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2020/12/29 11:43 Weather news
As for the number of earthquakes per month, the highest number was 213 in May. The number was 96 times in November. From April to May, a swarm of earthquakes occurred near the prefectural border between Nagano and Gifu prefectures, and in May, of the 213 cases that occurred across the country, nearly half of them were 104 times. (Until December 28)
It is the first time in three years since 2017 that no tremors with a seismic intensity of 6 less or greater were observed. It is the second consecutive year since last year that fewer than 10 earthquakes have occurred with a seismic intensity of less than 5. The effects of the giant earthquake that caused the Great East Japan Earthquake, including the total number of earthquakes, are believed to have occurred , have gradually decreased.
There is concern that a major earthquake will occur along the Chishima Trench, which is an extension of these earthquakes, and the government’s Earthquake Research Promotion Headquarters has established a 7-40% probability of it occurring. a magnitude of 8.8 or more in 30 years. I will.
The largest earthquake was a 7.8 magnitude earthquake off the coast of Alaska on July 22. The mechanism was analyzed as a type of reverse fault with a northwest-southeast pressure axis and a tsunami warning was temporarily announced in the surrounding area. In reality, the 0.24 m tsunami at Sandpoint, Alaska, USA was only observed and did not cause major damage.
One of the most devastating earthquakes was the 7.0 magnitude earthquake that struck the Aegean Sea off the coasts of Turkey and Greece on October 30.
In this earthquake, many buildings collapsed one after another on the island of Samos in Greece and Izmir on the west coast of Turkey. Since the source of the earthquake was as shallow as 20 km, a tsunami also occurred, and in Turkey it has reached about 50 meters from the coast. According to the Turkish government, the earthquake has killed more than 100 people.
The area from western Turkey to Greece is sandwiched between the Eurasian plate and the African plate. Microplates called “Anatolian plates” are said to lie between the Eurasian plate and the African plate, and the movement of these plates has caused a lot of major earthquake damage.
The source of this earthquake occurred on the Aegean plate, which borders the west side of the Anatolian plate. This area is believed to move north and south. The earthquake mechanism is analyzed as a type of normal fault with a stress axis in the north-south direction, and is in harmony with the movement of thought. The 6.6 magnitude earthquake that occurred on the same west coast of Turkey in 2017 is also analyzed as a normal fault type.
* Information on the source and intensity of seismic intensity in Japan comes from the Meteorological Agency, unless otherwise noted. Unless otherwise noted, overseas seismic source information comes from the American Geological Survey (USGS). Source information may differ depending on the issuing organization.
