[1] This paper presents S-inversion method to tunnel prediction to forecasting water-filled faults or fracture zones ahead of the front wall of a tunnel during tunnel excavation. S-inversion is an interpretation method of transient electromagnetic (TEM) data using the second derivative of the conductivity parameter based on the moving thin sheet approach. It is suggested for the technology of second derivative of vertical apparent conductivity, which is traditionally used in surface TEM data interpretation, the theoretical analyses and the method of numerical calculation in detail are also given. Finally, a real tunnel forecasting is studied for TEM surveys, and results show that the proposed method is effective and successful for exploring and predicting unfavorable geology during tunnel construction.

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Three emerging techniques for surface electromagnetic (EM) exploration with high detection accuracy and large depth of investigation, namely, WEM (wireless electromagnetic method), MTEM (multi-channel transient electromagnetic method) and SOTEM (short-offset grounded-wire TEM), are introduced. In detail, we proposed a newly developed sky-wave theory in which EM wave can propagate in full space of ionosphere-atmosphere-lithosphere. Correspondingly, we developed the WEM recording system to measure the sky-wave to obtain the structures down to ~10 km depth. We then introduced MTEM as a highly effective method for mineral exploration with target depth of 3km. Using selfdeveloped MTEM system, we presented the results obtained from mineral exploration study carried out in China. Lastly, we proposed the SOTEM method for a greater detection depth (1.5km) than traditional loop source TEM (500m) with a small offset and high resolution.

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