A finite element algorithm combined with divergence condition was presented for computing three-dimensional(3D) magnetotelluric forward modeling. The finite element equation of three-dimensional magnetotelluric forwar...A finite element algorithm combined with divergence condition was presented for computing three-dimensional(3D) magnetotelluric forward modeling. The finite element equation of three-dimensional magnetotelluric forward modeling was derived from Maxwell's equations using general variation principle. The divergence condition was added forcedly to the electric field boundary value problem, which made the solution correct. The system of equation of the finite element algorithm was a large sparse, banded, symmetric, ill-conditioned, non-Hermitian complex matrix equation, which can be solved using the Bi-CGSTAB method. In order to prove correctness of the three-dimensional magnetotelluric forward algorithm, the computed results and analytic results of one-dimensional geo-electrical model were compared. In addition, the three-dimensional magnetotelluric forward algorithm is given a further evaluation by computing COMMEMI model. The forward modeling results show that the algorithm is very efficient, and it has a lot of advantages, such as the high precision, the canonical process of solving problem, meeting the internal boundary condition automatically and adapting to all kinds of distribution of multi-substances.展开更多
In recent years, the data collecting and processing of magnetotelluric sounding （MT） have progressed greatly. How to improve the quality of field surveyed data and obtain the high quality parameters such as apparent...In recent years, the data collecting and processing of magnetotelluric sounding （MT） have progressed greatly. How to improve the quality of field surveyed data and obtain the high quality parameters such as apparent resistivity and phase is the most important link during the overall flow. It is closely related to the signal-to-noise ratio of magnetic sensors, the resolution of data collecting units and relevant processing methods as well. Produced by Germany Metronix Measurement Instruments and Electronics Ltd., the new type multi-channel geophysical measurement system GMS-06 was already adopted and used by domeslic units such as Institute of Geology and Geophysics of Chinese Academy of Sciences and Tongji University. Based on the brief introduction of GMS-06, this paper will give the comparisons and analyses of the synchronous surveyed MT data by GMS-06, MMS-03 MT system which was also produced by Metronix and V5-2000 MT system produced by Canada Phoenix Geophysics Ltd.. Then the preliminary processing and interpretation results of the long period MT data observed by GMS-06 in the area of Shanghai and Zhejiang are also discussed in the paper.展开更多
From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied...From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied area of the Tan-Lu fault's northern section,and have analyzed electrical characteristics of the relevant profiles.Deriving the following conclusions:(1)Jiamusi-Bureya plots,etc.,demonstrate the high resistance of Kernel;(2)Fold belt attributed to the land showed high and low resistance stitching,associated with not only terrane accretion,but also upper mantle upwelling;below the sedimentary basin,the resistivity of the upper mantle is lower and closer to the surface comparing with the adjacent area(100-150);(3)In the system of Tan-Lu fracture,Yishu and Dunmi fracture,etc.are expressed as vertical low-resistivity zone;(4)There may exist subducted old-fashioned piece under Jiamusi and Bureya plots.展开更多
The INDEPTH MT results show that there are no electrical features of deep fractures along the Yarlung Zangbo River, but a large high conductivity body exists in the area between Gyangze and Rinbung. It dips northwar...The INDEPTH MT results show that there are no electrical features of deep fractures along the Yarlung Zangbo River, but a large high conductivity body exists in the area between Gyangze and Rinbung. It dips northward, extends downward up to the depth of about 55 km and indicates the exposure of the possible real position of the Yarlung Zangbo suture. There are three sets of electrical gradient and distorted zones reflecting the structure of faults in the high conductivity region. These three fault belts, which dip northward and gradually converge downward to the main fault belt, and a series of south dipping faults in the north side form the exhaled structural characteristics of the Yarlung Zangbo suture. There is a close relationship between the large high conductivity body and the underground thermal state.展开更多
