Ka

LUGU, TAIWAN SEPTEMBER 18, 2022, Mw 6.9 EARTHQUAKEPRELIMINARY VIRTUAL RECONNAISSANCE REPORT (PVRR)

Virtual Assessment Team (VAT) Lead:
Erica Fischer, Oregon State University
Virtual Reconnaissance Assessment Team (VRAT) Authors:(in alphabetical order)

Sofía Aldea, Universidad Tecnica Federico Santa Maria
Jorge Archbold, Universidad del Norte
James Bantis, Stanford University
Miguel Bravo, University of Cambridge
Julian Carrillo, Universidad Militar Nueva Granada
Luis Ceferino, New York University
Katherine Cheng, UC Davis
Diego Cordero, CMG
Ahmed Elkady, University of Southampton
Hector Guerrero, UNAM
Selim Günay, UC Berkeley
Manny Hakhamaneshi, California High-Speed Rail
Authority
Pablo Heresi, U Técnica Federico Santa María

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Vedant Mathur, UC Berkeley
Amory Martin, Exponent
Amy Metz, Oregon State University
Zorana Mijic, Portland State University
Eduardo Miranda, Stanford University
Cesar Pajaro, Universidad del Norte
Alan Poulos, Stanford University
Maria Camila Lopez Ruiz, UC Berkeley
Claudio Sepulveda, UC San Diego
Elmon Toraman, New York University
Anne Wein, USGS
Kai Wu, Texas A&M University
Juan S. Zambrano, Oregon State University

1Chloe Hoepfinger, Oregon State University
Zeyad Khalil, Imperial College London

Jiachen (Charlie) Zhang, UC San Diego

Virtual Reconnaissance Assessment Team (VRAT) Editors:(in alphabetical order)

James Bantis, Stanford University
Manny Hakhamaneshi, California High-Speed Rail Authority
Michael Mieler, Arup
Khalid M. Mosalam, UC Berkeley
Alan Poulos, Stanford University
Ian Robertson, University of Hawaii

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PREFACE
The Earthquake Engineering Research Institute (EERI) is the leading non-profit membershiporganization that connects those dedicated to reducing earthquake risk. Its multidisciplinary members
include engineers, geoscientists, social scientists, architects, planners, emergency managers,
academics, students, and other like-minded professionals. EERI has been bringing people anddisciplines together since 1948. The objective of the Earthquake Engineering Research Institute is to
reduce earthquake risk by (1) advancing the science and practice of earthquake engineering, (2)improving understanding of the impact of earthquakes on the physical, social, economic, political, andcultural environment, and (3) advocating comprehensive and realistic measures for reducing theharmful effects of earthquakes.
Within EERI, this report has been produced by the Learning From Earthquakes (LFE) program. The
mission of the LFE Program is to accelerate and increase learning from earthquake-induced disasters
that affect the natural, built, social and political environments worldwide. This mission is accomplishedthrough field, remote or hybrid reconnaissance, data collection and archiving, and dissemination oflessons and opportunities for reducing earthquake losses and increasing community resilience. For
more information on LFE, please visit http://www.learningfromearthquakes.org/about.

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ACKNOWLEDGMENTS
Conducting post-earthquake reconnaissance is critically important to observe, document andanalyze the seismic performance of built and natural environments. While experimental work in
the laboratory and analytical modeling are extremely valuable, we will continue to rely on postearthquake reconnaissance for many years to come to learn about and understand the effects ofearthquakes on full-scale three-dimensional structures in the field which provide the ultimate testof our progress in mitigating the effects of natural hazards on society. Hence, post-earthquake
reconnaissance is at the very core of the missions of both the EERI’s Learning From Earthquakes(LFE) program. This report is the result of hard swift work and contributions by a large number ofindividuals and organizations.
The sharing of videos, damage reports and briefings via WhatsApp by the entire EERI
membership, the NHERI community in the United States as well as members of the earthquake
engineering community in several countries was extremely helpful and much appreciated.
This material is based upon work by the Learning for Earthquakes Endowment Fund of the
Earthquake Engineering Research Institute and by the National Science Foundation under Grant
No. CMMI 1841667.
Any opinions, findings, and conclusions or recommendations expressed in this report are thoseof the individual contributors and do not necessarily reflect the views of EERI or of the National
Science Foundation. All authors and editors listed on the cover page participated as volunteer
professionals. Thus, any opinions, findings, and conclusions or recommendations expressedherein are those of the individual contributors and do not necessarily reflect the views of theiremployer or other institutions and organizations with which they affiliate.
For more information about the Earthquake Engineering Research Institute please visit the
EERI website: https://www.eeri.org/
In particular, for a full listing of resources including Virtual Earthquake Reconnaissance Team(VERT) reports, datasets, and publications for over 300 different earthquakes occurring in
more than 50 countries during the last 70 years of EERI’s Learning From Earthquakes
program, please visit the EERI LFE earthquake archive:
https://learningfromearthquakes.org/archive/table-view

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TABLE OF CONTENTSPREFACE

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ACKNOWLEDGMENTS

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TABLE OF CONTENTS

4EXECUTIVE SUMMARY

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1.0 Introduction
1.1 Social Impacts
1.1.1 Casualties (Fatalities and Injuries)
1.2 Affected Population
1.3 Rescue and Relief
1.4 Building Damage
1.5 Infrastructure/Power Loss
1.6 Outside Assistance
1.7 “Did you feel it?” Reports
1.8 Impacts
1.8.1 Population exposure estimate by USGS Pager
1.8.2 Estimated Loss of Life and Injures

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2.0 Seismological Aspects
2.1 Tectonics of the Region
2.2 Seismicity of the Region
2.3 The September 18, 2022 Mw6.9 Earthquake
2.4 Ground Motion Intensities
2.5 Early Earthquake Warning (EEW)

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3.0 Local Codes and Construction Practices
3.1 Existing Building Stock
3.2 Building Codes
3.4 Bridge Codes

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4.0 Damage to Buildings
4.1 Healthcare Facilities
4.2 Schools
4.3 Low-rise Buildings
4.3.1. Residential housing
4.3.2. Mixed-use buildings
4.3.3. Industrial facilities
4.3.4. Commercial and religious structures

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4.4 High-rise Buildings
4.5 Government Facilities (Public Buildings)
4.6 Historical Buildings
4.7 Nonstructural components and building content
4.7.1. Schools
4.7.2. Commercial structures
4.7.3. Elevator impacts
4.7.4 Industrial facilities

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5.0 Damage to Infrastructure
5.1 Electric Power Infrastructure
5.2 Airport and Railway Infrastructure
5.3 Bridges
5.3.1 Railway bridges
5.3.2 Vehicular traffic bridges
5.4 Roadways

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6.0 Observed Geotechnical Failures
6.1 Geological Setting
6.2 Liquefaction
6.3 Building, Foundation, and Pavement Damages due to Ground Failure
6.4 Sinkholes
6.5 Landslides
6.5.1. Photos taken during active landslides
6.6 Video Documentation

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7.0 Current Conditions and Access
7.1 Power Outages
7.2 Water Disruption
7.3 Cellular Outage
7.4 Post-earthquake Safety Structural Evaluations
7.4.1 Bridge Inspections
7.4.2 Building Inspections
7.4.3 Water and Lake Inspections
7.5 Business and Economic Disruptions
7.6 Road conditions

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8.0 Summary and Recommendations

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References

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EXECUTIVE SUMMARY
On September 18th, 2022, at 2:44 pm local time, a moment magnitude 6.9 earthquake struck
42.7 km north of Taitung City, Taiwan. The epicentral coordinates reported by the U.S. Geological
Survey (USGS, 2022a) and the Taiwanese Central Weather Bureau Seismological Center(Central Weather Bureau Seismological Center, 2022) were 23.159°N 121.316°E and 23.14°N
121.20°E, respectively. The USGS reported a hypocenter depth of 10.0 km, whereas the Central
Weather Bureau Seismological Center reported a depth of 7.0 km. The earthquake was precededby a magnitude 6.5 earthquake in the same area 17 hours earlier. There have been several
earthquakes of magnitude 5.0 and larger in the sequence (USGS, 2022a).
Earthquake sequences with consequent large magnitude events separated by short time intervals
have been occurring at different parts of the world in the past years (e.g., 2019 Ridgecrest
earthquakes (Mosalam et al., 2019); 2022 Iran earthquake sequence (Mosalam et al., 2022)).
From a structural engineering and design perspective, this is a reminder that strong pre-shocks
and aftershocks (even with the same magnitude) can occur before and after the mainshock andtheir cumulative effects should be characterized and considered in the design codes of buildings
and other infrastructure systems.
This earthquake caused some geotechnical failures and damage to infrastructure, mainly bridges,
railroads, and highways. Damage to buildings was observed, but it was primarily concentrated onolder non-ductile structures and non-structural component damage. At least one building
collapsed and hundreds more had some damage. The earthquake resulted in at least one deathand 171 earthquake related injuries.
The earthquake highlighted the vulnerabilities of older non-ductile concrete buildings in seismic
regions, concrete bridges, and non-structural building components during an earthquake. This
event also highlighted the importance of an earthquake early warning system.

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1.0 Introduction
On September 18th, 2022, at approximately 2:44 pm local time, a moment magnitude (Mw) 6.9
earthquake struck 42.7 km north of Taitung City, in southeastern Taiwan. The epicentral
coordinates reported by the U.S. Geological Survey (USGS, 2022a) and the Taiwanese Central
Weather Bureau Seismological Center (Central Weather Bureau Seismological Center, 2022)
were 23.159°N 121.316°E and 23.14°N 121.20°E, respectively, which corresponds with the
Chishang township. The USGS reported a hypocenter depth of 10.0 km, whereas the Central
Weather Bureau Seismological Center reported a depth of 7.0 km. A tsunami warning was
triggered by this earthquake for Miyako Island in the East China Sea; however, it was later
withdrawn.
The purpose of this Preliminary Virtual Reconnaissance Report (PVRR) is to provide a summaryof the characteristics of the event, the seismicity of the impacted region, and an overview of themain effects of the earthquake as collected from publicly available information.
The earthquake was preceded by a magnitude 6.5 earthquake in the same area 17 hours earlier.
There have been several earthquakes of magnitude 5.0 and larger in the sequence (USGS,
2022a). Earthquake sequences with consequent large magnitude events separated by short timeintervals have been occurring at different parts of the world in the past years (e.g., 2019
Ridgecrest earthquakes (Mosalam et al., 2019); 2022 Iran earthquake sequence (Mosalam et al.,2022)). From a structural engineering and design perspective, this is a reminder that strong preshocks and aftershocks (even with the same magnitude) can occur before and after themainshock and their cumulative effects should be characterized and considered in the designcodes of buildings and other infrastructure systems.
This earthquake caused some geotechnical failures, specifically landslides. Infrastructuredamage consisted of bridge damage and a trail derailment. Damage to buildings was observed,
but it was primarily concentrated on older non-ductile structures. Non-structural damage was also
observed for components within buildings, such as collapse of ceilings, shelving falling over, anditems falling off shelves in stores.

