## 1 Introduction  
Earthquake prediction is an important topic in earth science [1] and requires a deep understanding of the development of earthquake nucleation. The earthquake nucleation process has been extensively studied using various methods [2; 3; 4; 5; 6; 7; 8] to achieve breakthroughs in earthquake prediction. Many studies have reported that the tectonic stress field and its dynamic changes are key to the nucleation process of earthquakes [9; 10; 11]. The deformation and rupture of the lithospheric medium under load may change the underground temperature of the regional bedrock [12]. The physical theories of extrusion heating and tension cooling during stress loading are verified by rock mechanics experiments; they demonstrated that the tectonic stress variation could be identified from changes in bedrock temperature [13; 14; 15]. In practical earthquake research, [PERSON] [16] found that surface thermal anomalies developed before the 2011 \(M_{\text{s}}\)9.0 giant earthquake in Japan, and [PERSON] et al. [17] also detected significant thermal infrared temperature anomalies before the 1989 \(M_{\text{s}}\)6.1 earthquake in Datong, Shanxi, China. [PERSON] [18] and [PERSON] et al. [19] reported that sliding friction caused by the rapid dislocation of the fault plane during the earthquake was the main reason for the sharp increase in temperature near the fault plane. [PERSON] et al. [20] studied the temporal and spatial evolution of the latent heat flux on the Earth's surface before the Chile \(M_{\text{s}}\)8.8 earthquake and also discussed the theoretical relationship between latent heat flux and surface temperature. The research shows that the strain, friction, and fracture of rock, which are caused by the change of stress, may change the temperature. The observed temperature change may help us understand the stress adjustment before an earthquake. Ground temperature changes have typically been observed by satellite thermal infrared remote sensing and other imaging technologies. [PERSON] et al. [21] studied the possibility of using thermal infrared anomalies to detect incoming earthquakes on the basis of the relationship between infrared brightness temperature and terrestrial heat flow. [PERSON] et al. [22] used surface temperature data from the Terra and Aqua satellites to study the co-seismic thermal response of the Wenchuan \(M_{8}8.0\) earthquake. [PERSON] et al. [23] and [PERSON] [24] studied pre-earthquake thermal anomalies using remote sensing technology. These studies showed that thermal infrared data on geothermal changes might contain information on the occurrence of earthquakes. However, observation accuracy and excessively uncertain space range are key scientific issues that urgently require a solution. The altitude of satellite thermal infrared observation is generally more than 30,000 km, with the anomaly covering a range of hundreds to thousands of kilometers [23] and the observation accuracy of the thermal imager reaching 0.01 degrees. However, the altitude of the ionospheric satellite observation is just 500 km, with an anomaly coverage area of several hundred kilometers. Thus, the ionospheric anomaly is selected to couple with the rock temperature observation to explore earthquake preparation [25; 26; 27]. Recent studies have suggested that earthquakes are closely related to bedrock fractures [28], and arranging a certain number of temperature sensors in key areas may be an effective way to detect temperature changes in bedrock before earthquakes. In fact, [PERSON] et al. [29; 30; 31] demonstrated the feasibility of bedrock temperature observation of earthquakes and analyzed changes in rock temperature observed before the Lushan \(M_{8}7.0\) and Kangding \(M_{8}6.3\) earthquakes. The pre-earthquake variation in rock temperature is thought to be related to variation in the tectonic stress field, which reflects regional stress enhancement. Using wavelet transform analysis, [PERSON] et al.