Sharp Changes of Crustal Seismic Anisotropy Across the Central Tanlu Fault Zone in East China

Abstract Both seismic and geodetic data suggested that the ∼120‐km long Weifang segment of the Tanlu fault zone, a large‐scale active strike‐slip system at east China, is a seismic gap with no obvious along‐strike shear motion at surface. Measuring crustal deformation around the segment is crucial to constrain stress/strain buildup and potential seismic risk at the fault. We measured crustal and upper mantle seismic anisotropy using P‐to‐S converted waves at the Moho ( P ms) and core‐mantle boundary (SKS) recorded by broadband arrays across the Weifang fault segment. The measured crustal anisotropy inside the fault zone shows a fast direction of ∼NNE, parallel to the fault orientation. Right east to the fault zone, the fast axis rotates by almost 90° to ESE. The crustal anisotropy within the fault zone could be caused by aligned microcracks and foliated minerals due to long‐lasting shear motion inside the fault zone.