Estimating lateral and vertical resolution in receiver function data for shallow crust exploration

In order to test the horizontal and vertical resolution of teleseismic receiver functions, we perform a complete receiver function analysis and inversion using data from the La Barge array. The La Barge Passive Seismic Experiment was a seismic deployment in western Wyoming, recording continuously between November 2008 and June 2009, with 55 instruments deployed 250 m apart—up to two orders of magnitude closer than in typical receiver function studies. We analyse each station separately. We calculate receiver functions and invert them using a Bayesian algorithm. The inversion results are in agreement with measurements from nearby wells, and from other studies using the same data set. The resulting posterior probability distributions (PPDs), obtained for each station, are compared to each other by computing the Bhattacharyya coefficients, which quantify the overlap between two PPDs. Our results indicate that (a) the lateral resolution of 8 Hz receiver functions is approximately equal to the width of their first Fresnel zone, (b) minimum investigable depth is about 400 m at 8 Hz, (c) lateral resolution depends on the local geology as expected and (d) velocity inversion in the shallow-crust can be resolved in the first few kilometres, even in case of dipping interfaces.