A 7.0-magnitude earthquake struck deep beneath the waters near Japan’s Ogasawara Islands, sending light tremors across Tokyo and other prefectures. The Japan Meteorological Agency confirmed that the deep-seated temblor posed no tsunami threat.
An earthquake with a preliminary magnitude of 7.0 struck waters near the Ogasawara Islands in the Pacific Ocean south of Tokyo on Sunday. The Japan Meteorological Agency reported that the shaking began at approximately 11:10 a.m. local time, originating deep within the earth west of the Ogasawara Archipelago.
The tremor measured 3 on the Japanese seismic intensity scale of 7 in Chichijima and Hahajima, the inhabited islands within the Ogasawara village administration. Although the epicentre sat far to the south in remote waters, the seismic wave reached thousands of kilometers across Honshu.
Depth and Regional Tremors Across Eastern Japan
The defining characteristic of the event was its extraordinary depth. Seismologists at the Japan Meteorological Agency placed the hypocenter at roughly 470 kilometers below the ocean floor, classifying it as a deep-focus earthquake.
Because seismic waves from deep-focus events travel efficiently through the earth’s dense mantle, the energy surfaced far from the epicentre. Residents in parts of Tokyo, Chiba Prefecture, and Kanagawa Prefecture reported gentle rolling motion, despite being more than 1,000 kilometers away from the Ogasawara island chain.
Instrumental readings recorded a seismic intensity of 2 across multiple prefectures in the Tohoku and Kanto regions. Affected areas included parts of Miyagi Prefecture, Fukushima Prefecture, Ibaraki Prefecture, Tochigi Prefecture, Saitama Prefecture, and parts of Tokyo’s Chiyoda ward and Aogashima village, alongside areas in Kanagawa, Niigata, Yamanashi, Nagano, and Shizuoka.
Deep Hypocenter Prevents Tsunami Threat
Despite the high magnitude, the extreme depth of the hypocenter prevented any displacement of the ocean floor powerful enough to generate destructive waves. The Japan Meteorological Agency confirmed immediately following the initial shock that no tsunami warnings or advisories had been issued, reassuring residents that no tsunami threat existed for the Japanese coastline.
The event coincided with separate seismic activity in southwestern Japan on the same morning, when a shallow magnitude-5.3 earthquake struck off the coast of Miyazaki Prefecture in Hyuga Nada, causing localized intensity-3 shaking in Kumamoto, Miyazaki, and Kagoshima.