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Magnitude 7.0 earthquake violently shakes southern Japan

A magnitude 7.0 earthquake struck southern Japan early Saturday morning, after two large quakes killed at least nine people and injured over 700 one day earlier. The quake was 32 times stronger than the foreshocks that preceded it.

The quake occurred at 1:25 a.m., Japan time, on Saturday near Kumamoto-shi, Japan on the island of Kyushu. The U.S. Geological Survey says it occurred at a shallow depth, which increases the intensity of shaking.

The Japan Meteorological Agency reported high shindo-6 seismic intensity near the epicenter, on a scale from zero to seven. Shindo-6 means that damage will be significant, and fatalities are likely. At this intensity, shaking will collapse some buildings. Even when standing outside, it will be difficult or impossible to stay standing. There may be landslides and fissures in the ground. Gas and water mains can be damaged. The agency issued a tsunami advisory for the surrounding areas, but lifted it less than an hour later.

The AP reports that residents were already on edge from Thursday’s strong quakes when they woke up to violent shaking early Saturday morning:

Sirens of patrol vehicles were heard on the background as NHK reported from the hardest-hit town of Mashiki. The asphalt outside the town hall had a new crack, apparently made by the latest earthquake.
The Nuclear Regulation Authority said no abnormalities were found at the Sendai nuclear plant, where the only two of Japan’s 43 operable reactors are online. NHK video showed that stones tumbled from the walls of historic Kumamoto Castle, and a wooden structure in the complex was smashing, adding to damage Thursday at the site.

Thursday’s earthquakes were rated 6.0 and 6.2 by the U.S. Geological Survey, which has stated the trembles were foreshocks to the larger quake. The quakes are happening along the Philippine Sea tectonic plate, which is bordered by the large Pacific and Eurasia plates, the USGS says.

This region tends to experience a lot of seismic shaking, but it’s usually never this shallow nor this strong. The USGS says just 13 earthquakes larger than magnitude-5 have occurred at shallow depths in the past century. The strongest shallow quake of recent years happened in 2005, when a 6.6 struck just off the northern coast of Kyushu, over 60 miles from Saturday’s quake.

Heavy rain and strong winds are also in the forecast for the region, and forecasters are concerned about the potential for landslides after the quakes loosened the ground.