1 Four earthquakes, including one with a magnitude of 5.3, rocked Japan in the past 24 hours, the Central Meteorological Agency said Tuesday morning.
2 None of the quakes were related the devastating Jan. 17 earthquake which killed more than 5,200 people in the Kobe region, agency officials said.
3 Police said Tuesday that there were no immediate reports of damage or injuries from any of the tremors.
4 The strongest quake struck at 11:51 p.m. (14:51 GMT) Monday at a depth of 50 kilometers (31 miles) beneath the floor of the Pacific Ocean about 125 kilometers (77 miles) east of the Aomori prefecture (state) town of Misawa.
5 Misawa, the site of a large U.S. air base, is 560 kilometers (350 miles), northeast of Tokyo.
6 Three minutes later, another quake with a magnitude of 4.5 struck from the same spot.
7 Service was temporarily suspended on train lines in the region as railway officials checked tracks for any damage.
8 The first of Monday's three earthquakes occurred off the coast of the northernmost main island of Hokkaido at 4:29 a.m. (19:29 GMT Sunday). It was centered at a depth of 60 kilometers (37 miles) in the Pacific about 150 kilometers (93 miles) east of Nemuro.
9 Nemuro is a port town 973 kilometers (608 miles) northeast of Tokyo.
10 Early Tuesday, a earthquake with a magnitude of 3.9 jolted Tokyo and its surrounding areas. The temblor struck at 4:23 a.m. (19:23 GMT Monday). It was centered 60 kilometers (37 miles) below the ground in eastern part of Saitama Prefecture (state), just north of Tokyo, the agency said.
11 A tremor with a magnitude 5 can produce moderate damage and one with magnitude of 6 can cause serious damage in populated areas.
12 Japan is one of the world's most seismically active countries, accounting for roughly 10 percent of the world's earthquakes and volcanic activity each year.
13 A total of 778 earthquakes strong enough to be felt by humans hit Japan last year, according to an agency official.

Misawa , the site of a large U . S . air base , is 560 kilometers ( 350 miles ) , northeast of Tokyo .
large U . S . air base ,
How large is this air base that the US controls?