It was a little deep for this area at 18.9km (11.7 miles). ‘Could be that relatively small motion is tectonically locked in down there, thus no after shocks. It could also be that this event was an aftershock of several others over the past 10 years or so. Though undoubtedly it’s a sign of accumulationg stress along at least that part of the overall SoCal system, which will eventually bust out somewhere therein sooner or later.