This velocity is also the approximate speed of sound in rock. This finite speed means that when the earthquake begins, the far extremities of the fault block are still motionless. It takes a few seconds for the signal to traverse a long distance. Assumption 2 violates the observation that fault motion propagates with time. Assumption 3 violates the laws of petrophysics.
All rocks have a certain amount of elasticity.
Some compression and rarefaction of rocks can occur without brittle failure. Assumption 4 is weak because if a small portion of the fault begins and completes all motion before the next section moves, the force of motion never exceeds the strength of the rock. The mechanical paradox of large overthrust faults originates iwth a fallacious assumption in the concpetual model upon which the mechanical analyses of overthrust faulting have been based. The model assumes, tacitly, that sliding is initiated, and occurs, simultaneously over the entire fault surface. This answer to the 'mechanical paradox' is not entirely new.