Abstract

We used 2D finite‐difference modeling and azimuthally binned receiver functions (RFs) to explore whether abrupt offsets in Moho depth can be detected by one or a few closely spaced P‐wave RFs. Our results show that 2D synthetic RFs generated in the immediate vicinity above a Moho depth change can provide important clues to the abruptness of the offset. In particular, diffraction of the waves impinging onto the Moho offset may generate a split PS arrival, causing systematic variation of peak‐to‐peak PPS delay times with increasing ray parameter, depending on the location relative to the Moho offset and the incidence direction of the RFs. We outline an approach using a slant‐stack method to constrain the location of a relatively abrupt depth change of Moho (forumla) using separate RF stacks incident from opposite directions. For a station located on the western border of the Caspian Sea in Azerbaijan (LKR), our 2D models with an ∼8  km transition from a shallower Moho to the east and deeper Moho to the west generate synthetic RFs with features in general agreement with observations. These models, which include step‐ and ramp‐like offsets of Moho, are in general agreement with estimates of crustal thickness from seismic data. Thus, our results suggest that characteristics in one or a few azimuthally binned radial P‐wave RFs can be used in concert with a slant‐stack analysis to pinpoint a relatively abrupt change in underlying Moho depth.

Online Material: Discussion and figures of a verification study of receiver functions (RFs) computed by different methods, crustal phases generated in our 2D model using animations of the simulated wave propagations, as well as estimated crustal structures, and RFs for Moho offset models, including realistic levels of noise.

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