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2020/12/20 11:23 Weather news
During the past week, the number of earthquakes observed in Japan has increased significantly compared to the previous week. There have been six earthquakes with a seismic intensity of 3 or more. In general, earthquakes on the Pacific side are conspicuous. (Added from December 14 to December 20 at 10:00)
The Meteorological Agency analyzes the earthquake mechanism as a type of landslide with a pressure axis in the north-northwest-south-southeast direction.
After that, the felt earthquakes occurred one after the other in the surrounding area, and tremors with seismic intensity 3 at 20:20, seismic intensity 4 at 20:36 and seismic intensity 3 at 21:39 were observed at Toshishima. On Saturday 19 there have been no earthquakes with a seismic intensity of 3 or more, but the situation with many sensation earthquakes continues.
So-called “group earthquakes” have often occurred on the Izu Islands in the past, and recently, in the waters near Izu Oshima, November 2019 and February 2019. Earthquakes frequently occurred in April 2018 near Niijima and Kozushima. Note that there is a possibility of a strong shaking earthquake on the island near the source of the earthquake for a time.
The depth of about 50 km in the southern part of Ibaraki prefecture where this earthquake occurred is close to the boundary between the Philippine Sea plate and the North American plate, and it is an area with many earthquakes that can be called a ” nest of earthquakes “. This is the ninth earthquake with a maximum seismic intensity of 3 or more that originated in the southern part of Ibaraki prefecture, even this year.
The Philippine neighborhood lies on the boundary between the Philippine Sea plate and the Eurasian plate, and as in Japan, many plate boundary-type earthquakes occur. The mechanism of this earthquake is a type of reverse fault with an axis of pressure in the east-west direction, which is a pattern often seen in earthquakes that occur at the edge of the plate.
In the south of the island of Mindanao, earthquakes with a magnitude of 6 or more have occurred in February and March since the beginning of this year, and an earthquake with a magnitude of 6.9 occurred in April 2017. If the source of the earthquake is close to land, it will be accompanied by strong shaking, and if the scale is large, it will be an area where there is a risk of tsunami.
* Information on the source and intensity of seismic intensity in Japan comes from the Meteorological Agency, unless otherwise stated. Unless otherwise noted, overseas seismic source information comes from the American Geological Survey (USGS). Source information may differ depending on the issuing organization.
