According to the CWB, the main quake of a moderate 5.6-magnitude struck Shio Lin Township at 5:34 p.m. yesterday. There were seven foreshocks prior to that quake, and ten aftershocks following it. CWU officials said the 18 quakes occurred between 9:26 a.m. and 8:04 p.m. in the same township, including ten quakes with a 4-magnitude tremor.

The whole of Hualien and Yilan Counties were able to feel a 5-magnitude shake, they added.

Officials said the pattern of the earthquakes was a rare type, with several foreshocks occurring before a main quake takes place and followed by some aftershocks.

The center points of most earthquakes were less than one kilometer away from each other, officials said.

Earthquakes frequently rattle Taiwan, although most are minor and cause little or no damage.

CWU officials added that quakes above a 5-magnitude occur more than 30 times on average per year in the country.