Weekly Earthquake Information 2023.2.26 First seismic intensity of 5 or more this year M6.0 earthquake off Kushiro – Weather News

2023/02/26 11:00 Weather news

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

Earthquakes are conspicuous on the Pacific Ocean side from Hokkaido to Tohoku and Kanto, and there are also many earthquakes on the Noto Peninsula in Ishikawa Prefecture. Five earthquakes with a seismic intensity of 3 or higher occurred. (Tally from February 20th to February 26th at 10:00)

Japan: Since 2005, the Kushiro-oki epicenter has experienced a seismic intensity of 5 lower or more

Earthquake off Kushiro

At around 22:27 on the 25th (Sat), an earthquake estimated to have a magnitude of 6.0 and a depth of 63 km occurred off the coast of Kushiro. In this earthquake, a maximum seismic intensity of 5 lower was observed in Nemuro City and Shibetsu Town, Hokkaido, a seismic intensity of 4 in Kushiro City, Rausu Town, Taiki Town, and Betsukai Town, and a seismic intensity of 3 in a wide area of ​​eastern Hokkaido and part of Aomori Prefecture. I’m here.

It was the first time in 18 years since January 2005 that an earthquake with a seismic intensity of 5 or more occurred off the coast of Kushiro. The epicenter was slightly deeper than the plate boundary, and is thought to have occurred inside the subducting Pacific plate.

Plate-boundary earthquakes occur frequently off the coast of Kushiro, and the most recent one in 2004 had a magnitude of 7.1 and a maximum seismic intensity of upper 5, injuring more than 50 people. Also, in 1993, an earthquake with a magnitude of 7.5 occurred due to the destruction of the interior of the Pacific plate, causing damage including death. (1993 Kushiro-oki Earthquake)

Along the Chishima Trench, there is concern about a huge earthquake occurring at the plate boundary. At the timing of such an earthquake, please check the evacuation route and disaster prevention goods again.

Epicenters where anomalous seismic regions are likely to appear

Abnormal seismic regions often appear in deep earthquakes off the southeast coast of Mie Prefecture. In many earthquakes, areas with strong shaking are distributed concentrically from the epicenter. On the other hand, in deep earthquakes, strong tremors are transmitted along the subducting plate, and a phenomenon in which tremors become stronger far from the epicenter can be seen, and this is called an “abnormal seismic zone.”

Other than the southeastern offshore of Mie Prefecture, similar deep earthquakes often occur in the Sea of ​​Okhotsk, the Sea of ​​Japan, the southern offshore of Tokaido, and the sea near Torishima, and once every few years, an earthquake with a magnitude of 6 or more also occurs.

Even if the tremors were small near the epicenter, strong tremors were transmitted far away. Mie Prefecture, which is close to the epicenter, did not have any locations where felt earthquakes were observed, and the maximum seismic intensity of 4 was observed in Ibaraki and Fukushima prefectures. A large-scale earthquake may cause tremors exceeding seismic intensity 5 lower, so caution is required.

Japan: The central Tokachi region was the epicenter, with a seismic intensity of 3 for the first time in two years.

Earthquake in central Tokachi

At around 3:55 on the 20th (Monday), an earthquake estimated to have a magnitude of 4.9 and a depth of 118 km occurred with an epicenter in the central Tokachi region of Hokkaido. In this earthquake, a maximum seismic intensity of 3 was observed in Obihiro City, Makubetsu Town, Urahoro Town, and Taiki Town in Hokkaido, and a seismic intensity of 1 to 2 was observed mainly on the Pacific Ocean side from Hokkaido to Tohoku.

It will be the first time in about two years since May 2021 that an earthquake with a seismic intensity of 3 or higher centered in the central Tokachi region, and the first time in five months since September last year, even if the area is expanded to the entire Tokachi region. The earthquake is believed to have occurred within the subducting Pacific plate.

Deep earthquakes with a depth of 100 km or more frequently occur from the central to the southern part of the Tokachi region, and large earthquakes exceeding magnitude 6 also occur. Recently, in 2013, an earthquake estimated to have a magnitude of 6.5 and a depth of 102 km occurred, and a maximum seismic intensity of 5 upper was observed.

In the Tokachi region of Hokkaido, in addition to the type that occurs at offshore plate boundaries, such as the Tokachi-oki earthquake, there is also the possibility of deep earthquakes like this one and shallow earthquakes caused by the activity of the Tokachi Plain fault zone. is a high-risk area for

Japan: A strong earthquake in January this year with a seismic intensity of 4 in Hyuga Nada

At around 3:06 on the 18th (Sunday), an earthquake estimated to have a magnitude of 5.4 and a depth of about 30 km occurred with an epicenter in Hyuga-nada. In this earthquake, a maximum seismic intensity of 4 was observed in Miyazaki City and Nichinan City, and a seismic intensity of 3 was observed in Miyakonojo City and Kobayashi City in Miyazaki Prefecture, Kirishima City and Kanoya City in Kagoshima Prefecture, and Kumamoto City in Kumamoto Prefecture.

This is the first earthquake with a seismic intensity of 4 or higher with its epicenter in Hyuga-nada since January 22, 2018. The mechanism of the earthquake was analyzed as a normal fault type with a tension axis in the east-west direction.

The epicenter is further south than the magnitude 6.6 earthquake that occurred in January, and the area is close to the magnitude 7.0 earthquake that occurred in 1961.

World: Tajikistan M6.8 No damage expected

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

There have been five earthquakes of magnitude 6 or greater according to US Geological Survey analysis. The largest earthquake of magnitude 6.8 occurred in Tajikistan. A 6.3-magnitude quake, which is believed to be an aftershock of the earthquake in Turkey, also occurred.

On the morning of the 23rd (Thursday) Japan time, an earthquake estimated to have a magnitude of 6.8 and a depth of about 21 km occurred with an epicenter in the eastern part of Tajikistan in Central Asia. The earthquake mechanism is analyzed as a normal fault type with a tension axis in the east-northeast-west-southwest direction.

In the vicinity of the epicenter, the quake was VII on the revised Mercalli seismic intensity scale.

Although Tajikistan is far from the plate boundary, large earthquakes often occur due to the movement of the Indo-Australian plate against the Eurasian plate.

In 2015, there was an earthquake of magnitude 7.2 near the epicenter of this time, and the shaking caused damage such as death. In Tajikistan, there were 7.5 magnitude earthquakes in 1949 and 7.4 magnitude earthquakes in 1907, both of which killed more than 10,000 people.

Turkey is a seismic country on multiple plate boundaries

Most of Turkey is located on a small plate called the “Anatolian Plate”. It is surrounded by multiple plate boundaries, with the African plate to the south, the Arabian plate to the southeast, and the Eurasian plate to the north.

The first magnitude 7.8 earthquake is believed to be the activity of the “East Anatolian Fault” formed on the boundary between the Anatolian Plate and the Arabian Plate.

The 7.6 magnitude earthquake in 1999 is one of the most damaging earthquakes in Turkey in recent years. The earthquake, also known as the Izmit Earthquake, was different from this one in that it was caused by the activity of the North Anatolian Fault, and caused extensive damage in the northwestern part of Turkey, including the large city of Istanbul.

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.