Abstract The Tan‐Lu Fault Zone (TLFZ), the largest lithosphere‐scale strike‐slip fault in eastern China, has experienced multiple tectonic stages and remains high seismic activity, including the 1668 Tancheng earthquake (M 8.5). Here we employ dense‐array receiver functions to resolve crustal thickness, Vp/Vs ratio, and seismic discontinuities in the Tancheng earthquake rupture zone. Our results reveal pronounced Moho variations and crustal heterogeneity controlled by the TLFZ. High Vp/Vs ratio and weaker Ps conversion from Moho spatially correlate with the eastern branch, which has been the primary active and seismogenic fault since the late Quaternary. We propose that the TLFZ provides a potential channel for asthenospheric upwelling, with the eastern branch recording stronger crustal modification than the western branch, which may enhance tectonic stress accumulation and result in major intraplate earthquakes. This study provides new seismological evidence for the role of crust‐mantle interaction and mafic intrusion in influencing seismicity of the central TLFZ.