A series of earthquakes in central and western Japan on Friday fueled fresh fears of a “Big One” and disastrous volcanic eruptions in the world’s most seismically active nation.

The first significant convulsion was a magnitude 4.8 temblor that struck the northern foot of Mount Fuji at around 6:37 a.m. The quake registered a weak 5 on the 7-point shindo seismic intensity scale in Otsuki in eastern Yamanashi Prefecture and 4 in some areas of Kanagawa Prefecture, the Meteorological Agency said.

While there was no threat of a tsunami following the quake, which was also felt in parts of Tokyo, the agency warned that shakes of similar intensity could occur within a week. The epicenter of the quake in the Fuji Five Lakes area was at a depth of about 19 kilometers, it said. There were no initial reports of injuries or serious damage to infrastructure, according to the authorities.