A Method for Estimating the Crustal Azimuthal Anisotropy and Moho Orientation Simultaneously Using Receiver Functions

Abstract

The P‐to‐S converted phase at the Moho (the Pms phase) contains important information regarding the crustal structure. Here, we employ a grid search approach to simultaneously extract the bulk crustal azimuthal anisotropy and Moho orientation using receiver functions. The solution of this approach is the weighted average of two individual subfunctions that separately analyze the birefringence and arrival time of the Pms phase. Since a tilted Moho deflects the polarized components of the Pms phase, the Pms birefringence subfunction minimizes the energy on all the transverse polarization components (i.e., the transverse polarization direction before Pms splitting). The implementation of this subfunction is similar to that of the transverse component minimization method, but the Moho orientation is considered. The Pms arrival time subfunction takes into account both the crustal anisotropy and the Moho orientation to predict and fit Pms arrivals. According to extensive synthetic experiments, this approach is remarkably robust to the presence of strong anisotropy, a steep Moho, and slightly tilted fast axes (less than 30°). This approach is also highly tolerant of random noise and data with uneven azimuthal coverage. We apply this approach to three permanent stations on the Tibetan Plateau. The resulting measurements boast a high quality and are consistent with the crustal anisotropy and Moho orientation revealed in previous studies.

Anomalous Radial Anisotropy and Its Implications for Upper Mantle Dynamics Beneath South China From Multimode Surface Wave Tomography

“…The Yangtze Craton exhibits a cold lithosphere with a high‐velocity anomaly, and the Cathaysia Block shows a low‐velocity anomaly. Anisotropy analyses of the SCB have mainly focused on azimuthal anisotropy, and some research has been based on waveform splitting, such as shear‐wave splitting (SWS) measurements representing mantle anisotropy (Huang et al., 2011; Zhu, 2018) and Pms splitting influenced by the crust (Wang et al., 2020; Zheng et al., 2018). However, the depth resolution of such splitting analyses is limited; therefore, it is difficult to determine whether the anisotropy lies in the lithosphere or asthenosphere (Pedersen et al., 2006, 2013).…”