Hazard deaggregation at each grid point of a probabilistic seismic hazard map can provide maps of the most probable seismic source distance and magnitude. Maps of predominant seismic source distance and magnitude for PGA, and 5% damped spectral acceleration (SA) at 0.3-, 1.0-, and 2.0-sec periods are produced for the first time for Los Angeles, Orange, and Ventura counties in southern California. These maps show that large earthquakes on faults local to any site generally dominate the 10% probability of exceedence in 50- and 100-yr hazards in southern California. Major faults, like the San Andreas, San Jacinto, and Elsinore faults, dominate mainly in their vicinity. At spectral periods beyond 2 sec, earthquakes on these major faults can dominate out to larger distances.