Last week I had an EQ sensor switch I recently installed (See thread on P-wave detector) in Pomona trigger without a USGS EQ showing up. Yesterday, I got a call that the same location had another problem, and it was in the mid-morning. If the sensor tripped again, I am going to check the job and get the data from the sensor, and see if there is some sort of correlation to current activity.
Cheers!