红河活动断裂中南段航片变位地形判读及野外检验

Interpretation of aerophotoes and field investigation on tectonic landforms of middle-south segments of the Honghe active fault zone

一、引言红河活动断裂是中国西南地区一条重要的NW向走滑活动断裂。它在中国境内全长约600km,其西北端起于洱源,向东南经大理、弥渡、元江、红河,在河口进入越南境内。红河活动断裂在卫星影像上的笔直线性特征及近几百年该断裂中南段没有中强地震发生而引起中外学者的关注。自80年代以来,不少地震地质学者对红河活动断裂的展布、晚第四纪活动特征及与强震关系进行了研究。

The Honghe active fault zone is an important strike-slip fault in South-west Region of China.Many researchers are abstracted by its linear feature on the satellite maps.Since 80/s,discusses have been continued about the geometric character of the active faults and its active times.Some persons reported in 1990’s that its southern segment has not,been active since the Late Pleistocene.This paper gives different result from the interpretation of the aerophotoes on tectonic landforms of its Middle-Southern segments.The result shows that its middle-south segments have strong Late Quaternary tectonic landforms.These tectonic landforms have the following characteristics:(l)These tectonic landforms aren,along the volley of rivers.It shows these aren:formed by erosion of rivers.(2)Most of these tectonic landforms consist of trenches on the slope,or called fault trenches.Because there aren,rivers along these fault trenches,the forming time of those trenches are very young.(3)The strike-slip ofFsets cutting different scale rivers can be seen along the Honghe active fault zone.The dextral ofTsets are from more than ten meters to several ten meters.Besides showing many times of activity,the zone also shows the latest activity of dextxal strike-slip.(4)Tectonic landforms of middle-southern segments of the Honghe active fault distribute single linear pattern intermittently.They are different from the saying which consists of two main fault zones.Seven places among the 32 places of tectonic landforms from aerophoto interpretation were inspected in field investigation.All of them show exact interpretation of tectonic landform on the use of aerophotoes.These vertical displacements and of Tsets which arc only more than ten meters are very probably the results of Holocene activities.So the middle—south segments of the fault zone aren,in their sleeping period in Holocene.The reason why there were not any record of strong earthquake during recent several hundred years is that the Honghe active fault zone has more than thousand years recurrent intervals.