TAIPEI (Taiwan News) —  The earthquake that struck Hualien County on April 3 had the power of 39 atomic bombs and has been followed by over 1,200 aftershocks, according to the Central Weather Administration (CWA).

Although aftershocks have continued since the magnitude 7.2 temblor earlier this month, the frequency increased and intensity rose this week. Starting from 5 p.m. on Monday (April 22), 237 aftershocks occurred within 19 hours, reported China Times. 

According to the CWA, after the main quake struck on April 3, there have been more than 1,224 aftershocks as of 9:36 a.m. Wednesday (April 24), with 306 of them being significantly felt aftershocks. There have been 374 aftershocks with magnitudes ranging from 4 to 5, 61 aftershocks with magnitudes ranging from 5 to 6, and four aftershocks with magnitudes greater than 6.

The CWA said that after a magnitude 5.5 earthquake occurred at 5:08 on Monday, the epicenter of the temblors began to move southward towards areas such as Shoufeng Township and Fenglin Township. Kuo Kai-wen (郭鎧紋), former director of the CWA Seismology Center, said that the energy released by the earthquakes since April 3 is equivalent to “42 atomic bombs” dropped on Hiroshima, but 39 atomic bombs' worth of energy was released on the first day.

Kuo said the situation seemed alarming over the past two days, but the actual amount of energy released was less than earlier in the month. Previously, aftershocks were concentrated in areas of Hualien County north of the epicenter of the main quake, but in the past two days, they have shifted southward to reach a “normal stress equilibrium” and people need not worry.

After nightfall on Monday, there were more than 80 intense tremors in Hualien, including a magnitude 6 earthquake off the coast of Hualien at 2:26 a.m. on Tuesday (April 23) and a magnitude 6.3 earthquake in Shoufeng six minutes later. In the latter temblor, Hualien experienced a maximum intensity of  5, and residents in 12 counties and cities received national alerts.

Wu Chien-fu (吳健富), director of the CWA's Seismological Center, told China Times that the recent series of intense earthquakes in Hualien, which began on Monday, are all aftershocks following the April 3 quake, based on their location and magnitude analysis. 

He added that after a magnitude 7.2 earthquake, the energy will not be released completely in the short term. 

Based on the experience of the 1999 Jiji earthquake, aftershocks may continue for six months to one year, said Wu.