《TAIPEI TIMES》 Bureau warns of aftershocks after two strong quakes
A Central Weather Bureau graphic shows information about Sunday night’s earthquakes in Hualien. Photo: Tsai Shu-yuan, Taipei Times
RATTLED: Aftershocks of magnitude 5 or greater could occur in the next two to three days after Sunday’s foreshock and magnitude 6.2 quake
By Shelley Shan / Staff reporter
The nation was on Sunday rocked by two consecutive earthquakes in Hualien County, the Central Weather Bureau said yesterday, adding that aftershocks greater than magnitude 5 could occur in the next two or three days.
No casualties were reported as of yesterday.
A magnitude 5.8 earthquake occurred at 10:11pm, with the epicenter 19.2km southwest of Hualien County Hall at a depth of 15km. Three minutes later, a magnitude 6.2 earthquake struck 20.2km southwest of the county hall at a depth of 13.9km, bureau data showed. The epicenter of both quakes was in Shoufong Township （壽豐）.
The magnitude 6.2 temblor was the main earthquake, and the magnitude 5.8 one that preceded it was a foreshock, Seismological Center Director Chen Kuo-chang （陳國昌） said.
The intensity generated by the main earthquake and the foreshock reached level 6 and level 5 respectively, he said.
The exact magnitude of the main earthquake was 6.29, making it the largest temblor this year, and the second one to exceed magnitude 6, he added.
“It is possible that aftershocks of magnitude 5 or greater could occur in the next two to three days. We could also experience aftershocks of magnitude 4 or larger this week,” Chen said.
The epicenter of Sunday night’s earthquakes was at a geologically fractured zone and is unlikely to trigger many aftershocks, he said, adding that they were not related to the magnitude 6.4 earthquake that struck Hualien on Feb. 6, 2018, killing 17 people and injuring 291.
The first strong earthquake this year was recorded on Feb. 7, when a magnitude 6.1 earthquake struck off the coast of Yilan County at 1:36am, Chen said.
Sunday’s earthquakes were caused by the Philippine Sea Plate colliding with and pressing against the Eurasian Plate, which subsequently triggered a ground motion of a geologically fractured zone at the East Rift Valley, a narrow strip of plain spanning Hualien and Taitung counties, he said.
Shoufong Township is near the Central Mountain Range and has recorded relatively fewer earthquakes, Chen said.
Since 1990, the township has had only 22 earthquakes greater than magnitude 5, including the two on Sunday.
Sunday’s magnitude 6.2 earthquake was the second-largest recorded in Shoufong, after a magnitude 6.5 earthquake in 1990.
On average, the nation has two to three magnitude 6 or stronger earthquakes per year, and 22 earthquakes greater than magnitude 5, Chen said.
So far, the nation has already recorded two earthquakes greater than magnitude 6, and 12 stronger than magnitude 5, he said.
“Seismic activities are indeed happening more frequently this year. However, considering that the nation had relatively fewer earthquakes in the past two years, the earthquakes on Sunday helped release accumulated seismic energy,” he said. “People should not worry.”