On the morning of the 4th, there was a magnitude 4.3 earthquake with an epicenter in the Noto region of Ishikawa prefecture, and a seismic intensity 4 tremor was observed in Suzu city, Ishikawa prefecture.
Seismic activity has been active in the Noto region since December 2020.
What the hell is going on ...
Earthquakes one after another
According to the Japan Meteorological Agency, there was a magnitude 5.1 earthquake last September, and we observed shaking with a seismic intensity of less than 5 in Suzu City.
Since then, seismic activity has been active, and the number of earthquakes with seismic intensity 1 or higher has increased sharply to 6 in January, 6 in February, and 22 last month.
Even in April, there were three earthquakes with a seismic intensity of 1 or higher only on the morning of the 4th, and we observed shaking with a seismic intensity of 4, seismic intensity 3, and seismic intensity 2, respectively.
Uplift of the ground continues slowly
Crustal movement has been pointed out as a related matter.
In the Noto region, uplift of the ground has been observed since the time when seismic activity became active.
Crustal movements have continued slowly even after entering, and the ground has risen by more than 3 cm so far at the observation point in Suzu City.
"Some fluid" flows in ...
According to Associate Professor Takuya Nishimura of the Kyoto University Disaster Prevention Research Institute, who specializes in crustal movements, it is rare to observe such changes in places where there are no volcanoes around, and some fluid flows into a place deep underground about a dozen kilometers. It is said that it may lead to crustal movements and seismic activity.
Regarding "some kind of fluid," Associate Professor Nishimura says that it is possible that water separated from the rocks of the plate that sank deep underground from the Pacific Ocean side and rose, but the details are unknown.
Kyoto University and Kanazawa University are observing detailed crustal movements by increasing the number of temporary observation points on the Noto Peninsula, and research is also underway to investigate the underground structure using magnetism.
Since crustal movements are still ongoing, Associate Professor Nishimura wants us to reconfirm our preparations for sudden shaking, saying that there is a possibility that a large-scale earthquake will continue to occur in the Noto region.
"A series of seismic activities are expected to continue for the time being"
The government's seismic investigation committee has also summarized the view that "a series of seismic activity is expected to continue for the time being, considering the situation of seismic activity and crustal movements."
Professor Emeritus Naoshi Hirata of the University of Tokyo, chairman of the Earthquake Research Committee, has revealed that the mechanism has been discussed among experts.
After the regular committee meeting held in March, "It is strongly suggested that the Noto Peninsula captures crustal movements that cause the ground to swell and is related to seismic activity, but it is clearly known. That's it. There are several indications that the mechanism is due to the movement of water underground, the spread of cracks in the sea ditch, and the movement of faults, but the consensus is that it cannot be traced from the current observation data. " I'm talking.
The Japan Meteorological Agency also said that seismic activity is expected to continue, and is calling for "preparation for strong shaking, such as fixing furniture and removing items that are prone to fall or placed on high places."Keywords: