A magnitude 5.0 earthquake struck northern Nagano Prefecture (a mountainous region in central Honshu, Japan's main island) on the 18th, registering an upper-5 intensity reading in Omachi City. Further tremors followed, including one measuring lower-5 intensity, as seismic activity in the area continued. Japan's Meteorological Agency has urged residents to remain vigilant for at least one week, noting that comparable earthquakes in this region have historically been followed by clusters of similar-magnitude aftershocks.