The memory of the earthquake of March 11, 2011, which preceded the tsunami leading to the Fukushima nuclear disaster, haunts the Japanese capital.
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Tokyo and his suburbs have undergone a jumper 3.5 at the end of the morning on Saturday 9 October. Anodine, she was, however, the third sensitive replica of the magnitude earthquake 5,9 occurred in the evening of October 7th. This earthquake revived the fear of a “Big One”, a large-scale earthquake in a capital that is still perceived as vulnerable in the persistence of seismic threats.
The earthquake of October 7 did “only” 43 wounded and material damage, mainly at the water pipe. Train traffic has been disturbed. A train from the NIPPORI-TONERI LINER automated line derailed. The earthquake occurred between the Philippine Sea and the Pacific Sea, explains Takuya Nishimura from the Disaster Prevention Research Institute of the University of Kyoto. Japan is at the convergence of four plates (Philippines, Pacific, North American and Eurasian). Its basement is crisscrossed many active flaws. The tectonic situation is complex and the archipelago suffers 20% of the earthquakes of magnitude 6 or more recorded in the world.
In the majority of cases, the consequences remain limited. The country applies strict antisismic construction standards. It has alert systems running from the detection of P (primary) waves near the epicenter, which allows to warn of the arrival of the (secondary), slower but more powerful and destructive waves. . Obtained up to one minute before the earthquake, the information is transmitted on mobile phones and on television. It causes the automatic stop of lifts, factory assembly chains or trains traffic.
More than 100,000 deaths in 1923
Despite this device, the earthquake of October 7 revived the memory of March 11, 2011, with a magnitude 9 and followed by a tsunami and the Fukushima nuclear disaster. This earthquake in northeastern country had been strongly felt in Tokyo, where he had seven dead. According to the Japanese scale of seismic intensity measurement on the ground surface, graduated from zero to seven, the level reached in the capital had been 5 +. It was the same on October 7th.
The authorities have, therefore, quickly called for prudence to the risk of replicas. “The observations of the past show that a similar earthquake occurs, in 10 to 20% of cases, in the week following a major earthquake,” said Tsukada Shinya, from the Japanese Meteorological Agency. In July 2005, a magnitude of magnitude 4.5 had occurred a week after a magnitude 5.9 earthquake in the same area as that of October 7th.
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