Seismic Anisotropy and Mantle Deformation Beneath Northeast China: Insight From Shear Wave Splitting Analysis

Abstract This study investigates upper mantle deformation beneath northeast (NE) China by reanalyzing shear wave splitting measurements from the WAVESArray network. We identify potential overestimations of anisotropy strength in previous studies, likely caused by sensor misorientation and misclassification of null measurements. Our analysis yields 110 well‐constrained splitting measurements from 66 stations and 43 high‐quality null measurements from 28 stations. The mean delay time is 0.82 ± 0.28 s, consistent with the global continental average (∼1.0 s) but significantly smaller than prior estimates. Based on the spatial coherence analysis of shear wave splitting parameters and previous P ‐wave anisotropy results, we conclude that the anisotropy mainly originates in the lithosphere or the upper mantle transition zone (MTZ), rather than the mantle wedge. Combining our measurements with previous shear wave splitting results, we infer that the predominant NNW‐SSE trending anisotropy reflects fossilized Mesozoic extensional deformation in the lithosphere or the influence of the Paleo‐Pacific Plate subduction within the MTZ. Additionally, in the easternmost Xing'an Block, localized ENE‐WSW fast directions may reflect preserved Proterozoic microcontinental fragments. The solely null measurements and weak anisotropy observed around the intraplate volcanoes suggest the possible presence of localized upwelling of hot material or oriented melt pockets. These findings highlight a complex interplay of multi‐scale mantle and lithospheric processes shaping seismic anisotropy in NE China, providing important insights into the geodynamic processes of the Central Asian Orogenic Belt.