In March 2012, a magnitude 9.0 earthquake—the fourth largest recorded since 1900—triggered a powerful tsunami that pummeled the northeastern coast of Japan. The earthquake occurred offshore, about 130 kilometers (80 miles) east of Sendai at 2:46 p.m. on March 11. Within 20 minutes, massive swells of water started to inundate the mainland.
The tallest waves and most devastating flooding from the 2011 T?hoku-oki tsunami occurred along the jagged coast of northern Honshu, a landscape dimpled with bays and coves known as ria coast. The steep, narrow bays of ria coasts trap and focus incoming tsunami waves, creating destructive swells and currents that can push huge volumes of water far inland, particularly along river channels.
That’s exactly what happened in the days before the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), an instrument on NASA’s Terra satellite, captured the middle image above (on March 14, 2011). It shows severe flooding along the Kitakami River three days after the earthquake struck.