Prediction of peak ground motion from earthquakes

A statistical analysis shows that the peak horizontal accelerations recorded from the San Fernando earthquake of February 1971 attenuate with focal distance as R−1.39. This attenuation rate is nearly identical to that reported for peak accelerations from underground nuclear explosions. Assuming that the derived attenuation is independent of source parameters and using data from a number of other California earthquakes, the scaling of peak horizontal acceleration with magnitude was determined statistically. Assuming that the attenuation of peak velocity and displacement with distance is identical for earthquakes and underground nuclear explosions, the scaling of earthquake peak velocity and displacement with magnitude was also determined. The equations resulting from these analyses are: a = 6.6 × 10−2 100.40MR−1.39, v = 7.26 × 10−1 100.52M R−1.34 and d = 4.71 × 10−2 100.57MR−1.18, where a, v, and d are maximum acceleration (g), velocity (in centimeters per second) and displacement (in centimeters), respectively, M is the local magnitude, and R is the focal distance (in kilometers). In this analysis, no attempt was made to account for effects of recording site geology.