We examine continuous data from the Southern California Seismic Network from 2003 and identify infrasound acoustic waves from 76 previously undetected events. Using waveform cross-correlation of the signal envelope functions, we determine their relative arrival times and estimate source locations. The waves travel at acoustic speeds of 320 m/s and are observed in seismic records up to 450 km from their probable source locations off the west coast of southern California. The dominant daylight occurrence of the events points to a man-made source related to military activity. The events are mostly recorded in the winter and spring when atmospheric conditions trap acoustic energy near the Earth's surface and favor propagation to the west. These results suggest that data from regional and global seismic networks can supplement observations from infrasound arrays for Comprehensive Test Ban Treaty monitoring and geophysical applications such as volcano monitoring, bolide detection, atmospheric acoustic sources and atmospheric tomography.