The 2008 MS8.0 Wenchuan earthquake ruptured the Longmenshan fault zone on the eastern margin of Tibetan plateau for 240 km long from Yingxiu Town to Beichuan County, then to Nanba town. The recurrence characteristic of such a large earthquake on the Longmenshan fault zone has been poorly studied. This study is based on field investigations and differential GPS measurements of offset landforms. It is found that the vertical offsets of river bed, river floodplain T0 and terrace T1 are equal to the coseismic slip of the Wenchuan earthquake, while the vertical offsets of terrace T2 approximately double the coseismic vertical slip. The recurrence interval has been estimated by three methods: offset landforms, earthquake moment rate and fault slip rate. Preliminary result indicates that characteristic earthquakes rupturing the middle-northern segment of the Longmenshan fault zone may have similar magnitude to the 2008 Wenchuan MS8.0 earthquake. The Longmenshan fault zone may behave as the characteristic earthquake model with a recurrence interval of 3000~6000 a. This work provides the basic data for large earthquake prediction and earthquake hazard assessment in the Longmenshan region.
