While neither caused any major damage, experts have warned that Monday's quake may have been associated with the Puente Hills thrust fault, which could one day cause a huge earthquake in Los Angeles.

That means it came from a region of faults called the Appalachian fold-and-thrust belt, which is much more ancient and quiet ...

The researchers measured the orientations of smaller faults that formed in the vicinity of the Liachar Thrust — a major fault where a massive slab of rock is being shoved upon another.