Effects of a V-shaped canyon with a circular underground structure on surface ground motions under SH wave propagation

The two-dimensional scattering and diffraction of plane SH waves by a symmetrical V-shaped canyon with a circular underground structure in a half-space is studied by using the wavefunction expansion method. The underground structure involved covers three common types: a cavity, a lined tunnel and a geological inclusion. By combining a domain decomposition strategy and the method of images, the wavefields in corresponding subregions are constructed in terms of infinite series of wavefunctions with unknown complex coefficients. The unknown coefficients are obtained by applying the Graf s addition formula and solving a matrix that represents the boundary conditions along subregion interfaces. To show effects of the surficial canyon and underground structure combined irregularity on ground motions, a parametric study is executed in both the frequency and time domain. A zone of ground motion amplification is found at the vicinity of the corner of the canyon with a lined tunnel buried nearby.