1.1 Social Impacts
1.1.1 Casualties (Fatalities and Injuries)
There was one fatality and 171 injured people (中央通訊社, 2022). The death occurred due to thefall of heavy machinery in a cement factory in Yuli township in Hualien County (Li-yun et al., 2022).
Earthquakes in Taiwan with higher death tolls include the 1999 Mw 7.7 Chi-Chi earthquake andthe 2016 Mw 6.4 southern Taiwan earthquake, which caused more than 2,000 and 100 fatalities,
respectively (Blanchard & Lee, 2022).

1.2 Affected Population
The earthquake was felt across Taiwan with reports of shaking in Taipei (Reuters, 2022).
Combined, the total population exposed to strong, very strong, or severe intensities was 438,000.

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The earthquake affects were most significant in the Chishang township, located in northern
Taitung county (The Associated Press, 2022). The Chishang township consists of ten villages
with a population of approximately 8,200 people.

1.3 Rescue and Relief
Within one day of the earthquake, 30 emergency rescue vehicles and 2,265 personnel had been
deployed for rescue efforts across Taiwan (Li-yun et al., 2022). 110 soldiers were deployed in
Hualien county alone, along the island’s eastern coast, to assist with disaster relief efforts (Picheta& Cheung, 2022). Four people were rescued from a collapsed mixed-use three-story building inYuli (the ground floor was a 7-eleven convenience store and two other stories were residential).
Those that were rescued were the owner (70 years old), the owner’s wife, a 39-year-old woman,and her 5-year-old daughter (Lai & Moritsugu, 2022). Figure 1.1 shows the 5-year-old girl being
rescued from the collapsed building covered with blankets.

Figure 1.1. Rescue efforts from a collapsed mixed-use building.
Three people were rescued after their vehicle fell off a bridge that collapsed in southeast Taiwan.
They were taken to the hospital for injuries but survived (Davidson & Associated Press, 2022).
Due to roads blocked by landslides, more than 600 people were stranded in the mountain areasof Chike and Liushishi around Sixty Stone Mountain, which is in eastern Taiwan (公視新聞網,2022). There were no injuries among the more than 600 stranded people and rescuers were
working to reopen the roads. 20 passengers were evacuated after a train derailed at Dongli station
due to debris hitting the train from a collapsed canopy (Picheta & Cheung, 2022). There were no

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1.4 Building Damage
Much of the building damage occurred in the town of Chishang, in northern Taitung county andin Hualien county (Davidson & Associated Press, 2022). The building damage occurred in older
non-ductile concrete buildings with a variety of uses, such as residential, schools, and mixed use.
Non-structural damage was much more common for buildings across the region. This damage
included items falling off shelves in stores, shelving falling over, and the collapse of ceilingsystems. Section 4.0 summarizes building damage due to the earthquake.

1.5 Infrastructure/Power Loss
Power lines were destroyed by the earthquake around Chike Mountain leaving about 22,024
households in Yuli without power (Li-yun et al., 2022). As of Monday, September 19th, power had
been restored to all but 445 households. Water pipe damage throughout Yuli was also reported
causing 4,842 households to lose access to water in Hualien and Taitung (Huang Li-yun et al.,2022). On Monday, September 19th, 1,801 households still did not have access to potable water.
Debris from a falling canopy on a platform at Dongli railway station in Fuli hit a passing train,
derailing six cars (Davidson & Associated Press, 2022).
The earthquake caused bridge and road damage throughout eastern Taiwan and groundsubsidence of the ground. At least two bridges were reported damaged. These bridges werelocated in rural areas and caused tourists and residents to be trapped. Gaoliao Bridge in HualienCounty collapsed with most damage occurring at its northern end at the Dongli section. The
Siouguluan River Bridge, which is a railway bridge, was also heavily damaged due to theearthquake (CNA, 2022). A section of Provincial Highway 30, which connects Taitung's Changbin
and Yuli townships was closed due to cracks and subsidence caused by the quakes (Li-yun etal., 2022).
Taiwan houses the largest production of semiconductors and advanced chips. As such, theSeptember 18 earthquake, which affected several manufacturing facilities, led to the temporary
suspension of production following the event (Trend Detail News, 2022). This can lead to further
supply chain issues for the technology sector similar to the disruption that happened following the1999 Mw 7.7 Chi-Chi earthquake. This earthquake demonstrated the importance of designing
manufacturing facilities not only for life safety performance objectives, but also consideringfunctional recovery performance objectives to prevent severe economic consequences. This isparticularly important with the recent signing of the Creating Helpful Incentives to Produce
Semiconductors (CHIPS) and Science Act in the US (White House, 2022), which aims to boost
American semiconductor research, development, and production.

1.6 Outside Assistance
There are no reports of outside assistance at the time of writing this report.

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1.7 “Did you feel it?” Reports
Did You Feel It? (DYFI) is a system developed by the USGS to make use of reports provided bypeople who felt the earthquake. By taking advantage of the vast number of Internet users, it ispossible to get a more complete description of what people experienced during the earthquake,the effects of an earthquake, and an empirical estimate of the spatial distribution of intensities(USGS, 2022a).
The DYFI Map and related products produced by the USGS are created within minutes of each
earthquake of magnitude 1.9 or greater. The origin information (location and time) of each
earthquake is provided by the Advanced National Seismic System (ANSS) and its regional andnational network partners in the U.S.
At the moment of writing this report, for this event, the DYFI survey available at the USGS website
had about 156 responses within the first 24 hours after the earthquake. The evolution over timeof these responses is shown in Figure 1.2. It is worth noting that only a few people know about
USGS’s DYFI in Taiwan.

Figure 1.2. “Did you feel it?” (DYFI) responses collected by the USGS (USGS, 2022a).
From DYFI responses shown in the maps of Figure 1.3, it can be observed that most of thereported intensities fall within levels IV, V, and VI along the western coast of the country, and a
few level IX intensities were reported close to the epicenter. The attenuation of intensity withincreasing hypocentral distance is presented in Figure 1.4.

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Figure 1.3. (a) Geocoded location and (b) City map of Modified Mercalli Intensity inferred fromDYFI responses (USGS, 2022a).

Figure 1.4. Attenuation of Modified Mercalli Intensity with increasing hypocentral distancecompared with empirical relationships (USGS, 2022a).

1.8 Impacts
1.8.1 Population exposure estimate by USGS Pager
PAGER (Prompt Assessment of Global Earthquakes for Response), a product of the USGS, isan automated system that produces order-of-magnitude estimates of the impact of significant
earthquakes around the world, informing emergency responders, government and aid agencies,

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and the media of the scope of the potential disaster. PAGER rapidly assesses earthquake impacts
by comparing the population exposed to each level of shaking intensity with models of economic
and fatality losses based on past earthquakes in each country or region of the world. USGS
utilized PAGER to estimate earthquake impacts rapidly after the event. For example, PAGER canquickly produce rough estimates of earthquake casualties and economic losses to informemergency responders, governments, and international aid agencies.
Figure 1.5 shows the isoseismals estimated for the Mw 6.9 earthquake based on the Modified
Mercalli Intensity (MMI) scale and the population exposed to the various levels of shaking
intensities. Figure 1.5 shows that approximately 138,000 people were exposed to the highest
levels of shaking intensities (MMI VII and VIII combined), while 300,000 people were exposed toa MMI VI (strong intensity). Combined, the total population exposed to strong, very strong, orsevere intensities was 438,000. To examine the breakdown of MMI felt in different cities
throughout Taiwan, Figure 1.6 shows the number of people exposed to different ground shaking
intensities (MMI) in selected cities as a result of the earthquake. Based on these populations, thetotal population of cities that experienced MMI of VI (strong) or higher is 215,000.

Figure 1.5. Isoseismals (curves of equal MMI) estimated for the Mw 6.9 earthquake (USGS,
2022a).

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Figure 1.6. Number of people exposed to different ground shaking intensities (MMI) in selected
cities as a result of the earthquake (USGS, 2022a).
1.8.2 Estimated Loss of Life and Injures
PAGER uses Shake Maps as input to estimate potential fatalities according to historical data of
the region. For this earthquake, PAGER quickly estimated a probability distribution of fatalities
and economic losses in U.S. dollars (Fig 1.7a). The number of shaking-related fatalities was
expected to be less than 10 with ~75% probability. At the time of writing this report, 1 fatality and
171 injuries have been reported (Lai & Moritsugu, 2022; 中央通訊社, 2022). PAGER also estimatedeconomic losses due to damage to be between $0 and $1 million, between $1 million and $10
million, between $10 million and $100 million, and between $100 million and $1,000 million withprobabilities of 11%, 27%, 35%, and 20%, respectively (Fig 1.7b).

Figure 1.7. PAGER Estimated probability of (a) fatalities and (b) economic losses due to theearthquake (USGS, 2022a).

2.0 Seismological Aspects
2.1 Tectonics of the Region
Taiwan is located in a region that is characterized by a complex tectonic arrangement comprising
two subduction zones of reverse polarities where it lies near the convergent boundaries of threemajor tectonic plates - the Eurasia plate to the north and west, the Philippine Sea plate to the eastand southeast, and the Sunda plate to the southwest, as shown in Figures 2.1 and 2.2 (Caltech

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Tectonics Observatory, 2005; USGS, 2022a; USGS, 2022c). Off Taiwan’s northeast coast, thenorthwestern margin of the Philippine Sea plate is subducting underneath the Eurasian Platealong the Ryukyu trench which is clearly marked by high seismicity along a north-dipping seismiczone extending down to about 300 km, and where the majority of seismic energy release near
Taiwan originates (Shing and Teng, 2001; Sun et al., 2015). Around Taiwan’s southern tip and off
its southwestern coast, the Eurasia plate is subducting eastward under the Philippine Sea plate,which outlines a region of east-dipping seismic zone extending down to about 200 km (Shing andTeng, 2001). The modern suture zone is located along the Longitudinal Valley along Taiwan’s
east coast and is characterized by occasional large shallow strike-slip earthquakes, where in thegeological past, this suture zone might have behaved more thrustlike (Shin & Teng, 2001). In theregion extending between these two subduction zones and in the midsection of western Taiwan,
there are a series of large thrust fronts which take up the bulk of the plate convergence rate (Shin& Teng, 2001). As a result, the interaction of these two plates gives rise to a very complex tectonic
structure.
As a young orogenic belt, Taiwan experiences very active tectonic motion, where the plateboundary is distinguished by a zone of arc-continent collision such that the northern end of theLuzon island arc in the Philippines, is colliding with the buoyant crust of the Eurasia continental
margin located offshore China, which resulted in the Taiwanese mountain range ~ 6.5 M years
ago (Caltech Tectonics Observatory, 2005; Lin et al., 2003; Smoczyk et al., 2013; Sun et al.,2015; USGS, 2022a; USGS 2022c). This collision zone transitions into the eastward-oriented
Manila subduction zone along Taiwan’s west coast, and extends south (USGS 2022a; USGS
2022c). The high seismic activity in this region is attributed to the rapid northwest convergence of
the Philippine Sea plate toward the Eurasia plate. The Philippine Sea plate moves towards the
Chinese mainland margin at around 82 mm/yr, which is considered to be one of the highest
convergence rates in the world and has an azimuth of 306° (Shin & Teng, 2001; Sun et al., 2015).
Across the Longitudinal Valley Fault, the velocity jumps by 30 mm/yr, which is the suture zone ofactive plate collision in Taiwan as demonstrated above (Sun et al., 2015). Additionally, rotations
at both tips of the Taiwan collision belt (clockwise in northeast Taiwan and anticlockwise insouthwest Taiwan) are observed, which can be related to the escape tectonics of Taiwan (Sun etal., 2015).

