Engineering data and analyses of the Whittier, California earthquake of January 1, 1976

Abstract

A magnitude 4.2 earthquake occurred near Whittier, California on January 1, 1976 at 09:20 Pacific Standard time. The shock was centered at 33.58N (Lat.) and 117.53W (Long.) in the Puente Hills of Los Angeles County. The ground shaking was recorded within a 14 Km (8.7 miles) radius of the instrumentally determined epicenter, and eleven strong-motion accelerograph records were obtained on 70 mm film from SMA-1 accelerographs operated as part of the U.S.G.S. Seismic Engineering Branch network. Although of relatively small magnitude, the earthquake did produce peak ground accelerations as high as 187% g, which merit an engineering analysis. The locations of the strong-motion accelerograph stations at the time of the earthquake are shown in Fig. 1. The eleven records were obtained from different structures as follows: (1) three records from a ten-story modern reinforced-concrete building in Whittier, (2) three records from the Carbon Canyon earth-dam site, (3) two records from the Brea earth-dam site, (4) two records from the Diemer Filtration Plant, and finally (5) one record from the Orange County Reservoir. Instruments located at Whittier Dam (16.4 Km from the instrumental epicenter) and at Puddingstone Dam (15.0 Km from the epicenter) were operational, but were not triggered by the event (Etheredge and Nielson, Ref. 1).