Study of shear zones and associated basins within an oblique rift can shed light on the development of a young transform continental margin. San Pedro Basin lies within the Inner Borderland Rift offshore southern California, where it is bisected by the San Pedro Basin Fault (SPBF). Based on seismic reflection and multibeam bathymetry data, we show that the SPBF attained continuity with the San Diego Trough Fault (SDTF) between 1 Ma and 800 ka, to form a 350-km-long shear zone. Prior to that time, the SDTF was linked to the Catalina Fault, forming a restraining bend that contributed to...