Taipei, Feb. 7 (CNA) The magnitude 6.0 temblor that struck Hualien late Tuesday has re-written Taiwan's earthquake history, as both the intensity and number of its foreshocks and aftershocks are higher than have ever been recorded in the region, according to the Central Weather Bureau.
Chen Kuo-chang (陳國昌), acting director of the Central Weather Bureau's Seismology Center, told CNA that the earthquake sequence -- starting from a magnitude 5.8 earthquake Feb. 4 that peaked with the main quake Tuesday -- is the strongest that the region has ever seen.
"This is unprecedented and not a normal release of energy," he said, explaining that between the two major earthquakes, 94 shocks were recorded, with five of them reaching magnitude 5.0 or higher.
Between 1 p.m. Wednesday and the magnitude 6.0 temblor, which is now defined as the main shock in the sequence, about 150 aftershocks were recorded, among which, four were magnitude 5.0 or higher, center data shows.
By comparison, he said, Taiwan sees 20-25 earthquakes with a magnitude of 5.0 or higher each year, and the sequence over the past few days has already accounted for nearly half of that.
It is uncommon for eastern Taiwan to see an earthquake pattern like this, Chen said, explaining that the geological structure there makes it difficult for energy to accumulate.
Eastern Taiwan is on the edge where the descending Philippine Sea Plate goes under the Eurasian Plate, which results in a broken tectonic area, he said.
While earthquakes often take place in that area, they do not tend to form a major sequence with strong shocks, he said, adding that if aftershocks continue and intensify, there are concerns that they will trigger more seismic movement.
The bureau cautioned that more aftershocks are expected in the coming two weeks, and it does not rule out the possibility of temblors with a magnitude 6.0 or higher.
