A reportedly long and violent earthquake has struck Sendai in northern Japan, shaking buildings in faraway Tokyo. Many people were reportedly been injured when the roof of a swimming pool collapsed in the city of around one million people.The tremor registered nearly seven on the Japanese seven-point scale of magnitude. A Tsunami warning has been issued for the coastal region of Miyagi, around 300 kilometres north of the capital. Damage in Sendai appears to be slight, and the worst may have been avoided due to the depth of the quake. The epicentre was some 20 kilometres under the seabed off Japan’s pacific coast.