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The earthquake giving rise to the tsunami occurred at 6,000 feet below sea level 80 miles from northern Japan and 240 miles from Tokyo. Seismic waves (sound traveling through the solid crust of the earth below the ocean floor) move at around 14,000 KM/hr or about 8,300 miles/hr. This means that the shock wave hit northern Japan (80 miles away) about 36 seconds after the quake. Japan knew, at least at this point, that a tsunami and probably a tidal wave were on their way and would hit the island nation within minutes. With the modern warning systems that are in place using both radio and sound equipment, Japan knew the moment the quake occurred that a tsunami was on its way.

A tsunami travels at about 600 mph which means that it would have reached northern Japan (80 miles away) about 8 minutes after the quake and Tokyo (240 miles away) in about 24 minutes. The actual time was probably slightly greater because a tsunami slows as it gets into shallow water so it was probably attenuated considerably from its spot of origin to the various points of contact with land thus increasing the time of travel somewhat.

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14y ago

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