High-angle fault responsible for the surface ruptures along the northern segment of the Wenchuan Earthquake Fault Zone: Evidence from the latest seismic reflection profiles

• The Yingxiu–Beichuan fault has a dip > 45° at 6 km depth.
• The dextral offset along the Y–B fault appears to increase slightly towards the NE.
• It is continuous at depth between its northern and southern segments.

The inverse/right-lateral Yingxiu–Beichuan fault ruptured during the Wenchuan earthquake for ~ 270 km. We investigated the northeastern segment of that fault by analysing 3 newly acquired and 3 older seismic lines that cross the fault. We combine this analysis with that of the surface ruptures and of the regional geology in order to discuss the geometry, the style and the amount of motion of the fault. We conclude that the Yingxiu–Beichuan fault is very steep (~ 70°) at the surface and has still a dip > 45° at 6 km depth. The fault offsets all previous structures and particularly the Tangwangzhai nappes from which a vertical offset of 3 to 6 km is evaluated. The right-lateral component of motion along the Yingxiu–Beichuan fault appears to be larger at the surface than at depth and increases only slightly towards the NE. We suggest that the Yingxiu–Beichuan fault is continuous at depth between its northern and southern segments.