This paper presents the modeling of 2D CSAMT responses generated by horizontal electric dipole using the separation of primary and secondary field technique. The primary field is calculated using 1D analytical solutio...This paper presents the modeling of 2D CSAMT responses generated by horizontal electric dipole using the separation of primary and secondary field technique. The primary field is calculated using 1D analytical solution for homogeneous earth and it is used to calculate the secondary electric field in the inhomogeneous Helmholtz Equation. Calculation of Helmholtz Equation is carried out using the finite element method. Validation of this modeling is conducted by comparison of numerical results with 1D analytical response for the case of homogeneous and layered earth. The comparison of CSAMT responses are also provided for 2D cases of vertical contact and anomalous conductive body with the 2D magnetotelluric (MT) responses. The results of this study are expected to provide better interpretation of the 2D CSAMT data.展开更多
We present a case study of applying MT （magnetotellurics） and CSAMT （controlled source audio-frequency magnetotelluries） for geophysical exploration in Jiangxia （江夏）, which is located in new industrial develop...We present a case study of applying MT （magnetotellurics） and CSAMT （controlled source audio-frequency magnetotelluries） for geophysical exploration in Jiangxia （江夏）, which is located in new industrial developing suburb, where artificial noises are severe. In order to know deep buried structure, fracture status, and characteristics of underground geothermal development about 2 km, we acquired MT and CSAMT data to image subsurface structure through inversion and joint interpretation. The electrical terms of the 2D MT inversion can be divided into three ranges of resistivity values： （1） a highly resistive （〉350 ~.m） layer mainly characteristic of limestone, dolomitic limestone, leuttrite, silicarenite, and packsand; （2） an intermediate resistivity （250-350 Ω·m） layer mainly constituted by siliceous shale, siltstone, battie, and ampelitic limestone; and （3） a low resistivity （20-250 Ω·m） layer, from surface to-100 m, which is related to lacustrine alluvium of Quaternary period; the deep low resistivity layer is interpreted to be representative of the geothermal field. The result of the 2D CSAMT inversion reveals two layers of different electrical resistivities： （1） the first resistive layer （20-250 Ω·m）, which is related to lacustrine alluvium of Quaternary period and the heat source, and （2） the second resistive layer （250-3 000Ω·m）. The heat source appears to be bounded within the middle of exploration area and shows the N-S trend. Its depth ranges from more than 1.2 to less than 0.7 km, and its resistivity values range from 20 to 250 Ω·m in the northeast part of Jiangxia. Comparing the results of MT and CSAMT method, the positive anomalies are similar and can be assumed to be generated by the same source.展开更多
文摘This paper presents the modeling of 2D CSAMT responses generated by horizontal electric dipole using the separation of primary and secondary field technique. The primary field is calculated using 1D analytical solution for homogeneous earth and it is used to calculate the secondary electric field in the inhomogeneous Helmholtz Equation. Calculation of Helmholtz Equation is carried out using the finite element method. Validation of this modeling is conducted by comparison of numerical results with 1D analytical response for the case of homogeneous and layered earth. The comparison of CSAMT responses are also provided for 2D cases of vertical contact and anomalous conductive body with the 2D magnetotelluric (MT) responses. The results of this study are expected to provide better interpretation of the 2D CSAMT data.
基金supported by the National Natural Science Foundation of China (No. 40974040)the Deep Exploration in China (No. SinoProbe-01-03-02)the Ministry of Land and Resources of China
文摘We present a case study of applying MT （magnetotellurics） and CSAMT （controlled source audio-frequency magnetotelluries） for geophysical exploration in Jiangxia （江夏）, which is located in new industrial developing suburb, where artificial noises are severe. In order to know deep buried structure, fracture status, and characteristics of underground geothermal development about 2 km, we acquired MT and CSAMT data to image subsurface structure through inversion and joint interpretation. The electrical terms of the 2D MT inversion can be divided into three ranges of resistivity values： （1） a highly resistive （〉350 ~.m） layer mainly characteristic of limestone, dolomitic limestone, leuttrite, silicarenite, and packsand; （2） an intermediate resistivity （250-350 Ω·m） layer mainly constituted by siliceous shale, siltstone, battie, and ampelitic limestone; and （3） a low resistivity （20-250 Ω·m） layer, from surface to-100 m, which is related to lacustrine alluvium of Quaternary period; the deep low resistivity layer is interpreted to be representative of the geothermal field. The result of the 2D CSAMT inversion reveals two layers of different electrical resistivities： （1） the first resistive layer （20-250 Ω·m）, which is related to lacustrine alluvium of Quaternary period and the heat source, and （2） the second resistive layer （250-3 000Ω·m）. The heat source appears to be bounded within the middle of exploration area and shows the N-S trend. Its depth ranges from more than 1.2 to less than 0.7 km, and its resistivity values range from 20 to 250 Ω·m in the northeast part of Jiangxia. Comparing the results of MT and CSAMT method, the positive anomalies are similar and can be assumed to be generated by the same source.
