Particle motion was examined along the following kinematic fault model: the fault plane is a rectangle so elongated that differences in particle motion in the shorter dimension can be neglected and rupture, once initiated, can be considered to propagate only in the longitudinal direction(s) at constant speed; the distribution of particle displacement along the ruptured fault segment maintains the same sinusoidal shape at different times until finally all particles stop simultaneously. It was found that the pattern of particle motion in this model depends on whether the rupture propagates unilaterally or bilaterally. For the bilateral case, particle displacement and velocity are nearly a finite ramp and a box-car function of time, respectively. The maximum particle velocity is the same everywhere along the final ruptured fault segment, but the average velocity is slightly higher for particles closer to the ends. For the unilateral case, particle velocity is approximately an impulse function of time for particles near the starting edge and gradually becomes a box-car function for particles near the ending edge of rupture. The maximum velocity is the same for all particles along the fault segment, but the average velocity is considerably higher for particles closer to the ending edge. It is not a good approximation for either of these cases to assume that all the particles along the fault segment have the same displacement-time function with only a time delay.

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