Intra-basement structures and their implications for rifting of the northeastern South China Sea margin

•Intra-basement structures in the northeastern South China Sea margin are imaged by reflection seismic data.•A group of intra-basement reflectors are shear zones inherited from the former Andean-type orogeny.•Offshore shear zones are similar to onshore counterparts in the footwall of extensional detachments.•Late Mesozoic orogenic collapse reactivated basement structures and changed basement rheology.