Northridge Earthquake Sequence

Map showing one month of aftershocks following both the 1994 M6.7 Northridge (red circles, scaled by magnitude) and the 1971 M6.6 Sylmar (San Fernando) (blue circles, scaled by magnitude) mainshocks. The locations of the mainshocks are shown by the large red (Northridge) and blue (Sylmar) circles. The focal mechanisms for both events (beach ball symbol linked to the two mainshock locations) indicate that both earthquakes were thrust events occurring on faults of different orientations. The fault traces (dark grey lines) show the complex network of faults in the region. Cities are indicated by labeled black squares.