Research In The Application Of 1D Transient Electromagnetic Method

Transient electromagnetic method(TEM)is a time domain electromagnetic method.It emits pulsed electromagnetic fields at a fixed time interval through a ground return line or without a ground return line.It records information of the secondary eddy current field in an intermittent period.Through analysis of the secondary field,We will get the distribution situation of the underground media.To improve the efficiency and speed of inversion in 1-D transient electromagnetic method,a constrained damped least squares transient electromagnetic inversion algorithm is used.The convergence and inversion effects are improved.The paper mainly discusses the forward modeling of the typical geoelectric model,the smoke loop inversion,the damped least squares inversion,and the measured data processing.In the forward modeling,the response formula of the central loop transient electromagnetic method is deduced and calculated numerically,which lays the foundation for the inversion.The forward modeling and the curve analysis of the classical multi-layer geological model are carried out.The factors influencing TEM response and their relationship are summarized.In terms of inversion,smoke loop inversion and improved damping least squares inversion method are respected used.Then with the results of the inversion of the smoke ring as the initial model,we can use the damping least squares inversion.From numerical simulation and inversion of measured data,we find that it reduces the number of iterations greatly.It not only improves the computational efficiency,but also improves the inversion accuracy.The program of the smoke loop of transient electromagnetic and improved damped least square inversion is written as GUI interface.It can procedure data processing of transient electromagnetic and provide conveniences for the future data processing and interpretation.