It’s 5am and I don’t feel like staying awake and looking super closely at a map, but I think that quake was in Sierra Madre fault zone, which basically runs along the base of the San Gabriels through the valley, parallel to the San Andreas on the other side of the mountains.

The red flag is the approximate epicenter of the 71 Sylamar quake (coordinates from wiki) and the white dot is this morning’s quake. Probably what’s called a thrust fault, which is a common fault type in the valley (Northridge quake was on one). I’m not a scientist.

That wasn’t the Big One but the Sierra Madre fault zone, like all the major faults in LA, is capable of being A Big One. If you’ve eaten your way through your earthquake kit in the last few months, take this as a reminder to restock if you can and create an emergency plan.