2022/12/18 10:36 Weather news
There is no particular concentration of earthquakes, and they occur all over Hokkaido, Kyushu, and the Nansei Islands. There were four earthquakes with a seismic intensity of 3 or higher. (Tally from December 12th to December 18th at 10:00)
Domestic: Multiple felt earthquakes in the Shiribeshi region of Hokkaido
At around 13:50 and 15:58, earthquakes with a maximum seismic intensity of 2 occurred at almost the same epicenter. The mechanism of the earthquake is presumed to be a reverse fault type with a pressure axis in the WNW-ESE direction.
There are not many earthquakes with epicenters in the western Shiribeshi region, since 1919 when detailed records of the Japan Meteorological Agency remain, and only on November 24th last month and this time there was a seismic intensity of 3 or more.
However, the epicenter of this quake is located in the area where the Kuromatsunai low-lying fault zone is distributed. The government’s Headquarters for Earthquake Research Promotion states that the probability of an earthquake of magnitude 7.3 or higher occurring within 30 years is 2-5% or less. Among the major active fault zones in Japan, it belongs to a group with a high probability of occurrence, so it is necessary to pay attention to the occurrence of future earthquakes.
Japan: Magnitude 6 or higher for the first time in 16 years near Amami Oshima
The sea near Amami Oshima is the area where the Philippine Sea plate is subducting. M6-class earthquakes occur occasionally at depths of around 30 km. It was the first time in 16 years since the M6.0 earthquake in November 2006 that the sea near Amami Oshima had an epicenter. In 1995, there was also a large earthquake with a magnitude of 6.9 and a maximum seismic intensity of 5 (the seismic intensity scale at that time), so we cannot let our guard down.
Japan: A strong earthquake in January this year with a seismic intensity of 4 in Hyuga Nada
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: M5.4 occurred last month in Texas, USA
On the morning of the 17th (Saturday) Japan time, an earthquake estimated to have a magnitude of 5.4 and a depth of about 8 km occurred in Texas, USA. The earthquake mechanism is analyzed as a normal fault type with a tension axis in the north-northwest-southeast direction. Because the earthquake occurred in a shallow place, it is believed that there was a quake of VI on the revised Mercalli seismic intensity scale near the epicenter.
Although there is no known active fault near the epicenter, seismic activity has increased in recent years. According to the U.S. Geological Survey, since 2018, there have been about 120 earthquakes with a magnitude of 2.5 or greater within 50km of this epicenter. Also, on the 16th of last month, an earthquake with a magnitude of 5.4 occurred about 200km to the west.
A study linked earthquakes in the area to human activity, and concluded that the 2020 earthquake was caused by a significant increase in wastewater injection. Many of the other earthquakes that are increasing in the central and eastern United States are thought to be related to human activities such as mining.
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.