TOKYO (AP) - A fairly strong earthquake with a preliminary magnitude of 5.1 shook Tokyo and surrounding areas Monday morning, Japan's Meteorological Agency said. There were no immediate reports of damage or injuries from the tremor, which struck at 7:56 a.m. local time (6:56 p.m. EDT Sunday), police said. The quake was centered about 50 miles underground in the northwestern part of Chiba prefecture, or state, just east of Tokyo. An earthquake of magnitude 5 can break windows and crack walls. Some high-rise buildings swayed during Monday's quake. Japan is one of the world's most earthquake-prone nations because it sits atop four tectonic plates, slabs of land that move across the earth's surface.