Why Hualien shock waves felt clearly in Taipei?

On 4th, more than one earthquakes occurred at the eastern coast of Taiwan in the evening. A 2-ton water tower built along the side of the International Second Road in Yingge District of New Taipei City was suspected of lying down in the alley due to the earthquake. (photo by CNA)

By Chen Wei-ting and S.C. Chang

Taipei, (CNA) ─ Two weather experts said Sunday Taipei is a basin that absorbs shock waves from a series of earthquakes centered in eastern Hualien County Sunday.

Lu Pei-ling (呂佩玲), a Central Weather Bureau official, said most of people live and work in high buildings in Taipei, so they would feel strong shakes even though the shock waves originated from more than 100 kilometers away on the Pacific coast.

Beginning at 9:12 p.m. Sunday, a string of quakes in magnitudes ranging from 3.6 to 5.8, hit Hualien until 10:28 p.m. The strongest, magnitude 5.8, was centered 27.8 km northeast of the county government site at a depth of 16 km. The highest intensity of 5 was registered in the Tailuge area of Hualien and other townships, including those in Yilan.

“The shock waves were focused when they gathered in the Taipei basin, plus the fact that people are staying in highrise buildings. That’s why they clearly felt the jolts,” Lu said. Another expert, the bureau’s former director general Shin Tzay-chyn (辛在勤), compared the Taipei situation to what happens to a shaking jello — people in Taipei have felt that the tremor lasted longer than people elsewhere.

Taipei, which saw only an intensity of 2, felt the jolt for 23.38 seconds, compared to 60.84 seconds in Tailuge, which recorded an intensity of 5, Shyn said, citing the bureau’s data. The latest string of quakes, all centered in Hualien, caused a “level” shaking, not an up-and-down “vertical” jolt in Taipei, meaning it is far from the quakes’ epicenters or the epicenters are located very deep in the earth, he explained.

As the weather bureau has forecast more aftershocks in the coming days, Shyn advised people not to go to the mountain areas because recent and continuing rain could cause landslides or rockfalls.