Seismogenic Mechanism of the 2024 Feidong Earthquake Swarm Constrained by Barriers: Insights from 3D Magnetotelluric Imaging

The 2024 Feidong earthquake swarm (maximum magnitude M 4.7) in the seismically quiet Hefei segment of the Tanlu fault zone (TLFZ) raises critical questions about its potential for larger earthquakes. We conducted 3D magnetotelluric imaging to obtain the crustal resistivity structure of the Hefei segment of the TLFZ. The results reveal a large-scale, Tanlu high-resistivity belt (TLRB) along the fault. Its southern segment (R1S) acts as a giant, rigid barrier that inhibits dextral strike-slip motion on the TLFZ. The Feidong earthquake swarm occurred in the structurally weak zone on the western flank of the central TLRB, near the western branch of the TLFZ. A local barrier effectively impeded northeastward rupture propagation. It shares geometric similarities with some seismogenic asperities observed in other strong earthquakes. However, the persistently low fault activity and seismic energy release indicate that current regional tectonic stresses are insufficient to overcome this local barrier, suggesting a low risk of strong earthquakes.