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

The Yunkai Magmatic Arc (YKMA) is located southwest of the South China Block. It has experienced amalgamation, splitting, and intracontinental orogeny caused by multistage tectonic thermal events. also a concentrated area strong earthquakes in China. On 12 October 2019, Beiliu M5.2 earthquake occurred hinterland YKMA. To reveal deep electrical structure YKMA seismogenic environment earthquake, 101 high-quality data from magnetotelluric (MT) survey points were acquired. images obtained three-dimensional electromagnetic inversion imaging. results indicated that part characterized mushroom-shaped composed ultra-high resistance (R1, with resistivity value exceeding 10,000 Ωm) sub-high (R2, about 1,000–10,000 bodies. epicenter was R1, close to contact region between R1 R2. There are broad low zones on southeast northwest sides considered be correspond extension Wuchuan-Sihui Hepu-Beiliu brittle-ductile shear zones, respectively. shearing boundary oblique upwelling mantle-derived magma Leiqiong main reasons for activation faults activity moderate In this geodynamic environment, local stress strain accumulation easily occur brittle high body (R1). When energy exceeded threshold rock could withstand, new fracture dislocations weak where R2 contact, which finally resulted 2019 earthquake.