In some simulations, large modulus reductions have been noticed in areas remote from regions of plastic flow (e.g., near the base of the model). It appears that the use of a single modulus-reduction curve is unrealistic in these cases. There is evidence (e.g., see Darendeli 2001) that degradation curves depend on the mean stress level: for example, at depth (high mean stress), there is less damping and modulus reduction. By making the hysteretic damping depth-dependent, the simulation should be more realistic.