The effect discussion of ramp time and some general corrective methods of transient electromagnetic method

The correction of ramp-time is an important part in TEM data procedure. The paper,aiming at the central loop transient electromagnetic method for its widely application,discusses two problems.At first,the paper analyses the effect of ramp in detail.Comparing with step wave,the feature of slanting wave is the high frequency components with rapid attenuation and simultaneous oscillation. The effect of slanting wave mainly influences the early channel of transient electromagnetic signal and the result shows lower response.The longer the ramp is,the lower the response is.Secondly,the paper discusses some general ramp-time corrective methods,the results shows: for the full data,the Eaton method should be chosen,and for late time data,the Eaton method or the moving coordinates method can all be chosen.Although the Fitterman method can be used as alternate,its application conditions must be considered carefully.The late time condition about the moving coordinates method can be made certain by experimenting according to the local area parameters.