ASP, a low-power, in-field Automated Seismic Processor of microearthquake network data has been designed, fabricated, and deployed for initial operation in four different field areas to monitor seismicity associated with two geothermal areas (The Geysers, California, and Cerro Prieto, Mexico), a nuclear explosion with its related collapse and aftershock sequence, and late (>1 year) activity in a major aftershock series (Livermore, California). A second ASP system, with a high-speed front-end, is used in acoustic emission (1 to 20 kHz) analysis for fracture monitoring. Each of the 15 channels of ASP (configured for up to 128 channels) automatically detects, measures times and amplitudes, and computes and fits FFT's for both the P and S waves on data sampled at 100 samples/sec. These data from each channel are then processed with a central microprocessor for hypocenter location, running b values, source parameters, event count, and P-wave polarities. The system is capable of processing a 15-station detection in approximately 40 sec, excluding printout. The initial trials have demonstrated that in-field real-time analysis of data maximizes the efficiency of microearthquake surveys allowing flexibility in experimental procedures, with a minimum of the traditional labor-intensive postprocessing. Current efforts are directed toward improving efficiency of computation and data output and in expanding software capabilities.