Weekly Earthquake Information 2022.3.27 The activities of Ishikawa and Noto, which continue the earthquake off the coast of Fukushima Prefecture, are also active –Weathernews

2022/03/27 10:48 Weathernews

The number of earthquakes observed in Japan in the past week has decreased compared to the previous week, but it remains at a high level.

Many earthquakes continue on the Pacific coast of Tohoku, and earthquakes are conspicuous on the Pacific side of Hokkaido and northwest of Okinawa. Seven earthquakes with a seismic intensity of 3 or higher have occurred. (Aggregation from March 21st to 27th at 10:00)

Domestic: Earthquake with seismic intensity 4 off the coast of Fukushima Prefecture

Earthquake off the coast of Fukushima Prefecture

Around 12:08 on the 25th (Friday), there was an earthquake with a magnitude of 5.2 and an estimated depth of 52km with the epicenter off the coast of Fukushima Prefecture. With this earthquake, we have observed shaking with a maximum seismic intensity of 4 in Okuma Town, Futaba Town, and Namie Town, Fukushima Prefecture, and a seismic intensity of 3 in Koriyama City, Fukushima Prefecture, Iwaki City, Shirakawa City, Ishinomaki City, Miyagi Prefecture, and Iwanuma City.

The mechanism of the earthquake is analyzed as a reverse fault type with a pressure axis in the west-northwest-east-southeast direction, which is the same as the earthquake with a magnitude of 7.4 and a maximum seismic intensity of 6 upper that occurred at midnight on Wednesday, 16th. However, there is a possibility of another activity because it is a little south of the area where followingshocks are concentrated.

Although it has been more than a week since the strong earthquake off the coast of Fukushima and Miyagi prefectures, the frequency of earthquakes with a magnitude of 4 to 5 is high, so caution is still required.

Mechanism similar to last February

The mechanism of the earthquake is analyzed as a reverse fault type with a pressure axis in the west-northwest-east-southeast direction. This is the first earthquake to observe shaking with a seismic intensity of 6 or higher since the earthquake of magnitude 7.3 that occurred off the coast of Fukushima Prefecture in February last year.

The epicenter of this earthquake is almost the same as that of February last year. The magnitude and mechanism of the earthquakes are very similar, and it seems that the earthquake occurred inside the subducting Pacific plate.

Looking at each seismic activity, the February last year’s earthquake (blue) is distributed on the southwest side of the epicenter, while this earthquake (red) is distributed in the northeast direction. It is probable that adjacent fault planes caused similar ruptures on a similar scale.

Domestic: Continued seismic activity in Noto region, Ishikawa prefecture

Earthquake in Noto region, Ishikawa prefecture

Around 9:23 on the 23rd (Wednesday), there was an earthquake with a magnitude of 4.3 and a depth of 14km with the epicenter in the Noto region of Ishikawa prefecture. A maximum seismic intensity of 4 has been observed in Suzu City, Ishikawa Prefecture due to this earthquake.

In the northern part of the Noto Peninsula, where active activity has continued since last spring, the number of earthquakes has increased slightly since March. Seismic intensity 3 and seismic intensity 4 occurred twice on March 8th, and seismic intensity 3 or higher occurred twice in this earthquake, which is the 5th time.

It is difficult to predict what will happen to seismic activity in the future. Please keep in mind that there is a possibility of an earthquake with a maximum seismic intensity of 4 to 5 lower, mainly in Suzu City, Ishikawa Prefecture, which is close to the epicenter.

Domestic: Earthquake swarm from Saturday, 4th in the Tokara Islands

Earthquakes have occurred frequently in the sea near the Tokara Islands in the Amami region of Kagoshima prefecture from around noon on the 4th (Sat). The first felt earthquake had a magnitude of 2.9 and a maximum seismic intensity of 1 at around 12:32 on Saturday, 4th, and an earthquake of magnitude 4.0 and a maximum seismic intensity of 3 occurred at 19:48. After that, the earthquakes continued, and as of 10 o’clock on the 5th (Sun), there were 87 felt earthquakes, of which 6 were earthquakes with a seismic intensity of 3.

These earthquake swarms often occur in the waters near the Tokara Islands. Recently, earthquakes have occurred frequently since April 9th ​​this year, and on April 10th, more than 100 felt earthquakes occurred in one day. During the three days from the 10th to the 12th, which was the peak of activity, we observed 229 felt earthquakes, 15 seismic intensity 3 and 5 seismic intensity 4.

In many cases, the active situation from past activities lasts for several days, and the maximum seismic intensity may reach 4 to 5 or higher. It is necessary to be careful regarding strong shaking for a while.

World: Shake equivalent to M6.7 seismic intensity 6 lower near Taiwan

World M4.5 and above earthquakes (USGS homepage quote / Weathernews processing)

Four earthquakes with a magnitude of 6 or greater have occurred, as analyzed by the United States Geological Survey. The largest earthquake was the magnitude 7.3 off the coast of Fukushima Prefecture mentioned above. (The magnitude of the earthquake is different from the analysis by the Japan Meteorological Agency)

An earthquake with a magnitude of 6.7 and an estimated depth of regarding 24 km occurred near Taiwan on the early morning of Wednesday, 23rd Japan time. The mechanism of the earthquake is analyzed as a reverse fault type with a pressure axis in the northwest-southeast direction.

According to the Central Weather Bureau of Taiwan, a seismic intensity of 6 lower was observed in Changbin, Taitung County, a seismic intensity of 5 lower in Hualien County, and a seismic intensity of 4th grade in a wide area of ​​Taiwan. Taiwan’s seismic intensity class has a total of 10 levels of seismic intensity 0-4, 5 weak, 5 strong, 6 weak, 6 strong, and 7 grade. Although the calculation process is slightly different from the Japan Meteorological Agency seismic intensity class, it is a very similar class.

The area around Taiwan is on the border between the Philippine Sea Plate and the Eurasian Plate, and is often hit by large earthquakes. In recent years, an earthquake with a magnitude of 7.7 occurred in 1999, causing enormous damage.

M5.0 earthquake in the middle of Africa

An earthquake with a magnitude of 5.0 and an estimated depth of regarding 10 km occurred in Congo, Africa, before noon on Wednesday, 26th Japan time. The epicenter of this earthquake is on the west side of the area called the “Great Rift Valley”.

Most African earthquakes occur around the Great Rift Valley. The African Continent is made up of African plates, and the Great Rift Valley is thought to be the area where the plates are being torn. In its activities, it has caused earthquakes, and in the past, magnitude 7 class earthquakes have also occurred.

Reference materials, etc.

* Information on the epicenter and seismic intensity in Japan is from the Japan Meteorological Agency unless otherwise stated. Information on overseas epicenters is from the United States Geological Survey (USGS) unless otherwise stated. The epicenter information may differ depending on the issuing organization.