关键词: 汶川8.0级地震, 龙门山断裂, 断错地貌, 阶地测量, 地震地表破裂, 古地震

Abstract: The May 12,2008 M_S 8.0 Wenchuan earthquake in Sichuan Province,China produced a 240km long co-seismic surface rupture zone along the Longmenshan Central Fault.Our investigation focuses mainly on the three regions along the co-seismic surface ruptures,i.e.the Nanba Town and the Fenghuang village on the northern segment of the rupture zone,and the Yingxiu town on the southern segment.We studied the river terraces in these regions offset by the active fault,measured the surface ruptures and the fault scarps on the multilevel terraces and obtained the height of the fault scarps on each terrace,namely,the cumulative vertical slip of the active fault recorded by terrace,through data calculation and analysis.If we use the vertical slip of this earthquake as the average vertical slip of the paleoearthquakes,then the ratio of the cumulative vertical slip of each terrace to this average vertical slip is the cumulative times of paleoearthquakes recorded by each terrace.The research results show that T₁ of every study area has undergone only one paleoearthquake event ever since its formation,T₂ about 5 paleoearthquake events,T₃ about 9～11 paleoearthquakes and T₄ about 20 paleoearthquakes.Based on the research result of this paper,and combined with the previously dating ages of the terraces,we can obtain some reliable data about the recurrence intervals of the paleoearthquakes.

Key words: M_S 8.0 Wenchuan earthquake, Longmenshan Fault, faulted landform, terrace measurement, earthquake surface rupture, paleoearthquake