Modeling of crustal layering using three-dimensional analysis of stress-drop slip zones in an elastic layer/half-space system

A numerical scheme for calculating the elastic fields in a layer over a hal f-space medium due to embedded slip zones of prescribed stress drop was dev eloped to examine how the layer influences fault mechanics. Although the me thod is general, for simplicity, only penny-shaped slip zones were consider ed in the current analysis. For slip zones that are embedded in the half-sp ace and near the interface, it was found that the layer causes the slip to depart from that for a uniform medium: softer layers tend to increase, but stiffer layers tend to decrease the magnitude and gradient of the slip near the upper end of a slip zone. Consequently, the layer causes an increase, if the layer is softer, or a decrease, if the layer is stiffer, in the ener gy release rate of the slip zone. The layer was also seen to have a strong effect on the surface displacements to the extent that the distance change predicted between a pair of stations across the slip zone could be biased b y a uniform half-space model. The results also showed that the layer can ca use a significant change in the uniform normal stress, which can alter the frictional resistance.