The mechanism of deep material transport and seismogenic environment of the Xiaojiang fault system revealed by 3-D magnetotelluric study

Two Unconnected Low-Velocity Zones in the Eastern Boundary of the Sichuan-Yunnan Block Revealed with High-Resolution Ambient Noise Tomography

“…Because of the presence of a series of mafic and ultramafic magma from upper mantle (Zhang, 1988;Zhou et al, 2005), this high-velocity zone is strong enough to obstruct the continuous eastward flow of crustal material from LV1, making it impossible for plateau material to cross, resulting in LV1 and LV2 not being connected. This is inconsistent with the crustal flow model beneath the Anninghe-Zemuhe fault zone proposed by Zhu et al (2017) and Yu et al (2022). If LV1 and LV2 are connected, the low-velocity material possibly flows from the lower crust or upper mantle of Panzhihua or bypasses the Panzhihua high-velocity zone to the Xiaojiang fault via the Red River fault.…”

“…The imaging results from Bai et al (2010) and Bao et al (2015) show that the boundary of the high-conductivity layers and low-velocity zones overlaps with the faults and suggest that the distribution of the two lowvelocity channels may be related to the shearing of the faults. Other studies suggest that the genesis of LV2 is different from that of LV1 and may be related to shear heating of the faults (Li et al, 2019b;Yang et al, 2020; and upwelling of mantle material (Wu et al, 2013;Li et al, 2019b;Yu et al, 2022).…”

“…In recent years, with the deployment of portable seismic stations and new imaging algorithms, such as ambient noise tomography, the resolution of the velocity structure in the southeastern margin of the Tibetan Plateau has been greatly improved. Many studies have consistently revealed that there are two low-velocity zones or high-conductivity layers in the middle and lower crust (Bai et al, 2010;Bao et al, 2015;Chen et al, 2014;Fu et al, 2017;Huang et al, 2010Huang et al, , 2018Li et al, 2016aLi et al, , 2019bQiao et al, 2018;Wang et al, 2017;Xia et al, 2021;Yao et al, 2008;Yu et al, 2022;.…”

“…Some studies have suggested that crustal flow exists in the low-velocity zones (Bai et al, 2010;Clark & Royden., 2000;Liu et al, 2014;Royden et al, 1997) and propose that the crustal flow is not continuous within the southeastern margin of the Tibetan Plateau (Bao et al, 2015;Chen et al, 2014;Huang et al, 2018;Yao et al, 2008;. However, these low-velocity zones have also been suggested to be associated with shear heating of the faults or the upwelling of mantle material along the faults (Li et al 2019b;Wu et al, 2013;Yang et al, 2020;Yu et al, 2022;. The highresolution velocity structure is the key to revealing the continuity of the two low-velocity zones and its genesis because it directly affects whether the genesis of the eastern low-velocity zone is related to the eastward escape of material from the Tibetan Plateau.…”

Deep electrical structure of the hinterland of Yunkai magmatic arc in South China and the seismogenic environment of the 2019 Beiliu earthquake

“…Some moderate and strong earthquakes have occurred near the boundary between high and low resistivity structure of underground media. Earthquakes always occurred in the transition zone of high and low resistivity structures, mainly close to the high resistivity side (Ye et al, 2021;Zhan et al, 2021;Yu et al, 2022;. In recent years, magnetotelluric exploration aimed at mineral resources has obtained a large-scale deep electrical structure framework of the South China Block Xu et al, 2019;Hu et al, 2020;Mao et al, 2021), but the deep electrical structure exploration of the Beiliu M5.2 earthquake region is still lacking.…”