Comparative Assessment and Application of Multiple Gravity Edge detection Methods in Thick-cover Regions of North China

To effectively identify faults beneath thick cover in North China, this study systematically compared and evaluated the performance of six gravity edge detection techniques. The results indicate that the second vertical derivative is highly sensitive to shallow faults but is readily affected by noise, whereas the total horizontal derivative and analytic signal amplitude are more effective for detecting deeper faults, although their responses weaken in thick cover settings. The tilt angle and theta map can jointly extract information on shallow and deep structures but are prone to generating spurious boundaries. By contrast, the softsign function derivative exhibited the best overall performance in our tests, effectively delineating major faults at different depths and within thick cover areas. Using a combined workflow incorporating these methods, we identified a possible concealed fault that is consistent with controlled source seismic and magnetotelluric profiles. We further inferred that the Jinhuo Fault may comprise two branches, one coinciding with the mapped surface trace and another trending NE toward the Handan Fault, consistent with the spatial distribution of relocated earthquakes. In addition, an approximately E–W trending anomalous belt was detected west of the Jianchangying Fault, the origin of which may be related to a westward continuation of this fault or to the deep southward extension of the Xinglong–Jianping Fault, pending further verification using additional geophysical methods.