A series of earthquakes have struck off the east coast of Chiba Prefecture this week, with more than 10 tremors registering 1 to 4 on the Japanese seismic intensity scale since Tuesday, according to data from the Meteorological Agency.

The frequency of these seismic events has notably increased, particularly on Thursday, when a total of 10 earthquakes occurred that day, the agency said.

Within the 24-hour period from 6:00 a.m. Thursday, two earthquakes measuring up to level 4 and three tremors measuring up to level 3 were recorded in the prefecture.

Thursday saw a cluster of seismic activity between 8:40 a.m. and 8:45 a.m., with three earthquakes of seismic intensity 1 or higher occurring consecutively off the east coast of Chiba Prefecture. This was succeeded by level 3 earthquakes striking at 11:13 a.m., 12:30 p.m. and 4:27 p.m.

Another earthquake with a maximum intensity of 4 rattled the region at 6:35 p.m. Thursday, followed by a magnitude 5.2 tremor at 5:43 a.m. on Friday, also registering a maximum intensity of 4. The early morning quake was felt in Saitama Prefecture and Tokyo, with seismic intensities reaching 4 and 3, respectively, in certain areas of those prefectures.

Local government officials have urged people to exercise caution as they cannot yet predict when a larger earthquake may occur.

Both earthquakes originated at a depth of approximately 30 kilometers, with their mechanism analyzed as a reverse fault type with a pressure axis in the north-northwest to south-southeast direction.

The area off the east coast of Chiba Prefecture features a complex subsurface structure, where the Philippine Sea Plate and the Pacific Plate subduct into the land plate. This geological setup results in a heightened level of seismic activity. The depth of the epicenter and the mechanism indicate that the earthquakes occurred near the upper surface of the Philippine Sea Plate, according to Weathernews.