DENVER, Oct. 25 (UPI) -- Thirteen strong aftershocks have struck the west coast of Japan after Saturday's magnitude 6.6 earthquake struck the area, U.S. scientists reported.
The first quake, which struck 5:56:00 p.m. local time, hit about 120 miles north-northwest of Tokyo, near the west coast of the main Japanese island of Honshu, according to the U.S. Geological Survey's National Earthquake Information Center.
It was followed by five strong aftershocks within two hours, all at least magnitude 5.5 in strength and one a magnitude 6.3, the agency reported. The sixth and seventh shocks occurred five hours and 13 hours after the main quake, respectively, and registered 5.2 and 4.4 on the Richter scale.
Six more aftershocks hit the same general area Sunday, with one temblor hitting magnitude 5.7.
The area remained quiet Monday, however, USGS reported.
The Richter scale describes a magnitude 6.6 quake as potentially destructive in areas up to about 100 kilometers (62 miles) from the epicenter.
