2022/06/05 10:12 Weathernews
Earthquakes have occurred over a wide area from Hokkaido to Okinawa, and the number of earthquakes has increased from off Fukushima prefecture to off Miyagi prefecture and on the Noto Peninsula in Ishikawa prefecture. There were three earthquakes with a seismic intensity of 3 or higher. (Aggregation from May 30th to June 5th at 10:00)
Domestic: Seismic intensity 3 for the first time in regarding 8 months in the Kumamoto region of Kumamoto prefecture
Since September last year, there have been earthquakes with a seismic intensity of 3 or higher originating in the Kumamoto region of Kumamoto prefecture, and the mechanism of the earthquake has been analyzed as a strike-slip type. The earthquakes in the active area of the Kumamoto earthquake that occurred in 2016 have calmed down considerably, and there were 26 felt earthquakes with the epicenter in the Kumamoto region of Kumamoto prefecture last year, and as of the end of May this year. Only 8 times.
Domestic: Abnormal seismic area due to deep-focus earthquake in Enshu-nada
With this earthquake, seismic intensity 2 has been observed from Kanto to southern Tohoku, including Chiyoda Ward, Tokyo, Kasu City, Saitama Prefecture, Utsunomiya City, Tochigi Prefecture, Tochigi City, Mito City, Ibaraki Prefecture, Kasama City, and Shirakawa City, Fukushima Prefecture. On the other hand, in Tokai and Kinki near the epicenter, no shaking with a seismic intensity of 1 or higher has been observed.
It is a seismic intensity distribution called “abnormal seismic area” seen in the case of a deep-focus earthquake with a deep epicenter. Although it is said to be abnormal, it is often seen when a similar earthquake occurs, and it is not an abnormal phenomenon.
In deep-focus earthquakes, strong tremors are transmitted along the subducted plate, and there may be a phenomenon in which the tremors increase in the distance near the plate boundary, which is called the “abnormal seismic zone”. Even if the shaking is small in the vicinity of the epicenter, strong shaking may be transmitted to a distant place, so caution is required.
Domestic: Another earthquake with a seismic intensity of 3 in Noto, Ishikawa Prefecture
Seismic activity in Noto, Ishikawa Prefecture has been active, and earthquakes with a seismic intensity of 3 or higher have been occurring since May 20. This is the 13th time this year that the seismic intensity is 3 or higher, with the epicenters in the Noto region of Ishikawa prefecture and off the Noto Peninsula. Even in the 24-hour epicenter distribution until following 9 o’clock on the 5th (Sunday), including earthquakes with a seismic intensity of less than 1, earthquakes are occurring frequently in this area.
There is no sign that the activity will subside, so please continue to be prepared for shaking with a seismic intensity of 3 to 5 or less near the epicenter.
In the past, there was a M6.0 earthquake
Most of the earthquakes are concentrated around 10km in depth even in the east-west cross section. There are few occurrences deeper than 20km, but slightly more deeper than 100km. Earthquakes that occur near the boundary between the Pacific plate and the Eurasian plate or inside the Pacific plate.
Most deep-focus earthquakes have a magnitude of around 4, but in May 2014, a large-scale earthquake with a magnitude of 6.0 occurred. In this earthquake, a maximum seismic intensity of 5 lower was observed in Chiyoda-ku, Tokyo, and a shaking with a seismic intensity of 3 to 4 was observed over a wide area in the Kanto region, causing damage such as injuries.
World: M5.9 earthquake in Sichuan, China Damage caused by strong shaking
An earthquake with a magnitude of 5.9 and an estimated depth of regarding 10km occurred in Sichuan, China, on the evening of June 1st (Wednesday), Japan time. The mechanism of the earthquake is analyzed as a reverse fault type with a pressure axis in the northwest-southeast direction.
Although the magnitude of the earthquake was not so large, the epicenter was shallow, and the area near the epicenter was hit by a strong VII tremor in the revised Mercalli Intensity Class. Although it is not possible to make a strict comparison, it seems to be a tremor equivalent to a seismic intensity of 4 to 5 lower when converted to the Japan Meteorological Agency seismic intensity class. According to local media reports, some people died due to landslides and collapsed houses.
Sichuan Province has a well-developed fault zone and is one of the most earthquake-prone areas in China. A so-called “Sichuan earthquake” with a magnitude of 7.9 occurred in 2008 near the epicenter. The number of dead and missing people is regarding 90,000, which is a huge damage.
M5.5 near the Strait of Gibraltar
The Strait of Gibraltar is the strait that separates Europe and Africa, and is also the boundary between the Eurasian plate and the African plate. Since it is not a subduction zone, there are many strike-slip earthquakes, and the magnitude 6.3 and 2004 magnitude 6.4 earthquakes that occurred in 2016 have the same mechanism.
Since there are many shallow earthquakes, if it occurs near the land or in the land area, it will cause strong shaking near the epicenter.
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.
