Hualien quakes sign that Taiwan has entered 100-year earthquake cycle: Researcher

NCU professor postulates that Taiwan could experience a magnitude 8 earthquake within 10 years

The photo shows Taroko Gorge in Hualien, Taiwan (Crecit: mlqultos/ flickr)

TAIPEI (Taiwan News) -- A geology professor at National Central University (NCU) theorizes that the recent cluster of earthquakes around Hualien indicate that Taiwan is now entering a 100-year earthquake cycle in which major temblors on a scale of a magnitude 8 could occur within a decade. 

From Feb. 4 - Feb. 5, there were 71 earthquakes recorded coming from just off the coast of Hualien, with 12 occurring in a single hour, the largest of which was a magnitude 5.8 temblor. 

In an interview with ETtoday, Lee Chyi-tyi (李錫堤), a professor at NCU's Graduate Institute of Applied Geology, said that earthquakes are cyclical and in the last century in Taiwan there were two quakes with a magnitude over 8: one in 1910, which was centered off the coast of Yilan and registered 8.3 on the Richter Scale, while and the other in 1920, which also registered a 8.3, was centered off the coast of Hualien. The country has already reached the centennial of one of the 1910 temblors and will soon reach the other in two years. 

Lee told ETtoday, "For the next 10 years in Hualien, The probability of a magnitude 8 earthquake occurring is high, and I predict that there will be another earthquake (similar in size) in 2025."

The multiple earthquakes that struck on Sunday, including the magnitude 5.8 quake, all originated from a relatively shallow depth of within 20 kilometers, therefore the effects were more obvious to the public, said Lee. 

Lee said that the multiple quakes experienced on Feb. 4 were part of an "earthquake swarm," which was caused by a small area experiencing great pressure and continued to "twitch" as tectonic forces continued to converge on the area. He said that the cluster of quakes makes it difficult to ascertain the pattern of the main earthquake,"and the quakes last night took place near sea cliffs and mountains beneath the ocean along a major fault line."

Lee said that the temblors were emanating from a rupture zone where the Philippine Sea Plate is subsiding under the Eurasian Plate. He said that, "Earthquakes are cyclical and it is about time again. I estimate that a magnitude 8 earthquake will strike in the next 10 years. This probability is too high and after 2/3 of the time (since the last major quake), the frequency of earthquakes will increase again."

Lee first put forward the theory that Taiwan has a hundred year cycle after a magnitude 5.6 earthquake struck off of Hualien on June 29, 2013. It was at this time that he theorized that the area off of Hualien where the Philippine Sea Plate and Eurasian Plate meet is on a 100 year cycle, with a magnitude 7.7 striking Hualien in 1815 and a magnitude 8.3 striking the same area in 1920. 

Seismological Center Acting Director Chen Kuo-chang (陳國昌) told the media at an exhibition commemorating the 2016 Taiwan earthquake today, that though he respects scholars, he said there is only a century's worth of data, therefore there are not other centuries to compare with to see a pattern. Chen added that the rupture zone where the Hualien quakes struck frequently sees earthquakes year in and year out, and the largest recorded earthquake in that particular rupture zone over the past 100 years was a magnitude of 5.8, the same as Sunday's quake. 

Though Chen also said the term "earthquake swarm" was being misused and that they would be better described as a sequence of aftershocks following a major quake, but he conceded that the 71 earthquakes reported in Hualien from Sunday through Monday were indeed a rare occurrence. He said that at one point, there were four successive earthquakes over a magnitude 5 reported within a single hour, representing a new record going back to 1972. 

When asked by the media whether the recent spate of quakes were a precursor of a major earthquake, Chen said that aftershocks could continue for up to two weeks, but based on long-term seismic observations, there are no signs of a major earthquake being imminent.