Taiwan hit by biggest earthquake in 25 years: why scientists weren’t surprised
A complex network of faults lies in the area that experienced Taiwan’s earthquake, with scientists warning to expect more shocks
Scientists warn that more shocks are likely after Taiwan was rocked by the most powerful earthquake to hit the island in 25 years, killing several people, flattening buildings, and triggering landslides. Geologists warn that the location of the epicentre is in a complex network of offshore faults, making aftershocks or even another quake a possibility.
The magnitude-7.4 tremor struck under the ocean, 18 kilometres south of the east-coast city of Hualien just before 8am on Wednesday morning local time, according to measurements gathered by the US Geological Survey. Since then, dozens of aftershocks have rattled the island, including a 6.4 magnitude tremor that occurred roughly two hours after the main quake. “Everyone experienced the shaking,” says Kuo-Fong Ma, a seismologist at National Central University in Taoyuan City, Taiwan.
The earthquake occurred at a relatively shallow 35 kilometres deep, resulting in stronger tremors than those produced by quakes that erupt farther below the Earth’s surface. Authorities issued tsunami warnings in Taiwan, Japan and the Philippines, though they later downgraded them. A 30-centimetre-high wave rolled into Yonaguni Island in the south of Japan about 15 minutes after the tremor. The earthquake’s effects were also reportedly felt in parts of mainland China.
Taiwan’s vulnerability to earthquakes is no surprise given it is situated in one of the most seismically active regions in the world, says Meghan Miller, a seismologist at the Australian National University in Canberra. The east coast of the island sits on top of two converging tectonic plates: the Philippine Sea and Eurasian plates. Many of the earthquakes that occur on the eastern side of Taiwan are due to the Philippine Sea plate sliding underneath the Eurasian plate, says Miller.
The location of the earthquake’s underwater epicentre offers clues to its mechanics, says Yu Wang, a geologist at National Taiwan University in Taipei. The earthquake occurred on a reverse fault, which means one chunk of rock shifted vertically relative to the other. “We believe this is the cause of the current earthquake,” says Wang. He adds that the area where the earthquake occurred contains a complex network of faults, and that the latest rupture probably produced a crack between 40 and 50 kilometres long.
In the coming days, dozens of aftershocks are expected to shake Taiwan further, says Wang. The force of the earthquake has already triggered landslides in mountainous areas, which could worsen with more tremors and make rescue efforts more challenging, adds Miller. In flat areas, aftershocks could also lead to the ground becoming soft and water-logged, which can amplify seismic waves and damage compromised buildings further. “There can be additional damage on top of what originally occurred in the first event,” says Miller.
Several earthquakes have occurred in Taiwan over the past century, with those reaching magnitude 7 usually occurring roughly every 30 years, says Ma. One of the most devastating earthquakes to hit the island occurred in 1999, when a magnitude-7.6 tremor struck the western side of the island. It resulted in more than 2,400 deaths and reduced thousands of buildings to rubble.
But in the past two decades, Taiwan has ramped up its efforts to reduce the impact of earthquakes, says Ma. The island has an early warning system that alerts cities and regions via a telephone call a few seconds after an earthquake strikes. She adds that many buildings have been modified to withstand strong earthquakes, and several seismology stations have been installed across the island to take real-time measurements. Ma and her colleagues are also developing sensors for measuring the shaking intensity inside buildings to help people determine their risk during an earthquake. “I think that will be the future,” she says.
doi: https://doi.org/10.1038/d41586-024-00988-8
This story originally appeared on: Nature - Author:Gemma Conroy