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Figure 2.1. Seismotectonic features of the extended Taiwan region (adapted from USGS, 2022c).

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Figure 2.2. Three-dimensional schematic diagram of Taiwan’s plate tectonics (adapted from Shin
& Teng, 2001).
Such a high plate convergence rate has resulted in many large faults across Taiwan. There area series of approximately north-south-trending and east-dipping large thrust faults in themidsection of western Taiwan that have generated occasional large, and consequently, damaging
earthquakes. Taiwan’s seismic energy release per unit area, is conceivably five times higher thanthat of California (Shin and Teng, 2001). In Taiwan, many of the earthquakes are related to thesubduction zones in the offshore area, either to the northeast or to the southeast, and have only
minor impacts on society due to their larger focal depth and hypocentral distance. However, withthe development of large population centers over the western coastal plain of Taiwan, occasionallarge and shallow earthquakes that occur along some of the large thrust faults in the western
foothills and over the Holocene plains further to the west can sometimes cause catastrophes(Shin and Teng, 2001). One example is the relatively recent 1999 Mw 7.7 Chi-Chi earthquake
which had a very energetic aftershock sequence, similar to many large Taiwan earthquakes in
the past, with 87 M > 5 aftershock events, which including 13 events with M > 6, and 7 eventswith magnitudes larger than or equal to the 1994 Mw 6.7 Northridge mainshock. Even one year
after the mainshock, another M 6.7 aftershock caused considerable damage in the areas near
the southern end of the Chelungpu fault (Shin and Teng, 2001).
The September 18, 2022, Mw 6.9 earthquake south-east of Lugu, Taiwan, occurred due to strikeslip faulting at a shallow depth, located near the plate boundary between the Philippine Sea andEurasia plates on the southeast coast of Taiwan (USGS, 2022a). The preliminary solutions forthe earthquake’s focal mechanism show that the rupture occurred on a steep fault striking either
east-southeast (right-lateral) or south-southwest (left-lateral) (USGS, 2022a). The Eurasia plateconverges with the Philippine Sea plate at a rate of approximately 73 mm/yr towards the northwest
at the location of this earthquake (USGS, 2022a). The location, depth, and focal mechanism of
the September 18, 2022 earthquake are consistent with its occurrence along a fault near thecomplex plate boundary in this region, where an earthquake of similar size and mechanism
generally has a rupture of about 50 km long and 15 km wide (USGS, 2022a).

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2.2 Seismicity of the Region
Because of its plate boundary location, Taiwan is a highly active seismic region and commonly
experiences moderate-to-large earthquakes. Figure 2.3 presents the location of earthquakes
within the region between 1898 and 1997, which closely follows the tectonic setting presented in
Figure 2.2. Figure 2.4 maps the epicenters of the events with Mw greater than or equal to 6.0 and
7.0 since 1900 within the region, whereas Figure 2.5 depicts the distribution of earthquake
epicenters with Mw ≥ 3.0 from 1975 to 2014. The region within 250 km of this September 18, 2022
earthquake has hosted 239 other Mw ≥ 6.0 earthquakes over the preceding century; 24 of theseearthquakes had Mw ≥ 7.0 (USGS, 2022a).
The region has experienced several major earthquakes in the last century, such as the 1906 Mw
7.1 Meishan earthquake, 1935 Mw 7.1 Hsinchu-Taichung earthquake, and 1999 Mw 7.6 Chi-Chi
earthquake. The latter and largest inland earthquake of the twentieth century in Taiwan, known
as ‘The great earthquake of September’, took place on September 21, 1999, in Central Taiwan
near the town of Chi-Chi. The epicenter had a focal depth of 8 km for a north-south trending andeast-dipping thrust faulting mechanism that ruptured a segment of approximately 100 km of theChelengpu thrust fault. The epicenter of this event is shown in Figure 2.5 by the largest circle
labeled ‘1999’. The densely populated central region of Taiwan was severely affected by theearthquake resulting in 2,470 fatalities, 11,305 injured, and over 100,000 structures destroyed
amounting to a total of US$10 billion worth of damage (Shin and Teng, 2001).

Figure 2.3. Location of earthquakes recorded in Taiwan over a 100-year period (1898-1997).
Note the relationship with the tectonic setting of the region (Figure 2.2). (Wang & Shin, 1998).

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Figure 2.4. Map of the epicenters of earthquakes with (a) Mw ≥ 6.0; and (b) Mw ≥ 7.0, in Taiwan
since 1900. Source: USGS ComCat. (USGS, 2022b).

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Figure 2.5. Map of the epicenter distribution of earthquakes in Taiwan with Mw ≥ 3.0 from 1975
to 2014. (Chang et al., 2017).

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2.3 The September 18, 2022 Mw6.9 Earthquake
On September 18, 2022, at approximately 2:44 pm local time (06:44:14 UTC), a moment
magnitude Mw 6.9 (ML = 6.8, according to the Central Weather Bureau Seismological Center 2022)
earthquake struck 42.7 km north of Taitung City, 87.1 km southeast of Lugu, 96.5 km southwestof Hualien City and 87.5 km east of Yujing, as shown in Figure 2.6. The USGS located the
hypocenter at 23.159°N 121.316°E, with a depth of 10 km (USGS, 2022a), whereas the Central
Weather Bureau Seismological Center located the hypocenter at 23.14°N 121.20°E, with a depthof 7 km (Central Weather Bureau Seismological Center, 2022).

Figure 2.6. Epicenter of the September 18, 2022, earthquake. The red star represents theepicenter located by the Central Weather Bureau Seismological Center (Central Weather Bureau
Seismological Center, 2022), whereas the yellow marker represents the epicenter located by
USGS (USGS, 2022a).
The September 18, 2022, mainshock was preceded by a foreshock sequence of multiple minor
earthquakes. According to the information provided by the Central Weather Bureau SeismologicalCenter (Central Weather Bureau Seismological Center, 2022), approximately seventy
earthquakes with magnitudes higher than ML = 3 and five earthquakes with magnitudes higher
than ML = 5 preceded the main event. The foreshock sequence began on September 17, 2022,
at 9:41 pm local time (13:41:17 UTC) with a Mw = 6.5 event (ML = 6.4) and culminated on
September 18, 2022, at 2:33 pm local time (06:33:25 UTC) with a ML = 4 event (Central Weather
Bureau Seismological Center 2022). As of September 20, 2022, more than 90 aftershocks with
ML > 3 have been identified after the main event (Central Weather Bureau Seismological Center2022). Figure 2.7 shows the epicenters of the foreshocks and aftershocks of the September 18
earthquake using data obtained from the Central Weather Bureau Seismological Center (Central
Weather Bureau Seismological Center, 2022).

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Figure 2.7. Epicenters of foreshocks (left) and aftershocks (right) of September 18, 2022,
earthquake (black and white dots). The red star represents the epicenter located by the Central
Weather Bureau Seismological Center (Central Weather Bureau Seismological Center, 2022),
whereas the yellow marker represents the epicenter located by USGS (USGS, 2022a).
The W-phase Moment Tensor inversion solution of the earthquake, as reported by the USGS(USGS, 2022a), indicates a strike-slip focal mechanism (Figure 2.8). As shown in Table 2.1, one
nodal plane corresponds to left-lateral movement on a fault striking in the NE-SW direction, andthe other indicates right-lateral movement on a fault striking SE-NW. Both nodal planes presenta slight thrust component and a steep dipping. The causative plane is more likely defined by Fault
Plane 1, striking in the SE-NW direction. For this solution, the cross section and the surface
projection of the slip distribution are shown in Figure 2.9 (USGS, 2022a). This fault plane is also
consistent with measurements of co-seismic offset tracking using Sentinel-2 satellite imagery of
the European Commission’s Copernicus program (Figure 2.10).

Figure 2.8. Fault plane solutions from USGS (USGS, 2022a). Moment Tensor solution for the
September 18, 2022 earthquake, according to USGS (USGS, 2022a).

Table 2.1. Fault plane solutions from USGS (USGS, 2022a). The causative plane is more likely
to correspond to the Fault Plane 1 solution.

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Fault Plane 1

Fault Plane 2

StrikeDip

Rake

Strike

Dip

Rake

203

69

25

103

67

157

Figure 2.9. Cross section and surface projection of the slip distribution (USGS, 2022a).

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Figure 2.10. North-South co-seismic offset tracking using Sentinel-2 satellite imagery. The yellow
star represents the epicenter of the mainshock earthquake, whereas the yellow circles represent
the largest foreshocks and aftershocks (Valkaniotis, 2022).

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2.4 Ground Motion Intensities
The USGS ShakeMap estimated a MMI of VIII and a Peak Ground Acceleration (PGA) ofapproximately 0.4 g in the epicentral region, as shown in Figure 2.11 (USGS, 2022a). Similarly,
the Central Weather Bureau Seismological Center (Central Weather Bureau SeismologicalCenter, 2022) of Taiwan estimated a maximum intensity (Central Weather Bureau seismic
intensity scale) of 6+, corresponding to “very strong” shaking, as illustrated in Figure 2.12. Figure
2.13 presents maps of peak ground acceleration (PGA) and peak ground velocity (PGV) within
Taiwan (Central Weather Bureau Seismological Center, 2022).

Figure 2.11. Intensity map estimated from ShakeMap (USGS, 2022a).

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Figure 2.12. Central Weather Bureau seismic intensity map estimated by the Central Weather
Bureau Seismological Center (Central Weather Bureau Seismological Center, 2022).

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Figure 2.13. Map of (a) PGA; and (b) PGV in Taiwan estimated by the Central Weather Bureau
Seismological Center (Central Weather Bureau Seismological Center, 2022).
At the time of this writing, the Central Weather Bureau Seismological Center (Central Weather
Bureau Seismological Center, 2022) had published PGA and PGV of 125 strong-motion stations
that recorded the event in Taiwan. Table 2.2 lists the PGA and PGV recorded by the 13 stations
closest to the earthquake epicenter, all within a distance of 50 km. Detailed information about therest of the stations can be found on the event website provided by the Central Weather Bureau
Seismological Center (Central Weather Bureau Seismological Center, 2022). As can be seen in
Table 2.2, the largest instrumental PGA was 0.51 g, which was recorded in the north-south
direction at Yuli station (EYUL), whereas the largest instrumental PGV was 97.14 cm/s, recordedin the east-west direction at Chishang station (ECS).

Table 2.2. List of the 13 stations closest to the earthquake epicenter (Central Weather Bureau
Seismological Center, 2022).

