A Study On The Activity Of Lijiang-Jianchuan Fault Zone, Yunnan

The uplift of Tibetan Plateau causes the Northwest Yunnan to form a zone withintense neotectonic movement and complicated geological conditions and frequentdestructive earthquakes. The uplift of Tibetan Plateau causes the Northwest Yunnan toform a zone with intense neotectonic movement and complicated geological conditionsand frequent destructive earthquakes. The research on the activity of the fault hasfar-reaching implications for not only the study on region seismic activitycharacteristics and control mechanism of earthquake, but also the disaster preventionand mitigation work.With the main purpose of studying the activity of Lijiang-Jianchuan fault, variousresearch means have been used in the paper. This paper has researched on these ways:①remote sensing data;②physiognomy and lithology characters, and tectoniccharacteristics of the superficial department, and microstructure feature;③deepgeophysical characteristics;④seismicity laws, and correlation of fault and seismicactivity. The following basic understandings were made:（1）Lijiang-JianChuan fault zone oblique in Lijiang basin, formed by twoparallel fractures. Two fractures are mutually to tilt. The Northwest branch to SE andSoutheast branch to NW. The angle of Northwest branch is steep, between50°and70°.The angle of Southeast branch is relatively gentle. The length of Gantangzi-Lijiangsection of this fault zone is20km. The length of Lijiang-Hualong section is60km.There are some tiny branch fractures around the main fault zone. It has been found thatthis fault was mainly sinistral strike-slip movement and secondarily thrust movement.The tectonite in the Lijiang-Jianchuan fault showed that the fault was mainly brittledeformation with trace ductile deformation. Surface survey on Quaternary system sediment showed there was no obvious sign of activity of this fault.（2）The area of seismic activity of Lijiang-Jianchuan fault has deep magmaticactivity. This area is also a seismic sounding speed with dramatic changes andaeromagnetic anomaly belt with abnormal gravity and high calorific value. Thesetypical earth the physical geography environment and tectonic environment were thekey influencers for causing seismic activity of Lijiang-Jianchuan fault.（3）Using special analysis function of GIS (Geographic Information System)software, statistic analysis was performed on earthquake and fault distribution of thisarea. It was found that seismic activities within7km of the Lijiang-Jianchuan fault wererelated to the activity of the fault. Compared with the fault around on the correlationcoefficient of fault activity level, it was found that Lijiang-Jianchuan fault was not astrong active fault in this area.（4）Through overlay analysis with a radius of7km, distribution of seismicactivity of Lijiang-Jianchuan fault show that:①medium-strong earthquakes distributeat opposite ends of the fault;②seismic activity in central region is relatively weak;③1-10km below the surface is the main ranges of seismic activity of Lijiang-Jianchuanfault and earthquakes show obvious phenomenon of layering around10km.Sensibleearthquakes magnitude between3.0and3.9show characteristics that moving fromnortheast section of the fault to southwest, then move from central section to northeast.Historical earthquake activity of this fault has three active periods.