Latest Earthquake Update: Kumamoto Hinagu Fault Zone Registers Seismic Intensity 3 on April 9, 2023 – Weekly Earthquake Information by Weather News

The past week in Japan has seen a similar number of felt-earthquakes as the previous week, with many occurring on the Pacific Ocean side from Kanto to Tohoku and also in Kyushu. Specifically, there were three earthquakes with a seismic intensity of 3 or higher. In the Kumamoto region of Kumamoto Prefecture, a new earthquake with a seismic intensity of 3 occurred, the third such occurrence this year. The earthquake’s epicenter was near the Hinagu fault zone, and the earthquake mechanism was analyzed as strike-slip type. Although Kumamoto Prefecture continues to experience frequent earthquakes, the frequency has not significantly increased compared to the past. Earthquakes in the waters near Hachijojima are either shallow or deep, depending on the epicenter’s location. Shallow earthquakes occur inside the Philippine Sea plate, while deep earthquakes occur near the boundary where the Pacific plate subducts into the Philippine Sea plate. Meanwhile, a magnitude 5.0 earthquake off the coast of Shimoetsu, Niigata Prefecture, with a seismic intensity of 3 for the first time in four years occurred. Lastly, a magnitude 7.0 earthquake occurred in Papua New Guinea, resulting in some casualties.

2023/04/09 10:10 Weather news

The number of felt-earthquakes observed in Japan over the past week is at about the same level as the previous week.

There are still many earthquakes on the Pacific Ocean side from Kanto to Tohoku, and earthquakes were also noticeable in Kyushu. Felt earthquakes frequently occur in the sea near Chichijima. There were three earthquakes with a seismic intensity of 3 or higher. (Tally from April 3rd to 9th at 10:00)

Domestic: In the Kumamoto region of Kumamoto Prefecture, a seismic intensity of 3 was recorded for the third time this year.

Earthquake in the Kumamoto region of Kumamoto Prefecture

At around 13:46 on the 7th (Friday), an earthquake estimated to have a magnitude of 3.8 and a depth of 9 km occurred with an epicenter in the Kumamoto region of Kumamoto Prefecture. In this earthquake, a maximum seismic intensity of 3 was observed in Yatsushiro City, Kumamoto Prefecture, and a seismic intensity of 2 was observed in Kumamoto City and Uki City.

This is the third time since February 11 that an earthquake centered in the Kumamoto region of Kumamoto Prefecture has recorded a seismic intensity of 3 or higher. The earthquake mechanism is analyzed as strike-slip type.

Seven years have passed since the devastating Kumamoto earthquake, but many earthquakes continue to occur in the focal region. The epicenter this time occurred near the Hinagu fault zone that stretches along the Yatsushiro Sea.

In the past week, felt earthquakes have occurred in other areas of Kumamoto Prefecture, with a maximum seismic intensity of 1 in the Aso region on the night of the 3rd (Monday) and a maximum seismic intensity of 1 in the Kuma region on the 8th (Saturday). doing.

The frequency of earthquakes in Kumamoto Prefecture has not increased significantly compared to the past.

Area where extremes of shallow and deep earthquakes occur

Earthquakes that occur in the waters near Hachijojima are roughly divided into earthquakes whose epicenters are shallower than 50km and deep earthquakes whose hypocenters are around 200km. Shallow earthquakes like this one occur inside the Philippine Sea plate.

On the other hand, deep earthquakes with a depth of 100 km or more occur near the boundary where the Pacific plate subducts into the Philippine Sea plate, and the epicenter becomes deeper as you go west.

In terms of past earthquake occurrences, larger earthquakes are more noticeable off the east coast of Hachijojima than in the waters near Hachijojima. More recently, in 2009, there was a magnitude 6.6 earthquake with a seismic intensity of 5-lower. Earthquakes that occur at the plate boundary off the east coast of Hachijojima are shallow, so they are accompanied by larger tremors.

Japan: Earthquake off the coast of Shimoetsu, Niigata Prefecture, with a seismic intensity of 3 for the first time in four years

At around 18:41 on Saturday, April 1st, an earthquake with a magnitude of 5.0 and an estimated depth of about 10km occurred off the coast of Shimoetsu, Niigata Prefecture. In this earthquake, a maximum seismic intensity of 3 was observed in Niigata City, Sado City, Yamagata Prefecture, Nakayama Town, Oguni Town, etc.

This is the first time since August 2019 that an earthquake with a seismic intensity of 3 or higher occurred off the coast of Shimoetsu, Niigata Prefecture.

Earthquakes with shallow epicenters occur occasionally off the coast of Shimoetsu, Niigata Prefecture. The most well-known of these is the 1964 magnitude 7.5 Niigata earthquake. The maximum seismic intensity recorded by the Japan Meteorological Agency is 5, but this is because there were few observation points at that time. Areas near the epicenter are believed to have been hit by even stronger tremors, and a tsunami was also generated.

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: M7.0 in Papua New Guinea kills some

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 quake of magnitude 7.0 occurred in Papua New Guinea.

An earthquake estimated to have a magnitude of 7.0 and a depth of about 70km occurred with an epicenter in Papua New Guinea in the early hours of the 3rd (Monday) Japan time. The mechanism of the earthquake is analyzed as a normal fault type with a tension axis in the WNW-ESE direction.

Because the epicenter was on land and large in scale, the quake near the epicenter was VII on the revised Mercalli seismic intensity scale. It is said that some people died due to the collapse of the building.

Papua New Guinea is located on the boundary between the Pacific plate and the Australian plate, and large earthquakes often occur on land. In September last year, a large earthquake with a magnitude of 7.6 occurred in the area southeast of this 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.

As we conclude this weather news report, it is important to note the frequent occurrence of earthquakes around the world, particularly in Japan where the seismic activity remains steady. The recent earthquakes observed in Kumamoto region of Kumamoto Prefecture have been of concern since the region has been hit by devastating earthquakes in the past. The earthquake off the coast of Shimoetsu, Niigata Prefecture, and the strong earthquake in Hyuga Nada also remind us of the unpredictable nature of natural disasters. We extend our thoughts and prayers to those affected by the earthquakes, particularly in Papua New Guinea where casualties have been reported. It is important to stay informed and prepared for such events as we move forward.