Permafrost thawing characterization in engineering scale by multi-geophysical methods: A case study from the Tibet Plateau

The freeze-thaw cycles in permafrost regions significantly impact infrastructure stability. While satellite sensing provides a broad perspective for engineering site selection, it lacks the in-depth assessments. Geophysical methods can effectively provide valuable insights into the states of permafrost thawing, but any single method has limitations. To address this, we applied an integrated geophysical approach using ground-penetrating radar (GPR), electrical resistivity tomography (ERT), ambient-noise seismic interferometry (ANSI), and Unmanned Aerial Vehicle (UAV)-based infrared imaging to assess permafrost conditions in the Tuotuo River Basin, Qinghai-Tibet Plateau. Our multi-method survey delineated thawed zones and active layers. The results revealed that a large-scale thawed zone was primarily caused by surface heat absorption, rain infiltration, and sandy soil conditions. We also evaluated the strengths and limitations of each geophysical method, demonstrating their complementarity in permafrost detection. These findings provide a valuable reference for geophysical site assessments and help mitigate engineering risks in permafrost areas.