Taiwan's Seismic Safety Evolution: A Journey from 1974 to now

While the 2 April 2024 earthquake in Taiwan, with a magnitude of 7.4, was tragic and sadly resulted in the loss of lives, many injuries, and significant damage to properties and infrastructure, other recent earthquakes have caused greater devastation. For instance, the February 2023 Gaziantep Earthquake in Turkey, with a magnitude of 7.5, led to over 50,000 deaths and 100,000 injuries. Similarly, the September 2023 Al Haouz Earthquake in Morocco, with a magnitude of 7.5, resulted in approximately 3,000 deaths and 6,000 injuries. The 2010 Haiti earthquake, with a magnitude of 7.0, saw over 100,000 deaths, and the 2008 Sichuan earthquake in China, with a magnitude of 7.9, caused over 87,000 deaths and 374,000 injuries. Thus, it is timely to review and reflect on how Taiwan has been progressing with its building codes over the years.

Taiwan is in a part of the world where earthquakes are common, so it has been updating its building safety rules over time to keep up with new technologies about earthquakes and to learn from past experiences.

• The Genesis: 1974

Taiwan first adopted seismic design codes in 1974, taking cues from the US Uniform Building Code. This initial step was vital, acknowledging the need for buildings to withstand the seismic forces unique to Taiwan's geography. Over the years, Taiwan has seen a series of updates to these seismic safety regulations. Each revision aimed to incorporate advanced research findings, global best practices, and the hard-earned lessons from earthquakes around the world and at home.

• 1982: Categorising Risk

The 1982 revision introduced differentiated safety requirements based on the intended use of buildings, recognising that not all structures bear the same risk nor serve the same purpose.

• 1989: Learning from Mexico

The devastating Mexico Earthquake in 1985 was a wake-up call. By 1989, Taiwan had updated its seismic codes to include acceleration response spectrums tailored to the unique seismic behaviours of regions like the Taipei Basin. It should be noted that large areas in Taiwan are filled with soft soil sediments that significantly affect how earthquake vibrations are felt in the area. Indeed, observation in later years during the 1999 Chi-Chi and the 2002 Hualien earthquakes, leading to structural damage and loss of life, further emphasised the importance of detailed considerations for soft soil site effects and the later 2005 revision of the code refined this.

• 1997: A Major Overhaul

In 1997, significant changes were made. The number of seismic zones increased, and the concept of peak ground acceleration was introduced, marking a shift towards a more nuanced understanding of seismic risks.

• 2005: Fine-Tuning for Local Conditions

The 2005 updates refined how seismic forces were calculated, emphasising local site conditions and introducing near-fault factors to address the enhanced risks close to fault lines. This revision also spotlighted the unique seismic behaviours of the Taipei Basin, introducing micro-zonation to tailor building designs to specific local conditions.

• The Latest Chapter: 2022

The most recent update in 2022 has been a comprehensive effort, integrating the latest technological advancements and research insights. Indeed, in response to the challenges posed by earthquakes, Taiwan's latest building regulations have identified four major items to receive further attention.

