What chance of a 'big one' in Tokyo?
Some generated tsunamis that claimed more than 100 lives; and it is thought they occurred because the original earthquake, on 26 December, increased stresses along the tectonic plate boundary that lies to the west of Sumatra and Java.
So what is the outlook for Japan now, especially for the great city of Tokyo and the Kanto plain on which it sits?
This is home to one-quarter of Japan's population, as well as being the country's administrative and commercial centre.
Big quakes struck the area in 1703, 1855 and 1923, with the latter claiming the lives of 100,000 people.
Were any one of these events to occur today, the economic losses alone would be expected to top $1 trillion (80 trillion Yen).