The March 11 tsunami inundated nearly 500 square kilometers of land--an area more than twice the size of Osaka city--and left wide stretches still under water, aerial photographs and satellite images showed.
The March 11 tsunami inundated nearly 500 square kilometers of land--an area more than twice the size of Osaka city--and left wide stretches still under water, aerial photographs and satellite images showed.
The Geospatial Information Authority of Japan (GSI) estimated that at least 443 square kilometers were submerged after analyzing 2,085 aerial photos of coastal areas stretching from Aomori Prefecture to Fukushima Prefecture.
"Vast expanses of land were struck by the tsunami," said Toshio Kitahara, head of the GSI's planning division. "We intend to offer detailed geological information about the affected areas, such as accurate heights of ground after the tsunami, to support efforts to build evacuation facilities and roads."
Pasco Corp., a Tokyo-based land survey company, put the estimate a bit higher, at about 475 square kilometers submerged.
Pasco based its analysis on satellite images of the coastal region running from Aomori Prefecture to Ibaraki Prefecture.
Pasco also said about 70 percent of the flooded land in Miyagi Prefecture remained under water two weeks after the disaster struck.
The GSI (http://www.gsi.go.jp/kikaku/kikaku60003.html) and Pasco (http://www.pasco.co.jp/disaster_info/110311) are posting maps of the tsunami-hit areas on their Japanese-language websites.
A strip of plain stretching 110 kilometers from Matsushima Bay in Miyagi Prefecture to near the city of Minami-Soma, Fukushima Prefecture, was flooded up to 5 km from the Pacific coast, the data showed.
"The wide areas of lowland, only 3 to 4 meters above sea level, were submerged," Kitahara said.
The tsunami also traveled far up rivers.
Flooding of the lower reaches of the Kitakamigawa river in Miyagi Prefecture extended more than 10 km from the river's mouth.
According to the GSI, Miyagi Prefecture was by far the hardest hit by the tsunami, with 326 square kilometers, or more than 70 percent of the total, swamped.
It was followed by Fukushima Prefecture, with 67 square kilometers inundated, and Iwate Prefecture, with 49 square kilometers flooded.
In Aomori Prefecture, 2 square kilometers were affected by the waves.
By municipality, the city of Ishinomaki in Miyagi Prefecture topped the list, with 73 square kilometers deluged, followed by Higashi-Matsushima in the same prefecture, with 37 square kilometers submerged.
The water inundated 35 square kilometers of the town of Watari, also in Miyagi Prefecture, and 29 square kilometers in Sendai's hard-hit Wakabayashi Ward.
In Higashi-Matsushima, 63 percent of the city's urban districts crowded with buildings and roads were flooded. The ratio for the town of Otsuchi, Iwate Prefecture, was 50 percent.
Some areas in Miyagi and Iwate prefectures were hit by tsunami more than 10 meters high.
Damage in some areas of northeastern Japan was as severe as the devastation in the Indonesian city of Banda Aceh caused by the massive tsunami triggered by the 2004 Indian Ocean earthquake, said Tomoya Shibayama, a professor of coastal engineering at Tokyo's Waseda University.
After examining the destruction in the Arahama district of Sendai's Wakabayashi Ward, Shibayama estimated that the waves that hit the area exceeded 9 meters in height.
The tsunami turned the bucolic landscape of small settlements along a beach dotted with pine groves into a desolate expanse covered with rubble.
The pine groves, which were supposed to weaken the destructive force of a tsunami, were leveled. Many bodies were found on the beach.
The Sanriku region, known for its complicated "rias" (sawtooth) coastline stretching from southern Aomori Prefecture to the Oshika Peninsula in Miyagi Prefecture, was battered by even higher waves.
Shibayama estimates that central parts of Onagawa, a coastal town in Miyagi Prefecture, were swallowed by waves as high as 17.6 meters that dislodged ferroconcrete buildings from their foundations.
In the city of Rikuzentakata, Iwate Prefecture, beaches with pine groves were widely eroded. The coastline appeared to have retreated inland by dozens of meters.
The coast of the city did not contain much rubble or wreckage, apparently because most of the buildings had been swept away.
Only a few buildings that withstood the hammering by the tsunami dotted central parts of the city.
The Tokyo University of Marine Science and Technology said it has found evidence that Rikuzentakata at one point was under 15 meters of water.
The city of Kesennuma in Miyagi Prefecture was hit by a tsunami close to 10 meters high, according to Waseda University.
Fumihiko Imamura, a professor of tsunami engineering at Tohoku University, estimated that the tsunami had carried more than five large fishing vessels with a length of about 80 meters into the city center, causing even ferroconcrete buildings to fall.
In Kamaishi, Iwate Prefecture, large breakwaters somewhat weakened the force of the tsunami against the city.
But roads close to the port became congested with cars as people tried to escape. The first tsunami wave swept away most of the vehicles trapped on the roads.
(This article was compiled from reports by Ayako Suzuki and Tsuyoshi Nagano.)