Earthquake off Sanriku Coast: Shindo 4 in Iwate and Miyagi, Tsunami Advisory Issued

At approximately 5:03 PM on November 9, 2025, an earthquake with its epicenter off the Sanriku Coast struck, registering a maximum seismic intensity (Shindo) of 4 in Iwate and Miyagi Prefectures. According to the Japan Meteorological Agency (JMA), the epicenter was estimated to be about 130 km east of Miyako, at a depth of 10 km, with a magnitude (M) of 6.7.

Following the earthquake, a tsunami advisory was issued for the coastal areas of Iwate Prefecture. At 5:39 PM, a 10-centimeter tsunami was observed in Ofunato City, Iwate Prefecture, and a minor tsunami was recorded in Miyako City. The government immediately established an information liaison office at the Prime Minister's Official Residence, and Ms. Sanae Takaichi urged the public via social media to evacuate coastal areas promptly. The JMA continues to warn that subsequent tsunamis could be larger than initially predicted, emphasizing the need for continued vigilance.

While Iwate and Miyagi Prefectures observed the maximum Shindo 4, some areas in Niigata Prefecture (including Chuo Ward of Niigata City, Murakami City, and Sanjo City) also recorded Shindo 2. Shaking was reported across a wide range of regions, including Kanto, Chubu, and Hokkaido.

Tohoku Electric Power Company confirmed no abnormalities at the Onagawa Nuclear Power Plant in Miyagi Prefecture due to this earthquake. However, many voices of concern have been shared on social media, with comments such as "Shindo 4 is still scary" and "There's a possibility that the main shock hasn't come yet," as well as warnings about aftershocks. Residents in the affected areas are urged to continue paying attention to future information and prioritize their safety.

The Context

The Sanriku Coast is a region in northeastern Japan, known for its rugged, rias-style coastline. It is highly susceptible to earthquakes and tsunamis due to its location near major tectonic plate boundaries. Historically, the area has been hit by devastating tsunamis, most notably the 2011 Great East Japan Earthquake and Tsunami, which caused widespread destruction and loss of life. Therefore, even relatively small earthquakes and tsunami advisories are taken very seriously in this region, leading to immediate public warnings and government responses.

In Japan, earthquake intensity is measured using the "Shindo" scale, which quantifies the degree of shaking at a specific location, ranging from 0 to 7. This differs from "Magnitude," which measures the total energy released by an earthquake. A Shindo 4 earthquake is strong enough to startle most people, cause hanging objects to swing considerably, and possibly move unstable items. Given the region's history, public awareness and preparedness for seismic events are exceptionally high.