Gusev's stochastic model for the seismic source: high-frequency behavior in the far zone

This paper discusses local features in the source function that generate in the far zone simultaneously (a) a quadratic decay of the source spectrum and (b) the loss of radiation directivity at high frequencies. A. Gusev drew attention to this problem and suggested that a positive solution can be obtained for earthquake rupture front with a rather complex ("lace") structure. Below we give a theoretical solution of the problem and show that the front structure can be simple enough, but not smooth.