6.4 quake hits southern Taiwan
The China Post news staffKAOHSIUNG, Taiwan -- A strong earthquake of Richter magnitude 6.4 struck southern Taiwan at 8:18 a.m. yesterday, reported the Seismology Center (SC) of the Central Weather Bureau (CWB). The quake centered at 17 km southeast of Jiasian Township in Kaohsiung County. It was the most powerful earthquake in Kaohsiung County since 1900. The energy released was equal to two Hiroshima nuclear bombs.
March 5, 2010, 9:29 am TWN
It was felt throughout the island, with the measured magnitude of six in Nansi in Tainan and Dapu in Chiayi, and five in Taoyuan in Kaohsiung, Chiayi City and Douliou in Yunlin.
The earthquake was a shallow-focus earthquake with a depth of 5 km. Lu Pei-ling, deputy head of SC said shallow earthquakes usually cause more damages than deeper earthquakes as they are released closer to the surface and there is less rock to absorb the shaking, and they tend to have a lot more aftershocks.
226 aftershocks were recorded, with the biggest one measured magnitude 5.7 at 4:16 p.m., at 17.1 km southeast of the epicenter of the main quake. 20 of these aftershocks were felt.
Shin Tzay-chyn, director general of CWB, said the earthquake was caused by the movement of Eurasian Plate against the Philippine Sea Plate. Though the Chauzhou Fault in Pingtung County is considered to be inactive, CWB believed that the earthquake was related to the fault, as the epicenter was only 8km away.
Kuo Kai-wen, director of SC, said the intensity of this earthquake is unusual for the area. This is the first time that an earthquake near the Chauzhou Fault measured a magnitude of more than six. The most recent earthquake within a 30-km radius of the epicenter was in 1998 with a magnitude of 5.51.
Shih Ruey-chyuan, professor of the Institute of Seismology in National Chung Cheng Univeristy did not think the Chauzhou Fault was related. He inferred that it was triggered by a blind thrust fault, a fault plane that terminates before it reaches the Earth's surface.
The earthquake has caused speculation that it was related to the recent big earthquakes that have occurred in the world: magnitude 8.8 earthquake in Chile on Feb. 27 and magnitude 7.0 earthquake in Haiti on Jan. 12. And that these earthquakes marked the start of a frequent earthquake period.
Kuo said the Kaohsiung quake was not geologically related to the Chilean earthquake. Those quakes are separate events and the frequency of earthquake occurrence worldwide is within the normal range.