Understanding Tsunami Predictions and Preparedness: The Case of Ishikawa Prefecture, Japan

2024-01-02 21:00:00

Residential area believed to have been damaged by the tsunami: 2:20 p.m. on the 2nd in Hodate-cho, Suzu City, Ishikawa Prefecture (Photo taken from the headquarters’ helicopter “Wakazuru”)

The Japan Meteorological Agency issued a major tsunami warning (5 meters) immediately following the earthquake occurred on the evening of the 1st. However, the largest tsunami actually observed was “more than 1.2 meters” at Wajima Port (Ishikawa Prefecture), and less than 1 meter at all other observation points. It seems that many people are saying that the predictions were too much, but experts say, “In the past, earthquakes of similar magnitude that occurred along the coast of the Sea of ​​Japan caused large tsunamis of several meters in height.” “This earthquake might have turned into a much larger tsunami, depending on the location of the fault that moved.”

◆ Major tsunami warning announced immediately following, unavoidable

A major tsunami warning is issued when a tsunami exceeding 3 meters is predicted. If the predicted maximum wave is less than 5 meters, the upper limit is indicated as “5 meters,” and if it is even larger, it is written as “10 meters” or “more than 10 meters.”

The scale of this earthquake was magnitude (M) 7.6.In the 1964 Niigata earthquake (M7.5), a tsunami of approximately 3 to 5 meters in height surged onto the coast. In the 1983 Chubu Japan Sea Earthquake (M7.7), a tsunami of up to 5 to 6 meters in height struck the coastal areas of Akita and Aomori prefectures, and the number of casualties from the tsunami alone reached 100.

It is said that there is an undersea fault running northeast to southwest off the northern coast of the Noto Peninsula. Meanwhile, swarms of seismic activity that are thought to be related to groundwater have continued at the tip of the Noto Peninsula since around the end of 2020. There were concerns that if a swarm of earthquakes triggered activity in submarine faults and caused them to shift significantly, a major earthquake might occur accompanied by a tsunami.

Akio Yoshida, visiting professor at Shizuoka University (seismology), said, “It was unavoidable that a major tsunami warning was issued immediately following the earthquake (we don’t know exactly where and how the fault moved). The fault that occurred was not an undersea fault as expected, but a fault that ran directly under the Noto Peninsula, so the crustal deformation of the sea floor that caused the tsunami may have been smaller than expected. Point out. (Akihiko Usami)


1704252297
#Experts #warn #concerns #largescale #tsunami #warnings #overpredicting