relatively high and early analysis (pre-digitalization) indicated that the mainshock was complex, with a double train of P-waves arriving with a 1.4–1.8 second interval. The National Strong-Motion Instrumentation Network (NSMIN) (a cooperative effort including the United States Geological Survey and other organizations) also monitored a set of 52 strong motion stations in the Los Angeles area. Most of the stations successfully captured the event, and the closest unit to the mainshock, a rock site at Garvey Reservoir, recorded a peak horizontal acceleration of 0.47 g. A twelve-story steel frame building in Alhambra was outfitted with accelerographs in the basement, at mid-level, and at the top of the structure. The top floor instruments recorded a peak acceleration of 0.18 g during the 1971 San Fernando earthquake and instruments on the sixth floor recorded a peak acceleration of 0.47 g at the time of the Whittier mainshock. A ten-story reinforced concrete building in Whittier (7215 Bright Ave.) saw a peak horizontal reading of 0.63 g in the basement. Aftershocks A magnitude 5.2 event occurred three days later on October 4, causing additional damage in Alhambra, Pico Rivera, Los Angeles, and Whittier. The shock's effects were assessed at VII (Very strong) on the Mercalli Intensity Scale with damaged chimneys, broken windows, and the collapse of two bell towers at the San Gabriel Civic Auditorium. This event was also responsible for several injuries and one additional death. On February 11 of the following year, another small aftershock again damaged chimneys, broke windows, cracked drywall, and some homes' foundations in Pico Rivera, Pasadena, and Whittier. The October 4 aftershock struck to the northwest of the mainshock, and was primarily a strike-slip event on a steeply dipping, northwest-striking fault. The origin of faulting for this event was at a depth of , which places it within the hanging wall of the thrust fault that was responsible for the mainshock. This aftershock was recorded on thirty of the NSMIN stations at distances of up to . The majority of the stations were located in buildings, but nine were located at dams or reservoirs, and four were at Veterans Administration buildings. Lighter accelerations were observed than the main shock, with peak accelerations in the range of 0.15 g–0.33 g, all occurring at six stations that were within of the epicenter. Other events The 1929 Whittier earthquake occurred on July 8 with a local magnitude of 4.7 and maximum