Remote HVGD Implying the Seismogenic Positions of 2025 Mandalay Earthquake Sequence

Abstract. Pressure-stimulated rock currents (PSRCs), widely documented in laboratory rock-loading experiments, have been proposed as a mechanism for pre-seismic geomagnetic disturbances. However, the relationship between horizontal vectors of geomagnetic disturbance (HVGD) and seismogenic fault processes remains unclear, particularly during large earthquakes with complex aftershock sequences. Using geomagnetic data from a station in southwestern China, we develop a spatial intersection method to investigate this relationship along the Sagaing Fault during the 2025 Mw 7.7 Mandalay earthquake sequence. The method identifies intersections between the mapped fault trace and horizontal lines normal to HVGD vectors, thereby constraining potential seismogenic locations. The intersection points migrate systematically along the Sagaing Fault and correspond to the rupture corridor and major earthquakes in the sequence. Notably, their distribution region coincides with the independently identified supershear rupture segment. The inferred locations are supported by positive anomalies in satellite-observed microwave brightness temperature. We attribute these observations to PSRC generation associated with stress activation in peroxy-defect-bearing lithologies along the fault. Under increasing tectonic stress at depth, stress-sensitive positive holes may be generated near frictional regions and propagate upward, producing electric currents detectable as geomagnetic disturbances at remote stations. The retrieved PSRCs, ranging from 7.3 to 91.9 MA, are broadly consistent with estimates scaled from laboratory specimens to seismogenic rock volumes. These results suggest that remotely observed HVGD can constrain evolving seismogenic processes along known active faults. The proposed HVGD–fault intersection approach provides a simple ground-based remote sensing method for tracking potential seismogenic positions and their migration during large earthquake sequences.