
damages through the government ministries' post-disaster field surveys and completed the required dataset on an
independent field survey. This study focused on Hihifo and Nuku'alofa on Tongatapu island. The method used todetermine fragility functions was the Grid Search method. Structural damages have two classifications: destroyed
and survived. Fragility curves for structural damages were developed for all building types of Hihifo andNuku'alofa, timber buildings of Hihifo and Nuku'alofa, and Reinforced Concrete (RC) buildings with masonry infillof Hihifo. The result showed that the Hihifo area has a stronger structural system than Nuku'alofa. The fragility
curves of Hihifo and Nuku'alofa were compared with those developed in other countries. It showed that the timberbuildings and RC structures with masonry infill of Hihifo are stronger than in other countries. However, American
Samoa's RC structures are more resilient than Hihifo at higher inundation depths. Therefore, the timber buildingsof Nuku'alofa need to be assessed in detail. The RC with masonry infill buildings of Hihifo must follow the buildingcode so that all RC buildings will be equally resilient to a tsunami. Lastly, areas exposed to tsunami disasters
should have RC structures instead of timber.

Damage probability

Figure
1.2
1
0.8
0.6
0.4
0.2
0
0

Fig. 1. A map showing the inundation area of
Tongatapu island (light pink shade), thestudy areas (black oval), contour lines
showing elevations (grey lines), and the
direction of incoming tsunami waves (redarrows).
Fig. 2. Typical examples of destroyed timber buildings (top and middle)
and destroyed RC with masonry infill structure (bottom).

5
10Inundation depth (m)HihifoPhang Nga
PhuketFig. 3. Comparison of tsunami
fragility curves for RC with masonry
infill structures (orange) and timberbuildings (blue) of Hihifo with those of
RC buildings in Phang Nga (grey)
and Phuket (red), Indonesia andAmerican Samoa (green).

Natural Resources Division, Ministry of Lands and Natural Resources
The Natural Resources Division (NRD) operates under the Ministry of Lands
and Natural Resources. One of the core duties of the NRD is monitoring,assessing, researching and advising the public on the status of geo-hazard
activities and potential threats to the Tonga Islands. These geo-hazard
activities include earthquakes, tsunamis and volcanic eruptions. We also
provide broad sector awareness on the causes, behaviour, response, andevacuation plans to reduce risk per disaster event.

15

Citation: Paul, I K., S. Nakai (2022), Seismic performance evaluation of typical residential RC buildings at different soil types with seismic
zones in Bangladesh, Abstract of IISEE-GRIPS Master's Thesis.

Seismic Performance Evaluation of Typical Residential RC Buildings
at Different Soil Types With Seismic Zones in Bangladesh
Indrajit Kumar Paul
Research Engineer, Soil Mechanics & Foundation Engineering Division, Housing and Building ResearchInstitute(HBRI), BANGLADESH.
E-mail: ikpaul99@gmail.com

Shoichi NAKAI (Supervisor)
Professor Emeritus, Chiba University, and Visiting Research Fellow, International Institute of Seismology and
Earthquake Engineering, Building Research Institute, JAPAN.

Using the average N-SPT(N30) values, the effect of different soil site classes
with seismic zones to evaluate the seismic performance level of the typicalresidential RC buildings in Bangladesh.
Soil site classes and seismic zones are the integral parts of building design. During the earthquake, the effect of
local soil site conditions with zone coefficient plays an important role in building vulnerability. The Bangladesh
National Building Code (BNBC-2020) recommends the guideline for design response spectrum to reduce thevulnerability during the seismic activity. This paper presents the maximum seismic performance level, forexample, Operational (OP), Immediate Occupancy (IO), Damage Control (DC), Life Safety (LS), and Collapse
Prevention (CP) of the two model buildings located in the different site classes (SB, SC and SD) of four seismic
zones. The model buildings used in this analysis are typical residential RC buildings in Bangladesh. The siteഥclassification is usually conducted using average shear wave velocity 𝑉ഥ𝑆 if available. Otherwise, the value of 𝑁
may be used for site classification. In this study, average N-SPT(N30) values of 160 boreholes locations were
determined based on soil properties up to 30m of site profile as per BNBC-2020. The seismic performance levelof the buildings was estimated by using the Capacity Spectrum Method (CSM), compared with the results ofnonlinear pushover analysis, and explained in detail based on the equivalent single degree of freedom (ESDOF)
system. Two maximum inter-story drift ratios of 0.5% (1/200) and 0.4% (1/250) are used to determine building
performance levels and to compare with code limitation allowable story drift. It has been observed that the twomodel buildings having the limited drift angle of 1/200, are only operational in soil site classes SB and SC with a
Peak Ground Acceleration (PGA) up to 0.12g. On the other hand, in both drift angles, these buildings in soil
classes SB, SC, and SD with a higher PGA than 0.12g are not operational. Even at a PGA of 0.12g with soil
classes SD and SC (only 1/250), the buildings are not operational. Therefore, the evaluation results of the building
performance levels for the lower drift angle (1/250) are more resilient than the higher one (1/200).

