Two earthquakes with magnitudes of 7.6 and 7.3 occurred in the Lancang and Gengma areas,respectively,in southwestern Yunnan on November 6,1988.The M7.6 earthquake showed complicated earthquake-generating tectonic characteristics; the seismogenic structure was the Heihe and Lancang faults and an obvious seismic deformation belt was formed separately along the two faults.The Longling-Lancang fault is located in southwestern Yunnan and was an active fault zone in the late Quaternary.It has a length of 500 km,a trend of 320°~340°,and is mainly right-lateral strike slip with dip slip.It starts north of Tengchong,stretches through Longling,Gengma,Lancang,and terminates in Menghun in the south.The fault is composed of a plurality of discontinuous secondary fault components with a diagonal or clustered distribution.A number of fault basins and offset drainage systems have been formed along the fault.According to differences in fault geometric distribution,mechanism,fault scale,boundaries,and seismicity,the Longling-Lancang fault can be divided into four secondary fault segments: the Gudong-Tengchong,Longling-Yongde,Hanmuba-Lancang,and Jiufang-Mengzhe.The focus of this paper is the Lancang fault in the Hanmuba-Lancang segment.The Lancang fault starts to the north of Lianhe,transverses south of Yanshuai in Cangyuan county,across Nanliu,Habuma,Zhanmapo,Datangzi,Datangzi,Laodazhai,and Makadi,and terminates in the southeast of Lancang county.It has a length of 85 km and a NNW trend.The Lancang fault was a Holocene-active right-lateral strike slip fault with a dip slip component.A variety of dislocation landforms have been formed along the fault,such as fault steep cliffs,fault scarps,dextral dislocation of gullies and ridges,fault trenches,fault passes,and pits.The fault intersects the Heihe fault with a NWW trend at Zhanmapo where the M7.6 Langcang earthquake occurred.In this paper,the geological and geomorphological characteristics of activity along the Lancang fault are studied in accordance with the use of satellite image interpretation and field geological investigations.The research focuses on the slip rate of the fault during the Holocene.Two level terraces appeared with synchronized displacement at Nanjingwa; the displacement of the T₂ terrace is about (40±2) m.No dating samples are available from this area,and therefore regional dating data is used to determine the slip rate.At a location near Makadi,five gullies have synchronous right-lateral displacement because of fault movement; according to differential GPS measurements in one of these gullies the displacement is about (19±3) m.Using age data for the corresponding landform surface,we thus determine that the right-lateral strike slip rate at this location is approximately (4.2±0.6) mm/a.Analysis of the slip rate and bedrock displacement leads us to infer that the fault was initiated in the late-early Pleistocene.