Second Significant Earthquake to hit Taiwan this Month

Earth Observatory Blog

Second Significant Earthquake to hit Taiwan this Month

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A magnitude-7.2 deep earthquake occurred offshore northeastern Taiwan on 31 May 2016. This is the second significant quake to have struck northern Taiwan this month, and it was powerful enough to generate strong ground motion throughout the whole of northern Taiwan.

The 31 May earthquake, that had occurred offshore northeastern Taiwan, rocked the entire northern Taiwan island. The coloured circles represent the different levels of ground-shake experienced in Taiwan, which are measured by Taiwan’s Earthquake Early Warning Network (Palert). The level of ground motion was strong enough to frighten residents in the building, but did not cause physical damage in the city (Source: TESIS)

Unlike the shallow Ilan earthquake that had occurred earlier this month on 12 May 2016, the Central Weather Bureau of Taiwan estimated the hypocentre of today’s M 7.2 earthquake to be located approximately 270 km below the seafloor. This suggests that this event is likely to have occurred at the northward subducting slab of the Philippine Sea Plate.

The collision and subduction of the Philippine Sea Plate with the Eurasian Plate are responsible for the creation of the island of Taiwan for the past several million years.

A deep earthquake usually generates widespread ground motions as compared to a shallow-focused earthquake event. This effect becomes evident when comparing the 12-May and 31-May earthquake events. Although both earthquakes occurred in, what may be considered to be, the same region, the 12 May Ilan earthquake generated smaller and more concentrated ground motions than the 31 May earthquake. The ground motion from the 31 May earthquake was so wide in spread that nearly all of Taiwan felt the power of this deep event.

The level of ground motion from the 12 May Ilan earthquake in eastern Taiwan was measured by Taiwan’s Earthquake Early Warning Network (Palert). Although the earthquake was much smaller than the 31-May earthquake, its proximimity to Taiwan and shallow earthquake hypocentre generated stronger shaking in Ilan. However, the 31 May earthquake’s felt areas were larger than the Ilan earthquake due to its deep hypocentre (Source: TESIS)

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Further reading:

U.S. Geological Survey significant earthquakes

Central Weather Bureau, Taiwan

Taiwan Earthquake Science Information System

 

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