Analysis Shows Tsunami Hit Suzu 1 Minute After Quake

The Yomiuri Shimbun
In this aerial view, a coastal area of Suzu, Ishikawa Prefecture that was hit by tsunami is seen on Tuesday.

The first tsunami may have reached the city of Suzu, Ishikawa Prefecture, only one minute after the earthquake that hit the Noto region of the prefecture on Monday, according to an analysis by Tohoku University researchers.

As data transmission from the Japan Meteorological Agency tide gauge set up in the city was interrupted immediately after the earthquake began, details of the situation were initially unclear. The university’s analysis shows that the tsunami reached the city before the residents started to evacuate.

According to the agency, after the earthquake which occurred at around 4:10 p.m. on Monday, Ishikawa Prefecture’s Wajima City was hit by a tsunami of over 120 centimeters and Nanao City was hit by one that was 50-centimeters-high, while an 80-centimeter-high tsunami was recorded in Toyama City, Toyama Prefecture. No data was available for Suzu.

Tohoku University Prof. Fumihiko Imamura, an expert on tsunami engineering, used a computer to simulate conditions at locations where 50 centimeter or higher tsunami reached, based on factors such as the fault that caused the earthquake.

The results showed that the first tsunami arrived in Suzu one minute after the earthquake. In Nanao, where the agency’s data indicated that the tsunami struck about 30 minutes later, the first wave may have arrived as early as two minutes after the earthquake.

The extremely quick arrival of these tsunami is believed to be because the fault that caused the earthquake is located near the coast. “Tsunami from earthquakes that occur along the Sea of Japan coast tend to arrive quicker than those on the Pacific Ocean side, so caution must be maintained in the future,” Imamura said.

Meanwhile, analysis has also revealed that a large-scale landslide may have occurred on Toyama Bay’s seafloor at about the same time as the earthquake. In Toyama City, it was calculated that tsunami should have arrived five minutes after the quake at the earliest under normal circumstances, but they were observed immediately after it happened.

Toyama Bay has steep slopes on its seafloor, and a large-scale seafloor landslide also occurred in the 2007 earthquake that hit the Noto Peninsula.