Over 360 aftershocks strike Taiwan following magnitude 7.2 quake

Taipei, April 4 (CNA) Central Weather Administration (CWA) statistics indicate that as of around 2 p.m. Thursday, a total of 365 aftershocks have hit Taiwan since a magnitude 7.2 earthquake rocked much of the island the previous day.

As of 1:57 p.m., aftershocks recorded by the CWA have included 207 of 3-4 magnitude, 140 of 4-5 magnitude, and 16 of 5-6 magnitude.

There were also two powerful aftershocks of magnitudes 6.5 and 6.2, which struck at 8:11 a.m. and 10:14 a.m. on Wednesday, according to the CWA data.

The magnitude 7.2 earthquake struck off the coast of Hualien County in eastern Taiwan at 7:58 a.m. Wednesday, with its epicenter in the Pacific Ocean, 25.0 kilometers south-southeast of Hualien County Hall, at a depth of 15.5 km, according to the CWA's Seismology Center.

The online group Taiwan Typhoon BBS (TWTYBBS), which focuses on weather subjects, said in a social media post on Thursday that the aftershocks mainly occurred north of the magnitude 7.2 earthquake and the peripheral area of Milun Fault, located in Hualien, and its extension to the sea.

A high number of these aftershocks were located on the Milun Fault and the Suhua coastal area between Yilan and Hualien counties, the group said.

● Taiwan earthquake island's strongest in 25 years: CWA

The Milun Fault, also called the Hualien Fault, is an 8-km-long north-south left-lateral fault stretching from the coastal area of Qixingtan Beach in Hualien County to the southwest side of Meilunshan (Mt. Meilun) in Hualien City.

The TWTYBBS did not offer more information about its observations of the aftershocks, saying only that more research and data from geologists were needed for it to know what exactly caused the geological phenomenon.

It said, however, on the post that although the aftershock frequency and scales have shown signs of declining, the geological environment of the mountainous areas in northern and central Taiwan is still very fragile.

"Risks are still high," it warned, advising people to refrain from hiking, camping and river tracing in the near future.

Speaking of the destructive earthquake that has caused 10 people dead and other 1,067 injured according to government figures released at 4:25 p.m. Thursday, Huang Hsin-hua (黃信樺), an associate research fellow with Academia Sinica's Institute of Earth Sciences, said it is pending an investigation into exactly which fault the earthquake is situated.

Currently, efforts are being made to collect data, however, "[they] cannot now provide clear and definite judgment" on the subject, Huang said.

Huang told CNA on Wednesday that the epicenter of the magnitude 7.3 earthquake that hit central Taiwan on Sept. 21, 1999 was the fault slip of the Chelungpu Fault on the western Taiwan surface, causing a rupture zone on the surface extending up to 85 km.

That of Wednesday's earthquake, however, was off the coast of eastern Taiwan, where "the structure is more complicated than that of the 921 earthquake," he said.

The researcher noted that now scientists need to figure out if the epicenter of the largest earthquake to hit Taiwan in 25 years is located along the Central Range Fault or the Longitudinal Valley Fault on the eastern side of the East Rift Valley, which stretches from Hualien to Taitung.

He explained that since 2018, the earthquakes that struck Hualien and Taitung had mostly occurred along the Central Range Fault, including the magnitude 6.8 temblor that jolted Chishang Township of Taitung County on Sept. 18, 2022.

If this is the case for Wednesday's earthquake, he sees there will be a smaller chance that a powerful earthquake will strike following the magnitude 7.2 temblor.

However, if it occurred along the Longitudinal Valley Fault, where there have been no big earthquakes in the past few years, Huang said he would be worried that big quakes could occur in the wake of Wednesday's temblor.

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