Just checked the Japan mega-quake of March 11, 2011

What I didn't realise was that there were several M6-7 foreshocks in the two days prior to it happening

Seems foreshocks are actually pretty common - even though the myth persists that smaller mid-size quakes are good coz they are 'releasing the build-up of energy' - quite often they are also heralding an even bigger shock to come