In the News

Experts warn of more quakes in western Taiwan

• Publication Date：03/10/2010
• Source： Liberty Times

In the wake of three large earthquakes in western Taiwan recently, the Central Weather Bureau and seismological experts have warned that “a period of frequent temblors has returned.”

The 6.4-magnitude earthquake in Jiaxian Township, Kaohsiung County March 4 was followed by quakes of magnitude 5.1 in Chiayi March 8 and 4.5 in Nantou March 9, as well as two aftershocks in the Jiaxian area registering 4.5.

The Nantou temblor struck at 1:52 p.m. March 9, with the epicenter 35.7 kilometers southwest of the Deji seismological sensing station, at a depth of 10.7 kilometers, making it a shallow quake. It registered 3 at Puli Township in Nantou County.

Kuo Kai-wen, director of the CWB’s Seismology Center, said the Nantou earthquake was a release of energy in the fault zone in the Puli area. It was roughly 100 kilometers from the Chiayi quake and 200 kilometers from the Jiaxian temblor. The three quakes occurred in different fault zones and were not related, Kuo added.

However, Chen Wen-shan of National Taiwan University’s Department of Geosciences said it was normal for there to be many earthquakes in the two weeks following a large quake like the one in Jiaxian. As the shock waves from the Jiaxian quake travel through the fault zone, they may draw out energy in other faults and trigger aftershocks.

In the three months after the major temblor of Sept. 21, 1999, there were over 20,000 aftershocks, Chen pointed out. “If the energy from an earthquake is large enough, it will definitely stimulate activity in other faults,” he said.

Kuo said in 2008 and the first half of 2009, there were no quakes of magnitude 6 or above, but in the second half of last year there were four in succession. As of February this year, 35 earthquakes over magnitude 4 had occurred, with 27 from magnitude 4 to 5 and 8 temblors between magnitude 4 and 6. Judging by the average of 26 quakes per year measuring magnitude 5 to 6, the frequency this year is on the high side.

Kuo said earthquake magnitude and frequency have clearly increased, so the public should be prepared for tremors at any time. Chen Wen-shan’s NTU colleague Hongey Chen said the recent Jiaxian, Chiayi and Nantou quakes all rattled western Taiwan, where relatively fewer earthquakes strike, indicating a quiet period has passed and the island is entering a period of higher quake frequency. People should be on the alert, he added.

Chen Wen-shan said Taiwan has many faults, and if their earthquake frequencies can be identified damage could be reduced to the minimum. In the Chishang fault in southeastern Taiwan, for instance, a 6.8-magnitude temblor takes place every 50 years, while in the Chelungpu fault, site of the major quake, an earthquake exceeding magnitude 7 hits every 300 to 400 years. Scientists are still in the process of investigating quake frequency in the many faults in the Jianan plain in the southwest part of the island, he noted. (THN)