Two M4.8 earthquakes off Taitung coast preliminarily deemed a swarm: CWA

(CNA, by reporter Chang Hsiung-feng, Taipei, 20th) Two magnitude 4.8 earthquakes occurred off the coast of Taitung today. The Central Weather Administration's (CWA) Seismological Center stated that it is preliminarily judging the event as an "earthquake swarm" and that further observation is needed. If it is indeed a swarm, the public should be aware that some small earthquakes may still occur in the next two to three days. According to the latest information from the CWA, a Richter scale magnitude 4.8 earthquake occurred at 8:25 PM today. The earthquake's depth was 27.3 kilometers, and its epicenter was located 63.9 kilometers north-northeast of the Taitung County Hall (off the coast of Taitung County), with a maximum intensity of 4 in Taitung County. The CWA Seismological Center pointed out that another Richter scale magnitude 4.8 earthquake occurred at 9:11 AM today, 65.3 kilometers north-northeast of the Taitung County Hall (off the coast of Taitung County). Its depth was 27.8 kilometers, with a maximum intensity of 4 in Taitung County, 3 in Hualien, 2 in Yunlin, Chiayi, and Changhua, and 1 in areas from Taichung to Kaohsiung. Wu Jian-fu, director of the Seismological Center, told a CNA reporter that because the two earthquakes had similar epicenters and magnitudes, they are preliminarily judged as a swarm for now. However, it is necessary to observe whether more earthquakes of similar magnitude occur in the vicinity, and a final determination will be made based on more complete monitoring data. Wu explained that a complete earthquake sequence has foreshocks, a mainshock, and aftershocks, with a difference in magnitude. A double mainshock event would involve two stronger earthquakes. As eastern Taiwan is a seismically active region and a magnitude 4.8 earthquake is not considered very large for this area, it is temporarily judged as a swarm, but more rigorous monitoring is needed to confirm. Wu said this area is where the Philippine Sea Plate pushes northwestward into the Eurasian Plate, causing some reverse faults (where the upper block moves up along the fault plane) or strike-slip faults (where rock masses on either side slide past each other horizontally), resulting in shallow earthquakes. Wu further stated that the definition of an earthquake swarm is that the quakes have very similar magnitudes, depths, locations, and occurrence times. Therefore, if it is truly a swarm, he reminded the public that some small earthquakes might happen again in the next two to three days. (Editor: Huang Ming-hsi)