• Near-Fault Safety: Recognising the increased risk near active faults, adopted provisions aimed to boost buildings' earthquake resistance by over 20% in such areas.
• Addressing Weak Ground Floors: The recent provisions also address the issue of weak ground floors, a known vulnerability in past disasters, by setting out clear guidelines for assessment and reinforcement to prevent collapses. For new constructions, the code imposes strict guidelines to prevent the creation of weak ground floors. However, the implementation of retrofit requirements for older buildings, which were designed and built before the latest updates to the design codes, is a challenging task, and the 2024 Hualien earthquake highlights the level of remaining work that still needs to be done. I have reviewed information, reports, videos, and photos coming out of the affected areas, and it is apparent that mid-rise buildings, which are between five and 15 stories, have suffered the most damage. Observations indicate that the damage and progressive collapse often began with the failure of structures at lower levels. It is important to recall that on 6 February 2018, an earthquake with a magnitude of 6.4 near Hualien also caused several buildings to tilt severely due to the collapse of some columns and walls on the lower floors. Indeed, soft stories—stemming from open spaces on the ground floor, like parking and commercial areas—can make buildings more vulnerable during earthquake shaking. Additionally, very narrow and tall buildings are also highly at-risk during earthquakes because of issues with the lateral support required for seismic resistance.
• Soil Liquefaction: A deeper understanding and recognition of soil liquefaction risks, achieved through extensive case study analysis, has been captured to avoid building tilting or subsidence. The retrofit work required for existing and older structures, to address the elevated seismic hazard levels in some regions and the increasing risk of liquefaction, is an area that demands further attention. In simple terms, liquefaction occurs during rapid shaking of non-cohesive materials like sand or silt that are saturated with water. Clays and other dense soils are less susceptible to liquefaction because they do not easily lose strength and stiffness during shaking. Loose soil consists of an interconnected network of semi-stable grains that support the load of structures such as buildings, as well as the weight of the soil above. Below this layer may lie firmer, deeper ground. When an earthquake strikes, the soil grains loosen and slide against each other, losing contact. This process breaks the continuous chains of grains. As a result, vertical and horizontal stresses are transferred to the water, causing it to become pressurised.
• Seismic Isolation and Damping: The latest regulations place a strong emphasis on the quality and performance of seismic isolation and damping technologies, which are used in over a thousand buildings in Taiwan, ensuring they meet high testing and quality control standards to provide effective earthquake protection. Here at the University of Technology Sydney (UTS), our team has developed a new foundation system using polymeric materials called geotextiles to reinforce the foundation. This system allows for the damping of seismic loads and adjusts the dynamic characteristics of the building to offer better protection against large earthquakes. We have also expanded this technology to protect buildings against fault rupture. New design codes now have the opportunity to review these recent design concepts and technologies, and provide provisions so that efficient and innovative solutions can be utilised. 

At 23:58:11 (UTC) on 2 April, 2024, a magnitude 7.4 earthquake occurred at a shallow depth of 34.8 km, approximately 18 km northeast of Hualien City (with a population of nearly 100,000) on the east coast of Taiwan. A subsequent major earthquake, with a magnitude of 6.4 at an even shallower depth of 12.6 km and located 5 km offshore, occurred 13 minutes later, 30 km northeast of the first quake. Since then, the same region in Taiwan has experienced 12 aftershocks (magnitudes between 4.7 and 5.7), with nine occurring offshore, the closest being 5 km from the shoreline. Consequently, the threat of a tsunami has been significant.

The two major earthquakes are classified as severe and violent, with moderate to heavy damage expected in the affected areas. Peak Ground Acceleration (PGA) of 5 m/s² (0.5g) and Peak Ground Velocity (PGV) of 5 cm/s are anticipated in the region, which are considered very large. The Yuli and Chishang faults are major fault lines running along the east coast of Taiwan within Quaternary deposits, and the recent earthquakes lie close to the north end of these two fault lines.

Research by my team at the University of Technology Sydney (UTS) indicates that, when subjected to a comparable level of seismic activity, mid-rise buildings (5-15 stories) on shallow foundations located on weak soil deposits may experience excessive soil deformation, leading to building tilting. Meanwhile, buildings on deep pile foundations could potentially suffer from structural failures in building columns or pile elements, resulting in total building collapse.

A significant potential problem after this earthquake is the occurrence of fault ruptures, which can damage numerous buildings and essential infrastructure, including pipelines and railway lines. The 1999 Chi-Chi earthquake in Taiwan, with a magnitude of 7.3, reactivated the central Taiwan Chelungpu fault and resulted in large ground displacement extending over 100 km. This earthquake led to more than 2,400 fatalities and injured 8,373 individuals, with damages surpassing US $10 billion. Notably, the 1999 Chi-Chi earthquake produced the second-longest ground fracture (approximately 105 km) ever recorded on a thrust fault and established a new global record for the largest displacement (maximum vertical offset: 11 m) in thrust faults.

The threat of ground liquefaction in this region is especially alarming. Given the presence of Pleistocene and more recent terrace gravels, alluvium, and loosely consolidated sediments along Taiwan's east coast, significant ground settlements, along with the sinking of buildings and roads due to liquefaction, are highly probable.

Landslides, rockfalls, and liquefaction can cause direct damage to local roads and bridges. Such destruction can impede search and rescue operations and block access to areas urgently requiring assistance, especially those near villages and towns close to the epicentre. An examination of the area's geology and topography indicates that routes out of Hualien, especially along Highway 11 and the roads leading to Shoufeng and Fenglin, are most at risk of landslides.

