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Weekly Earthquake Information August 14, 2022 Seismic intensity 5-lower and 5-upper consecutive occurrences in northern Kamikawa region of Hokkaido – Weather News

2022/08/14 10:13 Weather news

The number of felt-earthquakes observed in Japan over the past week is at a higher level than the previous week.

The occurrence of earthquakes is conspicuous in Hokkaido, not only in the northern part of the Kamikawa region, but also on the Pacific side. There are still many cases along the Pacific coast from Tohoku to Kanto. There were seven earthquakes with a seismic intensity of 3 or higher, six of which occurred in the northern Kamikawa region of Hokkaido. (Tally from August 8th to 14th at 10:00)

Japan: First earthquake with an epicenter in the northern Kamikawa region with a seismic intensity of 5 or more

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Earthquake in northern Kamikawa region

At around 0:35 on the 11th (Thursday), an earthquake estimated to have a magnitude of 5.2 and a depth of 4 km occurred with an epicenter in the northern part of the Kamikawa region of Hokkaido, and a seismic intensity of 5 lower was observed in Nakagawa Town. Eighteen minutes later, at 00:53, an earthquake estimated to have a magnitude of 5.4 and a depth of 4 km occurred, and a seismic intensity of upper 5 was observed in the same Nakagawa town.

This is the first time since 1919, when the Japan Meteorological Agency has detailed statistics, that an earthquake with an epicenter in the northern part of the Kamikawa region recorded a seismic intensity of 5 lower or more. The mechanism of both earthquakes is analyzed as a reverse fault type with an east-west pressure axis.

It is believed that there is a fault running north-south near the epicenter of this quake. Very shallow earthquakes have occurred in the past, and in 2012, an earthquake with a maximum seismic intensity of 4 occurred for three days in a row.

Many felt earthquakes continued until the 12th (Friday), but on the 13th (Saturday), the seismic activity calmed down. However, because the epicenter is a shallow earthquake, even if the scale is not so large, the shaking will be large. Be prepared for strong tremors for a while.

Japan: Seismic intensity 3 at eastern Kanagawa prefecture

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At around 19:10 on the 9th (Sat), an earthquake estimated to have a magnitude of 3.9 and a depth of about 30 km occurred with an epicenter in eastern Kanagawa Prefecture. In this earthquake, a maximum seismic intensity of 3 was observed in Kawasaki City, Kanagawa Prefecture, and a seismic intensity of 2 was observed in a wide area centered on Tokyo and Kanagawa Prefecture.

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 time an earthquake with a seismic intensity of 3 or more with an epicenter in eastern Kanagawa occurred in February this year. The February quake had an epicenter as deep as 100 km, which is the first since the February 2016 magnitude 4.6 earthquake with a depth of 26 km to be limited to a shallow type earthquake similar to this one.

At a depth of around 30 km in eastern Kanagawa Prefecture, earthquakes with a magnitude of around 5 have occasionally occurred. In November 1923, there was an earthquake of magnitude 6.3, which is thought to be an aftershock of the Great Kanto Earthquake or related activity.

The Cabinet Office’s assumption of an earthquake directly hitting the Tokyo metropolitan area includes an earthquake with an epicenter in Kanagawa Prefecture, so it is essential to take countermeasures on a daily basis.

Japan: Seismic intensity 3-4 in succession in the Soya region of Hokkaido

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At around 1:41 on the 4th (Thursday), an earthquake estimated to have a magnitude of 4.1 and a depth of 7 km occurred with an epicenter in the northern part of the Soya region of Hokkaido. In this earthquake, a maximum seismic intensity of 4 was observed in Horonobe-cho, Hokkaido, and a seismic intensity of 3 was observed in Teshio-cho.

Also, just 20 minutes later, at around 1:59, there was a magnitude 3.5 earthquake, and nearly three hours later, at around 4:28, there was a magnitude 2.9 earthquake, both with a maximum seismic intensity of 3. The hypocenters and depths are almost the same, and it seems to be a series of seismic activity. In addition, no felt earthquake has occurred since the earthquake at 7:09 on Friday, April 4th.

An earthquake with a magnitude of 4.4 occurred on June 20 near the epicenter, and a maximum seismic intensity of 4 was observed.

Although the Soya region has relatively few earthquakes compared to Hokkaido, displacement that appears to be a fault has been confirmed slightly north of the epicenter.

Also, the Sarobetsu fault zone is known along the coast of the Sea of ​​Japan in the Soya region. According to the government’s Headquarters for Earthquake Research Promotion, the probability of an earthquake of magnitude 7.6 or so occurring within the next 30 years is less than 4%. Although there have not been many major earthquakes in recent years, the area is not necessarily safe.

There have been earthquakes as large as M6.0 in the past.

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Shallow earthquakes associated with volcanic activity are well known when it comes to earthquakes in the Izu Islands, such as Izu Oshima and Miyakejima. Looking at the distribution of hypocenters of earthquakes that actually occurred around the Izu Islands, most of them occurred in the area from the northwest of Izu Oshima to the Izu Peninsula, and in the area from Miyakejima to Kozushima.

Most of the earthquakes are concentrated at a depth of around 10 km even in the depth of the east-west cross section. There are few occurrences at depths of 20 km or more, but there are a few at depths of 100 km or more. Earthquakes that occur near the boundary between the Pacific plate and the Eurasian plate or within the Pacific plate.

Most deep earthquakes are around magnitude 4, but in May 2014, a large earthquake with a magnitude of 6.0 occurred. In this earthquake, a maximum seismic intensity of 5 lower was observed in Chiyoda Ward, Tokyo, and a seismic intensity of 3 to 4 was observed in a wide area of ​​the Kanto region, causing damage such as injuries.

World: M5.2 earthquake hits Mediterranean Sea

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Earthquakes of M4.5 or higher around the world (quoted from USGS website/processed by Weathernews)

There have been no earthquakes of magnitude 6 or greater according to analysis by the United States Geological Survey. The largest quake of magnitude 5.9 occurred in Papua New Guinea.

On the 13th (Saturday) in Japan time, an earthquake with a magnitude of 5.2 and a depth of about 15 km occurred with an epicenter in the Mediterranean Sea off the coast of Libya. The earthquake mechanism is analyzed as strike-slip type. Since the epicenter was slightly away from land, there was no effect from the tremors.

The coastal regions of Italy, Greece, and Turkey on the north side of the Mediterranean Sea are located on the boundary between the Eurasian Plate and the African Plate, so many earthquakes occur. However, the offshore Libya that occurred this time is far from the plate boundary, so there is a tendency for relatively few earthquakes to occur. Even large ones are up to the same magnitude 5 class as this time.

M5.5 near the Strait of Gibraltar

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An earthquake estimated to have a magnitude of 5.5 and a depth of about 10 km occurred off the coast of Morocco near the Straits of Gibraltar on the evening of Friday, June 20, Japan time. The earthquake mechanism is analyzed as strike-slip type.

The Strait of Gibraltar is the strait that separates Europe and Africa, as well as the boundary between the Eurasian and African plates. Because it is not a subduction zone, many strike-slip earthquakes occur, and the magnitude 6.3 earthquake that occurred in 2016 and the magnitude 6.4 earthquake that occurred in 2004 have the same mechanism.

Since many earthquakes occur in shallow areas, if they occur close to land or on land, they will be strong near the epicenter.

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Reference materials, etc.

*Information on earthquake sources and seismic intensity in Japan is from the Japan Meteorological Agency unless otherwise specified. Overseas epicenter information is from the United States Geological Survey (USGS) unless otherwise specified. There may be differences in hypocenter information depending on the publishing organization.