Surface strong motion associated with a stick-slip event in a foam rubber model of earthquakes

In this paper, we present and interpret dynamic displacement data for a stick-slip event in a foam rubber model of earthquake faulting. Static displacement data are used to infer the stress drop of about 0.016 μ, where μ is the shear modulus. The rupture velocity 0.7 β, where β is the shear-wave speed, is also inferred from the data. The observed particle displacement and particle velocity data are compared with analytical and numerical predictions. Doppler focusing of energy by rupture propagation is clearly observed. No large transverse displacement pulse such as that observed at Station 2 of the Parkfield earthquake is observed. In addition to its value for testing analytical and numerical predictions, the laboratory model provides much needed information on the distribution of strong ground motion in the neighborhood of a fault and thus helps in the problem of microzonation for earthquakes.