Analysis of the anomalous characteristics of the modulation ratio of solid tide before the Linfen，Shanxi M4.1 and M4.2 earthquakes in 2025

The starting magnitude is one of the core parameters determining the scanning results of solid tide modulation ratio. Currently, the modulation ratio scanning analysis of solid tides is mostly based on a single specific magnitude as the starting benchmark, and comparative studies on scanning results across different magnitude bins remain scarce. From January 10 to July 25, 2025, two earthquakes with magnitudes 4.1 and 4.2 occurred consecutively in the southern section of the Fenwei Fault Zone in Linfen, Shanxi Province within six months, attracting high attention from seismologists. We scanned the solid tide modulation ratio images of the M_L1.7 and M_L2.5 magnitude ranges before the Linfen, Shanxi M4.1 and M4.2 earthquakes. The results show that there are significant differences in the abnormal evolution characteristics of the solid tide modulation ratio between different magnitude ranges. As the initial scanning magnitude increases, the range of the high-value anomaly of the solid tide modulation ratio expand significantly, and its amplitude increases obviously. Meanwhile, the correlation with the epicenter location and occurrence time becomes stronger. The high modulation ratio anomalies of solid tide obtained from pre-earthquake scanning are primarily attributed to the modulation effect of earthquakes M_L ≥ 2.5. Therefore, when using the solid tide modulation ratio method in earthquake tracking work, an appropriate starting magnitude for the research area should be selected through comparative analysis across multiple magnitude bins.