Stay Up to Date with the Latest Earthquake and Tsunami News Around the World – Weathernews

2023-05-21 01:19:00

2023/05/21 10:19 Weather News

The number of felt-earthquakes observed in Japan over the past week has decreased significantly compared to the last two weeks.

While earthquakes are somewhat conspicuous from western Japan to the Nansei Islands, seismic activity is low from the Kanto region to the Pacific side of northern Japan. There were only three earthquakes with a seismic intensity of 3 or higher. (Tally from May 15th to May 21st at 10:00)

Japan: M4.5 earthquake at Bungo Channel Maximum seismic intensity 4

Bungo Channel earthquake

At around 6:56 on the 19th (Friday), an earthquake estimated to have a magnitude of 4.5 and a depth of 46 km occurred with the epicenter at the Bungo Channel. In this earthquake, a maximum seismic intensity of 4 was observed in Ikata-cho, Ehime Prefecture, and a seismic intensity of 3 was observed in Uwajima City, Yawatahama City, Seiyo City, Sukumo City, Kochi Prefecture, and Kunisaki City, Oita Prefecture.

The mechanism of the earthquake is analyzed as a type with a large strike-slip component. The Bungo Suido is in the hypothetical focal region of the Nankai Trough megathrust earthquake, but the epicenter of this earthquake is in a slightly deeper region than the plate boundaries in this area. The mechanism of the earthquake is also different from what is assumed, and it seems that the earthquake occurred inside the plate.

However, on the 12th (Friday), an earthquake of magnitude 4.2 occurred with an epicenter in Nanyo, Ehime Prefecture, a little northeast, and felt earthquakes continued in the surrounding area. In 2017, an earthquake with a magnitude of 5.0 and a maximum seismic intensity of 5 upper occurred in the Bungo Channel, and in 1968, a magnitude of 6.6 and a maximum seismic intensity of 5 (class at the time) occurred. But you can’t let your guard down.

What is the seismic trend in southern Chiba Prefecture so far?

Underneath the southern part of Chiba Prefecture, the North American plate, the Philippine Sea plate, and the Pacific plate intertwine, creating a complex structure. Looking at the distribution of hypocenters since 2001, we can see that the areas with many earthquakes are roughly divided into areas with a depth of 10 to 20 km, around 40 km, which is the same as this time, and around 70 km.

The 5.2-magnitude earthquake that occurred in July 2012 occurred near the southern end of the Boso Peninsula, and was of a slightly deeper type with a depth of 88 km. Magnitude 5.2 in August 2007 is a shallow type with a depth of 20 km.

In this area, there are cases where strong earthquakes occur in the sea areas off the southeast of Chiba Prefecture and off the east of Chiba Prefecture, rather than land areas, so it is essential to be prepared on a regular basis.

Japan: More than 100 felt earthquakes in Noto, Ishikawa Prefecture since 5th (Friday)

Since the earthquake with a magnitude of 6.5 and a maximum seismic intensity of upper 6 on the 5th (Friday), as of 10:00 on the 15th (Sunday), the number of felt earthquakes with a seismic intensity of 1 or higher has reached 100 times, of which 5 earthquakes with a seismic intensity of 3 or higher have occurred. A total of 15 tremors were observed, including a seismic intensity of upper 6 on Sunday (Friday).

Although seismic activity has continued to be more active than before the 5th (Friday), an earthquake with a seismic intensity of 3 or more has not occurred since the night of the 10th (Wednesday), and the number of felt earthquakes has also increased. It is declining, and the activity is gradually calming down.

On the 5th (Friday), the epicenter that was conspicuous near the northern coast of the Noto Peninsula expanded offshore, and the magnitude 5.0 earthquake that occurred on the 10th (Wednesday) was centered near the northern end of a series of seismic activity. . Although the depth is different, the region is similar to the 1993 magnitude 6.6 earthquake.

Earthquakes in the Noto Peninsula have continued for more than two years, and even if immediate activity subsides, there will still be concerns regarding strong tremors. We are also seeing changes in the epicenter area, so please continue to pay attention to earthquake trends and be well prepared.

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

World: A tsunami occurs in the vicinity of earthquakes exceeding M7 in quick succession in the South Pacific

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

There have been four earthquakes with a magnitude of 6 or higher according to US Geological Survey analysis. The largest was a magnitude 7.7 event in the South Pacific.

Around noon on the 19th (Friday) Japan time, an earthquake estimated to have a magnitude of 7.7 and a depth of regarding 18 km occurred with an epicenter southeast of the Loyalty Islands in the South Pacific. The earthquake mechanism is analyzed as a normal fault type with a tension axis in the north-northwest-southeast direction.

The earthquake generated a tsunami, and tsunamis of up to 61 cm were observed on Tanna Island in Vanuatu.

This earthquake occurred in an earthquake-prone area where the Pacific plate and the Australian plate are intricately intertwined. Earthquakes of magnitude 7.7 occurred frequently, followed by a magnitude 7.1 earthquake 23 hours later.

In the South Pacific, a deep earthquake with a magnitude of 7.6 occurred in Tonga on Wednesday (Wednesday). If a shallow earthquake occurs in this area, depending on the scale, tsunamis may reach Japan, so be careful.

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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.

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