Ishikawa Pref. Fault May Have Ruptured over Wide Area, Triggering More Quakes

The Yomiuri Shimbun

Epicenters for the quakes that have rocked the Noto region in Ishikawa Prefecture since Monday evening have stretched over some 130 kilometers. Quakes used to strike mostly along an about 30-kilometer length running northeast to southwest at the tip of the Noto Peninsula.

“A fault extending into the sea shifted over a roughly 100-kilometer length,” said Shinji Toda, a professor of seismology at Tohoku University. The fault’s long rupture may have brought more seismic activity in its wake.

The Noto region has had more than 600 earthquakes that could be felt since December 2020.

In May last year, the region was hit by a powerful earthquake that registered a magnitude of 6.5 and an upper 6 on the Japanese seismic intensity scale of 7.

The quake that struck Monday with a magnitude of 7.6 was the strongest temblor for the area since the Japan Meteorological Agency began keeping records in 1885.

The series of jolts in the region are thought to have been caused mainly by the movement of water-like fluid underground that made it easier for the fault to slip.

A total of 653 earthquakes of intensity 1 or greater have shaken the region over the past three or so years to 9 a.m. Tuesday, including 147 that took place on Monday and Tuesday.

It is not clear when the quakes will subside. The agency has said people should be cautious even in areas that experience few quakes.