EFFECT OF SINUSOIDAL INTERFACES ON TELESEISMIC P-WAVE RECEIVER FUNCTIONS

Using the T-matrix, or extended boundary condition, method, we model s eismic wave scattering from earth models with irregular interfaces. Th is is motivated by numerous observations that surface and subsurface t opography is responsible for the amplification and de-amplification of seismic waves and the generation of coda waves. We demonstrate that i rregular Moho and free-surface scattering significantly affects telese ismic P-wave receiver function waveforms. Receiver functions are routi nely used to obtain detailed crustal and upper mantle structure. For a layer-over-halfspace model, we perform a sensitivity study on the eff ects of ray parameter, interface roughness and wavelength, receiver po sition, and incident wave frequency content. The free-surface response s vary significantly with receiver position, interface wavelength and with incident wave frequency content. Using frequency-wavenumber analy sis, the coda is shown to contain scattered Rg waves and S waves. Rece iver functions are formed from the free-surface responses by deconvolu tion, and these are then inverted, as synthetic 'data', for plane-laye red velocity structure, to show how scattered energy maps onto the fin al velocity models. Spurious structure models result, with the amplitu de of the spurious features (for example low-velocity zones) decreasin g with interface roughness. The resulting velocity models also vary ap preciably with receiver position.