Peak accelerations from the 17 October 1989 Loma Prieta earthquake

Peak accelerations of the Loma Prieta main shock have been tabulated from instruments maintained by a number of organizations. A subset of 86 records from nominally free-field sites have been analyzed which have been subdivided into rock, alluvium, and bay-mud categories according to data available in various reports. After correction for attenuation, the peak accelerations on rock, alluvium, and bay-mud sites are factors of 1.6, 1.8 and 4.5 larger, on the average, than Joyner and Boore's (1988) predicted values for a M=6.9 earthquake. The Loma Prieta earthquake provided the first opportunity to study the relative amplitudes from strong-motion recordings. -from Authors