Figure 1. Comparison of Fourier amplitude spectra of recorded (gray shade, above M = 4 and for f > 0.1 to 1 Hz and f < 20 Hz) and of destructive (dark gray shade) strong earthquake ground acceleration for epicentral distance R = 10 km, focal depth H = 5 km, geological and soil "rock" sites and 0.5 probability of exceedance, with: (1) Fourier spectra of acceleration from 10 calibration explosions at the Lyaur testing range; (2) seismological weak aftershock studies; (3) microtremor and microseism noise; and (4) numerical simulation of strong motion. The continuous lines labeled 1-7 show smoothed Fourier spectra of ground acceleration based on empirical scaling laws; f1 and f2 are corner frequencies (Trifunac, 1993) and fP is the magnitude dependent frequency of the spectral maximum