FigureFig. 1. Performance level of the 8-story building
with two different drift angles (1/200) and (1/250).

Fig. 2. Performance level of the 5-story building
with two different drift angles (1/200) and (1/250).

HOUSING AND BUILDING RESEARCH INSTITUTE (HBRI)
Housing and Building Research Institute” (HBRI) is a national research
institute in the field of the housing sector in Bangladesh. HBRI has conducted
research to formulate and update the Bangladesh national building code forsafe and sustainable building construction across the country. This institutehas conducted sub-soil investigation work for the different infrastructuredevelopment projects of the Bangladesh Government. This institution has
introduced a variety of environment-friendly construction materials. It isproviding regular training on various topics related to housing and building
construction.

16

Citation: Widiarso, A., A. Katsumata (2022), Rapid magnitude estimation using local earthquake waveform data and the application toearthquakes in Indonesia including the 2010 Mentawai tsunami earthquake, Abstract of IISEE-GRIPS Master's Thesis.

Rapid Magnitude Estimation Using Local Earthquake Waveform Dataand the Application to Earthquakes in Indonesia Including the 2010
Mentawai Tsunami Earthquake
Aziz WIDIARSO
Agency for Meteorology, Climatology, and Geophysics (BMKG), Indonesia
E-mail : aziz.widiarso@bmkg.go.id

Akio KATSUMATA (Supervisor)
Professor, Faculty of Sustainable Design, University of Toyama, JapanThe maximum amplitude of any earthquake’s wave phase can be used for
rapid magnitude determination for tsunami warning purposes.
We propose the MID magnitude formula for tsunami warnings. The MID was formulated using 135 earthquakes
from 2012 to 2021 recorded by Broadband Seismographs. Selected broadband seismographs were used toformulate integrated displacement data that is proportional to the seismic moment of an earthquake. We
performed instrument response correction (Katsumata et. al., 2021), numerical integration, and high-pass Bessel
filter (Katsumata et. al., 2013) with a cut-off of more than 100 seconds on the earthquake waveform. The selectionof the maximum amplitude value is carried out at any phase of the earthquake wave. The formulation uses theempirical formula as follows: 𝑀 = 𝑎 log10 𝐴 + 𝑏 log10 𝑅 + 𝑐, where A is maximum amplitude, R is hypocentral
distance, and a, b, c are constants.
We find the values of a, b, and c through the weighted least square method as 0.789; 1.167; and 5.359,
respectively. This formula shows a low standard deviation value of 0.1269 when compared to MW from Global
CMT (Fig. 1). In the 2010 Mentawai tsunami earthquake, we observed the changes in MID and MSUM over time.
MSUM is the weighted average magnitude installed in the Seiscomp3 system, and is currently used for tsunami
warnings in Indonesia. As can be seen in Fig. 2, MID gives a better estimation than MSUM, rising steadily andreaching the final value after 3 minutes, on the other hand, MSUM fluctuates in the first 2 minutes. However, those
2 magnitudes show underestimated values as expected for tsunami earthquake type in the empirical magnitude
formula.

FigureFig. 1. MID compared to MW from Global CMT
catalog. The open circle represents themagnitude differences for each earthquake.

Fig. 2. The application of MID to the 2010 Mentawai
tsunami earthquake over time. The blue dash line, reddash line, black line and grey line represents the MBA,
MW, MID, and MSUM , respectively.

Agency for Meteorology, Climatology, and Geophysics (BMKG)BMKG is a non-departmental government agency that carries out
government tasks in the fields of Meteorology, Climatology, Air Quality, andGeophysics to support public safety and the success of national
development. Moreover, BMKG also plays an active role at the international
level as the agency that provides earthquake information and tsunami
warning for ASEAN and Indian Ocean countries with Indonesia Tsunami
Warning System.

17

Citation: Pandadaran, S.H., H. Yanagisawa, B. Shibazaki, Y. Fujii (2022), Solving the puzzle of the 1996 Biak, Indonesia tsunami, Abstractof IISEE-GRIPS Master's Thesis.

Solving the Puzzle of the 1996 Biak Indonesia, Tsunami
Sidiq Hargo PANDADARAN
Indonesian Agency for Meteorology, Climatology, and Geophysics, INDONESIA
E-mail : sidiq.hargo@bmkg.go.id

Hideaki YANAGISAWA (Supervisor)
Department of Regional Design, Tohoku Gakuin University, JAPAN