Despite extensive efforts to understand the tectonic evolution of the Jiangnan Orogen in South China,the orogenic process and its mechanism remain a matter of dispute.Previous geodynamic studies have mostly focused on...Despite extensive efforts to understand the tectonic evolution of the Jiangnan Orogen in South China,the orogenic process and its mechanism remain a matter of dispute.Previous geodynamic studies have mostly focused on collisional orogeny,which is commonly invoked to explain the Jiangnan Orogen.However,it is difficult for such hypotheses to reconcile all the geological and geophysical data,especially the absence of ultrahigh-pressure metamorphic rocks.Based on the magnetotelluric data,we present a group of resistivity models produced through the combination of two-dimensional and three-dimensional inversions,revealing the geo-electrical structures of Jiangnan and a typical collisional orogen.In our models,the resistive crust is separated into three parts by a prominent conductive layer with opposite dipping directions on both sides.A special thrust-nappe system,which is different from that developed in a typical collisional process,is revealed in the Jiangnan Orogen.This structure suggests a process different from the simple collisional orogeny.To interpret our observations,an'intra-continental orogeny'is proposed to address the development of the Jiangnan Orogen in the Mesozoic.Furthermore,this'reworked'process may contain at least two stages caused by the decoupling of the lithosphere,which is revealed by an extra conductive layer beneath Jiangnan.展开更多
This paper deals with the results of the MT observations in the region of Zhongshan Station,Larsemann Hills area, East Antarctica and points out that the lithosphere thickness of the Larsemann Hills is 140 km and the ...This paper deals with the results of the MT observations in the region of Zhongshan Station,Larsemann Hills area, East Antarctica and points out that the lithosphere thickness of the Larsemann Hills is 140 km and the crustal high conductivity layer is situated in 22 km.展开更多
【目的】大地电磁测深是一种通过观测天然电磁场获取地下电性结构的勘探方法,较易受到噪声干扰。脉冲类噪声是大地电磁工作中的常见噪声,其幅值高、频带宽,会对数据质量产生较大影响。【方法】为了压制脉冲类噪声,以插补思想为基础,提...【目的】大地电磁测深是一种通过观测天然电磁场获取地下电性结构的勘探方法,较易受到噪声干扰。脉冲类噪声是大地电磁工作中的常见噪声,其幅值高、频带宽,会对数据质量产生较大影响。【方法】为了压制脉冲类噪声,以插补思想为基础,提出了基于时间序列双向循环插补模型(Bidirectional recurrent imputation for time series,BRITS)的大地电磁脉冲类噪声处理方法。首先,将噪声干扰段删除,此时大地电磁时间序列可视为待插补的缺失序列,而后利用该缺失序列构建训练集,对BRITS模型进行插补训练,训练完成后对缺失序列进行插补,即可得到去噪结果。通过仿真及实测含噪声数据处理,并与经验模态分解(Empirical mode decomposition,EMD)阈值方法进行了对比。【结果和结论】结果表明:BRITS方法对仿真噪声数据处理后与原始数据的归一化互相关系数可达0.999以上,信噪比可达29 dB以上,EMD阈值方法处理前后相关系数为0.778,信噪比为3.09 dB;在实测数据处理中,BRITS方法有效恢复了噪声干扰数据,相比EMD阈值方法,其阻抗奈奎斯特图更接近天然大地电磁信号特征。通过不同训练样本试验得出:对4分量大地电磁数据而言,数据中至少需包含两道正常分量,单个含噪分量中噪声占比不大于20%,且噪声连续干扰长度不超过10个采样点,此时,BRITS方法去噪后数据的相关系数在0.96以上,可以保证一定的去噪精度。展开更多
基金Project(60672042) supported by the National Natural Science Foundation of China
文摘A finite element algorithm combined with divergence condition was presented for computing three-dimensional(3D) magnetotelluric forward modeling. The finite element equation of three-dimensional magnetotelluric forward modeling was derived from Maxwell's equations using general variation principle. The divergence condition was added forcedly to the electric field boundary value problem, which made the solution correct. The system of equation of the finite element algorithm was a large sparse, banded, symmetric, ill-conditioned, non-Hermitian complex matrix equation, which can be solved using the Bi-CGSTAB method. In order to prove correctness of the three-dimensional magnetotelluric forward algorithm, the computed results and analytic results of one-dimensional geo-electrical model were compared. In addition, the three-dimensional magnetotelluric forward algorithm is given a further evaluation by computing COMMEMI model. The forward modeling results show that the algorithm is very efficient, and it has a lot of advantages, such as the high precision, the canonical process of solving problem, meeting the internal boundary condition automatically and adapting to all kinds of distribution of multi-substances.
基金National Natural Science Foundation of China (40104005) and National High Technical Research and Development Project (2004AA615010).
文摘In recent years, the data collecting and processing of magnetotelluric sounding （MT） have progressed greatly. How to improve the quality of field surveyed data and obtain the high quality parameters such as apparent resistivity and phase is the most important link during the overall flow. It is closely related to the signal-to-noise ratio of magnetic sensors, the resolution of data collecting units and relevant processing methods as well. Produced by Germany Metronix Measurement Instruments and Electronics Ltd., the new type multi-channel geophysical measurement system GMS-06 was already adopted and used by domeslic units such as Institute of Geology and Geophysics of Chinese Academy of Sciences and Tongji University. Based on the brief introduction of GMS-06, this paper will give the comparisons and analyses of the synchronous surveyed MT data by GMS-06, MMS-03 MT system which was also produced by Metronix and V5-2000 MT system produced by Canada Phoenix Geophysics Ltd.. Then the preliminary processing and interpretation results of the long period MT data observed by GMS-06 in the area of Shanghai and Zhejiang are also discussed in the paper.
