A Fractal Earthquake Source with a Slip Zone Generates Acceleration Time Histories with Flat Spectra

摘要

An important problem of the studies of earthquake sources is to clarify the mechanism of formation of radiated source spectra of the ω~(-2) ("omega-square") kind, or equivalently, of flat acceleration spectra. This spectral model is well established empirically and has the status of a classical one in source seismology; however, it lacks adequate theoretical foundation. It is shown that spectra of the ω~(-2) kind can be explained by combining the following three concepts regarding source rupture: (1) the fault asperity model of Das- Kos-trov; (2) the Andrews's concept that the field of the stress drop over the fault is a 2 D flicker-noise with amplitude spectrum of the 1/k type; and (3) the hypothesis that the distance of propagation of Rayleigh waves from a failing spot on a fault is determined by the width of the slip zone associated with the rupture front.