In the wake of the devastating earthquake in Taiwan, which tragically claimed lives and caused widespread destruction, it is imperative to recognise the urgent need for innovative seismic resilience measures. As an expert in earthquake engineering and vibration control, I emphasise the critical role of implementing advanced technologies in buildings to mitigate the impact of such catastrophic events. Passive, semi-active, or active vibration control systems offer indispensable solutions to safeguard structures against the destructive forces unleashed by earthquakes.

Taiwan's vulnerability to tsunamis further underscores the necessity for comprehensive disaster preparedness. The recent earthquake serves as a stark reminder of the potential devastation posed by natural disasters. The government's timely tsunami warning highlights the importance of proactive measures in safeguarding coastal communities.

Drawing from my expertise and experience in developing novel solutions, I stress the significance of prioritising seismic resilience in urban planning and infrastructure development. By integrating cutting-edge vibration control technologies and robust disaster preparedness strategies, we can minimise casualties and mitigate the socio-economic impacts of seismic events.

As we extend our condolences to those affected by this tragedy, let us reaffirm our commitment to advancing seismic resilience worldwide. Together, through proactive measures and technological innovation, we can build a safer and more resilient future for vulnerable communities facing the threat of natural disasters.

This magnitude 7.4 earthquake on the central east coast of Taiwan is the largest earthquake to have occurred since the New Year's Day earthquake on the Noto Peninsula of Japan. With the preliminary epicentre being close to the coast, a tsunami warning has been issued for countries bordering the Philippine Sea.

The city of Hualien is only 10-20km from the epicentre, and there have been reports of some building collapses in that city. Landslides along the coastline are also expected.

Taiwan’s earthquake early warning system provided some areas of the country with several seconds of warning before earthquake shaking arrived at their location, providing an opportunity for residents to take cover from potentially falling objects.

The magnitude 7.4 earthquake in Hualien, Taiwan, lies at an incredibly interesting plate tectonic setting.

The earthquake formed as a thrust, where the crust is compressed horizontally and a part of the Earth’s surface is pushed up over the bit in front of it - a bit like a piggy-back!

Taiwan lies at a plate tectonic location where the edge of the Asian mainland is being driven under the Philippine Sea Plate.

The earthquake epicentre lies just where this subduction zone system hits a second subduction zone that is trying to underthrust the whole lot down to the north under the East China Sea.

It is an incredibly interesting plate tectonic knot!

A 7.4 magnitude earthquake has hit the south east coast of Taiwan.  Although it is away from the main centres of population on the western side of the island, its magnitude and relatively shallow depth means that the potential for damage is high, as well as the risk that a tsunami may also follow.  

There have been a series of large aftershocks in the hour following the initial quake, and these are likely to continue.  

The east coat of Taiwan is particularly prone to earthquakes and has experienced events up to magnitude 8.2 in the past.  

This is a result of its position close to zones where the Philippine Sea tectonic plate is being subducted beneath eastern Asia, and the island itself represents a collision zone between the island arcs that extend north from the Philippines and the margin of the Eurasian continent.

Prior experience has shown that the Taiwan earthquake and tsunami will have catastrophic immediate impact, requiring our best efforts to assist the response, and longer term, often unanticipated consequences. The 2011 Japan Tsunami and Fukushima disaster demonstrated this phenomenon, with longer term impacts on fisheries, agriculture, employment in the affected areas and health consequences, especially for mental health.

Our communities are more complex and interconnected than in the past, with many interdependencies, and disasters will result in damage to the systems that we depend upon every day causing cascading consequences.

We expect immediate damage to buildings and infrastructure and widespread loss of life and injuries.  

Governments and their emergency responders, along with non-government organisations will be gearing up to respond to these immediate needs.

We will also need to be prepared for the damage caused to systems including those used for communication, effective logistics and supply, health care, public safety and security, and in the longer term in education systems, politics and government, and other essential social services such as supermarkets or pharmacies.

These more fundamental elements of our communities will need to be protected and repaired, to reduce longer-term harm, in addition to our focus on the immediate rescue of people affected.

