Scaling Law of Earthquake Source Time‐Function

Abstract

Further evidences support the scaling law of far‐field seismic spectrum based upon the ω‐square model (Aki) for earthquakes with MS > 6 and for periods T > 10s. Recent observations, however, unequivocally require the modification of the above law for periods T < 10s. Unfortunately, the presently available data are not sufficient for a unique revision of the scaling law. We propose two alternatives and discuss their implications and consequences. In either case, we have to conclude that a large earthquake and a small one are substantially different. One interesting feature of the ω‐square model appears to be unaffected by the required revision; that is, the spectral density of the fault‐slip time‐function for periods T < 5s takes the same absolute value, independent of magnitude, for earthquakes greater than Ms= 65. This result has important consequences in earthquake engineering because the seismic motion in the vicinity of an earthquake fault will scale as the fault‐slip motion. Copyright © 1972, Wiley Blackwell. All rights reserved