STUDY ON TEM′S RESOLUTION CAPABILITY FOR THE THIN LAYER OF LOW RESISTIVITY

Starting from frequency-domain electric field excited by vertical magnetic dipole,we derived one-dimensional forward method of Loop source,and calculated induced electromotive force on the thin layer of low resistivity while the ratio of depth and thickness and difference in the resistivity changes.In accordance with volume effect of electromagnetic method,we improved traditional dichotomy and proposed the method of calculating the whole stage apparent resistibity.And then on this basis we draw the curves of apparent resistivity when the ratio of depth and thickness is 1∶1.2,1∶1.5,1∶2,1∶4 and the ratio of resistivity is 1∶5,1∶10,1∶20 respectively.By comparing the characteristics of all kinds of apparent resistivity curve for different geoelectric models,we pointed out the resolution limit of TEM for low-resistivity thin layer of specific kinds and summarized the capacity of TEM for identifying and distinguishing low-resistivity thin layer,which is important to study the response of horizontal layered medium.