The effects of crustal heterogeneity on ray-based teleseismic imaging

We evaluate the efficacy of crustal scale receiver function imaging in the presence of crustal scattering. First, we show that the resolution of an image is not appreciably affected by geologically realistic crustal scattering. Rather, we show that the image contrast is reduced: the image of actual targets get 'buried' in the noise created by arrivals arising from crustal scattering. Then, we construct three classes of models in which we simulate a flat Moho, a Moho with topography, and a subduction zone. For all the models, we simulate the Moho as a finite-thickness velocity transition zone and the crust with a three-layer heterogeneous zone that contains binary von-Karman statistics with varying degrees of rms density and velocity contrasts. We use finite-difference simulations to generate a suite of varying-slowness seismograms, which we then image with pre-stack 2-D Kirchhoff migration and CCP stacking. We find that for a small degree of rms density/velocity contrasts, both imaging methodologies faithfully image the models, but for rms density/velocity variations greater than approximately 5 per cent per cent, we observed distortion and/or artefacts to the images. For migration, the distortion takes the form of amplitude variations for horizontal model features, whereas for the CCP imaging, the main affect is the enhancement of any horizontal feature in the model.