ROCK MOTION ACCELEROGRAMS FOR HIGH MAGNITUDE EARTHQUAKES

THE TIME HISTORY OF THE MOTIONS LIKELY TO DEVELOP IN ADJACENT ROCK FORMATIONS ARE EVALUATED TO DETERMINE THE RESPONSE OF SOL DEPOSITS AND THE INFLUENCE OF LOCAL SOIL ON GEOLOGIC CONDITIONS ON THE MOTIONS DEVELOPED NEAR THE GROUND SURFACE DURING EARTHQUAKES. BOTH THE AMPLITUDE OF ACCELERATIONS AND THE PREDOMINANT PERIOD OF THE MOTIONS DEVELOPED IN ROCK DURING EARTHQUAKES ARE KNOWN TO VARY WITH THE DISTANCE OF THE SITE FROM THE SOURCE OF ENERGY RELEASE. TYPICAL AVERAGE RELATIONSHIPS BETWEEN THE MAXIMUM ACCELERATION PRODUCED IN ROCK, THE PREDOMINANT PERIOD OF THE ACCELERATIONS, THE MAGNITUDE OF THE EARTHQUAKE PRODUCING THE MOTIONS, AND THE DISTANCE OF THE ROCK SITE FROM THE CAUSATIVE FAULT ARE SHOWN IN FIGURES. AN APPROXIMATE PROCEDURE FOR DEVELOPING THE FORM OF AN APPROPRIATE ACCELEROGRAM FOR ANTICIPATED ROCK MOTIONS TAKING THESE CONSIDERATIONS INTO ACCOUNT IS DESCRIBED. THE GENERAL PROCEDURE, WHICH GIVES CONSIDERATIONS TO THE RELATIVE POSITIONS OF SITE AND FAULT AND TO THE PREDOMINANT PERIODS LIKELY TO BE ASSOCIATED WITH DIFFERENT ACCELERATION LEVELS MAY PROVE USEFUL FOR OTHER PURPOSES. THE ACCELEROGRAMS PRESENTED ARE BELIEVED TO BE REASONABLY REPRESENTATIVE OF THE ROCK MOTIONS TO BE EXPECTED AT SITES LOCATED TEN MILES OR SO FROM THE CAUSATIVE OF MAJOR EARTHQUAKES AND THUS MIGHT BE USEFUL FOR ANALYSIS OF GROUND MOTIONS OR OTHER RESPONSE STUDIES.