Effect of earth layering on earthquake displacement fields

The displacement fields due to a very long vertical strike-slip fault are calculated for earth models consisting of two layers over a half-space. It is shown that if zones of low rigidity are present beneath the Earth's surface, they will result in an amplification of the displacement field observed at the Earth's surface. The amount of amplification depends both on the structure and the distance from the fault. If thin soft layers exist in the upper mantle, it is shown that they will have a very strong effect on the observed displacements. It may eventually be possible to use static observations at the surface to detect such layers.