Geochemical Characteristics of Soil Gases (Rn, CO ₂ ) in Ruichang Basin Section of the Ruichang‐Wuning Fault, Jiangxi, China

Within an area of approximately 140 km 2 in Ruichang Basin section of the Ruichang‐Wuning fault, concentrations of soil gases (Rn, CO 2 ) were measured at 139 sampling points. Two surveys of cross‐fault flow observation were conducted in areas with anomalous soil gas concentrations, during which CO 2 samples were collected for carbon isotope composition analysis. Geostatistical analysis revealed that the background concentrations of Rn, CO 2 in Ruichang Basin are 7.33 kBq/m 3 and 0.50%, respectively, while the anomalous threshold concentrations are 27.50 kBq/m 3 and 6.00%. The spatial distribution results indicate a significant correlation between the synchronous anomalies of Rn, CO 2 concentrations and the branch faults of the Ruichang‐Wuning fault, particularly aligning with the Liujiaba‐Fanjiaopu‐Chengmenshan fault zone (F 1 ) and the southeastern edge fault of Ruichang Basin (F 2 ). Comparative analysis of Rn, CO 2 concentration anomalies suggests that the fault activity in the southeast direction of Ruichang Basin is stronger than that in the northwest direction. This leads to the hypothesis that tectonic activities within the basin may be more closely related to the southeast‐directed faults. Moreover, flow observations and carbon isotope values along the F 2 indicate that the CO 2 primarily originates from shallow organic matter decomposition. Additionally, the temporal and spatial variations in soil gas concentrations demonstrate a notable relationship with tectonic activities surrounding the fault, making it suitable for long‐term continuous monitoring of geochemical soil gases related to earthquakes.