Wrinkle-like Weertman pulse at the interface between two blocks of foam rubber with different velocities

We verify the existence of self-sustaining wrinkle-like Weertman velocity p ulses along a prestressed interface between two dissimilar (Delta V = 60%) blocks of foam rubber. Properties of the observed velocity pulses are simil ar to the theoretical prediction of Weertman (1980), and the numerical calc ulations of Andrews and Ben-Zion (1997). Particle displacement, in the dire ction perpendicular to the fault, is much larger in the slower medium than in the faster medium, resulting in a separation of the interface during the passage of the slip pulse. The rupture velocity is neat the shear wave vel ocity in the slower material, and the direction of propagation is nearly al ways in the direction of the shear particle motion in the slower block. The pulse is self-maintaining, that is, it does not die out from radiation dam ping, obtaining the necessary energy by releasing locally stored shear pote ntial energy.