Hindered but Not Halted Crustal Flow: Implications From Lg‐Wave Attenuation Tomography Based on High‐Density ChinArray in SE Tibetan Plateau

Abstract In response to the continuous Indian‐Eurasian plate convergence, the mechanically weak crust of the Chuan‐Dian block in the SE Tibetan Plateau moves southeastwards, representing one of the significant expanding margins of the Tibetan Plateau. However, whether such crustal movement is impeded by the localized rigid crust associated with the Permian magmatic activities in the Emeishan Large Igneous Province (ELIP) remains controversial. Here, based on the high‐density ChinArray Lg data, we invert for a high‐resolution broadband attenuation model of the SE Tibetan crust. The Chuan‐Dian block is characterized by a low Q Lg below 200 over the frequency range 0.2–2.0 Hz. In contrast, at frequencies above 2.5 Hz, the low Q Lg is concentrated near major strike‐slip faults. This is consistent with a lower‐crustal flow model underlying the relative movement of upper‐crustal blocks. Between the significant low‐ Q Lg anomalies in the northern and southern Chuan‐Dian block, there is an abrupt ∼30% increase in Q Lg between 2.5 and 10.0 Hz, reflecting the magma‐modified crust in the ELIP core that gained mechanical strength during cooling. The lateral Q Lg variation corresponds to a ∼1 order of magnitude increase in strength, which may indicate an obstructive effect. However, the broadband Q Lg images suggest a depth‐varying crustal strength, possibly due to the impact of asthenosphere upwelling associated with eastward subduction of the Indian Plate. Combining with S‐wave velocity and Pg‐wave attenuation, our Lg attenuation suggests that the ELIP core can only partially hinder the crustal flow rather than completely halt it.