Effect of Transmitter Waveform on 1D Modeling and Inversion of Transient Electromagnetic Method Data

doi:10.19657/j.geoscience.1000-8527.2022.059

Abstract

Abstract:

We have developed a 1D modeling and inversion algorithm for transient electromagnetic method (TEM) data with transmitter waveform. The source is a horizontal rectangular loop for the implementation. Through the Duhamel integral, the step response was converted to the response generated by the trapezoidal waveform. In the inversion, the Occam strategy is adopted to obtain a smooth layered model. The synthetic examples show that the time derivatives of the vertical magnetic fields, dB/dt, and the inversion results are distorted to different extents by the turn-on, steady and turn-off times. The investigated model response shows that the turn-on, steady, and turn-off times mainly affect the TEM data at late, intermediate-late, and early gate times, respectively. Furthermore, the distortions become greater with increasing durations of the turn-on, steady and turn-off times. Inversion results of the synthetic data indicate that the turn-on times have only minor influence on the inversion results, whilst the turn-off and steady times affect the inversion results of the shallow and deep parts, respectively.

Key words: transient electromagnetic method, transmitter waveform, 1D forward modeling and inversion

CLC Number:

P631

WANG Shengtao, LIN Changhong, WANG Xudong. Effect of Transmitter Waveform on 1D Modeling and Inversion of Transient Electromagnetic Method Data[J]. Geoscience, 2023, 37(01): 99-106.

Figures/Tables 11

Fig.1 Comparison between the 1D solutions of the AarhusInv code and the responses calculated by the developed algorithm in this paper on a layered model

Fig.2 Comparison between the 1D inversion result of the AarhusInv code and that inverted by the algorithm in this paper

Fig.3 Investigated model in this study

Table 1 Some TEM system parameters

仪器名称	发射电流/A	上升沿时间t₁/ms	下降沿时间t₀/μs
TERRA TEM 24瞬变电磁仪	50	10~2000	22
JS06-MSD-1瞬变电磁仪	1~20	480	8
PROTEM 57-MK2瞬变电磁仪	28		20~115
PROTEM-TEM 47发射机	3		2.5
SkyTEM瞬变电磁仪	30		4
SkyTEM306 HP(高频)	9	0.8	1018
SkyTEM306 HP(低频)	220~250	5	15×10³
SkyTEM312 HP(高频)	220~250	5	15×10³
YCS 150矿井瞬变电磁仪	2.5		0.5×10³
SkyTEM312 HP(低频)	220~250	8	32×10³

Fig.4 Parameters of trapezoidal wave

Fig.5 The dB/dt responses on the uniform half-space (a), three-layered (b) and five-layered (c) models in Fig.3 with different turn-on time and the relative error ((d), (e) and (f)) with the response of step waveform (t1=1 fs)

Fig.6 The dB/dt responses on the uniform half-space (a), three-layered (b) and five-layered (c) models in Fig.3 with different steady time and the relative error ((d), (e) and (f)) with the response of triangular wave (t2=1 μs)

Fig.7 The dB/dt responses on the uniform half-space (a), three-layered (b) and five-layered (c) models in Fig.3 with different turn-off time and the relative error ((d), (e) and (f)) with the response of step wave (t0=1 fs)

Fig.8 Inversion results of synthetic data for three-layered model (a) and five-layered model (b) in Fig.3 with different turn-on time

Fig.9 Inversion results of synthetic data for three-layered model (a) and five-layered model (b) in Fig.3 with different steady time

Fig.10 Inversion results of synthetic data for three-layered model (a) and five-layered model (b) in Fig.3 with different turn-off time

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