I would guess the first was a forshock to the second. Of course, if another larger quack were to occur, then the first two would become forshocks to the third.

This link show the standard USGS line to a Calfornia aftershock sequence (Bolinas EQ), including the odds of a larger quake. They put it at 5-10%, which is typical for the shallow Calfornia type EQ. Of course, your milage may vary. The recent Washington EQ have very few aftershocks, supposedly because of the mainshock's depth. I have no idea if the 5-10% forshock could be applied to that EQ, my guess would be you could not apply it. In addition, the seismic history in the washington area is not nearly as well defind as California.

http://quake.usgs.gov/recent/reports/bolinas/nc40104152.afterwarn.html

I haven't checked the depth of the India EQs. If the mechanism in the offshore India EQs were similar to California, I would guess one could apply the same odds to the forshock concept.

Michael

• USGS Bolinas Aftershock Info