【摘要】 汶川MS8.0地震发生在青藏高原东缘著名的龙门山断裂带上,造成了从映秀、北川至南坝长约240km的同震地表破裂带.然而目前关于龙门山断裂带的大震复发特征研究较少.通过地震地质科学考察和断层断错地貌的差分GPS测量,发现第一级河流阶地、河床和河漫滩上的垂直断距大致相当,均代表汶川地震的位错,而第二级河流阶地上的累计位移大致是最新地震垂直位移的2倍.利用断错地貌、地震矩率和滑动速率3种方法,分别估算了龙门山断裂带大地震的复发间隔.结果表明:龙门山断裂带中北段可能发生与汶川大地震相当的地震,大震复发符合特征地震模型;大震复发间隔为3000—6000a.该结果可为龙门山断裂带的大震预测和地震危险性评价等研究提供重要的定量数据.更多还原

【Abstract】 The 2008 MS8.0 Wenchuan earthquake ruptured the Longmenshan fault zone on the eastern margin of Tibetan plateau for 240 km long from Ying-xiu 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.更多还原