A note on the surface motion of a semi-cylindrical alluvial valley for incident-cylindrical SH waves radiating from a fault with arbitrary orientation

• Adequacy of approximating cylindrical SH waves by plane SH waves.
• Cylindrical SH waves radiated from finite faults.
• Effects of fault orientation on amplification of surface motions.

Faik Kara and Trifunac [1] showed that the plane-wave assumption for incident SH waves is often a good approximation for cylindrical waves that radiate from a finite source even when the source is at a distance as close as twice the size of inhomogeneity and when the source and inhomogeneity are described within the same coordinate system. In a geometrically more general setting, for arbitrary orientation of the fault—and when the radiation pattern must be considered—cylindrical waves from the source cannot always be approximated by plane waves. Thus, amplification of surface motions in the vicinity of an inhomogeneity becomes more complicated. Examples presented in this paper illustrate the effects of incident cylindrical waves on surface motion in and near semi-cylindrical soft inhomogeneity when the causative faults have different curvatures and orientation.