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PGA [g]StationCode

StationName

StationLon [°]

StationLat [°]PGV [cm/s]

Distance
[km]
NS

EW

GeomeanNS

EW

Geomean

EHD

Haiduan

121.21

23.15

1.28

0.31

0.22

0.26

28.1

27.6

27.8

ECS

Chishang

121.22

23.10

4.94

0.43

0.43

0.43

90.2

97.1

93.6

FULB

Fuli

121.29

23.20

11.46

0.46

0.42

0.44

44.8

30.5

37.0

CHK

Chenggong

121.37

23.10

17.91

0.18

0.26

0.22

22.8

34.1

27.9

EDH

Donghe121.30

22.97

20.97

0.09

0.11

0.10

15.8

10.9

13.1

EYUL

Yuli

121.32

23.35

26.06

0.51

0.43

0.47

54.3

52.7

53.5

LONT

Luye

121.13

22.91

26.68

0.11

0.20

0.15

11.1

21.0

15.2

ECB

Changbin

121.45

23.32

32.17

0.26

0.22

0.24

32.8

25.5

28.9

TWG

Beinan121.08

22.82

37.61

0.03

0.03

0.03

4.5

7.1

5.6

EHY

Hongye121.33

23.50

42.58

0.41

0.33

0.37

16.5

24.5

20.1

TTN

Taitung City

121.15

22.75

42.94

0.04

0.06

0.05

10.5

15.4

12.7

STYH

Taoyuan

120.78

23.18

43.50

0.05

0.05

0.05

3.3

4.0

3.6

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Free-field ground motions recorded by the Taiwan Strong Motion Instrumentation Program
network (TSMIP) were obtained from the Taiwan Geophysical Database Management System(CWB, 2022). The ground motion accelerograms were first filtered and instrument corrected,
resulting in 341 stations with usable recordings. The corrected accelerograms were then used tocompute RotD50 values (Boore, 2010) of two ground motion intensity measures: PGA andspectral acceleration at a period of 1s, Sa(1s). Figure 2.14 shows a map with the distribution of
the computed PGA and Sa(1s) values.

Figure 2.14. Map of RotD50 values of (a) PGA and (b) Sa(1s) recorded by the 341 strong-motion
stations of the TSMIP network. The finite fault model (FFM) estimated by the USGS is also shown
for reference.
The computed intensity measures were also compared with the ground motion model (GMM)
developed by Boore et al. (2014). The comparisons for PGA and Sa(1s) are shown in Figure 2.15
and Figure 2.16, respectively. The left panels of these figures show the intensity values as afunction of Joyner-Boore distance, which were computed using the finite fault provided by USGS
(2022a), and are compared to predictions of the GMM for reference sites with time-averaged
shear wave velocity over the upper 30 meters of the earth's surface (VS30) of 200 m/s and 500
m/s. The depth to the shear-wave velocity horizon of 1 km/s (z1) was assumed to be unknown forthese reference sites. The right panels of Figures 2.15 and 2.16 show the normalized residualsof all stations for PGA and Sa(1s), respectively. The residuals were computed using VS30 and z1
values obtained from the Engineering Geological Database for TSMIP (NCREE, 2022a). For
stations not included in this geological data, VS30 values were obtained from a recently developed

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standard deviation of the median, on average, the GMM tends to slightly overpredict PGA andunderpredict Sa(1s).

Figure 2.15. Comparison of recorded PGA values to those predicted by the Boore et al. (2014)
ground motion model: (a) attenuation for reference sites of 200 and 500 m/s; (b) normalized
residuals as a function of distance.

Figure 2.16. Comparison of recorded Sa(1s) values to those predicted by the Boore et al. (2014)
ground motion model: (a) attenuation for reference sites of 200 and 500 m/s; (b) normalized
residuals as a function of distance.

2.5 Early Earthquake Warning (EEW)
Taiwan has several Early Earthquake Warning (EEW) systems in place that broadcast warnings
via a system of texts, TV, and public broadcast systems (Wu et al., 2021). The Central Weather

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Bureau (CWB) EEW system is for the entirety of Taiwan. During recent earthquakes, the EEW
system provided a 2 - 8 seconds warning around the epicenter. The National Taiwan University(NTU) system is a hybrid (regional and onsite) system based on Micro-Electro-Mechanical
System (MEMS) sensors. The NTU system has Twitter (https://twitter.com/eew_p) and Facebook(https://www.facebook.com/Palert.Shakemap) accounts. Both CWB and NTU systems are able
to produce EEW warnings within 20 seconds of an earthquake occurrence. The threshold for aregional warning to be broadcast is that the earthquake is to be above magnitude 4 or scale 5(Earthquake Report-Central Meteorological Administration, 2022). The National Center for
Research on Earthquake Engineering (NCREE) also has an EEW system that serves as a conduit
for the NTU and CWB system warnings and also has its own network of around 98 stations.
The CWB EEW system operates on an Earthworm-based system (eBEAR) that includes 511
accelerometers, 68 short-period instruments, and 9 cable-based ocean bottom seismometers.
Epicenters are calculated via both Geiger’s (GE) method and the effective epicenter (EE) method(Chen et al., 2019). The effective epicenter method was introduced to shorten reporting times forearthquakes in offshore and poor station coverage areas (Wu et al., 2021). The average
processing time for EEW reports between April to December 2020 was 10.5 sec for inland
earthquake events and 20.9 sec for offshore earthquake events.
The NTU EEW system is composed of MEMS sensors installed in various elementary schools on
the ground floor or first-floor building walls throughout Taiwan, which are shown in Figure 2.17.
They are P-Alert-based instruments that record three-component data at 100 samples per second
with 16-bit resolution and a full dynamic range of ± 2 g (Wu et al., 2021; Hsieh et al., 2015). If thethreshold (PGA ≥ 80 Gal or progressive displacement value, Pdv ≥ 0.35 cm) within arecommended three-second window is triggered for an earthquake warning, an on-site warning
within the school is issued and the data is sent to the CWB to be processed further for a potential
regional warning (Hsieh et al., 2015). The average lead time is 13.8 s with a standard deviationof 4.5 s for a sample size of seven earthquake events (Wu et al., 2021). From the data,
ShakeMaps covering PGV, Sa, CWB intensity maps, and PGA are plotted and sent to national
disaster relief agencies for rescue operation planning.

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Figure 2.17. Distribution of NTU P-Alert MEMS sensors (Wu et al., 2021).
The NCREE EEW onsite system ties into alert broadcast systems at 3,514 schools across Taiwan
to receive onsite alerts as well as CWB regional alerts. Whichever alert is received faster isbroadcasted. The PGAs predicted by the NCREE stations are based on support vector machine
algorithms with improved lead time performance with some stations recently upgraded to PGA
prediction for every second of feature extraction (Hsu et al., 2013; Hsu et al., 2020). There is anoverestimation for larger earthquakes and an underestimation for smaller earthquakes, but thepredicted PGAs are within one scale of the true earthquake intensity (Wu et al., 2021).

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3.0 Local Codes and Construction Practices
This section provides information on the existing building stock in Taiwan and the evolution ofseismic codes in the past decades.

3.1 Existing Building Stock
According to 2020 statistics, the total housing stock in Taiwan is 8,900,427 units (Advanced
Developers Association, 2020). There are 8.38% of units in detached houses, 68.87% of units in
mid-rise structures with 2 to 5 floors, and 21.75% of units in high-rise structures. The average ageof the housing stock is 30 years. In 2019, 116,079 housing units started construction (Advanced
Developers Association, 2020) and received building permits two months prior to construction.
Soft stories are a common issue in many mid- to high-rise buildings in Taiwan constructed before
the 1999 Mw 7.7 Chi-Chi earthquake (Yin, 2018; Naeim et al., 2000). Figure 3.1 shows a typicalbuilding with a soft story shored for stability following a previous earthquake.

Figure 3.1. Typical soft story building with masonry infill walls and temporary shoring (Naeim etal., 2000).

3.2 Building Codes
In 1974, Taiwan implemented a minimum seismic design force for buildings following the formatof the US Uniform Building Code. In 1982, important factors for various building occupancy
categories were further incorporated into the seismic design code (Chai et al., 2009). After the
Mexico Earthquake in 1985, the basin effect of the Taipei Basin was recognized and a modified
design spectrum for this region was developed. In 1997, major changes were adopted, including
new dynamic analysis procedures using the response spectrum method, an increase in thenumber of seismic zones from 3 to 4, and a zoning factor that directly represents the design peakground acceleration associated with a hazard level of 10% chance of exceedance in 50 years(Chai et al., 2009).

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Taiwan has also revised its building codes after earthquakes that caused substantial damage.
Particularly, after the 1999 Mw 7.7 Chi-Chi earthquake when it became a legal requirement forbuildings and infrastructure to comply with standards such that buildings and infrastructure shouldbe able to resist earthquakes of Mw 6.0 or greater. In addition, after the 1999 Mw 7.7 Chi-Chi
earthquake, the significance of near-fault ground motions on buildings was acknowledged by theseismic code in Taiwan adding two “near-fault factors” to amplify the spectral value at longer
periods (Chai, et al., 2009). The near-fault factors, which are functions of the distance from thefault, are determined by the characteristic earthquake model as well as the seismic hazard
analysis for Taiwan (Chai & Teng, 2012). Figure 3.2 shows the shape of the design response
spectrum developed by site-adjusted parametersandin Taiwan. More detailed
information can be obtained from the seismic design code of Taiwan (CPA, 2011; Chai, et al.,2009).

Figure 3.2. Design response spectrum in Taiwan (Chai & Teng, 2012).

As compared to US codes (ASCE, 2016), in Taiwan, three seismic demand levels are considered:(1) Minimum Seismic Force (MSF), with an 80% probability of exceedance in 50 years; (2) Design
Base Earthquake (DBE), with a 10% probability of exceedance in 50 years; and (3) Maximum
Considered Earthquake (MCE), with a 2% probability of exceedance in 50 years. The MSF
requirement is prescribed to avoid any nonlinear demand on structural elements during frequently
occurring small earthquakes (Chai et al., 2019). For DBE level, the design response spectrum
can be developed for general sites, near-fault sites, and the Taipei Basin (Chai & Teng, 2012).
Figure 3.3 shows the comparison of response spectra computed from recorded horizontal (NSand EW) and vertical (U) accelerations at different stations during the September 18 earthquake
to the elastic design spectrum for the DBE and MCE levels (NCREE, 2022b). It is noted that the
response spectra are shown for a wide range of periods (i.e., up to 10 sec). Longer period
structures can be tall buildings or long bridges, such as the collapsed 600 meter long Gaoliao
bridge. From these response spectra, it can be observed that the response spectra of some of
the recorded motions are close to and slightly above the design levels for short period structuresand below the design level for longer period structures.

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(a)

(b)

(c)

(d)

(e)

(f)

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(g)

(h)

(i)

(j)

Figure 3.3. Comparison of response spectra computed from recorded horizontal (NS and EW)
and vertical (U) accelerations at different stations to the elastic design spectrum for the Design
Base Earthquake (DBE) and Maximum Considered Earthquake (MCE): (a) Chishang, (b) Yuli, (c)Sea Test, (d) Changbin Testing, (e) Bonanza, (f) Yushan Test, (g) Luye, (h) Hongye, (i) Optical
Complex, (j) East River (NCREE, 2022b).

Based on the uniform hazard analysis, the mapped design 5%-damped spectral acceleration atshort periods (SSD) and at 1 s (S1D) have been tabulated for each municipal unit on a village, town,
and city level. Figures 3.4 and 3.5 present the distribution of mapped spectral acceleration
parameters for the DBE and MCE levels, respectively. Similar to the current US design codes(ASCE, 2016), the site-adjusted spectral accelerations at short periods (SDS) and at 1.0 s (SD1)
are obtained by multiplying the site coefficients:
SDS = FaSSD, SD1 = FvS1D
where Fa and Fv are given in Table 3.1.