Bunichiro SHIBAZAKI, Yushiro FUJII (Supervisor)
International Institute of Seismology and Earthquake Engineering, Building Research Institute, JAPANSolving the unsolved hypothesis regarding the contribution of thesubmarine landslide in the 1996 Biak, Indonesia tsunami case
On February 17, 1996, an earthquake occurred northeast of Biak Island, Indonesia, and caused a tsunami.
Interestingly, the southwest side of Biak Island, which was not facing the epicenter, had a higher tsunami runup
than the facing side. Previous researchers assumed that the earthquake triggered submarine landslides. As no
one has addressed this phenomenon, this assumption remains an unsolved hypothesis.
The tsunami arrival time obtained from local people's eyewitness testimonies was used to perform backward
tsunami raytracing. Considering the raytracing result and multibeam topography, we found two submarine
landslide candidates: one large submarine landslide and a small submarine landslide were located in thesouthwest and south of Biak Island, respectively. Since the small submarine landslide only had a small effect on
the land, we only performed a tsunami simulation for the large submarine landslide. The result showed that thesubmarine landslide located at 135.62oE and -1.01oS with a geometry of about 950 m x 5000 m and a thickness ofabout 50 m seems to explain the observed runup and arrival time.
Previous researchers made a slip distribution without considering the submarine landslide event. As a result, theirmodel could not explain the observed runup in the southwest coastal area of Biak Island. To accommodate thisproblem, we propose a new model by combining the submarine landslide model with a modified fault model fromthe previous researchers. Our new model explains observed runup heights well; we obtained a geometric mean of
1.00 and a geometric standard deviation of 1.40.

FigureFig. 1. Backward tsunami
raytracing to estimate thepossible submarine landslide location.

Fig. 2. Our suggested combination model for the 1996 Biak,Indonesia tsunami.

Fig. 3. Maximum tsunami heightfrom our suggested combination
model.

Indonesian Agency for Meteorology, Climatology, and Geophysics (BMKG)
In general, BMKG has duties in meteorological, climatological, air quality,and geophysical services. BMKG is responsible for being the frontline indelivering earthquake and tsunami information in Indonesia. Also, BMKG
actively disseminates earthquake and tsunami information in Southeast
Asia and surrounding countries around the Indian Ocean.

18Citation: Putra Y. M. K., Y. Fujii (2022), Slip distribution of the 2006 West Java earthquake by inversion of tide gauge data using phasecorrected Green’s functions, Abstract of IISEE-GRIPS Master's Thesis.

Slip Distribution of the 2006 West Java Earthquake by Inversionof Tide Gauge Data Using Phase-Corrected Green’s Functions
Yogha Mahardikha Kuncoro Putra
Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG), INDONESIA
E-mail : yoghamkp@gmail.com
Yushiro FUJII (Supervisor)
International Institute of Seismology and Earthquake Engineering, Building ResearchInstitute, JAPANThe slip models of the 2006 West Java earthquake are updated by tsunami
waveform inversions of tide gauge data including far-field stations.
In this study, we re-estimated the slip distribution of the 2006 earthquake by tsunami waveform inversions of tidegauge data using phase-corrected Green’s functions. Then, to evaluate our slip models, we performed tsunami
inundation simulations and computed the K and 𝜅 numbers. The slip distribution obtained with an assumed
rupture velocity of 1.25 km/s shows that the maximum slip was around 5.9 to 11.8 m in the shallower part near the
trench, as shown in Figure 1a. The total source length was 300 km, while the seismic moment calculated from thissource was 6.4 x 1020 Nm (Mw = 7.8). To make a comparison, we also show the slip model obtained withoutphase correction in Figure 1b. The dominant shallow slips in our slip models support the previous study thatclassified the 2006 earthquake as a tsunami earthquake event. We successfully updated the source model basedon the previous study, as shown in Figure 2, although we found that the K and 𝜅 numbers of our slip models were
unsatisfied with recommended standard values. We also found that the tsunami inundation simulation results
were still underestimated around the Pangandaran, Cilacap, and Binangun. One possible reason for theunderestimation at some survey points may be local (near coasts) bathymetry effects. Furthermore, we tried toassess the possible locations of the landslide source in front of the Permisan region. We found that a near-coast
landslide source looks better to reproduce the extreme tsunami heights in the Permisan region. However, alandslide source far from the coastline was preferable to reproduce the tsunami heights for the western andeastern sides. Nevertheless, further studies are needed to determine more accurate landslide sources.

FigureFig. 1. Slip distributions estimated for the 2006 WestJava earthquake by tsunami waveform inversions
using Green’s functions (a) with phase correction and(b) without phase correction in cases of rupture
velocity 1.25 km/s.

Fig. 2. Comparison of measured tsunami heightsfrom the four data sources and tsunami
inundation simulation results using the threedifferent slip models.

Indonesia Agency for Meteorology, Climatology, and Geophysics (BMKG)BMKG is an Indonesian non-departmental government agency that carriesout government responsibility in the fields of Meteorology, Air Quality, andGeophysics. BMKG is a member of the World Meteorological Organization(WMO). BMKG also has responsibilities as the service provider for Tsunami
Early Warning Center (InaTEWS), ASEAN Earthquake Information Center(AEIC), and Indian Ocean Tsunami Warning and Mitigation System(IOTWMS).

19