Foam rubber model studies of problems in seismology and earthquake engineering

We validate the foam rubber modeling technique by comparing the experimental results of soil-structure interaction for simple structures with rigid, cylindrical foundations on a homogeneous foam rubber block with the analytical results. Then we construct a 3-D layered model representing the soil and structure of the El Centro Terminal Substation. For vertically incident SH/-waves, the response amplitude of the building at frequencies above 4 Hz is up to a factor of 3 lower than the response of the free field in approximate agreement with 2-D numerical model results. This study also indicates that at higher frequencies most of the reduced response is due to the energy being scattered by the shape of the foundation and not by its inertial mass. Results for incident angles of 50;A study of topographic amplification is made by constructing a 3-D model of the actual topography around the Pacoima Dam accelerograph site. Results indicate a clear amplification and resonance due to ridge topography, and a pronounced oscillation of the dam crest, but in neither case does the frequency and character explain the high acceleration observed during the San Fernando earthquake. The dynamic interaction between the Pacoima Dam and the ridge is less than 2% at about 10 Hz and less than 12% at about 5 Hz. Results from non-vertically incident SH-waves show that the topographic effect is dependent on the direction of approach of the seismic energy.