12:36 PM Jul 30th
• Using earthquake data produced by the USGS and Caltech, undergraduate interns at the Southern California Earthquake Center have produced an animation showing the Chino Hills earthquake sequence, which began with a mainshock at 11:42 am on July 29 and has thus far produced over 40 aftershocks. The animation reveals that the earthquakes occurred near the intersection of three faults, the strike-slip Whittier fault, the Chino Hills fault, which dips southward toward the Whittier fault, and the Peralta fault, which dips northward toward the Whittier fault. The data indicate that the mainshock was most likely to have been caused by oblique slip (part thrust motion and part strike-slip motion) on one of these faults. The majority of the aftershocks are deeper than the mainshock, which is unusual and seems to indicate slip on the Whittier fault. …
full story
