A microgravity data set presented in a previous study exhibits distinct short-wavelength anomalies over a longwall coal mine panel at Soma-Darkale Coalfield. Nevertheless, our preliminary models suggest that the wavelength after the coal removal from a panel at a moderate depth and fracturing alone should be incomparably greater than that of the measured anomalies. Understanding the mechanism that causes these anomalies usually becomes critical to provide credible evidence for longwall mining-related legal cases. This study improves the model by including the post-subsidence drainage as it occurs because of fracturing that causes an increase in water storage and local density change. Since no water-level information was available at the site, we attempted to infer the drained zone from the dc-resistivity sounding measurements acquired shortly before the gravity field survey. The wavelengths of the model anomalies became reasonably comparable with that of the residual anomalies after the inclusion of the inferred drainage information. This presented approach that does not require water level measurements shows that the inclusion of the inferred drained zone to the model became an amplifying indicator of a coal panel at a moderate depth. Therefore, it may easily find application in settling the mining-related legal cases, understanding the longwall mining-related geohazard, and environmental impact assessments.