By Jonathan Amos
Another day, another earthquake. Except the Magnitude 8.9 tremor off the coast of Honshu, Japan, will be a standout event for 2011 - if not in terms of the eventual death toll it brings, then certainly in scale.
There are usually only one or two quakes of M 8.0 and above every year. And even for a country such as Japan, which is very familiar with seismic hazards, this is extraordinary.
The history books show there have been seven quakes rated at M 8.0 or greater since 1891 in Japan. And with big tremors come big aftershocks.
Following the initial M 8.9 event at 1446 local time (0546 GMT), a sequence of major tremors was initiated - six of them within an hour-and-a-quarter that were all bigger than or all equal to last month's quake in Christchurch, New Zealand (M 6.3). The largest of the aftershocks was a M 7.1.