Mechanical Analysis of the Accumulation of Stress and Slip on the San Andreas Fault at Parkfield

ABSTRACT: An analytical model, based on deformation of the half-spaces defining the fault, is used to analyze stress accumulation and slip on a segment of the San Andreas Fault near Parkfield. The study includes an analysis of the spatial and temporal relationship of 333 clustered earthquakes that occurred during the 32 month period from May, 1987, through December, 1989. The model predicts a progressive form of failure that results from mechanical interaction between contacting asperities. The results show that mechanical interaction can lead to clustering of events in time and space as is observed on the Parkfield segment. The spatial distribution of the asperities is shown to be an important factor in determining the progression of failure of the fault segment.