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Figure 3.4. Distribution of mapped spectral acceleration parameters for the DBE level (CPA,2011).

Figure 3.5. Distribution of mapped spectral acceleration parameters for the MCE level (CPA,2011).

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Table 3.1 Values of site coefficients Fa and Fv (adopted from Chai and Teng, 2012)

Based on the site-specific spectral acceleration parameters SDS and SD1, the design spectral
acceleration SaD for a given period, T, can be obtained by using:with T0D = SD1/SDS.
The seismic design base shear is expressed as:

where I is the importance factor, W is the total gravity dead load of the structure, αy is defined as
the first yield seismic force amplification factor that depends on the structure type and design
method, and Fu is defined as the structure system seismic reduction factor that can be defined by
the allowable ductility capacity Ra and the fundamental period T as:with Ra = 1 + (R - 1)/1.5, where R is the structural system ductility capacity that can be found in
the seismic design code for most basic types of seismic-force-resisting systems. (SaD/Fu)m is
modified as:

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The modified ratio (SaD/Fu)m is defined to reduce the seismic demand since damping ratios higher
than 5% can be considered for structures with short periods due to soil-structure interaction. The
constant 1.4 indicates the over-strength factor between the ultimate and the first yield force andis taken as a constant for simplicity (Chai et al., 2009).

3.4 Bridge Codes
Bridge design based on earthquakes in Taiwan has a long history with four major stages. Startingfrom 1960, the 1960 Highway Bridge Design Specifications had no seismic design guidance, anddesigners used earthquake coefficients recommended in the Engineer’s Manual published by the
Chinese Institute of Engineers. Then the 1987 Highway Bridge Design Specifications included
horizontal seismic force calculations by a coefficient method and incorporated factors forearthquake zoning, site condition, importance, and fundamental period adjustment. The 1995
Highway Bridge Seismic Design Specifications, which were based on earthquake hazard analysis
from seismic codes and research in the US and Japan, define two design objectives. For small tomoderate earthquakes, bridges should remain in the elastic range and no significant structural
damage should occur. For large earthquakes that have a minimum 475-year return period,
collapse of all or part of bridges should be avoided. Although plastic responses were permitted,
shear or brittle failure were not allowed. Finally, the 2000 Highway Bridge Seismic Design
Specifications incorporated some lessons learned from the 1999 Chi-Chi Earthquake to revise
earthquake zoning, peak ground accelerations, response spectra, vertical seismic forces, andfailing prevention design (Chang, 2006).
Similar to the seismic design code for building, three demand levels are considered for horizontal
seismic forces, Level I (frequently occurring small earthquakes), Level II (10% probability ofexceedance in 50 years), and Level III (2% probability of exceedance in 50 years) earthquakes.
The mapped design 5%-damped spectral acceleration at short periods (SSII) and at 1 s (S1II) havealso been tabulated for each municipal unit on a village, town, and city level. Figures 3.6 and 3.7
present the distribution of mapped spectral acceleration parameters for Level II and Level III,
respectively.

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Figure 3.6. Distribution of mapped spectral acceleration parameters for Level II (MOTC, 2019).

Figure 3.7. Distribution of mapped spectral acceleration parameters for Level III (MOTC, 2019).

The horizontal seismic design force for Level II earthquakes is calculated by:

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where VII is the design force and should not be smaller than .

.
,,, I is the importancefactor, W is the total gravity dead load of the bridge, and αy is the first yield seismic force
amplification factor.

.

,

,

is calculated by the following equation with Sa,II replaced by 0.4SII,S:

where Sa,II is the spectral response acceleration of the bridge and Fu,II is the structural system
seismic reduction factor calculated both using the fundamental period of the bridge in the directionof design consideration:

where SII,S and SII,1 are the site-specific spectral acceleration parameters, T0II is the corner period,and Ra is the allowable ductility capacity, which are defined as:

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where Fa and Fv are the site coefficients, and R is the structural system ductility capacity that
depends on substructure of the bridge, which can all be found in the Specifications for Seismic
Design of Highway Bridges (MOTC, 2019). It should be noted that the site coefficients, Fa and Fv,
are slightly different from the values used in the building code.

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4.0 Damage to Buildings
4.1 Healthcare Facilities
No reported damage to healthcare facilities were found.

4.2 Schools
A total of 532 schools in 19 counties and cities were affected by the earthquake, as reported on
Monday, September 19. Initial damage estimates have reached NT115.7 million (US$3.68 million)(Everington & Taiwan News, 2022). Table 4.1 shows the breakdown of the number of damaged
schools by city or county.
Table 4.1. Number of reported damaged schools by city and county (Everington & Taiwan News,2022).
City or County Name

Number of Schools
Reporting Damage

City or County
Name

Number of Schools
Reporting Damage

Taipei City

31

Nantou County

16

Keelung City

2

Chiayi County

23

New Tapipei City

54

Yunlin County

18

Yilan County

7

Tainan City

44

Hsinchu City

7

Kaohsiung City

115

Hsinchu County

14

Penghu County

3

Taoyuan City

18

Pingtung County

22

Miaoli County

27

Taitung County

46

Taichung City

24

Hualien County

49

Changhua County

12

Kaohsiung City reported the largest number of school damage with 115 schools. Miaoli County
reported the greatest financial losses, estimating damage at NT$16.94 million, followed by
Hualien County and Pingtung County with NT$16.7 million and NT$15.67 million, respectively.
Not all damage was structural as there was a lot of non-structural damage in the schools that
required financial assistance to repair and clean up.
The school with the most losses was the National Yuli High School in Hualien County, which
reported damage to the building tiles, cracked walls, damaged ceilings, and partially collapsed
walls. The repairs of this school are estimated at NT$43.7 million. Chun-Rih Elementary School
in Yuli Township in Hualien County experienced damage to the corridor connecting two buildings.

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This corridor was originally two stories and due to column failure, the first story of the corridor
collapsed, which is shown in Figure 4.1.

Figure 4.1. Damage to a double level corridor at Chun-Rih Elementary School (Yotaka, 2022;
公視新聞網, 2022; Everington & Taiwan News, 2022).

4.3 Low-rise Buildings
4.3.1. Residential housing
Yuli Township as a population of about 25,000 people and is located in the central Huadong Valleyin Hualien County, Taiwan. Yuli Township consists of 15 villages, one of which is Songpuli.

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Songpuli’s residential buildings were heavily impacted by the earthquake with about 25% of thehouseholds being damaged. One of the most severely damaged residential structures had aresidual drift of approximately 40 - 50 centimeters, walls collapsed in the kitchen of the house,
and there was differential settlement of the ground (鏡新聞, 2022). An example of a damaged
house in Songpuli is shown in Figure 4.2. This house has residual deformation after theearthquake and cannot be occupied.

Figure 4.2 House with residual deformation in Songpuli (公視新聞網, 2022; 葉怡瑩, 2022).
Taitung County Government took stock of the damages in various towns. There were 24 buildingsthat showed signs of earthquake damage. The owners of these buildings were notified. Damaged
homes were also observed in Taitung City, as shown in Figure 4.3. Figure 4.3a is the house
before the earthquake and Figure 4.3b is a photo of the collapsed house after the earthquake.

Figure 4.3. House in Taitun city (a) photo of house before the earthquake and (b) photo ofhouse after the earthquake (柯振中、楊漢生, 2022).

4.3.2. Mixed-use buildings
A three-story concrete building collapsed in Yuli Township (Figure 4.4). The building consistedof a 7-11 convenience store on the ground floor and residential occupancies on the upper two
floors (The Associated Press, 2022). Based on the photo of the building before the earthquake(Figure 4.4d) and these two different occupancies, the reason for the collapse can be a softstory, weak story or any other irregularity, such as torsion due to openings at one side of thebuilding, combined with nonductile reinforced concrete characteristics. The photos in Figure 4.4
show that the collapsed building impacted the neighboring building at the first-floor level. If the

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impact occurred during the strong part of the ground shaking, it likely introduced additional
lateral forces into the inertia forces, which could have led to the collapse of the neighboringbuilding. These photos also highlight that identifying and retrofitting vulnerable buildings, suchas nonductile concrete buildings, is not only beneficial for the vulnerable building itself, but also
it is beneficial for an entire block or neighborhood, which is essential for community resilience.

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(a)

(b)

(c)

(d)

(e)
(f)
Figure 4.4. Three story mixed-use building collapse in Yuli town. Collapsed building and rescue
efforts showing damaged structural components (CNA, 2022 September 19). (a) - (c) collapsedbuilding state, (d) building before collapse, (e) aerial view of collapsed structure (CNA, 2022
September 20), (f) collapsed building impacting the neighboring building (NPR, 2022)
4.3.3. Industrial facilities
The conveyor belt of a ready mix concrete production facility in Guanshan Township, Taitung
County collapsed (Figure 4.5) (CNA, 2022 September 17). This is the location where the one
fatality from the earthquake occurred. A worker at the plant was killed during the collapse of this

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structure. The initial estimated loss of equipment damage was about NT$134million to NT$180
million.

Figure 4.5. Partial collapse in a ready-mixed cement factory in Taitung’s
Guanshan Township resulting in one fatality (CNA, 2022 September 20).
4.3.4. Commercial and religious structures
Taitung County's Guoguanshan Industrial and Commercial loss amounted to NT$35.5 million.
This cost includes both structural and non-structural damage such as damage to computerequipment, cracks in the walls of buildings, and damage to ceiling systems. A Tianxuan Taoist
Temple in Yuli collapsed such that the bottom story of the three-story concrete building collapsed
thereby leaving the top two stories. Figure 4.6 shows this damage.

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Figure 4.6. The Tianxuan Taoist Temple first floor collapsed in Yuli Township (Zhenghong,2022).

4.4 High-rise Buildings
The tallest building in Yuli Township is a 9-story residential building. A soft-story mechanism
occurred in this building such that the first story collapsed. Damage throughout the rest of thebuilding included brick facade damage such that bricks have fallen off the building due todifferential settlement (Figure 4.8). The building is now leaning. Elevation differences and groundcracks are observed in the surrounding of this building (Figure 4.8).

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(a)

(c)

(b)

(d)

(e)
(f)
Figure 4.8. Damage to the tallest building in Yuli Township (a) Elevation view of building showingbuilding leaning; (b) View looking up the side of the building showing the building leaning; (c) brickfacade damaged due to earthquake; (d) and (e) cracks in the ground surrounding the building(Source:ETTV News ); (f) cracks in the wall leading into the parking garage under the building (張寓科 張家寶, 2022).

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4.5 Government Facilities (Public Buildings)
At the time of writing, reports of damage to government facilities were unavailable.

4.6 Historical Buildings
According to the Ministry of Culture, Culture and Information, 12 national monuments, 1
municipally designated monument, 2 county-designated monuments, and 8 historical structures
were damaged. Except for the partial collapse of Wan'an brick factory kiln in Chishang, Taitung,which is listed as a "historical building", there was no major damage. The partial collapse of thisunreinforced masonry building is shown in Figure 4.9.

Figure 4.9. Partial collapse of Wan 'an brick factory kiln in Chishang, Taitung [Photo by ChuanMi, Cao (曹釧蜜)].

4.7 Nonstructural Components and Building Content
Common nonstructural component damage included falling ceiling tiles, items falling off shelvesin stores, and fallen shelving units. This section is divided by occupancy type to demonstratecommon themes of non-structural components across occupancies.

