Taipei and the coastal regions of northern Taiwan are less likely to be hit by a strong earthquake than other parts of the country, a local seismologist said.
“The Earth’s crust under Taipei and the coastal areas of north Taiwan, where three of the country’s four nuclear power plants are located, is only 30km thick, far less than beneath the Central Mountain Range,” said Wang Chien-ying (王乾盈), a professor at National Central University’s Graduate Institute of Geophysics.
The thickness of the continental crust beneath the Central Mountain Range, which makes up two-thirds of the land surface in central and southern Taiwan, is 45km, exceeding the world’s average crustal thickness of 35km, Wang said.
“The figure indicates that the Earth’s crust beneath the Central Mountain Range is still being squeezed by the Eurasian and Philippine plates and is consequently less stable,” Wang said.
“This means that the areas near the mountain range are more prone to be hit by earthquakes,” he added.
In comparison, the crustal thickness under Taipei and northern coastal areas is about 30km, which indicates that mountain formation in these areas has entered a stable period and they are thus less likely to be struck by major earthquakes, he said.
The possibility of the Tatun (大屯) volcano group on the outskirts of Taipei causing big earthquakes is very low because Tatun volcanoes are just small hills in the Earth’s subduction zone, which means they are unlikely to become active or grow into mountains, Wang said.
The Earth’s crust beneath the plain and basin areas in Taiwan is less than 30km thick, which suggests that only mild or moderate earthquakes may occur in those areas, he said.
Wang’s research team reached the conclusions after eight years of study in a joint project with the US that was financed by the National Science Council.
Wang said the height of a mountain depends on the thickness of the Earth’s crust beneath it.
The thickness of the crust beneath the Himalaya Mountains, for instance, is 80km, which allows some of its peaks to stand 8,000m above sea level, Wang said.
With the absence of advanced measuring tools, Wang said, Taiwan has previously had difficulty correctly measuring the thickness of the crust beneath its major mountains.
“Through cooperation with the US, we managed to determine the crustal thickness under our major mountains,” Wang said.
The data will allow seismologists to more accurately forecast the areas that may experience strong tremors during a major earthquake, he said.
Such data is useful when selecting a site for facilities such as nuclear power plants or reservoirs, he added.