A 6.8 magnitude earthquake struck southwest Japan on Monday, causing small tsunamis that did not cause significant damage. The earthquake occurred around 9:19 p.m. (12:19 GMT) at a depth of 36 km, some 18 km off the coast of Miyazaki Prefecture in the Kyushu region, according to the United States Institute of Geophysics (USGS).
The USGS revised its initial magnitude estimate downward from 6.9 to 6.8, adding that“there is no threat of tsunami linked to this earthquake”. The Japanese Meteorological Agency, for its part, warned of possible waves up to one meter high and asked the population to stay away from coastal areas.
“Do not enter the sea”
“The tsunami can strike several times. Please do not enter the sea or approach coastal areas”the agency said on X. A few small tsunamis of around 20 cm in height were detected in ports in the region, the meteorological agency noted. Images broadcast live on public television channel NHK showed calm seas and ships moving normally.
Only minor damage was reported by the media, such as a broken window at a train station and items falling from shelves in a few stores. A man was slightly injured when he fell at his home. Located at the convergence of four major tectonic plates along the western edge of the “ring of fire” of the Pacific, Japan is one of the countries most exposed to earthquakes.
This archipelago of 125 million inhabitants experiences some 1,500 tremors per year and 18% of the earthquakes that occur in the world. The majority of them are of low intensity, although the damage varies depending on their location and depth. On January 1, 2024, a 7.5 magnitude earthquake struck the Noto peninsula, killing more than 470 people, including many elderly people.
“At any time”
In August, the weather agency warned of a possible “megaseism” after a 7.1 magnitude earthquake which injured 15 people. This is a particular type of earthquake, occurring in a subduction zone, capable of triggering massive tsunamis. In its warning, the meteorological agency noted that a “megaseism” could be triggered in the «zone de subduction» of the Nankai Trough, off the southern coast of Japan, where other earthquakes have occurred in the past, usually in two phases. The alert was lifted a week later.
On Monday, the meteorological agency conceded that the latest earthquake did not meet the criteria justifying a megaquake alert like those of the Nankai trench. “However, it is important to keep in mind that an earthquake can occur at any time and it is important to ensure that earthquake preparations are carried out on a daily basis”added the agency.
Japan imposes strict construction regulations so that buildings can withstand strong shaking and regularly organizes exercises to improve capacities to cope with a major disaster. The most powerful earthquake ever recorded in Japan was the magnitude 9 earthquake that occurred on March 11, 2011 off its northeastern coast, which triggered a tidal wave that left around 20,000 people dead or missing. This tsunami also caused the Fukushima nuclear accident, the most serious on the planet since Chernobyl in 1986.
