Structural geometry and kinematics are important to understand the growth of the Tibetan Plateau margins. In this study, several high-resolution seismic reflection profiles were combined with well data and the fault-bend fold theory to determine the geometric and kinematic characteristics of the Pengxian buried structures located in the piedmont of central Longmen Shan (LMS). Seismic interpretations indicate that the Pengxian buried structures were involved in multi-period, superimposed deformation during the Cenozoic. The structural deformation of the frontal LMS was controlled by a Triassic detachment fault (f2), which extended forward at a low angle, and formed a fault-bend fold during the Late Miocene. The high-angle Pengxian blind fault developed on the f2 with little offset during the Pleistocene. Three-dimensional imaging of the Pengxian buried structures shows that the f2 horizontally propagated into the western Sichuan Basin with a fault slip of c. 3.3–3.5 km. The Longquan Shan (LQS) anticline has a total slip of c. 3.0 km since its initiation. Our study suggests that the average slip rate of the f2 is <0.4 mm a−1 in the central LMS front. The Pengxian buried structures and the LQS anticline have been slowly shortening since the Late Cenozoic, which could provide a constraint on the growth pattern of the eastern Tibetan Plateau margin.