© Norio Miyamoto, JAMSTEC This 8-inch-wide (20 cm) crevasse stretches for at least tens of meters in a north-south direction; its depth is unknown. The crack, at a depth beneath the water's surface of 10, 558 feet (3,218 m) was imaged on Aug. 10, 2011.
The March 2011 megaquake off the coast of Japan opened up fissures as wide as 6 feet (3 meters) in the seafloor, a new study finds.
The fissures now scar the seafloor where peaceful clam beds once lay, according to Takeshi Tsuji, a researcher at Kyoto University in Japan. Along with seismic studies, the fissures, revealed by manned submersible vehicles that investigated the seafloor after the quake, show how the crust around the quake's epicenter expanded and cracked.
Tsuji and his colleagues had a unique opportunity to
see how the seafloor changed after the magnitude-9.0 quake struck on March 11. Before the quake, the researchers had taken video and photographs of the seafloor on the continental side of the Japan Trench, near where the crust would later rupture, generating an enormous tsunami that killed about 20,000 people.
Those videos showed a quiet seafloor broken only by occasional clam beds, Tsuji reported here today (Dec. 6) at the annual meeting of the American Geophysical Union (AGU). After the quake, however, the seabed shows evidence of the massive forces released there.