Four earthquakes occurred in Wanrong Township, Hualien County, near the junction of Nantou County at 9:45 this morning in just 14 minutes. The magnitudes were 5.3, 4.4, 3.9, and 3.7. The maximum magnitude was 4, and the depth ranged from 3.4 to 7.2 kilometer.
(The picture is taken from the Central Meteorological Bureau)
[Reporter Chen Xinyu/Taipei Report] Four earthquakes occurred in Wanrong Township, Hualien County, near the junction of Nantou County at 9:45 this morning in just 14 minutes. , The depth is between 3.4 and 7.2 kilometers. Chen Guochang, director of the Earthquake Forecasting Center of the Central Meteorological Administration, said that these earthquakes are of the same sequence. The main shock is the first earthquake with a magnitude of 5.3. However, the frequency of aftershocks is still due to the incomplete release of energy. It is estimated that aftershocks of magnitude 3 to 4 will occur today and tomorrow.
Chen Guochang said that the geology of the epicenter is hard metamorphic rock. There have been few earthquakes in this area in the past half century, including today's magnitude 5 earthquake, a total of 15 times, including an earthquake of magnitude 6 or above on November 31, 2013. , the main cause is the compression of the Philippine Sea plate and the Eurasian continental plate. The first line of plate compression here is the rift and the coast, and then it continues to deform inland. Because it will encounter relatively hard rock mass, Hard rock mass tolerates deformation to a greater extent, so it takes a long time to accumulate energy before releasing energy once.
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Chen Guochang said, therefore, such a hard rock formation has an obvious characteristic. Generally speaking, the first earthquake is the main shock. For example, today's magnitude 5.3 earthquake, if the energy release is not complete, it will continue to occur for the second or second time. For the 5th or 6th consecutive time, it will stop until the energy is released, and the aftershocks will be very few. For example, if there are 3 to 4 aftershocks within 14 minutes today, the probability of aftershocks will be very low. If there are no afternoon today Aftershocks, it is estimated that there will be no more tomorrow.
Chen Guochang also said that some opinions believed that the series of earthquakes were caused by faults in the Central Mountain Range, but he thought it was unreasonable because there is a certain distance and far from the Central Mountain Range. In addition, the fault section of the Central Mountain Range is very steep, and it is impossible to It is this sequence of earthquakes that is only 7 kilometers deep.