There was a magnitude 4.4 earthquake in southern California this morning at 1:35 AM, centered about three miles north of Fontana along the southeastern edge of the San Gabriel Mountains in a complex zone where three major fault systems intersect: the San Andreas, the San Jacinto, and the Cucamonga. Very minor damage was reported.
The picture above was taken relatively close to the epicenter area and shows the incredibly steep and rugged topography produced by the faults that have been active in the region. Cucamonga Peak on the left rises to an elevation of nearly 9,000 feet. The mountains have been pushed up in a very short period of time geologically speaking, only a few million years.
The focal mechanism suggests right lateral motion, consistent with the expected stresses on the San Jacinto fault.
For the official information on the earthquake, check out the USGS page: http://earthquake.usgs.gov/earthquakes/eventpage/ci11413954#summary