Magnetotelluric Insights into Resistivity Structure and Seismogenic Process of the 1988 Lancang-Gengma Earthquakes

The 1988 Lancang M7.6 and Gengma M7.2 earthquakes in southwestern Yunnan, China, provide a unique opportunity to study intraplate seismicity. A 3D magnetotelluric model reveals a prominent high-resistivity crustal body (R1), interpreted as a rigid asperity, located between the epicentres of the earthquake doublet. This resistive body is flanked by conductive fault zones (C1 and C2), associated with major NW-trending seismogenic faults. The resistivity transition zone correlates with aftershock distributions, with larger aftershocks concentrate near fault conductors, while the high-resistivity body hosts smaller aftershocks. These findings suggest that stress accumulation in R1 and its susequent release along the fluid-enriched fault conductors controlled the rupture process of the earthquake doublet, within the context of a prevailing NNE-oriented compressive stress regime. This study underscores the importance of resistivity structures in seismogenesis, offering new insights into intraplate earthquake mechanisms and providing valuable perspectives for improving earthquake hazard assessment in active tectonic regions.