Three Dimensional Lithospheric Conductivity Structure Of Jiaoliao Block And Model Construction Methods Of "Standard Grid"

To study the Chinese mainland evolution-dynamics model in the Mesozoic-Cenozoic,the disintegration of the craton in the eastern part of the ancient continent of North China and the thinning process of its deep lithosphere are important scientific problems to be studied.However the main geophysical methods to study the lithosphere is by natural earthquakes and the magnetotelluric methods.This article relies on the study named "Experimental study of standard parameters of the electromagnetic network in the mainland(SinoProbe-01)",which is established by the project named "Deep exploration techniques and experimental research projects"and studies the deep electrical structure of lithosphere in Jiaoliao area and methods related to it.Jiaoliao area is located on the plastic block named Jiao-liao-chao Block,eastern of The North China Block.It's on the west coast of The Yellow Sea,and separated by Bohai Sea as two parts,the southern part is eastern Jiao island,the northern parrt is eastern Liao island.Because some of the sites are several kilometers away from the water of the sea,leading to the distortion of the data owing to the coast effects,so part of this article is studying the coast effect.The water of the sea is simplified as a layer of low resistance material in the surface of the model.By forward modeling and inversion,we concluded that the sea effect is distance related,which means that the further the sites away from the sea,the less distortion we will get.When the skin depth of the object is shorter than the distance between it and the water,the data we observed will be severely affected.What's more,as the depth of the sea water increases the distortion of data observed from the same site arises.By using the G-B impedance tensor decomposition method and Swift skew analysis of the data derived in this area,we get the strike directions and dimension information of the underground structure in different regions of this area.The overall regional structure strike tends to be NE with some local structure developed as SN or EW.The development of this area is controlled by Tanlu Fault and some other deep faults,moreover some blocks are obviously separated by faults.We obtain several two-dimensional structural model of resistance by using NLCG inversion method.Relying on that,some analysis of the Tanlu fault,Wulian-qingdao-rongchen fault is make and a high-conductivity layer in the upper mantle is found at a depth of about 70km in the Liaohe basin.The conclusions above are verified by the geological and geophysical data obtained before.We also doing some three-dimensional inversion of the MT data using the code developed by professor Siripunvaraporn of the Bangkok University.Comparing to the two-dimensional inversion,three-dimension inversion has a shallow depth detection of the structure underground and the resistance tends to be uniform below 60km.The horizontal location of the anomalies in both inversion are nearly the same but on the contrary the vertical location are different.