Assessing the Impact of Local Geology on Ground Motion Amplification in South East England

Standard methods for modelling the impact of near surface geology on ground motion, such as SHAKE91 (Idriss & Sun, 1992), require knowledge of the shear wave velocity profile of the subsoil. While field gathered velocity profiles provide the optimum input to this type of analysis, invasive investigation methods, such as seismic cone penetrator, may not always be efficient due to cost and access (Anderson et al., 2007). Non-invasive, surface-wave methods do not always achieve the depth of investigation required, and in the absence of field data shear velocities can be estimated using physical property relationships. Alternatively, deeper geophysical investigation using the H/V spectral ratio technique on ambient vibrations can be used to obtain site velocity profiles (SESAME 2004). We have used a combination of these methods to assess stratigraphic controls on site characteristics and ground motion amplification in South East England.