Study On The Method Of Grounded-wire TEM For Whole Fied Exploration

Now it is difficult for prospecting and exploration with the easy finding of theshallow mineral resources decrease.and that what we have always used become use-less,it can not acquire good results.Therefore,it become more and more important tofind new ways and new methods for exploration.To meet the country’s strategic needsof mineral resources,it is of great significance to carry out effective technology suitedfor deep geophysical prospecting.Electric source TEM in the form of a long grounded wire transmit pulse currentin the ground to establish a pulsed magnetic field,when the first magnetic fielddisappears,we start to receive the secondary electromagnetic.comparing to Loopsource, LOTEM,CSAMT,the electric source TEM has a strong signal,less labor inten-sity,and it can take a great advantage of achieve greater probing depth with smalleroffset.At first,the article proposed a1D Grounded–wire TEM forward program,theauthor divided the response into two parts,one is contributed by the two groundingterminals and the other by the line which can reduced the calculation time remark-ablely.Secondly he studied the electric field of transient electromagnetic field diffusion process underground,analyzed the difference between magnetic source andelectric source.The diffusion law and feature of electromagnetic response is studiedby means of the plane figures and decay curves. We compare the response at differ-rent offset and time in order to choose the suited component and range for the fieldwork. And by calculation of1D Grounded–wire TEM,he obtained the B z (t)/tres-ponse of the different electrical structure.Then studied IP effect in the Grounded-wire TEM using Cole-Cole model on the polarizable earth,the influence of the IPeffect on the component is weaker than for the Ex component in the sensethat the decay to zero is not as perturbed. Usied iterative fitting to strike the implicitexpression of apparent resistivity which is more accurately reflect the true geo-electricstructure than the early time apparent resistivity and late time apparent resistivity.Then studied the the sensitivity of electric source TEM the to the low-resistivity thinlayer,dicussied from12,thickness and exploration depth three aspects to affect theinvestigation.Then studied the rapid inversion methods of TEM,learnd the time-depth conversion and resistivity conversion methods. finally we apply this method to Minedwater-rich area detection and obtain good result.