Brian,

I went back into the PDE files to see if I could see anything prior to the Whittier Narrows quake on 10/01/1987. It appears there are no quakes below 3.0 in that time frame of the file. So it is quite possible that other swarms of around 2.5 mag could have occurred before that date. The Whittier Narrows aftershock sequence lists no quakes under 3.0. I am sure there were dozens if not hundreds of 2.0 micros associated with that event. Thought that info might be a clue to something...but.

Glen