3D geometry and kinematics of the Niudong Fault, Baxian Sag, Bohai Bay Basin, Eastern China—Insights from high-resolution seismic data

Baxian sag is a typical half-graben-like depression whose controlling boundary is a normal fault, the Niudong Fault. We studied the three-dimensional (3D) geometry and kinematics of this fault based on high-resolution 3D pre-stack depth migration seismic data and drilling data from the Baxian Sag. By analysing the geometries and structural deformation of the hanging wall units of the Niudong Fault, we defined the spatial variation and kinematical characteristics of the fault. The Niudong Fault is marked by a major listric normal fault that soles into a detachment surface at depth. Based on fault strikes and dips, we divided the Niudong Fault into three sections and seventeen zones. Geometrically, the Niudong Fault seems to be a single fault. While kinematically, it is not a single fault in the strict sense as various blocks of the fault have their own growth activities dominated by unidirectional and lateral growth. Map-view restoration of the Niudong Fault shows that the hanging wall was dominated by anticlockwise rotation; while cross-section restoration demonstrates that, the hanging wall was deformed by inclined shear.