Weekly Earthquake Data 2021.2.21 Peak Seismic Intensity 4 in Wakayama on 15 (Monday) Aftershocks of Fukushima Prefecture Offshore Earthquake Stabilize –Weathernews

The Japan Meteorological Agency held a press conference after 1:00 on Sunday the 14th and stated that this earthquake occurred at the epicenter of the great earthquake of March 2011 and is considered an aftershock. Since 2011, earthquakes with a magnitude of 7 or greater have frequently occurred off the coast of Tohoku, and in April 2011, an earthquake with a magnitude of 7.2 similar to this one occurred off the coast of the prefecture. by Miyagi. The Fukushima prefecture earthquake in November 2016 is a different type of earthquake with a slightly shallow depth.

In addition, long wavelength tremors called long period ground movements were also observed over a wide area, making it the strongest “class 4” in Nakadori, Fukushima prefecture. In “Class 4”, a situation in a building is assumed as a building, “I cannot stand, I cannot move without moving. I am influenced.”

The aftershock activity was not as active at 10 o’clock on the 14th (sun), and the seismic intensity 3 was observed only twice, 28 minutes and 43 minutes after the occurrence of the magnitude 7.3 earthquake. However, there is a possibility of strong shaking for about a week after the earthquake, so when cleaning the room, be sure to ensure safety immediately after the shaking.

In addition, attention needs to be paid to sediment-related disasters on steep slopes and avalanches in areas with heavy snowfall.

Aftershock activity due to an earthquake with a magnitude of 7.3 and a maximum seismic intensity of 6 or more that occurred off the coast of Fukushima prefecture on Saturday the 13th is steadily decreasing. At 24:00 hours on the 18th (Thursday), there were 77 earthquakes with a seismic intensity of 1 or more and 5 earthquakes with a seismic intensity of 3 or more. The number of earthquakes was until the 15th (Monday), and after the 16th (Tuesday), the number of earthquakes with a seismic intensity of 1 or more was 5 or less.

The largest aftershock was a magnitude 5.5 that occurred at 9:26 p.m. on Monday the 15th, and two other earthquakes of magnitude 5 or more occurred. Although aftershock activity has subsided, earthquakes of magnitude 4 and above occurred on Friday the 19th and Saturday the 20th, and there is still a high possibility of an earthquake with a seismic intensity of about 3.

In addition, the Government Headquarters for the Promotion of Seismic Research foresees the occurrence of similar types of earthquakes along the Japan Trench, called “submerged plate earthquakes” and “smaller interplate earthquakes” as in Fukushima prefecture. . The probability that an earthquake with a magnitude of 7 to 7.5 will occur in the next 30 years is as high as 26% or more, so it is safe to think that an earthquake of the same level as this moment will come at any moment and be prepared. .

In shallow earthquakes, areas with strong tremors are often concentrically distributed from the epicenter, but in deep-focus earthquakes, tremors are transmitted to distant areas along the Pacific plate where seismic waves are easily transmitted. . It can be a distribution.

Similar deep-focus earthquakes often occur where the Pacific plate is deeply subducted, with earthquakes of magnitude 6 and above occurring once every few years. On the other hand, it is also characterized by the fact that there are almost no aftershocks in a single earthquake.

There have been four earthquakes of magnitude 6 or greater, as analyzed by the United States Geological Survey. The largest was a 6.2 magnitude earthquake off the coast of Vanuatu.

A 6.2 magnitude earthquake struck off the coast of Vanuatu in the South Pacific on Tuesday, Japan time. Although the depth was very shallow, about 6 km, there were no strong shaking on the islands and no damage was caused.

The area around Vanuatu is an earthquake-prone area on the border between the Australian and Pacific plates. At the same boundary, there was a large earthquake with a magnitude of 7.7 on Wednesday the 10th and a tsunami was observed in Vanuatu. The earthquake mechanism is analyzed as a type of reverse fault with an east-west axis of pressure.

Also, although the scale is a bit small, on Thursday the 18th a magnitude 5.6 earthquake occurred in the southwestern part of Iran. Since it was an earthquake on the ground, strong tremors occurred around the epicenter and injuries have been reported.