New Year’s Day M7.5 Earthquake Shakes Japan’s West Coast

While the exact number of fatalities is still uncertain, at the time of writing there are reports of at least 64 fatalities. Based on the intensity of shaking, our impact estimates indicate that property and economic damages could potentially exceed $1 billion.

The quake caused severe shaking in the city of Nanao (population 45,000), with the shaking in Tokyo being much lighter.

Monday’s quake induced a tsunami of nearly 3 feet (0.8 meters) in Japan. No tsunami warning was issued for the United States or any of its territories, nor did the tsunami reach the U.S.

For many, the quake and tsunami invoked memories of the March 2011 Tōhoku earthquake, a powerful magnitude 9.1 that produced shaking 250 times stronger than Monday’s magnitude 7.5 earthquake. Although the most recent earthquake drew comparisons to the one in 2011, it actually had more in common with the 2016 magnitude 7.0 Kumomoto earthquake and the 1995 magnitude 6.9 Kobe earthquake, both in southern Japan. Like Monday’s earthquake, those events were shallow crustal earthquakes that occurred close to and among populated areas.

As many recall, the 2011 Tōhoku earthquake and tsunami led to the Fukujima nuclear accident. While there were two nuclear plants in the vicinity of Monday’s quake, one was inactive and the other, the Kashiwazaki-Kariwa plant near Niigata, has been idle since being shut down in 2011. Japanese officials indicated these plants, along with all others in Japan, were not adversely affected by the recent earthquake’s shaking or the resulting tsunami. 

The magnitude 7.5 mainshock, which was preceded by a magnitude 5.5 foreshock just 4 minutes earlier, has produced dozens of aftershocks. So far, the USGS has detected at least 15 aftershocks of magnitude 5 or larger, with the largest being a magnitude 6.2 that occurred 8 minutes after the mainshock.

“We expect that earthquakes will continue in the region over the next few days, weeks, and months,” said Gavin Hayes, Senior Science Advisor for Earthquake and Geologic Hazards. “While future aftershocks are most likely to be felt near the ruptured fault, they may also be felt further away.”

While earthquakes are common in Japan, they are most frequent along the east coast of Japan’s largest island of Honshu, where the Pacific and Philippine Sea plates subduct beneath Japan. There was a magnitude 7.6 earthquake in June 1964 near Niigata on Japan’s western coast approximately 125 miles (200 km) from Monday’s quake that claimed over 300 lives. However, since the Niigata earthquake, no magnitude 7 or larger quakes have occurred along the island’s west coast within 155 miles (250 km) of Monday’s quake. Most of Japan’s 55 earthquakes of magnitude 7 or larger since 1950 were along the eastern coast, including several aftershocks from the magnitude 9.1 quake in 2011.

The Japanese Meteorological Agency (JMA) reported Monday’s earthquake as magnitude 7.6. It is not uncommon for agencies’ measurements to vary due to different sensors and methods. The USGS uses a global dataset of sensors to maximize our ability to compare earthquakes around the world.

For updated information on this earthquake, see: https://earthquake.usgs.gov/earthquakes/eventpage/us6000m0xl/executive 

Reporters with questions can contact: earthquakemedia@usgs.gov

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