A Systematic Comparison of the Transverse Energy Minimization and Splitting Intensity Techniques for Measuring Shear‐Wave Splitting Parameters

Abstract

Over the past several decades, shear-wave splitting (SWS) analyses have been increasingly utilized to delineate mantle structure and probe mantle dynamics. However, the reported splitting parameters (fast polarization orientations and splitting times) are frequently inconsistent among different studies, partially due to the different techniques used to estimate the splitting parameters. Here, we report results from a sys- tematic comparison of the transverse minimization (TM) and the splitting intensity (SI) techniques. The study was motivated by the fact that recent comparative studies led to conflicting conclusions, which include the suggestion that TM, which is arguably the most widely used SWS-measuring technique, performs significantly poorly relative to SI under most circumstances in terms of stability and reliability of the resulting splitting parameters. We use both synthetic and real seismograms to evaluate the performance of the techniques for noise resistance, dominant period dependence, and complex aniso- tropy recognition. For one-layer anisotropy models with a horizontal axis of symmetry, our results show the two techniques can provide measurements with similar reliability. The testing confirms conclusions from previous studies that, although SI cannot distin- guish between simple and complex anisotropy models with a horizontal axis of sym- metry, TM can serve as a powerful tool in recognizing the existence of complex anisotropy, which is characterized by a systematic dependence of the splitting param- eters on the back azimuth of the events. Therefore, when the existence of complex anisotropy beneath a study area is unknown, TM is a better choice. Ⓔ A FORTRAN program for the calculation of Wiener-filtered wavelet and splitting intensity using SI technique is provided as an electronic supplement to this article. Online Material: FORTRAN code to calculate splitting intensity.