Tue, Feb 09, 2016 - Page 2 News List

Earthquake Aftermath: Destruction in Tainan caused by ‘site effect’: experts

Staff writer, with CNA

The destruction in Tainan following a strong earthquake on Saturday was largely due to a geological factor called the “site effect,” which was why the city sustained more serious damage than the area of the quake’s epicenter, Central Weather Bureau (CWB) Director-General Shin Tzay-chyn (辛在勤) said.

Kaohsiung’s Meinong District (美濃), the center of the magnitude 6.4 earthquake, hardly suffered any damage, while parts of neighboring Tainan were devastated, Shin said.

He said most earthquakes in southern Taiwan are concentrated along a fault line stretching from Jiasian (甲仙) in Kaohsiung to Sinhua (新化) in Tainan.

The Jiasian quake in 2010, for example, occurred along that fault line, about 10km from Meinong, and was of the same magnitude as Saturday’s temblor, Shin said.

There were also other similarities, he said.

Both earthquakes were centered in a mountainous area at a shallow depth — the one on Saturday at 16.7km below the surface and the Jiasian quake at 22.6km, he said.

However, Shin said that while the Jiasian quake caused no damage or casualties, Saturday’s quake toppled several structures in Tainan, including a 17-story residential complex, killing at least 38 people.

Lin Tzu-wei (林祖慰), head of the bureau’s Earthquake Forecast Center, said the Meinong earthquake was more destructive mainly because of Tainan’s soft soil.

Surface ground motion can be strongly amplified in such geological conditions, which are known as the “site effect,” Lin said.

The seismic waves in Saturday’s earthquake apparently traveled northwest from the epicenter to Tainan through the soft soil in the Chianan Plain, which stretches from Tainan to Chiayi County to the north, Lin said.

He said structural factors in the city also contributed to the devastation caused by the earthquake.

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