Three-Dimensional Electrical Structure of the Crust-Mantle in the Southern Section of the Longmenshan and Its Relation to the Lushan Earthquake

A three-dimensional crust-mantle electrical structure of the Lushan earthquake area in the southern section of Longmenshan (LMS) is studied. The 3D inversion results of 108 MT array data showed that high-conductor layers (HCL) in the Songpan-Ganzi terrane (SGT) middle crust, Sichuan Basin (SCB) shallow surface, western Sichuan foreland depression (WSCFD) and LMS Moho. The Lushan earthquake area is subject to compressional deformation horizontally as the eastwards migration of Qinghai-Tibet Plateau material is blocked by the SCB and vertically by the upwards extension of high-conductor plastic material at depth. The aftershocks of the Lushan earthquake area are mainly confined within the Baoxing-Zhonglin-Daxing-Lushan high-conductor region, which has noticeable electrical structural differences compared to the overall high-resistivity structure of the LMS southern section; these differences explain why the aftershocks of the two earthquakes did not expand in the northeast and southwest directions of LMS. Because the 2022 and 2013 Lushan earthquakes both occurred in the same high-conductor region in the deep part of the Dachuan-ShuangShi fault to the Danyi blind fault, the 2022 Lushan earthquake was a strong aftershock of the 2013 Lushan earthquake in terms of electrical structural characteristics.