On December 18, 2023, a significant M_S6.2 earthquake struck Jishishan County, Gansu Province, China, resulting in heavy casualties and severe infrastructure damage. This earthquake occurred within a seismically active northeastern margin of Qinghai-Xizang Plateau, characterized by complex fault systems including the Lajishan south margin fault and the Lajishan north margin fault. The event provides a valuable case for studying coseismic deformation, fault mechanics, and potential precursor signals using advanced remote sensing techniques. This study combines interferometric synthetic aperture radar （InSAR） and thermal infrared remote sensing technology to comprehensively analyze the coseismic deformation field, source parameters, fault slip distribution, Coulomb stress changes, and spatiotemporal characteristics of thermal infrared anomalies of the Jishishan earthquake.

Coseismic deformation fields of the 2023 Jishishan earthquake were derived from Sentinel-1A synthetic aperture radar （SAR） data of both ascending and descending tracks. Differential InSAR （D-InSAR） processing results revealed a dominant uplift pattern with maximum line-of-sight （LOS） displacements of approximately 6.5 cm and 7.2 cm for the ascending and descending tracks, respectively. The deformation field, spanning approximately 18 km in the east-west direction and 22 km in the north-south direction, is mainly distributed between the Lajishan south and north margin faults, without clear surface rupture observed, indicating a blind thrust fault mechanism.

To constrain the fault geometry and slip distribution, a Bayesian inversion framework was implemented using the Geodetic Bayesian Inversion Software （GBIS）, incorporating quadtree-sampled InSAR data. Nonlinear inversion results indicate that the seismogenic fault is characterized by a length of （12.85±0.35） km, a width of （7.8±0.2） km, a top depth of （5.5±0.3） km, a strike of 324°±1°, and a dip angle of 32°±2°. The fault exhibits a predominantly thrust mechanism with a minor right-lateral strike-slip component. Finite fault slip inversion, constrained by the downsampled InSAR data, reveals that the rupture was confined to depths between 10 km and 20 km, with a maximum slip of 0.54 m occurring at approximately 14 km depth. The total seismic moment released is estimated at 1.29×10¹⁸ N·m, corresponding to a moment magnitude M_W6.0, consistent with solutions from international agencies such as USGS and GCMT.

Coulomb stress change analysis was conducted at depths of 5, 10, 15, and 20 km using a layered viscoelastic crustal model. The results indicate significant stress loading （ΔCFS＞0） on several segments of the surrounding faults. Specifically, positive Coulomb stress changes are observed along the entire Lajishan south margin fault, the WNW-trending segment of the Lajishan north margin fault, and the NNW-trending segment to the south of the epicenter. This suggests an elevated seismic hazard potential in these regions, necessitating ongoing monitoring and risk assessment.

Complementing the InSAR deformation analysis, this study investigated pre-seismic thermal infrared anomalies using brightness temperature data from the Fengyun-2G （FY-2G） geostationary meteorological satellite. The relative power spectrum method was applied to the nighttime brightness temperature data to extract thermal infrared anomalous signals. The results reveal significant pre-seismic thermal infrared anomalies in the epicentral region. These anomalies exhibit notable spatiotemporal consistency with the deformation processes inferred from time-series InSAR, reflecting the process of strain energy accumulation and release. Spatially the thermal infrared anomalies were primarily concentrated along the Lajishan fault zone. We hypothesize that these thermal anomalies were primarily induced by stress-induced micro-fracturing, which enhances the release of deep subsurface gases or geothermal energy, followed by a closure of microfractures as the local stress field intensifies prior to the mainshock.

Time-series InSAR analysis, utilizing both persistent scatterer InSAR （PS-InSAR） and small baseline subset InSAR （SBAS-InSAR） techniques, was performed on a stack of 21 Sentinel-1A images covering the period from April 2023 to January 2024. The results delineate the pre-, co-, and post-seismic deformation evolution. The pre-seismic period （January to September 2023） was characterized by minor and gradual deformation, with a maximum cumulative displacement of approximately 15 cm, interpreted as pre-seismic creep. A rapid and significant increase in deformation occurred around the epicenter from October 2023 to January 2024, with displacements exceeding 10 cm, which is coincident with the mainshock. Post-seismic deformation rates subsequently decreased, indicating a relaxation phase.

The integration of InSAR-derived deformation fields and thermal infrared observations provides robust evidence for a deformation-thermal coupling mechanism associated with the Jishishan earthquake. The consistency between the spatial patterns of pre-seismic thermal infrared anomalies and the coseismic deformation field, coupled with the calculated stress loading on adjacent fault segments, further demonstrates the application potential of multi-source remote sensing data in earthquake monitoring and earthquake hazard assessment.

In conclusion, this study demonstrates that the 2023 Jishishan M_S6.2 earthquake was a blind thrust event with a significant uplift component. The seismogenic fault did not rupture the surface, with slip concentrated at depths of 10−20 km. Pre-seismic thermal infrared anomalies were detected and show correlation with the deformation process. Coulomb stress transfer has increased the seismic risk on several segments of the Lajishan fault system. The synergistic use of InSAR and thermal infrared remote sensing proves to be a powerful approach for elucidating the complex processes of earthquake preparation, occurrence, and post-seismic adjustment, offering valuable insights for understanding seismic hazards in similar tectonic settings.