Investigating the control of subsurface structures on rainfall-induced ground instability using integrated geophysics and remote sensing in Jixi, China

Landslides are common geological hazards worldwide, often associated with by heavy rainfall. Jixi City, located in southeastern Heilongjiang Province, experiences frequent rainstorms from July to September. Long‑term unregulated quarrying has destroyed vegetation and reduced slope toe stability in the area. In early August 2023, Typhoon Doksuri increased rainfall. The Jixi landslide occurred on August 10 following this heavy rainfall. This study integrates aeromagnetic data, electrical resistivity tomography (ERT), multi‑temporal satellite and UAV remote sensing, borehole data, and surface displacement monitoring. Aeromagnetic anomalies support a magnetically quiet basement without deep magmatic activity. ERT 2D and quasi‑3D inversions, calibrated by six boreholes, reveal a three‑part electrical structure: a shallow discontinuous high‑resistivity landslide deposit, a continuous low‑resistivity slip zone interpreted as mudstone with elevated moisture content and fault fracture zones, and a deeper blocky high‑resistivity slip bed. Steeply dipping low‑resistivity belts are interpreted as possible water‑bearing faults. Multi‑temporal images show progressive quarry expansion. Post‑landslide UAV orthophotos indicate that the main landslide body showed approximately 20 m of cumulative displacement toward the southwest between 2020 and 2023, with a fan‑shaped morphology exhibiting apparent retrogressive geomorphic characteristics. Surface monitoring from August 17 recorded horizontal displacements of 0.2–35.2 cm, with the dominant direction toward the southwest and elevation changes showing rear subsidence and frontal uplift. Boreholes support the transition from intact slip bed to fractured landslide mass. Based on these results, a possible evolutionary chain is proposed as an evidence‑supported interpretation: quarrying disturbance, typhoon‑induced rainfall infiltration, fault‑controlled water conduction, slip zone softening, and retrogressive sliding. The multi‑method approach provides cross‑scale constraints from regional background to shallow detailed structures, offering a scientific basis for post‑disaster identification, investigation, and mitigation of similar landslides.