Weekly Earthquake Information 2022.4.10 Frequent earthquakes with seismic intensity 4 in eastern Aichi Prefecture, etc. 6 times in the past week –Weathernews

2022/04/10 10:47 Weathernews

The number of earthquakes observed in Japan in the past week has decreased slightly compared to the previous week.

The epicenters are dispersed over a wide area from Tohoku to Okinawa. There have been many earthquakes with a seismic intensity of 3 or higher, and they have occurred eight times. It has occurred 5 times or more for 5 consecutive weeks. (April 4th to April 10th at 10:00)

Domestic: M4.7 seismic intensity 4 observation in eastern Aichi prefecture for the first time in three and a half years

Earthquake in eastern Aichi Prefecture

Around 9:30 on the 7th (Thursday), there was an earthquake with an epicenter in the eastern part of Aichi prefecture, with a magnitude of 4.7 and an estimated depth of 11km. Due to this earthquake, we have observed shaking with a maximum seismic intensity of 4 in Shinshiro City, Aichi Prefecture, a seismic intensity of 3 in Toyohashi City, Toyota City, and Gamagori City, and a seismic intensity of 2 in Nagoya City.

The mechanism of the earthquake is a reverse fault type with a pressure axis in the east-west direction, and it is analyzed that it has a slight strike-slip component. It is the first time in regarding three and a half years since October 7, 2018 that an earthquake with a maximum seismic intensity of 4 or more originated in the eastern part of Aichi Prefecture.

Although there are no known active faults near the epicenter, large earthquakes have occurred in the eastern part of Aichi prefecture in the past. On March 16, 1997, a magnitude 5.9 earthquake occurred at a depth slightly deeper than this time, and a maximum seismic intensity of 5 upper was observed. It is known from historical sources that an earthquake with a magnitude of 6.5 to 7.0 occurred in 715 and an earthquake with a magnitude of 7.0 occurred in 1686.

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 magnitude 7.3 earthquake 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: Seismic intensity 4 occurs 6 times in a week

Recent earthquakes with a seismic intensity of 4 or higher

During this period, there were six seismic intensity 4 earthquakes, including the aforementioned eastern Aichi prefecture earthquake. There were many earthquakes, four times the previous week and three times the previous week.

The epicenter of the 13 earthquakes is divided into 10 areas, and the same epicenter has occurred multiple times only off the coast of Fukushima prefecture and in the Noto region of Ishikawa prefecture. (Note: A series of activities can be seen in the Noto region of Ishikawa prefecture and off the Noto Peninsula, although the names of the earthquake centers are different.) Although the number is large, the magnitude of the earthquake is not so large, and magnitude 5 or more is only 4 times, and magnitude less than 4.5. It is 6 times.

While it is unlikely that these individual earthquakes are directly related to each other, it can be said that the Japanese archipelago, which is located at the boundary of the four plates, is an earthquake-prone area. Current science cannot predict the occurrence of a major earthquake with the accuracy of meteorological prediction. It is important to be prepared on a regular basis so that you will be safe in the event of a major earthquake.

Domestic: M4.4 in southern Kyoto

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 a little over 4-5. It is necessary to be careful regarding strong shaking for a while.

World: M4.7 earthquake in Poland

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

Two earthquakes with a magnitude of 6 or greater have occurred, as analyzed by the United States Geological Survey. The largest earthquake was a magnitude of 6.3 in the waters near Vanuatu.

The earthquake we are paying attention to this time is the one that occurred in Poland. An earthquake with a magnitude of 4.7 and an estimated depth of regarding 8 km occurred in the southwestern part of Poland before dawn on the 8th (Friday) of Japan time. The mechanism of the earthquake is unknown.

Poland is located on the Eurasian plate and is a country with few earthquakes. However, in the southwestern part near the epicenter this time, earthquakes with a magnitude of around 5 occasionally occur. In 1983, there was a rather strong earthquake with a magnitude of 5.8, and the surrounding area was hit by strong tremors. In 2016, the earthquake killed a mine in the suburbs.

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.