Earthquake Research at Parkfield, California, for 1993 and Beyond--Report of the NEPEC Working Group to Evaluate the Parkfield Earthquake Prediction Experiment [open pdf - 5MB]
From the Summary: "During the past century, earthquakes of M ~ 6 have occurred with remarkable regularity on the San Andreas fault at Parkfield, California. Events occurred in 1857, 1881, 1901, 1922, 1934, and 1966. At least two of these events were preceded by large foreshocks and there is evidence for precursory creep of the shallow segment of the fault prior to the 1966 event. In 1984-1985, scientists developed and published a prediction, based on a model of 'characteristic' earthquakes, that the next M ~ 6 Parkfield event was expected in a time window centered on 1988, with 95% probability that the earthquake would occur by the end of 1992 [...]. Shortly after the publication of this prediction, with endorsement by the National Earthquake Prediction Evaluation Council ('NEPEC'), the United States Geological Survey ('USGS') initiated the Parkfield Earthquake Prediction Experiment (the 'Experiment'). With additional support from the state of California, the Experiment took on a public services aspect, as well as a geophysical aspect. By late summer, 1992, the predicted event had not yet occurred. NEPEC chartered a Working Group to evaluate the Parkfield Earthquake Prediction Experiment. This group was asked a series of questions which are summarized below, along with the responses of this Working Group."
U.S. Geological Survey Circular 1116
U.S. Geological Survey: https://pubs.usgs.gov/