Rock temperature reflects the adjustment in crustal stress, and the fluctuation of ionospheric electron concentration is closely related to short-term disturbances of the stress field. Their coupling may reveal short-term effects before strong earthquakes. This study explores the rock temperature changes and mechanical-electrical coupling in the lithosphere–ionosphere before the Jiashi M_s6.4 earthquake on 19 January 2020. The observed data were detrended by general polynomial piecewise fitting; three observation points within 150 km of the epicenter were found to show significant temperature fluctuations in the 15 days before the earthquake. The peak occurred synchronously five days before the earthquake, and the variation range was approximately 10⁻³ orders of magnitude. Five days before the earthquake, the electromagnetic satellite Zhangheng-1 synchronously observed an anomalous electron concentration in orbit near the epicenter, with a maximum value of 2.01 × 10¹⁰ m⁻³. The loading/unloading response ratio (LURR) was calculated using small earthquakes within 100 km of the epicenter; it showed that the large changes in rock temperature and the ionosphere occurred at high LURR, indicating high-stress accumulation in the region. Various anomalies appeared simultaneously and may indicate fault rupture, which may be caused by an acoustic-gravity wave, indicating a synchronous coupling between the lithosphere atmosphere and the ionosphere.

Stress may induce apparent resistivity changes. Clarifying the deformation process of the source media is critical for determining the correlations between resistivity variations and earthquake occurrence. In this study, the stress state of a medium was analyzed by integrating GPS measurements, the spatiotemporal evolution of the load/unload response ratio (LURR), geochemical monitoring, and synchronous apparent resistivity changes preceding the 2020 Mw 6.0 Jiashi earthquake. The medium hosting the Kalpin Observatory underwent elastic deformation before 2019, and the synchronous decreases in the E–W and N–S apparent resistivities from 2015 can be attributed to N–S-dominated compressive stress. The microdamage stage occurred in 2019, with subsequent E–W apparent resistivity variation amplitudes that were ~0.4 Ωm higher than those in previous years. This difference is a result of microdamage to the medium owing to tensile stress during the seismogenic process. The spatiotemporal evolution of the LURR and gas seepage monitoring data also indicate that the medium was damaged prior to the earthquake. Variations in the apparent resistivity measured at the Kalpin Observatory indicate that the medium underwent elastic deformation, followed by microdamage, until stress triggered the earthquake.