基金the Project 12-05-91158 of the National Natural Science Foundation of China(NSFC)the Russian Academy of Sciences"Deep structure,evolution of the sedimentogenesis and tectonics of Northeastern China and southeastern Far East Russia"
文摘From China to Russia,Tan-Lu fault system stretches for thousands of kilometers,towards NE 30°.The authors have collected more than ten magnetotelluric profile that China and Russia have carried out,in the studied area of the Tan-Lu fault's northern section,and have analyzed electrical characteristics of the relevant profiles.Deriving the following conclusions:(1)Jiamusi-Bureya plots,etc.,demonstrate the high resistance of Kernel;(2)Fold belt attributed to the land showed high and low resistance stitching,associated with not only terrane accretion,but also upper mantle upwelling;below the sedimentary basin,the resistivity of the upper mantle is lower and closer to the surface comparing with the adjacent area(100-150);(3)In the system of Tan-Lu fracture,Yishu and Dunmi fracture,etc.are expressed as vertical low-resistivity zone;(4)There may exist subducted old-fashioned piece under Jiamusi and Bureya plots.
基金The study is supported by National Natural Science Foundation of China
文摘The INDEPTH MT results show that there are no electrical features of deep fractures along the Yarlung Zangbo River, but a large high conductivity body exists in the area between Gyangze and Rinbung. It dips northward, extends downward up to the depth of about 55 km and indicates the exposure of the possible real position of the Yarlung Zangbo suture. There are three sets of electrical gradient and distorted zones reflecting the structure of faults in the high conductivity region. These three fault belts, which dip northward and gradually converge downward to the main fault belt, and a series of south dipping faults in the north side form the exhaled structural characteristics of the Yarlung Zangbo suture. There is a close relationship between the large high conductivity body and the underground thermal state.
基金funded by the Anhui Province Science Program(2018-g-1-4)the National Science Program(Nos.41630320,42174087)the National Key R&D Program of China(No.2016YFC0600201)。
文摘Despite extensive efforts to understand the tectonic evolution of the Jiangnan Orogen in South China,the orogenic process and its mechanism remain a matter of dispute.Previous geodynamic studies have mostly focused on collisional orogeny,which is commonly invoked to explain the Jiangnan Orogen.However,it is difficult for such hypotheses to reconcile all the geological and geophysical data,especially the absence of ultrahigh-pressure metamorphic rocks.Based on the magnetotelluric data,we present a group of resistivity models produced through the combination of two-dimensional and three-dimensional inversions,revealing the geo-electrical structures of Jiangnan and a typical collisional orogen.In our models,the resistive crust is separated into three parts by a prominent conductive layer with opposite dipping directions on both sides.A special thrust-nappe system,which is different from that developed in a typical collisional process,is revealed in the Jiangnan Orogen.This structure suggests a process different from the simple collisional orogeny.To interpret our observations,an'intra-continental orogeny'is proposed to address the development of the Jiangnan Orogen in the Mesozoic.Furthermore,this'reworked'process may contain at least two stages caused by the decoupling of the lithosphere,which is revealed by an extra conductive layer beneath Jiangnan.
文摘This paper deals with the results of the MT observations in the region of Zhongshan Station,Larsemann Hills area, East Antarctica and points out that the lithosphere thickness of the Larsemann Hills is 140 km and the crustal high conductivity layer is situated in 22 km.
文摘【目的】大地电磁测深是一种通过观测天然电磁场获取地下电性结构的勘探方法,较易受到噪声干扰。脉冲类噪声是大地电磁工作中的常见噪声,其幅值高、频带宽,会对数据质量产生较大影响。【方法】为了压制脉冲类噪声,以插补思想为基础,提出了基于时间序列双向循环插补模型(Bidirectional recurrent imputation for time series,BRITS)的大地电磁脉冲类噪声处理方法。首先,将噪声干扰段删除,此时大地电磁时间序列可视为待插补的缺失序列,而后利用该缺失序列构建训练集,对BRITS模型进行插补训练,训练完成后对缺失序列进行插补,即可得到去噪结果。通过仿真及实测含噪声数据处理,并与经验模态分解(Empirical mode decomposition,EMD)阈值方法进行了对比。【结果和结论】结果表明:BRITS方法对仿真噪声数据处理后与原始数据的归一化互相关系数可达0.999以上,信噪比可达29 dB以上,EMD阈值方法处理前后相关系数为0.778,信噪比为3.09 dB;在实测数据处理中,BRITS方法有效恢复了噪声干扰数据,相比EMD阈值方法,其阻抗奈奎斯特图更接近天然大地电磁信号特征。通过不同训练样本试验得出:对4分量大地电磁数据而言,数据中至少需包含两道正常分量,单个含噪分量中噪声占比不大于20%,且噪声连续干扰长度不超过10个采样点,此时,BRITS方法去噪后数据的相关系数在0.96以上,可以保证一定的去噪精度。