The M7.4 earthquake that occurred ~35 km beneath the east coast of Taiwan was the result of the convergence between the Philippine Sea plate and the Eurasian plate.  

There was a large aftershock (M6.5) just 13 minutes after the main event. This will be followed by hundreds more aftershocks over the next few days and weeks.  

The ground shaking from the mainshock was felt across the island of Taiwan and as far as mainland China.  

The most intense shaking occurred close to the epicentre and along the northeast coast, which has resulted in structural damage and most likely casualties.

This complex tectonic setting has produced many other large (M7+) earthquakes historically.  The largest earthquake in the past 25 years was in 1999 – called the Chi-Chi earthquake – which resulted in at least 2,300 fatalities.

Taiwan is situated at a convergent plate boundary between the Philippine Sea Plate and the Eurasian Plate with high seismicity and therefore the coastline is highly susceptible to tsunami hazards. 

However, there is no record of a tsunami occurring in the past one hundred years, and only very few historical records indicate that possible tsunami events occurred.

Among them is the 1867 Keelung event, which is the only historical tsunami incident officially recognised by the Taiwanese government.

Few studies have looked into extending our understanding of tsunami frequency and magnitude beyond the historical record and carried out palaeotsunami studies based on sedimentary evidence and modelling. Thus, our understanding of Taiwan’s tsunami history is scarce.

Globally, earthquakes cause significant loss of life and damage. Taiwan has a long history of earthquakes and is positioned close to tectonic plate boundaries where large earthquakes are common. 
 
Tsunamis can result from large undersea earthquakes that displace water causing a series of waves that can threaten coastal communities. Today's earthquake occurred close to the coast of Taiwan and had a magnitude measured at M 7.7.
 
The Australian Tsunami Warning Centre has confirmed that there is no threat to the Australian mainland, islands or territories. 
 
Australia has a moderate earthquake risk. Fortunately, Australia is located away from tectonic plate boundaries, and though we can experience large earthquakes and tsunamis their occurrence is rare.

The earthquake hit Taiwan with a magnitude 7.5, this is slightly smaller than Mount St. Helens' eruption in 1980.

Taiwan has a historical record of intense seismicity, due to its location at a subduction zone, where the tectonic plates slide past each other, creating recurrent earthquakes of all sizes. These zones are known to host the most energetic earthquakes on Earth, thus facing potential frequent strong shaking and possible tsunamis.

However, the magnitude of an earthquake is not the sole determinant for tsunamis, and the risk is also significantly influenced by the mechanics of the earthquake, specifically the direction of ground motions. Ground motions can be horizontal or vertical, thus triggering waves with different sizes.

While we have methods and tools to estimate magnitudes rapidly, the ground movements need more time to be assessed, justifying the warnings.

The additional complications of the Taiwan earthquakes come from the complex geometry of the subduction zone and the local climate.

Over geological time (tens of million years), the resistance to subduction of the thick Taiwan continental lithosphere has distorted and dissected the subduction zone in a way not seen elsewhere, making this zone a unique natural laboratory, as well as a zone at high seismic risk.

The recent 7.7 earthquake in Taiwan is definitely of a high magnitude, but it is not only the magnitude of the natural hazard that caused devastation, particularly to buildings – when the hazard met conditions of vulnerability, the disaster resulted. These conditions include the type of buildings and the timing of the earthquake, among other factors. The timing of the earthquake was unfortunate, at 8:00 am, when people were mostly at home and crushed by collapsing structures. 

It is uncertain to what extent buildings there were built to earthquake codes. Given that the last earthquake was 25 years ago, possibly newer buildings followed codes and older buildings were damaged. This is an indication of the necessity of retrofitting older buildings in seismically active regions.

Earthquakes in coastal areas often generate tsunamis, which happened in this case, however, the warning to southern Japan coasts has recently been downgraded, although extensive evacuations were carried out. It is a positive sign that Japan has such a high level of preparedness for tsunamis, drawing from its experience such as the 2011 East Japan earthquake and tsunami.

Recovery will require significant resources and would possibly be a protracted and difficult process, as is the case around the world. One should hope that this disaster will be a lesson for improved risk reduction and preparedness measures in the future, especially stringent application of earthquake-resilient building codes and regulations and retrofitting of older building stock. It should be accompanied by training for professional competency in the built environment sector.