But on that fateful Friday, when the North American plate slid over the Pacific plate along a subduction zone running 130km (80 miles) off the Pacific coast of northern Japan, the shock leapt from the first segment to a second and on to a third, extending the fault zone some 400km and increasing its intensity more than 30-fold.

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If the euro-zone crisis, which is flaring up again, leads to a break-up, the shock-waves will hit Britain.

ECONOMIST: Britain's economy

Some observers said the attack came as a particular shock given that safety has improved at least in the city's tourist-friendly, seaside South Zone neighborhoods.

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