It has been 26 days since the earthquake that observed severe shaking with a seismic intensity of less than 6 in the Noto region of Ishikawa prefecture.
Although seismic activity continues to be active in the Noto region, experts familiar with active faults have pointed out that it is necessary to prepare for larger earthquakes and tsunamis caused by surrounding active faults.
Number of earthquakes per year Average 23 → 8000
In the Noto region, there was a magnitude 5.4 earthquake in Suzu City on the 19th of this month, observing a seismic intensity of 6 lower, and active seismic activity has continued since then.
Professor Shinji Toda of Tohoku University, who is familiar with the mechanism of earthquakes and active faults, analyzed changes in earthquakes with a magnitude of 1 or more around Suzu City.
▽ From January 1988 to November 1988, before seismic activity became active, the average number of earthquakes per year was about 23, while
▽ activity became particularly active from July last year to 22nd this month. Until then, the annual average was about 8,000 times, which
is about 350 times higher than the annual average.
Strain accumulation due to small earthquake increase “Be careful of larger shaking”
According to Professor Toda, when small earthquakes increase, strain accumulates underground and affects the surrounding active faults, making it easier for larger earthquakes to occur.
Professor Toda says, "If seismic activity continues, there is a possibility that an earthquake with a magnitude of 5.4 or more will occur the other day. We need to be careful about larger shaking."
Active fault off the Noto Peninsula
On the other hand, according to the survey conducted by the National Institute of Advanced Industrial Science and Technology, active faults have been found intermittently in the four sections east and west off the northern coast of the Noto Peninsula.
It is analyzed that a magnitude 6.9 earthquake occurred in the western section in 2007, and the epicenter of the earthquake on the 19th of this month is about 5 km away from the easternmost section.
Yukinobu Okamura, an honorary researcher at the National Institute of Advanced Industrial Science and Technology, who is familiar with active faults, said, "This earthquake is not caused by active faults, and it is unknown at this point how much it will affect active faults in the future."
On top of that, "If there is an active fault, a big earthquake can occur eventually. Since there are many mechanisms called" reverse faults "that uplift the Noto Peninsula side on the seabed, it is necessary to be alert to tsunamis. I want you to be aware of the risks of earthquakes and tsunamis throughout the Noto Peninsula. "
When the active fault shifts, the height of the tsunami is
What kind of tsunami will occur if the active fault shifts?
The Earthquake Research Institute, the University of Tokyo, etc. conducted a survey of possible earthquakes and tsunamis on the Sea of Japan side in eight years until last year as part of a national research project. I also simulated.
When multiple faults are linked and shift over about 84 km, the magnitude is 7.3, and the maximum tsunami height is
about 2.9 meters in Wajima City ,
, about 2.5 meters in Noto Town, and
It was said to be about 2.3 meters in the city.
In addition, it is said that a tsunami of about 1 meter will come along the coast from Akita prefecture to Fukui prefecture.
The characteristic of the tsunami on the Sea of Japan side is that it reaches the land in a short time, and even if it occurs off the coast of the Noto Peninsula, the tsunami will flood the Noto region in a short time of a few minutes.
Rhagades in a part of paddy field dry up and affect rice cultivation
In Suzu City, a crack has occurred in a part of the paddy field and the water has flowed out, which has affected rice cultivation.
In a paddy field owned by an agricultural corporation in Wakayamamachi, Suzu City, a crack with a length of about 20 meters was created on the ground due to the impact of the earthquake that observed the shaking with a seismic intensity of 6 lower on the 19th of this month.
According to the agricultural corporation, the water that had spread in the paddy fields flowed out due to this effect, and it is now dry.
The water flowed out to about 1000 square meters, which means that we will give up on rice cultivation in this area.
Hiroshi Suemasa, CEO of the agricultural corporation "Suehiro", which owns the paddy fields, said, "I was worried that the rice fields would be damaged someday because the earthquake continued. I'm worried that another earthquake will cause further damage. "
Check the state of the parents' house on the weekend
In Suzu City, the temperature became harsh at over 30 degrees Celsius from the morning.
Before the 26th day after the earthquake that observed the shaking with a seismic intensity of 6 lower, I was worried that my family living outside the city would be suffering from a series of earthquakes during the weekend break, so my parents' house I was seen coming to see the situation.
A woman in her thirties who came to see the state of her parents' house from Kanazawa said, "I'm trying to help because I live only with elderly parents and the inside of the house is not tidy, but I think that it is difficult to work because it is hot. I want to get rid of it little by little while taking a break. "
In addition, a man in his 50s who rushed to his parents' house from Nagoya city said, "I came to see my parents during the holidays. The fence in front of my house had collapsed, so I asked an acquaintance's contractor to repair it. It is said that the earthquake will continue, and I am worried about the heat and heavy rain, which may lead to more serious damage. "Keywords: