Reporting Wednesday in the British journal Nature, US experts said they found the 8.1 temblor unleashed two more extremely powerful quakes in very quick succession.
Each measured 7.8 magnitude and occurred close to each other, at a location more than 50 kilometres (31 miles) from the initial event.
I linked to this article, rather than the original Nature thing, because of 'triple whammy'. I love it!
This is nothing new in earthquake land. With better instrumentation you can divide out all the 'sub-events' or 'co-events'. No large earthquake is one big, smooth 'whoosh'. It's more like dominoes.