Transient EM screening in two concentric spherical shell model

Abstract

Different results have been obtained by Negi and Wait in connection with the effect of overburden in electromagnetic exploration by assuming different definitions of screening factor. Both definitions are based on frequency domain considerations. We shall describe the screening characteristics for a transient field with a two-concentric shell model with screening factor=(magnetic field of target and screen-magnetic field of screen alone)/(field of target alone). It is found that the screening factor does become more than one in some situations which means that the EM response of target is more in some cases when the screen is present than when it is absent.