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進入《TAIPEI TIMES》 Magnitude 6 earthquake strikes off the east coast
Several of the dozen or more earthquake alerts sent out by the Central Weather Bureau are displayed on a smartphone yesterday. Photo: Hsiao Yu-hsin, Taipei Times
STAYING ALERT: Some people reported receiving as many as a dozen earthquake warning messages, which the Central Weather Bureau said was due to an error
By Shelley Shan / Staff reporter
A magnitude 6.1 earthquake yesterday struck off Taiwan’s east coast at 1:36am, the Central Weather Bureau said, adding that aftershocks of magnitude 4 or higher could occur in the next three days.
No casualties were reported as of press time last night.
Data from the bureau’s Seismology Center showed that the epicenter was 85.1km east of Yilan County Hall at a depth of 112km.
The largest intensity generated by the earthquake was level 4, which was felt in Yilan and Miaoli counties. Level 3 intensity was recorded in New Taipei City, Taoyuan, Hsinchu City and Hsinchu and Hualien counties.
Taipei and Taichung, as well as Changhua, Chiayi, Nantou, Taitung and Yunlin counties reported level 2 intensity. Kaohsiung, Keelung, Tainan and Chiayi City recorded level 1 intensity, the data showed.
Seismology Center specialist Wu Chien-wen （吳建文） said the earthquake was the largest so far this year, adding that it was caused by the Philippine Sea Plate and the Eurasian Plate pressing against each other.
Five magnitude 5 or larger earthquakes occurred within a 50km radius of the epicenter last year, Wu said.
“Aftershocks of magnitude 4 or larger could occur in the next three days. As the epicenter was more than 100km underground, there would not be too many aftershocks,” Wu added.
Annually, Taiwan experiences about 18 earthquakes of magnitude 5 to 6 and an average of 2.3 earthquakes exceeding magnitude 6, Seismology Center Director Chen Kuo-chang （陳國昌） said.
However, the center has already recorded five magnitude 5 or larger earthquakes since last month, including yesterday’s, he said.
Last year, there were 25 magnitude 5 to 6 earthquakes, whereas there were only four earthquakes larger than magnitude 6, Chen said.
“Last year, we started seeing magnitude 5 or larger earthquakes more frequently than the long-term average, and the number of medium to small earthquakes was significantly below average,” Chen said. “This is a special phenomenon and requires further observation.”
Many people said that they were awoken not by the earthquake, but rather by numerous alerts sent to their smartphones through the public warning system.
In addition to triggering a loud alarm, which cannot be manually turned off, the system also repeatedly sent the same earthquake warning message, with some people reporting receiving it more than a dozen times.
Bureau Director-General Cheng Ming-dean （鄭明典） wrote on Facebook that the multiple messages were due to an error.
He wrote that after the earthquake early warning system determined that yesterday’s earthquake met its criteria for issuing an alert — a magnitude 5 or larger earthquake generating level 3 intensity in Taipei or level 4 intensity elsewhere — an advance message was sent to localities that could be affected.
As more data gradually arrive from observation stations after the first detection of an earthquake, the early warning system is designed to process the data and deliver an additional alert if there was any change in the earthquake’s magnitude or the location of the epicenter, he added.
“The earthquake’s epicenter was far from Taiwan’s northeast coast and was more than 110km deep, which presented a challenge to the early warning system,” he said. “Meanwhile, the calculation errors caused the system to constantly update the information, which caused it to send out multiple warning messages,” he said.
To prevent the system from repeating the same warning message, the bureau has begun to improve the automatic detection modules in the earthquake early warning system, Cheng said.
新聞來源：TAIPEI TIMES