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4.7.1. Schools
School damage occurred across the country. This damage varied from shelving falling over todamage to the ceiling tiles. Both of these damages present a life safety hazard for occupants.Nonstructural damage occurred at about 148 schools across the country due to the earthquake (Chen& Van Trieste, 2022). Figure 4.10 shows damage to the ceiling of a gymnasium at a school in
Pingtung County. Figure 4.11 shows damage to interior walls of the school near a window. It is
not clear if these cracks extend beyond the dry wall to the structural components. Figures 4.12
and 4.13 show non-structural damage consisting of items falling off bookshelves and shelving
units fall over. At Hualien Three Republics Middle School the septic tank ruptured and flooded thefirst floor of the building (Yanhua & Sihui, 2022) (Figure 4.14).

Figure 4.10. Damaged ceiling tiles at a school in Pingtung County (CDNS E, 2022).

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Figure 4.11. Cracks on walls inside schools (Chen & Van Trieste, 2022).

Figure 4.12. Fallen bookshelves due to the earthquake at Kasuga Elementary School in Yuli
Town, Hualien County (Picture taken by reporter Xu Zhenghong) (Sihui et al.,2022).

Figure 4.13. Items fallen off bookshelves and shelving units collapsed at the affected schools in
Hualien County (Yanhua & Sihui, 2022).

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Figure 4.14. Flood from ruptured septic tank at Yuli Spring Elementary School (Yanhua & Sihui,2022).
4.7.2. Commercial structures
The ceiling of an indoor badminton court, on the fifth floor of Bade Civil Sports Center in Taoyuan
City's Bade District, collapsed (Figure 4.15) (Everington, 2022). The facility had finished installing
the lights within the structure one week prior to the earthquake. No one was injured during thecollapse although a badminton game was occurring at the time of the earthquake. This
demonstrates an example of the need for nonstructural components not only to be functional, butalso to remain undamaged to avoid falling hazards and other threats to human life and health.
Ceiling tile damage was also observed in a mall in Kaohsiung City, called Kaohsiung Dream Era(Figure 4.16).

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(a)

(b)
(c)
Figure 4.15. Ceiling of the badminton facility (a) before the earthquake; (b) and (c) after theearthquake (Everington et al., 2022; Yilong, 2022).

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Figure 4.16. Ceiling tile damage within mall in Kaohsiung City called Kaohsiung Dream Era(Baoguang, 2022).
The collapse of non-structural storage racks occurred within a columbarium (Figure 4.17 andFigure 4.18) located in Taitung. The photo also shows damage to several suspended ceiling
panels.

Figure 4.17. Damage due to dynamic overturning of wooden storage racks at a columbarium in
Taitung (CNA, 2022 September 18; CNA Southern Local Group, 2022; Manda, 2022).

Figure 4.18. Damage to the columbariums of Matsuura and Changliang in Hualien Yuli Town
showing damaged ceiling tiles on the floor and open doors to urn chambers (Photo courtesy ofYuli Town Office) (Sihui, 2022).
In grocery stores and other convenience stores, items fell off the shelves and shelving units fellover (Figure 4.19) this same behavior was observed in other retail stores (Figure 4.20). In the
IKEA store in Xinzhuang (Figure 4.21a) and within a mall in Kaohsiung City (Figure 4.21b),
sprinkler lines ruptured causing water damage. In commercial structures, damage to the partition
walls within hallways were damaged (Figure 4.22).

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Figure 4.19. Collapsed -overturned- shelves and fallen products in supermarkets in Chishang,
Taitung

Figure 4.20. Items fell off shelves in a mall in Kaohsiung City

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(a)
(b)
Figure 4.21. Rupture of sprinkler lines (a) in IKEA in Xinzhuang (Picture originally retrieved from
Aixinzhuang, Facebook); (b) in a mall in Kaohsiung City called Kaohsiung Dream Era(Baoguang, 2022; 三立新聞網, 2022; 鐘如庭, 2022).

Figure 4.22. Damage to non-structural walls within a shopping center (CDNS L, 2022).
4.7.3. Elevator impacts
There were multiple reports of people trapped in elevators. A total of 21 reports were made in
Kaohsiung and 35 people were rescued from these instances. It is noted that the functioning ofelevators is a major requirement for preoccupancy and functional recovery of medium-rise andhigh-rise buildings.

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4.7.4 Industrial facilities
Industrial facilities experienced damage to storage tanks. Specifically the Qiankun Rice Factory
and a concrete manufacturing facility. The front and rear equipment of the new Qiankun Rice
Factory in Guanshan Town were damaged. The damage consisted of damage to (21) 100-ton
low-temperature silos, 6 drying furnaces, and 1 coarse bran furnace line was damaged (Figures
4.23 and 4.24). The bottom of the two 150-ton low-temperature silos in the factory were damaged
and overflowed with rice husks. The rice grain conveying line connecting 20 silos in the rear plant
had residual deformation after the earthquake. The initial loss was estimated at NT$223 million.
Another rice silo conveying line in Guanshan Town was also damaged, and the loss wasestimated at about NT$9 million.The Agriculture Department reported earthquake damage to 25
silos, affecting about 3,400 metric tons of rice. It is estimated that the second phase of rice harvest
will be affected by about 570 hectares, accounting for 28% of the 2,042 hectares of rice planting
area in Guanshan Town. To assist the rice factory in resuming operations as soon as possible,
the Taitung County Government has written a letter to the Agricultural Committee to subsidize theGuanshan Farmers Association and provide low-interest loans to two rice milling factories, so as
to carry out post-disaster reconstruction work as soon as possible (地方中心／台東報導, 2022).

Figure 4.23. Damage to the refrigerated storage and drying equipment of a rice milling plant
located in Guanshan Town (地方中心／台東報導, 2022; CNA, 2022 September 17).

Figure 4.24. One of four rice storage tanks that collapsed due to the earthquake at the Farmers
Association’s Rice milling plant (Xin Qinkun Rice Factory) in Guanshan Township, Taitung

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County (a) view at base of the storage tank and (b) elevation view of storage tanks (Congguang,2022; NCREE, 2022b).

Figure 4.25. Collapsed concrete storage tank next to power lines in Taitung County’s Guanshan
Township (Shan, 2022).

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5.0 Damage to InfrastructureThis chapter presents the observed damage to the electric power and transportation
infrastructure.

5.1 Electric Power Infrastructure
Electricity services were briefly disrupted as a result of damaged infrastructure but there were noreports of issues at nuclear power plants on the island. These power outages were due to downed
electricity lines caused by landslides near Chike Mountain in addition to approximately 40
electricity poles damaged (Wang & Hsiao-han, 2022). A total of 22,024 households were without
power immediately after the earthquake (Li-yun et al., 2022) with a total of 7,073 of thosehouseholds in Hualien’s Yuli Township (Hsien-feng & Lo, 2022), 300 in Lidao (Minzheng, 2022),
and neighborhoods in Taipei, New Taipei, Tainan and Kaohsiung also reported blackouts. As of
9/19, power had been restored to all but 445 households.

5.2 Airport and Railway Infrastructure
A canopy at the Dongli station collapsed. The debris from this canopy caused a train derailmentof six cars. There were about 20 passengers within the cars, but none were injured (Figure 5.1)
(Associated Press, 2022). More than 10 routes of the Taiwan Railway and 3 railway bridges weredamaged (Newtalk, 2022). Officials suspended rail services between Hualien and Taitungcounties along a 106 km (66 miles) section following damages to overhead power lines, tracks,and multiple railway bridges (Taiwan: Rail, 2022). Services were restored by 9/22, including trains
running between Hualien Station and Fenglin as well as between Fuli, Hualien County and
Taitung Station (Taiwan: Rail, 2022). However, rail transport disruptions remained along a sectionof the Eastern Trunk Line in eastern Taiwan as of 9/22 due to collapsed bridges (Gaoliao andLuntian Bridge) (Taiwan: Rail, 2022). In addition, several rail stations remain closed, such as Yuli
Station (Taiwan: Rail, 2022).
Several railway track segments buckled during the earthquake (Figure 5.2) (Liao, 2022). Six
buckled segments of the railway line in the Hualien and Taitung area were repaired by 9/21, but
about 40 broken electricity poles along the damaged section are still being repaired (Liao, 2022).
The Minister of Transportation and Communications Wang Kwo-tsai (王國材) inspected therailway damage on 9/19, and estimated that it would take over a month to restore the railway line
(Liao, 2022).

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(a)

(b)

(c)

(d)

Figure 5.1. (a) Train derailment at Dongli station in Hualien. Photo taken by Taiwan Railways
Administration; (b) - (d) Collapsed train platform canopy at Dongli Station in Hualien County(NowNews, 2022).

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Figure 5.2. Buckled rail tracks and collapsed train power lines (Qiongyu, 2022; CNA, 2022
September 20).

5.3 Bridges
The Taiwan Bridge Management System (TBMS) has an inventory of about 28,000 bridges, withapproximately 30% of them over 30 years old and another 30% with an unknown construction
date. Figure 5.3 shows the age distribution of bridges in the inventory corresponding to eachmanaging agency.

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Figure 5.3. Age distribution of bridges by management agency (Chuang & Yau, 2017).
Since the creation of the TBMS in 2000, the Ministry of Transportation and Communications(MOTC) has been funding studies to determine decisions of prioritization of bridge maintenanceand allocation of maintenance budgets across central and local governments in the country.
These studies include finding correlations between bridge deterioration and inspection data;
developing prioritization factors based on deterioration, traveler use, and social costs, anddeveloping life cycle costs analysis (Chen, 2007; Chuang & Yau, 2017; Lin, 2007; Safi et al.,2014; Su, 2003; Zhu, 2013).
Currently, in order to determine the structural safety and maintenance needs of the bridges the
MOTC has implemented the inspection methodology shown in Figure 5.4. This criteria assigns a
0 to 4 rating to four indices abbreviated as DER&U which stand for D: degree of deterioration, E:
extent of deterioration, R: relevancy, and U: urgency for repairing. It is worth noting that as of2017 Taiwan did not yet have minimum qualifications requirements for inspectors (Liao et al.,2017). This lack of training may lead to overlooking important condition indicators during
inspection that only trained professionals could recognize. Furthermore, while some of theresearch findings have been implemented to improve maintenance actions, there is still much still
investigations in the developing stages for the management system.

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Figure 5.4. Taiwan’s MOTC Bridge Inspection Criteria (Liao et al., 2017)
Several bridges were damaged or collapsed in the earthquake. This section will provide a
discussion of these bridges. In total, the bridge damage reported in the media and by government
officials include the following (梁國榮, 2022).
●
●
●
●
●
●
●
●
●
●
●
●

Xinwanlixi Bridge
Lelexi Bridge
Xinxiu Guluanxi Bridge
Gaoliao Bridge (collapsed)
Luntian Bridge (collapsed)
Yuchang Bridge
Yuxing Bridge
Yuli Bridge
Wanning Land Bridge (collapsed)
New Xiugulan River Bridge
Changfu Bridge
Lishanli No. 1 Bridge

The location of these damaged bridges with respect to the earthquake epicenter is shown in
Figure 5.5.

