The data acquired in the Parkfield, California experiment are unique and they are producing results that force a new look at some conventional concepts and models for earthquake occurrence and fault-zone dynamics. No fault-zone drilling project can afford to neglect installation of such a network early enough in advance of the fault-zone penetration to have a well-defined picture of the seismicity details (probably at least 1000 microearthquakes--an easy 2-3 year goal for the M<0 detection of a borehole network). Analyses of nine years of Parkfield monitoring data have revealed significant and unambiguous departures from stationarity both in the seismicity characteristics and in wave propagation details within the S-wave coda for paths within the presumed M6 nucleation zone where we also have found a high Vp/Vs anomaly at depth, and where the three recent M4.7-5.0 sequences have occurred. Synchronous changes well above noise levels have also been seen among several independent parameters, including seismicity rate, average focal depth, S-wave coda velocities, characteristic sequence recurrence intervals, fault creep and water levels in monitoring wells. The significance of these findings lies in their apparent coupling and inter-relationships, from which models for fault-zone process can be fabricated and tested with time. The more general significance of the project is its production of a truly unique continuous baseline, at very high resolution, of both the microearthquake pathology and the subtle changes in wave propagation
