Investigating the amplification pattern of non-prismatic canyons using boundary element method

Scattering seismic waves from topographic features can lead to big changes in the displacements caused in free field of canyons. This effect has been observed as a result of different earthquakes and extensive damages in certain areas of the site, rock failure, and landslides were experienced. In analysis related to scattering of seismic waves, in order to evaluate the effects of topographic resonance, canyons are generally assumed to be in an arbitrary and prismatic shape. However, in reality, canyons are often non-prismatic in line with the longitudinal axis of the canyon. Therefore, the narrowed areas of canyons are selected and studied as a suitable site for structures such as dams and bridges. This study provides the comparison between prismatic and non-prismatic canyons, evaluating the amplification pattern of different part on non-prismatic under P, SH and SV waves. The boundary element method was employed for the analyses as a very powerful numerical method for studying wave propagation issues. Also, the effect of soil types, direction of wave propagation and incident wavelength on the amplification of different part of canyon have been studied. The results of this study indicate that, in the parameters which have been studied, the incident wavelength has a significant influence on amplification pattern, especially in the near parts of canyon.