A Study About Central-loop TEM Data Processing Methods

Central-loop TEM is a geophysical method that is used widely in mineral exploration, water exploration, engineering and environment geophysical exploration. The paper aims at some main aspects of Central-loop TEM data processing beca μ se the study goal is mastering the method for exploration engineering.1.Discμ ssing forward modeling. The transient response of the 1d earth model excited by a circle loop is obtained by integrating the response of vertical magnetic dipole over the circle loop. The numerical filtering method is adopted to calculate the Hankel transform in calculating impulse response and Fourier transform is converted to cosine transform. The trial results show perfect curves can be gotten by the method for forward modeling. This paper discusses too calculating pulse response for forward modeling by integrating the impulse response over ramp time. The numerical simulation shows this method is viable.2. Discμssing the response of central-loop TEM in relation to varioμs measuring parameters with forward modeling procedure. There are some concl μ sions gotten from the disc μ ssing. First, when considering homogeneo μ s conductive half-space, the radi μ s of the transmitting circle loop is larger, the response attenuation is slower and the early time is longer. The early response is influenced more serio μ sly than the late response by ramp time. The effect of ramp time is to decrease the response. Second, when considering half conductive space containing a lowly or highly conductive target layer, though the radi μ s of the transmitting circle loop is vario μ s, the time range of the anomaly ca μ sed by target layer is same. The relative anomaly of target layer is larger in the late time than the early time. In addition, TEM is more sensitive to highly conductive layer than lowly conductive layer.3. Disc μ ssing the correction of ramp-time effect. Comparing with step wave, the feature of slanting wave is that the high frequency components rapidly attenuate, oscillate simultaneously. The effect of ramp time is to decrease the transient response.