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Figure 5.5. Location of damaged bridges with respect to earthquake epicenter.
5.3.1 Railway bridges
Two railway bridges experienced severe damage. These include the New Xiugulan River Bridge
and the Wanning Land Bridge. The out-of-plane deformation of the piers of the New XiugulanRiver Bridge displaced more than 100 cm. In addition, the Wanning Land Bridge collapsed (中央通訊社, 2022).
5.3.2 Vehicular traffic bridges
According to statistics from the Hualien County 918 Disaster Response Center, the earthquake
caused two bridges in Hualien County to collapse, and five bridges to have permanent
deformation and heavy damage. Gaoliao Bridge and the Yuxing Bridge collapsed in theearthquake. The Hualien County Government issued a message stating that the earthquake
caused damage to most of the piers and columns of the Gaoliao Bridge, causing collapse. The
Gaoliao Bridge is the main linkage between Chike Mountain and Yuli Township. Drone footage
demonstrated that the entire straight portion of the bridge collapsed in the transverse direction. It
is observed from Figure 5.6 that the bridge bents are single-column bents, and the columns
collapsed in mixed shear and flexural modes of failure. Because the bridge is very long, thetorsional and transverse stiffness values provided by the abutments, if any, become ineffective
and the columns essentially behave as cantilevers. Accordingly, the deck serves as a rigid
diaphragm to the columns between the in-span hinges without providing much rotational restraint
at the top of the columns. Considering the rigid diaphragm constraint provided by the deck andthat all columns have similar geometry and longitudinal reinforcement; all columns likely reachedtheir drift capacity almost simultaneously and collapsed. Considering that the bridge is a longbridge with a long period in the transverse direction, displacement demands were large during
the shaking, which exceeded the drift capacity. Therefore, the single column bents behaving as

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cantilevers moving synchronously, without any redundancy and possibility of redistribution.
Additional detailed analysis is required to confirm the collapse mechanism of the bridge
The Yuxing Bridge had a widening construction project that started in 2020. Out of 32 I-shaped
beams, four collapsed and 12 had large deformations. There were no casualties due to thecollapse of either of these bridges. The Yuli Bridge damage disrupts traffic from Fuli and Taitungas this is the only bridge connecting these two regions.
Deck damage to a number of vehicular bridges was observed (see Figure 5.7). In particular thiswas for the Yuli Bridge spanning the Xiuguluan River in Hualien County, the Luntian Bridge in
Hualien County, and the Baohua Bridge in Luye Township. Vehicles were trapped on both theYuli Bridge and Luntian Bridge; however, there were no casualties associated with those trapped.

(a)

(b)

(c)

(d)

(e)
Figure 5.6. Gaoliao bridge (a) Before collapse (Photo by reporter Hua Mengjing); (b) - (e)Photos of the Gaoliao bridge after the earthquake (華夢靜, 2022; 華夢靜, 2022; Public TelevisionNews Network,2022).

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(a)

(b)

(c)

(d)

(e)
Figure 5.7. Deck damage to bridges (a) Yuli Bridge (CNA, 2022 September 20); (b) - (c) Luntian
Bridge (NCREE, 2022b); (d) collapse of the Luntian Bridge (華夢靜, 2022); (e) Baohua Bridge inLuye Township (CNA, 2022 September 18).

5.4 Roadways
Rockfalls and landslides on the Sixty Stone Mountain Road in Hualien and the Liushishan Road
in Fuli Township caused 400 people to be trapped in the mountainous area (Figure 5.8). On the

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road, people lined up to descend the mountain on September 22 around noon local time oncecleared by authorities (CNA, 2022 September 20).
Due to the continuous aftershocks, the Taitung Forest District Management Office closed six
forest roads and six hiking trails in the area on September 18, and completed the safety inspectionof the trails after the aftershocks slowed down. On September 21, the Forestry Department
announced through its official website that four forest roads including Jinping, Wulu, Yanping andZhiben would be reopened due to the elimination of hazards related to rockfalls. Redstone 2 trails,
Jiaming Lake Trail and Guanshan Red Rock reopened on September 22. Other trails such as theDulan Mountain Trail, the eastern section of Antong Yueling Ancient Road, and the Machinao
Trail, continue to be closed due to rockfalls (王瑞琪, 2022). Additional roadway damage includes
cracks in the roads and buckling of roads as shown in Figure 5.9.

Figure 5.8. Rockfalls on the Sixty Stone Mountain Road in Hualien (CNA, 2022 September 20;
CNA Southern Local Group, 2022 September 18).

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Figure 5.9. Roadway damage (a) Crack in the roadway close to the collapsed Kaoliao bridge ineastern Taiwan's Hualien county (Incredible Images, 2022); (b) Buckling of roadway on Dongli
Road (NCREE, 2022b); (c) Buckling of road on Provincial Highway No. 9 in Fuli Township (華夢靜., 2022); (d) Buckling of road in Hualien County; (e) Cracking of road near Gaolin Bridge(Public Television News Network, 2022a); (f) Pavement failure (Hicks, 2022); (g) Road damage
due to landslide in Huadong, Taitung area. Photo by Kang Zhongcheng (王瑞琪, 2022); (h) Road
near Zhuofu Bridge in Zhuoxi Township was severely cracked (CDNS C, 2022).

6.0 Observed Geotechnical Failures
This section provides an overview of geological setting and geotechnical damages.

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6.1 Geological Setting
Taiwan is an island composed of Cenozoic geosynclinal sediments more than 10,000 m thick on
a pre-Tertiary metamorphic basement. In Eastern Taiwan where the earthquake occurred, thecomposition is of a Neogene andesitic magmatic arc with a variety of volcaniclastic and turbiditic
sediments. The volcaniclastic sediments that make up the basement are Neogene andesitic
volcanic units and the turbiditic sediments are flyschoid and turbidite sediments. The Eastern
Taiwan region was formed with Miocene andesitic flows, anglomerates, tuffs, and associatedvolcanogenic sediments forming an igneous complex. Then the layer transitions into turbiditic
sandstones, siltstones, mudstones, and conglomerates containing disseminated volcanic
materials. On top of that layer is the Lichi melange composed of detritus from the western Asiatic
continental margin and the eastern Luzon volcanic arc. On the Southern end of the Eastern coast
is a layer of Pleistocene piedmont gravels (Ho 1986). A spatial distribution of different geologicalconditions throughout Taiwan is shown in Figure 6.1.

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Figure 6.1. Generalized geological map of Taiwan (Garzani and Resentini 2016)

6.2 Liquefaction
As of September 23, there were no reports of liquefaction due to the earthquake.

6.3 Building, Foundation, and Pavement Damages due to Ground Failure
Observations of cracking of mat foundations, pavements, and ground uplift were reported.
Pavement cracking was also observed through roadway damage (Section 5.4). The pavement
cracking shown in this section is due specifically to ground failure. Figure 6.2 shows pavement
cracking around where the Central Range Fault is located in the Longitudinal Valley. These cracks

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could be indicative of segmentation of the faults. Further surface rupture was seen on sports
fields, including deformation of a track in Yuli Township (Figure 6.3a) and surface rupture on a
baseball field (Figure 6.3b). Both of these occurred in Yuli Township. Additional cracks infoundations due to ground failure are shown in Figure 6.4. There were no reports on the locationsof these damages.
Increase in lateral earth pressures caused structural damage in two cases. The first consisted oflateral pressure causing damage to the Gaoliao Bridge abutment, which subsequently contributed
to the collapse of this bridge (Figure 6.6). Damage to a retaining wall along Highway 9 in theLongitudinal Valley was due to increased earthquake pressure on the retaining wall (Figure 6.7).

Figure 6.2. Segmentation of faults in the Longitudinal valley potential to be distributed thrustand strike slip movements (Huang, 2022)

Figure 6.3. Surface rupture on sports fields (a) Running track at Yuli Township (Yu, 2022 a) and(b) En echelon cracks on the baseball field in Yuli Township (Yu, 2022 b)

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(a)

(b)

(c)
(d)
Fig. 6.4. Additional foundation damage due to ground failure (a) Crack in foundation (Lee, 2022a); (b) Crack in courtyard flooring (Lee, 2022 b); (c) Observed separation of foundations withvisible rebar (Yongbo & Yuhan, 2022); (d) Pavement failure due to ground failure (Yen, 2022)

Figure. 6.5. Vertical crack formation on the roadway forming headscarp of the landslide at Fuli
township Hualien. (Liu, 2022)

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Fig. 6.6. Collapse of the bridge abutment and the excessive lateral movement of the retaining
wall contributed to the collapse of the Gaoliao Bridge in Hualien (Chenghan, 2022)

Figure. 6.7. Failure of the retaining wall along Highway 9 in the Longitudinal Valley(Yen, 2022)

6.4 Sinkholes
There were no reports of sinkholes.

6.5 Landslides

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Landslides occurred throughout Taiwan due to the earthquake. Below is a list of the landslides
collected through media sources and in-field reporting. Figure 6.7. shows the Landslide map
developed by USGS. Multiple mountain roads were blocked by landslides, trapping tourists in themountains. There was a quick response to clear out the roads, but the response was hampered
by aftershocks (Public Television News Network, 2022a). About 3,400 tourists were trapped on
Chike Mountain due to roads blocked from landslide debris and rockfalls. Meishankou and
Xiangyang road was blocked due to landslides. The debris was cleared; however, additionallandslides occurred during aftershocks. The road was scheduled to be reopened on September
19; however another landslide occurred, causing the reopening to be delayed. Several more
aftershocks caused more delays (Public Television News Network, 2022b). Rockfalls occurred ona Sixty Stones Mountain road that also experienced surface road ruptures and collapsed powerlines. As of September 18, the road was still damaged but open enough to evacuate tourists(Public Television News Network, 2022b). Photos of these rockfalls and landslides are shown in
Figure 6.9.
●
●
●
●
●
●
●
●

Hualien County Yuli Township.
Meishankou and Xiangyang Road. Additional landslides occurred here in aftershocks.
Sixty Stones Mountain Road (rockfalls)
Chikeshan Industrial Road
Mount Liushishi in Hualien (rockfalls and landslides)
Pingtung’s Jiufawan Road
Orange Mountain in Chenggong Town
Luye Luming section of the Taiwan-Ninth Line

Figure 6.8. Landslide map developed by USGS. The number and/or spatial extent of landslides
is estimated as significant, while the number of people affected by landslides is estimated aslimited.(USGS, 2022)

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(a)

(b)

(c)

(d)

(e)

(f)

(g)

(h)

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(i)

(j)

Figure 6.9. Landslide debris (a) Hualien County’s Yuli Township (Shan, 2022); (b) Nanheng
Highway, between Meishankou and Xiangyang (Public Television News Network, 2022 b); (c)Chikeshan Industrial Road (Xuesheng, 2022); (d) Rockfall on Sixty Stones Mountain Road
(Radio Taiwan International, 2022); (e) Repair of Sixty Stones Mountain Road (Radio Taiwan
International, 2022); (f) (Radio Taiwan International, 2022), and (g) Rockfall and landslide
observed in Mount Liushishi in Hualien (Liu, 2022 a); (h) Chikeshan Industrial Road (CNA,2022); (i) Pingtung’s Jiufawan Road (CNA-南部地方組, 2022); and (j) Luye Luming section of
the Taiwan-Ninth Line (Taiwan Posts English 2022)
6.5.1. Photos taken during active landslides
Citizens throughout Taiwan posted videos and photos of landslides taken while they were
occurring. This section aggregates these photos for use by researchers. All of these landslides
are discussed within the main section and listed at the beginning of the section.

