GUNMA - A magnitude 5.5 earthquake struck eastern Japan at around 7:46 p.m., with a maximum seismic intensity of lower 5 recorded in parts of Gunma and Saitama prefectures, though no injuries or major damage had been confirmed and there was no risk of a tsunami.
According to the Japan Meteorological Agency, the earthquake's epicenter was in southern Ibaraki Prefecture at a depth of approximately 50 kilometers.
The strongest shaking, measuring lower 5 on Japan's seismic intensity scale, was recorded in Ota City and Chiyoda Town in Gunma Prefecture, and in Kazo City, Honjo City, and Misato Town in Saitama Prefecture. Intensity 4 shaking was observed across parts of Ibaraki, Tochigi, and southern Saitama prefectures, while intensity 3 was felt in Tokyo's 23 wards and surrounding areas.
The Fire and Disaster Management Agency said no injuries or building damage had been confirmed as of the latest reports.
The earthquake also affected transportation. East Japan Railway said services on portions of the Hokuriku and Joetsu Shinkansen lines were suspended in both directions following the tremor, with operations expected to resume at around 10:15 p.m.
Seismologists noted that the earthquake originated in a seismically active area near the boundary where the Philippine Sea Plate subducts beneath the continental plate. A similar earthquake measuring lower 5 on the Japanese scale occurred in nearly the same area on April 1, suggesting the latest event was caused by comparable tectonic activity.
Experts said the region frequently experiences earthquakes of intensity 3 or greater and is considered one of the more active seismic zones in the Kanto region. The latest quake is believed to have been a reverse-fault event caused by compressional forces generated by plate movement.
Long-period ground motion, classified at the lowest level on Japan's scale, was also observed in southern Gunma, northern Saitama, and nearby areas. Such shaking can cause taller buildings to sway slowly for extended periods even when overall seismic intensity is relatively moderate.
Reports from residents indicated that many people near the epicenter experienced a sharp upward jolt followed by rapid shaking. Experts said short-period vibrations can cause unsecured household items to fall, increasing the risk of injuries inside homes even when structural damage is limited.
Authorities advised residents returning home to remain cautious of broken glass and fallen objects. Seismologists also warned that earthquakes of similar strength could occur over the coming week and that smaller aftershocks remain possible. They urged people to secure unstable items that may have shifted during the quake, as additional tremors could cause them to fall.
Analysis of seismic data indicated that many areas first experienced small, rapid vibrations before stronger shaking arrived, a pattern consistent with observations from residents across the affected region. Experts said the area is likely to remain susceptible to further seismic activity and urged continued vigilance in the days ahead.
Source: ウェザーニュース
