Thursday, 21 October 2021

Japan’s 400 Kilometre Tsunami Shield


"The B1M" Channel on Youtube shows one of the most important pieces of concrete in Japan.

Keep in mind, the geophysical effects that Japan has. Portions of northeastern Japan shifted by as much as 2.4 metres (7 ft 10 in) closer to North America, making some sections of Japan's landmass wider than before. Those areas of Japan closest to the epicenter experienced the largest shifts. A 400-kilometre (250 mi) stretch of coastline dropped vertically by 0.6 metres (2 ft 0 in), allowing the tsunami to travel farther and faster onto land. One early estimate suggested that the Pacific plate may have moved westward by up to 20 metres (66 ft), and another early estimate put the amount of slippage at as much as 40 m (130 ft). On 6 April the Japanese coast guard said that the quake shifted the seabed near the epicenter 24 metres (79 ft) and elevated the seabed off the coast of Miyagi Prefecture by 3 metres (9.8 ft).

The 9.1-magnitude (Mw) undersea megathrust earthquake occurred on 11 March 2011 at 14:46 JST (05:46 UTC) in the north-western Pacific Ocean at a relatively shallow depth of 32 km (20 mi), with its epicenter approximately 72 km (45 mi) east of the Oshika Peninsula of Tōhoku, Japan, lasting approximately six minutes.

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