ACOUSTIC EMISSION ALONG THE SAN ANDREAS FAULT IN SOUTHERN CENTRAL CALIFORNIA

A pilot study to determine the feasibility of monitoring acoustic emissions for possible use in prediction of earthquakes along the San Andreas fault, successfully demonstrated that audio frequency microseismic activity can be detected, that certain types of areas will make the best sites for further study, and that certain types of instrumentation and techniques will be most successful for this purpose. The acoustic detection devices consist of two siesmotion units which amplify sound up to 2.5 million times and can detect movement that is smaller than the diameter of a hydrogen atom. The seismophone or sensing transducer is a piezoelectric crystal device of high sensitivity designed to pick up vibrations in the medium upon which it rests, and to supress sound carried in the air. The laboratory analysis of the taped records is described. The problems encountered by the operator, and problem ares associated with determination of the distances to the points of origin of the acoustic emission the identification and elimination of extraneous noise, and the achievement of representative results are discussed.