Since June 1960, several hundred natural microearthquakes having S-P intervals of less than 2.3 seconds have been recorded by high-magnification seismographs located in the mountains 3 miles west of Socorro, New Mexico. Two seismographs have been used in this study, a single-channel seismograph (magnification 9 million at 20 cps) recording 24 hours a day at 3.5 mm/sec and a three-channel seismograph (magnification variable from 0.08 to 10 million at 20 cps) recording a few hours each day at either 15, 30, or 60 mm/sec. Data from continuous recording indicate: (1) Rate of microearthquake activity is significantly greater in the fall months; (2) more shocks occur in groups than were predicted for a random and mutually exclusive distribution of events. Analysis of high-resolution seismograms (three-component, tripartite, and others) indicates: (1) Epicenters for most shocks are within a 36-km2 area southwest of Socorro; (2) depths of focus range from 2.7 to 6.3 km; (3) energy release for the weakest shocks recorded is of the order of 107 ergs; (4) number of microearthquakes and energy release are related by log10 N = C2 - 0.496 log10 E.
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