A car crushed by a collapsed house, a huge rock hitting a house.
On May 5, a massive magnitude 6.5 earthquake struck the Noto Peninsula. Suzu City in Ishikawa Prefecture was hit with an intensity of 6 on the Japanese seismic scale. The chief priest of a temple in Shoinmachi, Suzu City, was horrified.
There was another big earthquake on the Noto Peninsula in June of last year, but this time it was much more intense than that. It felt as if it was being pushed up from below, and the horizontal shaking lasted for a long time. Many Buddhist statues and gravestones in the main hall collapsed. It is very eerie.”
Since the end of 2008, more than 300 earthquakes have occurred in the Noto Peninsula area. Toshihiro Shimoyama, Earthquake Information Planning Officer of the Japan Meteorological Agency, who held a press conference that evening, pointed out that “fluids (such as groundwater) may have been involved. It is believed that hot, high-pressure water pushed up the bedrock and entered a gap in the fault line, triggering the earthquake. Manabu Takahashi, a specially-appointed professor at Ritsumeikan University’s Center for Pacific Rim Civilizations, said, “Underground temperatures are generally higher in the Pacific Ocean than in the Pacific Ocean.
The temperature of the subsurface generally rises by about 3°C for every 100 m drop. In places like the Noto Peninsula, where a plate (a huge bedrock) is plunging 300 to 500 km underground, the temperature is extremely high. Fluid does not mean liquid water.
Geophysicist Hidenori Shimamura, a professor at Musashino Gakuin University, agrees.
I think the fluid underground is magma,” he said. The Noto Peninsula used to be an earthquake swarm zone. However, there is a danger that rising magma could cause major tremors even in areas that have not been hit by major earthquakes before.
The fear of a massive earthquake is creeping across the Japanese archipelago. Along with the magma, the movement of the Pacific Plate to the east of Japan, which triggered the Great East Japan Earthquake, is also eerie.
The Pacific Plate is moving from east to west, which is causing other adjacent plates to become more active. The Noto Peninsula earthquake occurred at the boundary between the North American plate, which is compressed by the Pacific plate, and the Eurasian plate further to the west. Similar to the Noto Peninsula, there are other areas that require caution. The boundary between the Philippine Sea Plate, which is also under pressure from the Pacific Plate, and the Eurasian Plate,” said Takahashi.
The boundary in question covers a wide area from the Philippines to Okinawa and the Sagami Trough (an oceanic trench off the southern Kanto region). In fact, M7-class earthquakes have occurred in the Philippines and around the main island of Okinawa. The impression is that it is propagating from the south to the east. Takahashi continues.
If a huge earthquake were to occur in the Nankai Trough (the trench off the coast of Shikoku to the Tokai region), which is on the borderline, the government predicts that more than 320,000 people would be killed. This is not a tragedy in the distant future. Based on past examples, there is a strong possibility that it will happen at least within a few years. The Sagami Trough, which triggered the Great Kanto Earthquake, is also in imminent danger of an earthquake. The Tokyo metropolitan area will also suffer tremendous damage, and the total casualties will amount to more than half a million people.”
The massive earthquake that struck the Noto Peninsula is by no means an isolated event. An unprecedented earthquake of far greater power could devastate the Tokyo metropolitan area at any time.
From the May 26, 2023 issue of FRIDAY
PHOTO： Junpei Kota