Crustal thickening in northern Yunnan, SE Tibet, linked to the control of the regional abyssal faults on mid-lower crustal flow: evidence from ambient noise tomography

It is generally recognized that the crustal flow in the Yunnan region is attributed to the continental collision between the Indian and Eurasian plates. Therefore, studying the crustal flow and its dynamic processes in this region can provide valuable insights for understanding the collision process and crustal thickening. The S-wave velocity can provide constraints on the lithological state, interface delineation, and geodynamic processes of the Earth's interior, which are critical for explaining the properties of the crustal flow within a particular region. In this study, we employ 2-year continuous waveforms of the vertical component of 58 seismic stations using ambient noise tomography in the Yunnan region to build a 3-D S-wave velocity crust model. On this basis, the spatial distribution and dynamic processes of regional crustal flow are discussed. Our model reveals the distribution features of the mid-lower crustal flow with different deformation mechanisms at different depths. Finally, a dynamical model is proposed to interpret the dynamic processes of the regional mid-lower crustal flow. The model reveals that a large amount of crustal flow material on the northeastern side of the Red river fault is partially blocked by the Emeishan large igneous province, resulting in the lateral escape and rotation of the mid-lower crustal flow. Another part of the crustal flow material is controlled by the strike of the Red river fault, and the high-velocity Indo-China block on the southwestern side of the Red river fault prevents the crustal flow not escape to this area. We believe that the control effect of the Red river fault on the mid-lower crustal flow may be one of the main reasons for the crustal thickening and surface uplift on the northeastern side of the Red river fault.