We developed a three-dimensional（3D） conjugate gradient inversion algorithm for in-verting magnetotelluric impedance tensor measurements.In order to show the importance of including diagonal components of magnetotel...We developed a three-dimensional（3D） conjugate gradient inversion algorithm for in-verting magnetotelluric impedance tensor measurements.In order to show the importance of including diagonal components of magnetotelluric impedance tensor in 3D inversion,synthetic data were inverted using the 3D conjugate gradient inversion,and the inversion results were compared and analyzed.The results from the 3D inversion of synthetic data indicate that both the off-diagonal and the diagonal components are required in inversions to obtain better inversion results when there are no enough data sites to recover the target resistivity structure.These examples show that lots of information about 3D structure is also contained in the diagonal components;as a result,diagonal components should be in-cluded in 3D inversions.The inversion algorithm was also used to invert the impedance tensor data ac-quired in the Kayabe area in Japan.Inversions with the synthetic and real data demonstrated the va-lidity and practicability of the inversion algorithm.展开更多
Considering the uncertainty of the electrical axis for two-dimensional audo-magnetotelluric(AMT) data processing, an AMT inversion method with the Central impedance tensor was presented. First, we present a calculatio...Considering the uncertainty of the electrical axis for two-dimensional audo-magnetotelluric(AMT) data processing, an AMT inversion method with the Central impedance tensor was presented. First, we present a calculation expression of the Central impedance tensor in AMT, which can be considered as the arithmetic mean of TE-polarization mode and TM-polarization mode in the twodimensional geo-electrical model. Second, a least-squares iterative inversion algorithm is established, based on a smoothnessconstrained model, and an improved L-curve method is adopted to determine the best regularization parameters. We then test the above inversion method with synthetic data and field data. The test results show that this two-dimensional AMT inversion scheme for the responses of Central impedance is effective and can reconstruct reasonable two-dimensional subsurface resistivity structures. We conclude that the Central impedance tensor is a useful tool for two-dimensional inversion of AMT data.展开更多
Computation of impedance tensor elements is one of the important steps in magnetotelluric data processing. Conventionally, the impedance tensor is defined as a 2 x 2 matrix with Zxx, Zxy, Zyx, and Zyy as elements. In ...Computation of impedance tensor elements is one of the important steps in magnetotelluric data processing. Conventionally, the impedance tensor is defined as a 2 x 2 matrix with Zxx, Zxy, Zyx, and Zyy as elements. In the present study, the six-element impedance tensor is computed with a 2 × 3 matrix using Zxx, Zxy, Zyx, Zyy, Zxz, and Zyz. The properties of the impedance tensor elements have been analyzed for these above two types. The methodology has been tested with five component magnetotelluric data from the Kutch sedimentary basin, Gujarat, India. From the computation of apparent resistivity computation and phase we observed that there is small difference between the four and six impedance elements of Zxy and Zyx for most of the frequency band. However for longer period data, more than 100 sec, an increase in the apparent resistivity and decrease in the phase is observed. We also note that the tipper magnitude is nearly zero for most of the periods, but gradually shows an increasing trend for longer periods （〉100 see）. The Kutch sedimentary basin geoeleetric section shows near horizontal layers at shallow depths and anomalous high conductivity heterogeneous layers at deeper depths may be responsible for the large Hz component at longer periods. This indicates that the vertical component of the magnetic field, Hz, does play an important role in the estimation of electric field parameters in the region with large 2D/3D structures.展开更多
A new method relying on the Stroh formulism and the theory of the surface impedance tensor was developed to investigate the dynamic instability of interfacial slip waves.The concept of the surface impedance tensor was...A new method relying on the Stroh formulism and the theory of the surface impedance tensor was developed to investigate the dynamic instability of interfacial slip waves.The concept of the surface impedance tensor was extended to the case where the wave speed is of a complex value,and the boundary conditions at the frictionally contacting interface were expressed by the surface impedance tensor.Then the boundary value problem was transformed to searching for zeroes of a complex polynomial in the unit circle.As an example,the steady frictional sliding of an elastic half-space in contact with a rigid flat surface was considered in details.A quartic complex characteristic equation was derived and its solution behavior in the unit circle was discussed.An explicit expression for the instability condition of the interfacial slip waves was presented.展开更多
