The role of deformed craters in understanding fault geometries and kinematics

Understanding subsurface fault systems has always been difficult, especially on planetary bodies where direct observations are limited. However, fault-controlled deformed craters, impact craters modified by fault displacement, provide valuable surface expressions that can be used to infer underlying fault geometries and kinematics. This study aims to understand and reconstruct subsurface faults by analyzing deformation patterns of fault-controlled deformed craters, using both numerical simulation models and observations. A model study was conducted in which three crater shapes, bowl-shaped, frustum-shaped, and ellipsoid-shaped, were deformed at three fault angles (30°, 60°, and 90°), intersecting either the crater floor or wall. The model deformation produced two distinct surface patterns: concave U-shaped and truncated V-shaped traces, whose curvature and orientation indicate slip direction. The variations in curvature orientation across deformed craters were used to infer the possible presence of complex fault geometries, such as backthrusts on the Moon. Additionally, using deformed model craters, we reconstructed fault dips using a reconstruction method developed in this study. The reconstructed fault angles closely matched the original model input angles (30° and 60°), with deviations within ±5°. Following validation, the method was successfully applied to observed fault-controlled deformed craters on Mars and the Moon, yielding fault angle estimates of ∼20°–62° for Mars and ∼33°–36° for the Moon. Overall, the study developed a method for fault dip measurement using deformed craters and demonstrates that deformation patterns can be used to infer slip direction and identify complex fault geometries, such as backthrusts, in regions where direct access is not possible.