CRUSTAL SCATTERING AND SOME ARTIFACTS IN RECEIVER FUNCTION IMAGES

Abstract

The existing 2D and 3D depth imaging approaches using multichannel teleseismic receiver functions (RFs) can result in significant artifacts caused by misinterpretation of signal-generated noise resulting from broadside scattering within the crust. A synthetic example using acquisition geometry of the 1993 Cascadia experiment shows that scattering of the primary P-wave arrivals from a sedimentary accretionary wedge could produce RF events close to those observed in real data. Quasi-linear crustal structures with significant velocity contrasts near Moho depths, such as subduction zones, should create particularly strong and coherent noise arrivals. Conventional interpretations of these arrivals based on assumptions of their origin in mode conversions could lead to images of spurious dipping structures of landward dips steeper than ∼10° that may be very difficult to distinguish from the true structures. Detailed analysis of prestack, premigration RF data is required for correct identification of the signal-generated noise and validation of the resulting depth images. Identification of scattered events in RF records could also help constrain major crustal structures, such as crustal sutures and subduction fault zones, and particularly those with strong Moho expressions.