Scalar CSAMT is only suitable for measurements in one and two dimensions perpendicular to geological structures. For complex 3D geoelectric structure, tensor CSAMT is more suitable. In this paper, we discuss 3D tensor...Scalar CSAMT is only suitable for measurements in one and two dimensions perpendicular to geological structures. For complex 3D geoelectric structure, tensor CSAMT is more suitable. In this paper, we discuss 3D tensor CSAMT forward modeling using the vector finite-element method. To verify the feasibility of the algorithm, we calculate the electric field, magnetic field, and tensor impedance of the 3D CSAMT far-zone field in layered media and compare them with theoretical solutions. In addition, a three-dimensional anomaly in half-space is also simulated, and the response characteristics of the impedance tensor and the apparent resistivity and impedance phase are analyzed. The results suggest that the vector finite-element method produces high-precision electromagnetic field and impedance tensor data, satisfies the electric field discontinuity, and does not require divergence correction using the vector finite-element method.展开更多
Currently, most of MT （magnetotelluric） data are still collected on sparse survey lines and interpreted using 2D inversion methods because of the field work cost, the work area environment, and so on. However, there...Currently, most of MT （magnetotelluric） data are still collected on sparse survey lines and interpreted using 2D inversion methods because of the field work cost, the work area environment, and so on. However, there are some 2D interpretation limitations of the MT data from 3D geoelectrical structures which always leads to wrong geological interpretations. In this paper, we used the 3D inversion method to interpret the MT sparse lines data. In model testing, the sparse lines data are the MT full information data generated from a test model and processed using the 3D conjugate gradients inversion code. The inversion results show that this inversion method is reasonable and effective. Meanwhile, we prove that for inversion results with different element parameters, the results by joint inversion of both the impedance tensor data and the tipper data are more accurate and closer to the test model.展开更多
In Dangjialiang area of Ningqiang County, the terrain is severely cut, the vegetation is relatively developed, and the covering layer is relatively thick. In order to carry out geothermal resources exploration, the au...In Dangjialiang area of Ningqiang County, the terrain is severely cut, the vegetation is relatively developed, and the covering layer is relatively thick. In order to carry out geothermal resources exploration, the author obtains two-dimensional apparent resistivity model of audio magnetotelluric sounding profile by two-dimensional inversion of TM model of 74 sounding points in two audio magnetotelluric sounding profiles. The inversion result shows that that stratigraphic-lithologic boundary and fault structure location shown in section AA are basically consistent with those shown in section BB. This audio-frequency magnetotelluric sounding survey has completed the division of stratigraphic sequences and fault structures in the areas controlled by the exploration lines, delineated the favorable geothermal resources storage scope in the study area, and given the well location arrangement suggestions, which provide the basic basis for the later exploration and development.展开更多
基金supported by the National Natural Science Foundation of China (Nos. 40774029, 41004028)the Special Fund for Basic Scientific Research of Central Colleges (No. 2010ZY53)the Program for New Century Excellent Talents in University (NCET)
文摘We developed a three-dimensional（3D） conjugate gradient inversion algorithm for in-verting magnetotelluric impedance tensor measurements.In order to show the importance of including diagonal components of magnetotelluric impedance tensor in 3D inversion,synthetic data were inverted using the 3D conjugate gradient inversion,and the inversion results were compared and analyzed.The results from the 3D inversion of synthetic data indicate that both the off-diagonal and the diagonal components are required in inversions to obtain better inversion results when there are no enough data sites to recover the target resistivity structure.These examples show that lots of information about 3D structure is also contained in the diagonal components;as a result,diagonal components should be in-cluded in 3D inversions.The inversion algorithm was also used to invert the impedance tensor data ac-quired in the Kayabe area in Japan.Inversions with the synthetic and real data demonstrated the va-lidity and practicability of the inversion algorithm.
基金supported by National Natural Science Foundation of China (grant 41674080)Higher School Doctor Subject Special Scientific Research Foundation (grant 20110162120064)
文摘Considering the uncertainty of the electrical axis for two-dimensional audo-magnetotelluric(AMT) data processing, an AMT inversion method with the Central impedance tensor was presented. First, we present a calculation expression of the Central impedance tensor in AMT, which can be considered as the arithmetic mean of TE-polarization mode and TM-polarization mode in the twodimensional geo-electrical model. Second, a least-squares iterative inversion algorithm is established, based on a smoothnessconstrained model, and an improved L-curve method is adopted to determine the best regularization parameters. We then test the above inversion method with synthetic data and field data. The test results show that this two-dimensional AMT inversion scheme for the responses of Central impedance is effective and can reconstruct reasonable two-dimensional subsurface resistivity structures. We conclude that the Central impedance tensor is a useful tool for two-dimensional inversion of AMT data.
