| Abstract: | To identify the key features of the free-field response for antiplane motion, a vast parametric study is performed, varying the location of the control point, the nature of the wave pattern and the site properties. Harmonic and transient seismic excitations for a site consisting of a layer on bedrock and an actual soft site and a rock site are investigated. When the control point is selected at the outcrop of the bedrock, the amplification of the motion to the free surface of the site depends on the angle of incidence of the incoming wave in the bedrock. Vertically incident, inclined SH-waves and Love-waves result in a very similar variation of the motion with depth. In contrast to Love-waves the attenuation of the motion in the horizontal direction for inclined body waves depends on the damping of only the bedrock. Love-waves thus attenuate more strongly than body waves, especially for soft sites and in the higher-frequency range. Generally, higher Love-modes attenuate less than the first. To determine the seismic input motion for a structure at a soft site, it seems sufficient to examine only extremely shallow body waves. For a rock site, however, Love-waves should be investigated. |