(a)

(b)

Figure 6.10. Rockfall and landslide at Sixty Stone Mountain (a) (Ren, 2022) (b) (Photo captured
by Henry Hsu)

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Figure 6.11. Landslide occurred in Orange Mountain in Chenggong Town, Taitung city (2022)

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7.0 Current Conditions and Access
7.1 Power Outages
As of September 19, within one day after the earthquake, power had been restored to all but 445
households.

7.2 Water Disruption
A total of 4,842 households lost access to water due to the September 18th earthquake (Huang
Li-yun et al., 2022). Approximately 3,500 of these are located in Fuli and Yuli Townships.
Temporary water towers are being erected and households without water are relying on at-homewater storage tanks in the interim (Public Television news Network, 2022c). Any households
affected by lack of access to water due to the earthquake or aftershocks are exempt from water
bill payments in the current post-earthquake period. Basic fees are waived and bills are exempted
if the households apply for water resumption. The water municipality provided a notice tocustomers to be aware of potential water leaking out of pipes (CDNS E., 2022).
●●●

September 19: The Taiwan Water Corporation erected temporary water towers inresidential areas for residents. Water is manually pumped in by water trucks supplied by
the Taiwan Water Corporation.
September 20: 1,801 households are still without access to water (Li-yun, 2022)
September 21: 962 households in the Hualien area are still without water. (中央通訊社.,
2022)

Specific damage to water infrastructure includes rupture of a potable water pipe below Kaixuan
Road, located next to the Fengshan Zhongzheng Preschool (Figure 7.1). Around 100-200 people
were affected by this pipe damage, with nearby residents reporting the water from the tap was
yellowish. (Source: PTS https://www.youtube.com/watch?v=jBCsQ09JDvU )Some aboriginal areas in Taitung have lost both water and power. To provide health care andwater to these populations, about 480 health stations were opened by the Aboriginal Committees(歐陽夢萍, 2022).

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Figure 7.1. Repair of water pipes in Hualien following the earthquake (Yourong, 2022)

7.3 Cellular Outage
No reports of cellular service outages were found.

7.4 Post-earthquake Safety Structural Evaluations
7.4.1 Bridge Inspections
There are 356 bridges in Taitung county and inspections commenced immediately postearthquake. There are currently no reported problems with the highways. (Newtalk, 2022b). For
additional investigations of the bridges, the Ministry of Transportation is planning for aprofessional consultant company to conduct investigation and testing of bridges on 9/27 to begin
planning for emergency repairs (中央通訊社, 2022).
7.4.2 Building Inspections
The Construction Administration office coordinated with the National Architects Association and
the Civil Engineers Association to dispatch 44 people to participate in the emergency assessmentof buildings. The number of red-tagged buildings and buildings of concern are shown in Table
7.1. As of September 21, two buildings had been demolished. All emergency assessments ofbuildings in both counties were completed by September 21 (Xu, 2022).

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Table 7.1. Breakdown of building tagging by County as of 8 PM (local time), 9/21 (中央通訊社,
2022).

Building Label

Hualien County

Taitung County

Buildings of concern(yellow or red tagged)

160

53

Red tagged

17

10

7.4.3 Water and Lake Inspections
After the earthquake, the Seventh River Management office immediately inspected any dykes inregions that experienced ground shaking equivalent to a magnitude 4 or higher earthquake
through unmanned aircraft and on-site visual inspections. Water distribution structures in Qishan,
Liugui, Taoyuan, and Pingtung City were also inspected. For high-risk sections such as the
Linyuan embankment levee structure, non-destructive testing equipment was deployed (Figure7.2). Inspections also occurred at a project under construction at the Sanye Creek in Tainan city(黃副主任, n.d.).
In addition to the physical infrastructure inspections, several lakes were inspected (Lushan,
Toukeng Yexi Confluence, Caoling, Chexinlun and Heliuping) in addition to the Zhuoshui River
Basin. Aerial photography surveys were deployed in regions with higher ground accelerations,such as the Chen Youlan River and the Sheqiao river upper stream. No significant damage has
been reported in the Zhuoshui River Basin, and constant monitoring post-earthquake will be
conducted via CCTV networks and local volunteers (蔡榮宗, 2022).

Figure 7.2. Non-destructive testing of Linyuan Embankment (黃副主任, n.d. )PVRR: Lugu, Taiwan September 18, 2022
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7.5 Business and Economic Disruptions
No semiconductor manufacturing companies were damaged, despite temporary shutdown offoundry equipment due to automatic earthquake triggering shutdowns. All three science parks in
Hsinchu, Taichung, and Tainan had no major damage from the earthquake. No water or power
supply was interrupted to these facilities (Lin, 2022).
Due to earthquake damage of the mountain roads in the Sixty Stone Mountain area, the Orange
Day-lilies tourist season was prematurely ended. This season normally lasts through the end of
September. Local business owners are noting a 50-60% loss of potential earnings as the damage
was too severe to continue tourism operations on the mountain (Waksman, 2022). It is estimatedthat the local businesses will lose about 2,000 tourists/day for the remainder of September (民視新聞網, 2022).
Local agricultural products that are grown in Chike Mountain and Sixty Stone Mountain will be
impacted by the road damage along the mountain from the earthquake. About NT$200 million isestimated for agricultural losses. Disaster cash relief is being developed for these businesses(Source: 民視新聞網).
Hotel room cancellations have begun in Hualien due to fears of another large quake within the
coming month (Public Television News Network, 2022c). In Taitun, premature check-out of hotel
rooms have reached 50% as of September 21. To provide support to the tourism industry, travelsubsidies of NT $10 million have been announced by the Taitung County Mayor (Newtalk, 2022c).
Economic impacts due to the rice milling factory damage in Taitung County’s Guanshan Townshipan estimated loss of about NT $70 million (歐陽夢萍, 2022). The total industrial and commercial
loss in Taitung County's Guoguanshan is estimated to be about NT $7.95 million, including
damage to computer equipment, cracks in the walls of buildings, and damage to the ceilings(CDNS E, 2022).

7.6 Road conditions
The Guluanxi Bridge repair is estimated to take more than 2 years. Roadways in the Hualien area
are being repaired. Figures 7.3 and 7.4 show the road repair sections on September 20 and
September 22, respectively.

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Figure 7.3. Taken at 9/20/2022 7:52PM PST from https://168.thb.gov.tw/thb168 showcasing roadconditions in the Hualien area. Red barricade icon is showing “under construction”, while orange
is showing slightly more congested traffic flow.

Figure 7.4. Taken at 9/22/2022 3PM PST from https://168.thb.gov.tw/thb168 showcasing roadconditions in the Hualien area. Red barricade icon is showing “under construction”, while redroads are currently down due to the earthquake.
The two train routes “Hualien to Yuli” and “Taitung to Fuli" will be repaired so that the originaldisaster-damaged rail section will be reduced from 150.8 km to 18.8 km. The northbound route istargeted to be open to rail traffic before the end of September and there is an alternate route from

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Yuli to Fuli along the Southeast side of Taitung. The remaining 18.8 km will be connected via ashuttle bus transfer.

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8.0 Video Documentation
Post building collapse video of mixed-use 7-eleven building:https://news.pts.org.tw/live/6326c6757283d50f9f7c13fa.
Video overview of tallest building in Yuli Township:https://www.youtube.com/watch?v=dXjhn5EBCPk
Video of ceiling collapse of Bade Civil Sports Center in Taoyuan City:
https://www.facebook.com/groups/147881205898665/posts/1325131751506932/.
A video of the Dongli station during the earthquake can be seen using the following link:
https://udn.com/news/story/123030/6627558?from=udn-relatednews_ch2
Video documentation of the geotechnical impacts described in this section can be found in thefollowing links:●●●

https://www.youtube.com/watch?v=mKhwWXRaPQc
https://www.newsflare.com/video/516929/taiwan-earthquake-cracks-and-buckles-roads
https://www.youtube.com/watch?v=GvEjATrFnrA&t=12s

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9.0 Summary and Recommendations
On September 18th, 2022, at approximately 2:44 pm local time, a Moment Magnitude (Mw) 6.9
earthquake struck 42.7 km north of Taitung City, in southeastern Taiwan. Damage was observed
through Hualien and Taitung counties to buildings and infrastructure in addition to rockfalls andlandslides. Based on the information gathered by this PVRR, the following are recommendations
for future study.
Study of the operation and response to the Early Warning System: Taiwan has operated an
Early Warning System (EWS) in Hualien County since after the 1999 Chi-Chi Earthquake. For thelast 20 years this earthquake EWS has been instrumental for the response phase of earthquakes.
This event provides an opportunity to learn about technical challenges and operational aspectsof the early warning system in addition to public response to the warnings. Specifically, why theEWS did not stop the train going through Dongli Station and thereby resulted in derailment of the
train when debris from a canopy collapse hit the train.
Study of the behavior of reinforced concrete bridges: This earthquake caused substantial
damage and collapse of multiple reinforced concrete bridges used for both vehicular traffic andrail. Damage to transportation infrastructure can have a severe impact on the economy given
increased traffic time and transportation of goods and services. Given the rigor of Taiwan’s
seismic codes, this event provides an opportunity to learn about the seismic behavior of thesebridges, repair and retrofit strategies, and the impact of bridge damage on traffic patterns
throughout the region.
Study of landslides and rockfalls: This earthquake caused major landslides and rockfalls
throughout the impacted region and therefore provides an opportunity to study the triggering
effects towards such damage and the impact of this damage on the functionality of the region
itself. Hualien County’s economy relies on ecotourism within the mountain regions during themonths of August and September. The earthquake effects blocked roads thereby impacting thisindustry for the remainder of the season, and also trapping tourists.
Study of non-structural components: There was a variety of impacts to non-structuralcomponents in various building occupancies. However, common themes of these damages
occurred across occupancies such as damage to ceiling systems and shelving units. Therefore,
this earthquake provides an opportunity to study the behavior of these non-structural components
in buildings throughout the impacted regions, repair strategies, and repair times.
Identification of vulnerable buildings: Building damage in this earthquake was more prominent
for non-ductile concrete buildings. This highlights the importance of developing methods for
identifying specific nonductile concrete buildings that are vulnerable to collapse, such that theirretrofit can be prioritized. The mandatory retrofit programs under several ordinances of the Cityof Los Angeles (LADBS, 2022), which requires the retrofit of pre-1978 wood-frame soft-story
buildings and nonductile concrete buildings, is a great initiative in this regard, which should be
adopted by other cities in the US and other countries.

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Earthquake sequences: Similar to this earthquake, sequences with consequent large magnitude
events separated by short time intervals have been occurring at different parts of the world in thepast years. The cumulative effects should be characterized and considered in the design codesof buildings and other infrastructure systems. The ground motion data recorded during this event
is beneficial for this purpose. To enable the study of the effects of earthquake sequences, it isrecommended to consider documenting the ground motion time series at a particular station in a
collocated manner in relevant ground motion databases.

PVRR: Lugu, Taiwan September 18, 2022
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PVRR: Lugu, Taiwan September 18, 2022
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PVRR: Lugu, Taiwan September 18, 2022
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