A series of aftershocks jolted northern Japan on Saturday following several earthquakes, and police reported landslides, cracked roads and damaged buildings. There were no reports of injuries from the series of quakes Friday evening near Takada, 140 miles north of Tokyo. A total of 10 aftershocks had been recorded following the first and strongest earthquake Friday evening, which registered 5.5 on the Richter scale, the Central Meteorological Agency said. No Richter readings were available for the aftershocks. All the quakes on Friday were centered at a depth of about three miles in western Niigata Prefecture along the coast of the Sea of Japan, it said. Police said the earthquakes caused a 75-foot section of a road to sink, set off 30 landslides, and created cracks in roads and the ground at 60 locations. The hardest-hit area was Takayanagimachi, a town of 4,000 people, where a dozen homes suffered minor damage, including broken furniture and window panes, police said. The Richter scale is a measure of ground motion as recorded on seismographs.