The 6.4-magnitude quake in Taiwan and the more than 100 reported aftershocks that rattled the region

Experts disagree on whether Taiwan is facing an ‘earthquake swarm’ or not

On February 6^th, a magnitude-6.4 earthquake hit Taiwan’s east coast, killing at least 9 people and injuring 270 others. The quake was centered 22 km (13 miles) northeast of the coastal city of Hualien, where buildings, bridges and roads were severely damaged, while the more than 100 reported aftershocks make the situation even more alarming. In fact, many people were trapped inside the still-tilting Yun Men Tsui Ti building and rescuers had to use steel supports to prop it up. However, their efforts were halted temporarily Wednesday as the supports began to slide and the building tilted more, local officials said.

Taiwan sits at the intersection of the Philippine Sea tectonic plate and the Eurasian plate which move in opposite directions, so the island experiences frequent seismic activity. This time however, the series of quakes that followed made the residents worry. “It wasn’t a normal earthquake, there have been more than 100 aftershocks,” said Wu Ching-hua, 62, a native of Hualien . “We’ve had bigger quakes here many times before, but the aftershocks taper off gradually. Right now we don’t know what will happen.”

‘Earthquake swarm’

According to a report recently published in Taiwan News, a geology professor at National Central University in Taoyuan City believes the country is entering an earthquake cycle that could last for the next century. "For the next 10 years in Hualien, the probability of a magnitude 8 earthquake occurring is high. I predict that there will be another earthquake [similar in size] in 2025," says Lee Chyi-tyi, the academic who has been proposing this theory since 2013. "Earthquakes are cyclical and it is about time again."

Other experts prefer not to use the loaded phrase. Alexandre Canitano, a postdoctoral fellow at Academia Sinica's Institute of Earth Sciences in Taipei explains that "long-term earthquake forecasting is a tricky exercise, and there is no evidence supporting the occurrence of a destructive earthquake in a near future". He believes that Taiwan is being hit by a "preshock-mainshock-aftershock" sequence, and it's unclear how the sequence will develop in the coming days and weeks.

For the geology professor Afroz Ahmad Shah in Universiti Brunei Darussalam though, these earthquakes seem different from a normal sequence, in which smaller aftershocks follow a larger mainshock. He says these quakes seem more like a swarm because they all have similar magnitudes and occurred over a short period of time, but again a closer look for more accurate magnitude information is necessary, which can change based on how clear the data are.

Image source: CNN