To prevent inadvertent triggering of earthquakes by fluid injection, the Geophysical Laboratory of the University of Southern California is engaging in a detailed study of microearthquake activities along a portion of the Newport-Inglewood Fault where the accumulating tectonic stress is interacting with massive oil pumping and water flooding. Microearthquake monitoring began in February 1971 and has since operated without interruption. A detailed crustal structure was obtained of the Los Angeles basin from well-logging data and is used satisfactorily in accurate epicenter location. Many seismic events connected with the Newport-Inglewood fault system were accurately located to a third of a kilometer and fault-plane solutions were obtained for some. Hundreds of other events were recorded throughout southern California including the complete aftershock sequence of the San Fernando earthquake of February 9, 1971. Also recorded were the Amchitka nuclear shot and several Nevada Test Site events. Water flooding and oil production data have been compiled for several oil fields in our network operating area. Correlation between microearthquake events and water flooding is suggested.