The Taiwan earthquake 03/04/24 - by David Redfern
Figure 1. Distribution of intensity
Impact
On 3rd April 2024, a 7.4MMS earthquake struck the eastern coast of Taiwan at 07.58 local time (Figure 1). The depth of the quake was relatively shallow at 34 kms. It was the strongest in over 25 years. The quake killed 10 people (including 3 hikers), and 3 days later a further 12 were missing, over 600 (many of them tourists) were left stranded, though safe and alive, and over 1100 people were injured. There were up to 100 collapsed and/or damaged buildings trapping people, and there were many landslides particularly on the east coast that blocked both rural and coastal roads, road tunnels and railway lines. A tsunami warning was issued for Japan and the Philippines which was soon lifted.
Cause
Taiwan is located at an intersection of two subduction zones, where two oceanic plates are negotiating their way past each other into the mantle (Figure 2). To the north, the Ryukyu Trench, which extends southwest from Japan, curves to the west and ends against the northeastern part of Taiwan. To the south, the Manila Trench terminates below the southern part of Taiwan. In between, the island of Taiwan rises as a volcanic fragment of the Philippine Sea Plate collides with the continental crust of Eurasia. The north-westward convergence rate across Taiwan is about 8cm per year. This is extremely fast - more than twice as fast as the slip rate on the famous San Andreas Fault system.
The strong tectonic forces at this zone of deformation have resulted in the development of several active faults within the country - in addition to exposing it to the threat of subduction earthquakes on the megathrusts to the north and the south. Hence, the island is essentially a zone of active collision and uplift. One large fault system dips eastward beneath the high mountain chain - the fault system that produced the last major earthquake in 1999.
The April 2024 quake occurred to the east, on a fault within a complicated wedge system, where the Philippine Sea Plate is pushing into the island, but not subducting beneath it.
Figure 2. Tectonic setting
Image by Mikenorton, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=116285712
Economic impact
The main economic impact was on the semi-conductor industry which has several factories on the east coast of Taiwan. TSMC and United Microelectronics, the world’s largest makers of advanced chips for Apple and Nvidia, both halted chipmaking machinery and evacuated staff. Work quickly restarted after the event.
Figure 3: Hualien: The red brick Uranus building is seen leaning precariously.
IMAGE SOURCE,REUTERS
Figure 4. The Qingshui road tunnel (before and after)
Left: Image of the Suhua Highway before the earthquake - either hugging the side of the cliff, or going through tunnels. Source: Fred Hsu, https://en.wikipedia.org/wiki/Suhua_Highway#/media/File:Taiwan_2009_CingShui_Cliffs_on_SuHua_Highway_FRD_6762_Pano_Extracted.jpg.
Right: the same tunnel mouth after the earthquake. Source:
https://twitter.com/foreignersinTW/status/1775341882912203216
A wider view:
Management
All new buildings in Taiwan are now required to meet a basic earthquake resistance level that means they can withstand a certain level of shaking without major structural failures. The government also constantly revises the resistance levels required of buildings - identifying those that need upgrading. After 1999, they carried out a lot of seismic retrofitting - typically adding a framework of steel beams to a building's exterior or adding reinforcements such as extra pillars. That applied to infrastructure like bridges too.
Other forms of management include:
Early warning system: sensors placed around the island can pick up the early vibrations of an earthquake and provide mobile and TV alerts to the public near an epicentre with up to 8 seconds lead time.
Public awareness: the Taiwanese are used to quakes and know what to do, after school and workplace drills were made compulsory after 1999.
The island's disaster response team actively tracks social media and monitors surveillance cameras to assess damage – determining which locations to send aid to.
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