Strong earthquakes Tuesday aftershocks of 7.2-magnitude quake: CWA

Taipei, April 23 (CNA) The magnitude 6.0 and 6.3 earthquakes that rattled Hualien County early Tuesday are aftershocks of the April 3 magnitude 7.2 earthquake in the eastern county that left at least 17 people dead, the Central Weather Administration (CWA) said Tuesday.

Wu Chien-fu (吳健富), director of the CWA's Seismological Center, said most of the aftershocks of the mainshock over the past three weeks have been concentrated in northern Hualien, but the ones occurring since Monday have been centered in central Hualien, around Shoufeng Township.

Although the intensity and number of aftershocks will decrease over time, there will still be sudden spikes in aftershocks due to stress adjustments, Wu said at a press conference.

A total of 103 earthquakes of magnitude 4 or higher hit Hualien County from 5:08 p.m. Monday to 10:27 a.m. Tuesday, with 27 of them exceeding a magnitude of 5.

Though their epicenters were mostly in the vicinity of Shoufeng Township, rocking Hualien County, the earthquakes were felt all over northern and central Taiwan, unnerving residents of those areas in the middle of the night.

Wu said the aftershocks were felt more strongly over the last two days than in the previous two weeks because they were shallow and their epicenters were on land or closer to Taiwan than the mainshock on April 3, which was centered off the Hualien coast.

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Given its scale, Wu predicted that the energy of the mainshock will not be fully released in the short term and more aftershocks can be expected.

Wu said that based on the experience of the 7.3-magnitude 921 Jiji earthquake in 1999, which left more than 2,000 people dead, aftershocks may continue for the next six months to a year.

Although the number of aftershocks will gradually decrease, there is still a possibility of larger earthquakes, although they are unlikely to reach magnitude 7 or higher, he said.

As of 8 a.m. Tuesday, a total of 1,110 aftershocks had occurred since the April 3 earthquake.

Four of the aftershocks had a magnitude of 6 or higher; 56 had a magnitude between 5 and 6; 344 had a magnitude between 4 and 5; and 706 had a magnitude between 3 and 4, according to CWA statistics.