Just after 9 a.m. on March 21st, an earthquake with a seismic intensity of lower 5 was observed in Tochigi and Saitama prefectures. It is the first time since March 16, 2022 that a tremor with a seismic intensity of lower 5 was observed in Tochigi Prefecture, and since October 7, 2021 in Saitama Prefecture. We asked experts about this earthquake.
A seismic intensity of lower 5 was observed in Shimotsuke City and Kazo City.
According to the Japan Meteorological Agency, there was a magnitude 5.3 earthquake with its epicenter in southern Ibaraki Prefecture at around 9:08 a.m. on the 21st.
As a result of this earthquake, shaking with a seismic intensity of lower than 5 was observed in Shimotsuke City, Tochigi Prefecture and Kazo City, Saitama Prefecture. There was no tsunami caused by this earthquake.
〇Tochigi Prefecture Past Earthquakes
According to the Japan Meteorological Agency, the last time a magnitude 7.4 earthquake was observed in Tochigi Prefecture was on March 16, 2022 off the coast of Fukushima Prefecture. I observed shaking.
〇Saitama prefecture past earthquakes
In addition, the last time a magnitude 5 earthquake was observed in Saitama Prefecture was on October 7, 2021, when a magnitude 5.9 earthquake with an epicenter in northwestern Chiba Prefecture occurred.At this time, a tremor with a magnitude 5 magnitude was observed in Kawaguchi City, Saitama Prefecture. Did.
“Beware of earthquakes with a maximum seismic intensity of lower 5 for about a week”
According to the Japan Meteorological Agency, the epicenter was at a depth of 46 kilometers, and the earthquake appears to be at the boundary where the Philippine Sea plate subducts beneath the land-side plate, and is a type of earthquake known as a “reverse fault,” where the plates shift as they push against each other. is.
The Japan Meteorological Agency warns that areas with strong shaking may be more susceptible to rockfalls and landslides, and is urging people to be careful about earthquakes with a maximum seismic intensity of 5-lower for about a week.
Professor Emeritus Nao Hirata, University of Tokyo (Chairman, Government Earthquake Research Committee)
“The southern Kanto region, including the southern part of Ibaraki Prefecture, where the epicenter was, is a place where earthquakes with tremors of about 5 on the seismic intensity scale frequently occur. Be careful of earthquakes of similar magnitude over the next few days, especially the next few days. Please also refer to information from the Japan Meteorological Agency regarding the status of seismic activity.If you live in a house that has not been made earthquake resistant, there is a risk that the building will be affected, so please move to a safe place.”
What to watch out for when shaking in urban areas
According to the Japan Meteorological Agency, in general, when a tremor with a magnitude of 5 or lower occurs, dishes and books on shelves may fall, and unstable items such as unsecured furniture may fall. In addition, when outdoors, shaking can cause cracks in the ground, falling rocks, and landslides. Avoid getting close to dangerous places such as objects that can easily fall or near cliffs.
Indoors, if there are broken dishes or glass, there is a risk of unexpected injury when cleaning up. Don’t overdo it and always wear slippers or shoes when walking indoors.
When the elevator stops
Also, if the elevator stops in an emergency in a city, please press and hold the emergency button that connects to the outside. Even if you cannot connect immediately, it is important to try again and again without giving up.
Also, making sounds is an effective way to let the outside world know that you are trapped. If you hit it with a hard object, it will be easier to hear outside, and if you use a whistle, it will make a loud sound.
Expert “Considered to be conventional seismic activity”
We asked Professor Kenji Satake of the Earthquake Research Institute, the University of Tokyo, about this earthquake, in which shaking with a seismic intensity of lower 5 was observed in Tochigi and Saitama prefectures.
Professor Kenji Satake, Earthquake Research Institute, University of Tokyo
“The Kanto region is subducted by the Pacific Plate from the east and the Philippine Sea Plate from the south, so earthquakes occur in various locations and depths. Ibaraki Prefecture is also an area where many earthquakes occur, Considering the magnitude of the earthquake, it is not that rare.There is no connection with the Tokyo Metropolitan Earthquake, the Noto Peninsula Earthquake, or the earthquake off the eastern coast of Chiba Prefecture, and it is considered to be conventional seismic activity. I want you to proceed with your preparations.”
The national estimate for an earthquake directly hitting the capital is
The underground structure of the southern Kanto region is complex, with the Philippine Sea Plate and the Pacific Plate subducting beneath the land plate called the North American Plate, and the mechanisms of earthquakes vary.
The Tokyo Metropolitan Earthquake is a magnitude 7 class earthquake that occurs at the boundary between the Philippine Sea Plate and the North American Plate, or within each plate, and a magnitude 8 class earthquake that occurs at the boundary between the Philippine Sea Plate and the North American Plate. Refers to the class earthquake.
Of these, the government estimates that there is a 70% probability that a magnitude 7 class earthquake will occur within the next 30 years.
According to the Japan Meteorological Agency, this earthquake occurred at the boundary between the Philippine Sea Plate and the North American Plate. On social media, there are many posts saying, “I thought it was an earthquake directly hitting the Tokyo metropolitan area,” but the magnitude was 5.3, which is significantly different from the earthquake directly hitting the Tokyo metropolitan area.
Experts also say that this earthquake is conventional seismic activity and is not related to the Tokyo earthquake.
100 years have passed since the Great Kanto Earthquake: prepare again
On the other hand, last September marked 100 years since the Great Kanto Earthquake, and it has been pointed out that an earthquake directly hitting the Tokyo metropolitan area could occur at any time.
Taking advantage of this earthquake, it is important to take another look at your home’s stockpiles, secure furniture, and discuss with your family what to do in the event of an earthquake.