A magnitude 5.9 earthquake that struck off the coast of southeastern Taiwan yesterday had nothing to do with a rare transit of Venus in front of the sun on the same day, according to a local seismologist.
“Some people believe that the gravitational pull between planets might trigger an earthquake, but Venus is too far away for its gravity to cause a tremor on the Earth,” said Shih Ruey-chyuan (石瑞銓), an associate professor with National Chung Cheng University’s Graduate Institute of Seismology.
Earthquakes here simply reflect the island’s geography, Shih said, because Taiwan is located in a region where the Philippine Sea Plate borders the Eurasian Plate.
“Seas off the eastern Taiwan coast are especially vulnerable to earthquakes, and [yesterday’s] tremors in the region were normal releases of energy that were completely unrelated to the rare transit of Venus earlier in the day,” he said.
Also, atmospheric pressure only has an effect up to 4m beneath the ground, but the earthquake struck at a depth of 16.6km.
“Therefore, we don’t have to spend time thinking about whether the tremor had anything to do with the transit of Venus,” he said.
According to the Central Weather Bureau’s Seismological Center, four earthquakes, including one of magnitude 5.9, struck Taiwan yesterday. No casualties or damage were immediately reported.
The four tremors shook Taiwan’s southeastern coast near Taimali Township (太麻里) in Taitung County between 9:08am and 10:24am.
The magnitude 5.9 earthquake hit first, with its center located at sea about 49.9km southeast of Taitung City at a depth of 16.6km, the center said.
It was followed by a magnitude 4.7 tremor at 9:10am and two magnitude 4.8 aftershocks at 10:09am and 10:24am respectively.
The first temblor swayed buildings in Taitung County for more than 10 seconds. The magnitude 5.9 quake was felt throughout Taiwan, with intensity levels reaching 4 in Taitung and on Green Island (綠島).
The Seismological Center said the four tremors struck in the area where the Philippine Sea Plate borders the Eurasian Plate. The transit of Venus, in which the planet passes across the face of the sun and appears as a small dark disk from Earth, began at 6:11am and lasted into the early afternoon.
It was widely believed in ancient China that the “heavens” could alert people to a major calamity through special celestial events or special astronomical signs, and some continue to make such connections today.
However, the connections are haphazard because many natural seismic events actually go unnoticed unless they cause serious human casualties, Shih said.
Four earthquakes of magnitude 8 or above occurred in various parts of the world in 2007, for example, but none of them drew attention because their centers were located in uninhabited areas or under water, he said.
The seismologist further cited the absence of any special celestial event ahead of the devastating earthquake and subsequent tsunami that struck Japan on March 11 last year, to disprove the notion that the “heavens” alert people to natural catastrophes with rare or special celestial events.