云南中甸-大具断裂上新发现的地震地表破裂带

中甸-大具断裂是川滇菱形块体的西南边界，总体走向310°—320°。近年来我们对该断裂进行了1:50000条带状地质填图，发现了断裂活动的地质地貌证据。其中，在丽江大具盆地内（金沙江右岸）沿断裂新发现一处典型地震地表破裂带，长约600m，宽120m左右，主要表现为地表挤压鼓包、挤压垄脊、张裂缝、挤压阶区等，呈NW走向，与中甸-大具断裂走向基本一致。野外工作中，我们详细记录和测量了地表破裂的破裂样式、破裂规模和相关定量数据，利用旋翼无人机测绘了地表破裂带的形态和展布，获得了高精度DEM，分析了地表破裂表现出的运动性质。在已有资料的基础上讨论了地表破裂的形成时代、归属、震级大小，简要分析了其发震断层。新地震地表破裂带的发现为进一步研究中甸-大具断裂活动特征、古地震及地震危险性提供了基础资料。

New Finding of Earthquake Surface Rupture on Zhongdian-Daju Fault

The Daju fault is the south segment of the Deqin-Zhongdian-Daju fault zone, with an overall trend of 310°-320°. In recent years, the fracture has been scaled by 1:50000, and the geomorphological evidence of the fault activity has been discovered. A typical earthquake surface rupture zone was newly found along the fault in the Daju Basin (the right bank of Jinsha River) in the Majiacun-Dadong segment, about 600 meters long and about 120 meters wide, mainly represented by mole track, uplifts, transtensional crack, and extrusion-apart. The trend of the rupture is basically the same as that of Daju fault in NW direction; the right-lateral dislocation of the left bank of the ancient gully trench was found 12m on the southeast side of the rupture zone. The trenche excavated nearby revealed that the latest activity of the fault was broken to the near surface, and the age of the undistorted strata was (50±5) aB.P. Comprehensive analysis of the rupture characteristics of the surface rupture and the ruptureintensity distribution and focal mechanism of the Lijiang earthquake in 1996 are carried out.. It is believed that the surface rupture zone of the earthquake may not be directly related to the Lijiang earthquake, but it should be a new one. The rupture event represents an undiscovered ancient earthquake event. Based on the existing data, the formation age, coseismic displacement and magnitude of surface rupture are discussed. The discovery of the surface rupture zone of the new earthquake provides basic data for further study of the characteristics of large fault activities, paleo-earthquakes and seismic hazards.