In the hours that followed the June 18 Tsuruoka quake, aftershocks ranging from magnitude-2.7 to magnitude-4.1 were recorded around Yamagata and Niigata. Credit: HI-Net/NIED

In the hours that followed the June 18 Tsuruoka quake, aftershocks ranging from magnitude-2.7 to magnitude-4.1 were recorded around Yamagata and Niigata. Credit: HI-Net/NIED

In the hours that followed the June 18 Tsuruoka quake, aftershocks ranging from magnitude-2.7 to magnitude-4.1 were recorded around Yamagata and Niigata.
Credit: HI-Net/NIED