Aftershocks of magnitude 4 or over are expected over the next three days after the strongest earthquake recorded in Taiwan this year struck Yilan County Sunday afternoon, a Central Weather Bureau (CWB) official said.
The two earthquakes of magnitude 6.5 and 5.4 that occurred in Yilan's Nan'ao and Datong townships at 1:11 p.m. and 1:12 p.m., respectively, are in a subduction zone, where two plates converge, and one plate is thrust beneath the other, said Chen Kuo-chang (???), head of the CWB's Seismological Center.
The region is at the west end of the Ryukyu Trench in the Pacific Ocean between Taiwan and Japan, and had seen relatively fewer earthquakes, even though a magnitude 4.5 earthquake hit Nan'ao on Jan. 1, Chen told reporters.
The magnitude 6.5 quake, at a depth of 66.8 km, is also this year's strongest recorded by the bureau in Taiwan and water surrounding the island, as well as the largest in the area in the subduction zone 40 km under the surface since 1973, Chen said. However, the CWB was unable to provide the scale of that earthquake in 1973.
According to the CWB, it had also recorded a magnitude 4.2 earthquake in Nan'ao at 2:05 p.m., which was at a depth of 63 km.
While Sunday's earthquake was felt around Taiwan and in the offshore county of Penghu, the intensity of 4 that was registered in a large part of northern Taiwan was not the highest on Taiwan's 7-tier system used to gauge the actual effect of a temblor this year, according to CWB data.
A 6.2 magnitude earthquake that hit Shoufeng Township, Hualien County on April 18, the second-largest in terms of scale, led to the highest intensity of 5+ this year, as it was at a depth of 14.4 km, CWB data showed.
Chen also talked about the magnitude 4.5 earthquake that was recorded at 12:38 p.m. on Sunday, the epicenter of which was located in the water 8 km north-northeast of the Hualien County Hall, at a depth of 23.8 km.
He said that earthquake, along with five others recorded on Saturday, are considered to be aftershocks of a magnitude 6.2 earthquake that occurred in Hualien on Feb. 6, 2018. An intensity of 7 was registered in the 2018 earthquake, according to CWB data.
Source: Focus Taiwan News Channel