Frictional resistance of a fault zone with strong rotors

Abstract

As a possible mechanism to explain the lack of a heat flow anomaly along the creeping section of the San Andreas Fault, we have determined the effect of placing hard rotors along a surface between two deformable media, in this case styrofoam balls between two blocks of foam rubber. The probable presence of Franciscan rocks at depth along the creeping section of the San Andreas Fault suggested this mechanism, since the Franciscan is characterized not only by basic serpentinous rocks which are weak, but also by embedded, more or less equidimensional, blocks of very strong rocks (knockers), e.g., high grade blueschists and eclogites, which might act as rotors. The results suggest that knocker rotation may be a viable mechanism for reduction of friction on the creeping section of the San Andreas fault, and thus be at least a partial explanation of the lack of any observed frictional heat flow anomaly there.