The Landslide Blog is written by Dave Petley, who is widely recognized as a world leader in the study and management of landslides.
At 07:58 local time on 2 April 2024 an earthquake struck the central East Coast of Taiwan, close to the city of Hualien. Initial reports from the Central Weather Administration Seismological Center, the local seismic agency, estimates that this was a ML=7.2 event at a depth of 15.5 km with an epicentre at [23.77, 121.66]. Such an event is inevitably damaging, although the high level of earthquake preparedness in Taiwan will hugely mitigate the human losses. This area is known to have a very high level of seismic hazard, so much has been done since the 1999 Chi-Chi earthquake in west Taiwan to build resilience.
However, eastern Taiwan is also one of the most landslide prone locations on Earth, thanks to the active tectonics, weak rocks and extremely high rainfall totals. In such an environment, we would expect to see thousands of landslides, with a high level of damage to the local infrastructure. Early reports are true to this, with videos posted to Twitter of landslides occurring on a large scale:-
There is also some very impressive footage on Youtube:-
Most of these early videos show rockslides, which one would expect given the setting. These generate huge amounts of dust, especially as the earthquake has occurred in the dry season.
At the time of writing, seven deaths have been confirmed, all of which appear to have been the result of landslides and rockfalls. These include (but remain to be confirmed):-
- A man killed in a rockfall that struck his car close to the Huide Tunnel on the Suhua Highway;
- Three hikers killed by a rockfall on the Dekalun Trail in Taroko National Park;
- One hiker killed by a rockfall on the Xiaozuilu Trail;
- A truck driver killed by a landslide on the Suhua Highway between the Daqingshui and Jinwen Tunnels;
- A person killed in the TCC Heren mining district (I am unclear about the circumstances or location of this accident)
The Google Earth image below highlights the challenges that landslides will pose in the aftermath of this earthquake, especially as multiple aftershocks rattle the area:-
Closest to the epicentre is the Hai’an (Coastal Mountain) Range, with Highway 11 running down the coast. Whilst not high, the hills here consist of weak lithologies that are very prone to landslides.
Running down the spine of the island is the Central Mountain Range, which is extremely rugged. The geology in this area consists of marbles and schists, with high peaks and very steep slopes. Landslides occur extremely frequently, as the Google Earth image shows. The valley between the two ranges (the Huadong Valley, sometimes called the Longitudinal Valley) has Highway 9 running through it. This is likely to have been affected by landslides.
To the north of Hualien the Central Mountains meet the sea, leaving a very narrow space for roads and the railway line. This is the Suhua Highway, probably one of the most dramatic major roads in the world. Many of the videos that have been posted show this area. This is the major artery to the rest of Taiwan, but photographs show that it has been profoundly impacted.
Finally, running towards the west is the Central Cross Island Highway, through Taroko National Park. i spent much of my early career working on landslides in this area – its is dramatic and thrilling, but extremely prone to rockfalls. I was there in September last year – this sign was somewhat prescient:-
Taiwan is remarkably well placed to deal with an earthquake of this type, a testimony to what can be achieved with high quality preparedness. But in this terrain, and with an earthquake on this scale, heavy damage to infrastructure is inevitable.