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進入《TAIPEI TIMES》 Earthquake alerts’ scope to be broadened: CWA
A presidential alert message about an earthquake is displayed on a mobile phone screen on Aug. 16. Photo: CNA
INCREASING RESPONSE TIME: Although some people say they find alert messages ‘annoying,’ an official said that the frequency should be reasonable and tolerable
By Wu Liang-yi and Esme Yeh / Staff reporter, with staff writer
Presidential earthquake alerts from tomorrow are to include areas experiencing an estimated intensity of 3 or higher, down from an intensity of 4, for quakes measuring 6.5 or higher on the Richter scale, the Central Weather Administration （CWA） said yesterday.
The Public Warning System currently sends alert messages to people whose locations are anticipated to be affected by earthquakes with a magnitude of 5 or higher, and an intensity of at least 4, the agency told a news conference.
To allow for two to three more seconds for people to take cover, the system would also issue presidential alerts for areas that could experience an intensity of 3 or higher during a magnitude 6.5 or higher quake, it said.
CWA Seismological Center Director Wu Chien-fu （吳健富） said the agency decided to lower the threshold for triggering a presidential alert in the wake of the Hualien earthquake on April 3, which measured 7.2 on the Richter scale.
Some earthquakes of lower magnitude have long duration and strong low-frequency waves, he said, adding that the effect of such temblors is more noticeable in high-rise buildings.
For example, if the intensity measured on the first floor is level 3, then it would be level 4 when seismic waves are transmitted to the ninth floor, Wu said.
Meanwhile, the Hualien earthquake indicated that the system’s initial forecast tended to underestimate severity, so quakes with a magnitude of 6.5 or higher are included to allow for more response time, he said, adding that quakes of this level are usually followed by aftershocks.
Although some people have found presidential alert messages “annoying,” the frequency should be reasonable and tolerable, Wu said.
There have been eight earthquakes of magnitude 6.5 or higher since 2022, he said, adding that based on this frequency, only 1.4 more alerts would be issued on average in the same period under the new scheme.
People in northern Taiwan might be alerted more frequently due to site effects, in which seismic waves are amplified by changing geological conditions, Wu added.
He cited Taipei as an example, where the Hualien earthquake reached the greatest intensity 16 to 17 seconds after it occurred, saying that the alert messages could have been issued two to three seconds earlier if the system had been triggered by quakes with an intensity of as low as 3.
The CWA uses cell broadcast technology to send alert messages via the system within seconds after an earthquake happens, he said, adding that the response time is crucial for people to escape from objects that would fall or pull over their car if they are driving.
新聞來源：TAIPEI TIMES
