Earthquake Monitoring in Southern California for Seventy-Seven Years (1932-2008)

SCSN earthquake catalog from 1932 to the present, a period of more than 77 yrs. This catalog consists of phase picks, hypocenters, and magnitudes. We present the history of the SCSN and the evolution of the catalog, to facilitate user understanding of its limitations and strengths. Hypocenters and magnitudes have improved in quality with time, as the number of stations has increased gradually from 7 to ∼400 and the data acquisition and measuring procedures have become more sophisticated. The magnitude of completeness (Mc) of the network has improved from Mc ∼3:25 in the early years toMc ∼1:8 at present, or better in the most densely instrumented areas. Mainshock–aftershock and swarm sequences and scattered individual background earthquakes characterize the seismicity of more than 470,000 events. The earthquake frequency-size distribution has an average b-value of ∼1:0, with M ≥6:0 events occurring approximately every 3 yrs. The three largest earthquakes recorded were