Electrical Structure Study Of Northeastern Margin Of The Tibetan Plateau

The study area is located between ( 102°E~105°E)and ( 34°N~38°N ) in NortheasternMargin of the Tibetan Plateau,from south to north the region goes through Qinling block,Qilian block,Haiyuan arcuate tectonic region and Alashan block.The paper aims to take advantage of MT technology and the latest acquired long-period MT sounding data using advanced data processing and inversion techniques to get reliable crust-upper mantle electrical structure from Hezuo,Lanzhou to Dajing.Combined with previous geological data to study Electrical Structure of Northeastern Margin of the Tibetan Plateau.Such as the location,type and extension of the faults and the causes and distribution of the high conductivity layer of the crust-upper mantle.First of all ,introduced the MT sounding basic theory,data processing and the process of data interpretation and recurring problems.Such as static shift correction,eletrical axis azimuth solution and dimension determination.And introduced the principal of different inversion methods, advantages and disadvantages of the choice of different magnetotelluric sounding data frequency on the inversion results and so on.Then introduced the basis geology of the northeastern margin of Qinghai-Tibet Plateau,using exsiting MT data to analyze the area.The study area magnetotelluric curve are mainly K and HK type. Both sides of the fault zone of apparent resistivity curve are different in form and magnitude.The changes in apparent resistivity and phrase curves could be the basis of block division and determine the location of the faults.Using reduced basis OCCAM(REBOCC) inversion to acquire the 2-D electrical structure model of Hezuo-Lanzhou-Dajing profile.Finally,interpreted the obtained 2-D electrical structure.The resulets shows that Western Qinling fault ,Haiyuan fault and Tianjingshan fault divided the study region into four blocks:Qinling block,Qilian block , Haiyuan arcuate tectonic region and Alashan block.The electrical structure shows that Western Qinling fault and Lenglongling-Haiyuan-Liupanshan fault are super crust faults and Tianjingshan fault is relatively small basement faults.In study area there are large scale and discrete low resistance body ,considering that in areas of relatively serious structural deformation 10Ωm is normal electrical structure.Analyzed the low resistance area and considered that the high conductuivity region was mainly due to fluid with salt water.