Bulletin of the Seismological Society of America

Near-source ground motion at four azimuths but constant epicentral range 1s computed from a buried circular strike-slip fault in a half-space. Particle acceleration, velocity, and displacement at each station on the free surface is computed in the frequency band 0.0 to 5.0 Hz. The assumed dislocation is denved from the Kostrov (1964) displacement function for a continuously propagating stress relaxation. The azimuthal vanations in the amplitudes and waveforms directly result from spatially varying slip on the fault, spatially varying radiation pattern over the fault, and the magnitude and direction of the rupture velocity. The near-source ground motions are dominated by the rupture in the direction of the receiver. Using a 1 00-bar effective stress (initial stress minus sliding friction) in a Poisson solid with p = 3.0 kmjsec the shear wave speed, and shear modulus p. = 3.0 x 10 dynejcm , the simulated earthquake has a moment Mo = 4.5 X 1025 dyne-em. Using a rupture velocity of 0.9/1, the peak acceleration is 1195 cmjsec2 and velocity 104 em/sec for the receiver directly on strike. For a receiver 30° off strike, the maximum acceleration 236 cmjsec occurs on the vertical component.