文摘Computation of impedance tensor elements is one of the important steps in magnetotelluric data processing. Conventionally, the impedance tensor is defined as a 2 x 2 matrix with Zxx, Zxy, Zyx, and Zyy as elements. In the present study, the six-element impedance tensor is computed with a 2 × 3 matrix using Zxx, Zxy, Zyx, Zyy, Zxz, and Zyz. The properties of the impedance tensor elements have been analyzed for these above two types. The methodology has been tested with five component magnetotelluric data from the Kutch sedimentary basin, Gujarat, India. From the computation of apparent resistivity computation and phase we observed that there is small difference between the four and six impedance elements of Zxy and Zyx for most of the frequency band. However for longer period data, more than 100 sec, an increase in the apparent resistivity and decrease in the phase is observed. We also note that the tipper magnitude is nearly zero for most of the periods, but gradually shows an increasing trend for longer periods （〉100 see）. The Kutch sedimentary basin geoeleetric section shows near horizontal layers at shallow depths and anomalous high conductivity heterogeneous layers at deeper depths may be responsible for the large Hz component at longer periods. This indicates that the vertical component of the magnetic field, Hz, does play an important role in the estimation of electric field parameters in the region with large 2D/3D structures.
文摘A new method relying on the Stroh formulism and the theory of the surface impedance tensor was developed to investigate the dynamic instability of interfacial slip waves.The concept of the surface impedance tensor was extended to the case where the wave speed is of a complex value,and the boundary conditions at the frictionally contacting interface were expressed by the surface impedance tensor.Then the boundary value problem was transformed to searching for zeroes of a complex polynomial in the unit circle.As an example,the steady frictional sliding of an elastic half-space in contact with a rigid flat surface was considered in details.A quartic complex characteristic equation was derived and its solution behavior in the unit circle was discussed.An explicit expression for the instability condition of the interfacial slip waves was presented.
基金supported by the National Natural Science Foundation of China(No.41104068)the Deep Exploration in China,Sino Probe-03-05
文摘Scalar CSAMT is only suitable for measurements in one and two dimensions perpendicular to geological structures. For complex 3D geoelectric structure, tensor CSAMT is more suitable. In this paper, we discuss 3D tensor CSAMT forward modeling using the vector finite-element method. To verify the feasibility of the algorithm, we calculate the electric field, magnetic field, and tensor impedance of the 3D CSAMT far-zone field in layered media and compare them with theoretical solutions. In addition, a three-dimensional anomaly in half-space is also simulated, and the response characteristics of the impedance tensor and the apparent resistivity and impedance phase are analyzed. The results suggest that the vector finite-element method produces high-precision electromagnetic field and impedance tensor data, satisfies the electric field discontinuity, and does not require divergence correction using the vector finite-element method.
基金supported by the National Hi-Tech Research and Development Program of China (863 Program) (No. 2007AA09Z310)National Natural Science Foundation of China (No. 40677037, 40774029, 41004028)+1 种基金Fundamental Research Funds for the Central Universities (No. 2010ZY53) Program for New Century Excellent Talents in University (NCET)
文摘Currently, most of MT （magnetotelluric） data are still collected on sparse survey lines and interpreted using 2D inversion methods because of the field work cost, the work area environment, and so on. However, there are some 2D interpretation limitations of the MT data from 3D geoelectrical structures which always leads to wrong geological interpretations. In this paper, we used the 3D inversion method to interpret the MT sparse lines data. In model testing, the sparse lines data are the MT full information data generated from a test model and processed using the 3D conjugate gradients inversion code. The inversion results show that this inversion method is reasonable and effective. Meanwhile, we prove that for inversion results with different element parameters, the results by joint inversion of both the impedance tensor data and the tipper data are more accurate and closer to the test model.
文摘In Dangjialiang area of Ningqiang County, the terrain is severely cut, the vegetation is relatively developed, and the covering layer is relatively thick. In order to carry out geothermal resources exploration, the author obtains two-dimensional apparent resistivity model of audio magnetotelluric sounding profile by two-dimensional inversion of TM model of 74 sounding points in two audio magnetotelluric sounding profiles. The inversion result shows that that stratigraphic-lithologic boundary and fault structure location shown in section AA are basically consistent with those shown in section BB. This audio-frequency magnetotelluric sounding survey has completed the division of stratigraphic sequences and fault structures in the areas controlled by the exploration lines, delineated the favorable geothermal resources storage scope in the study area, and given the well location arrangement suggestions, which provide the basic basis for the later exploration and development.
