2000 Vol. 25, No. 6
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2000, 25(6): 553-556.
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Abstract:
This paper presents the discussion of the stratigraphic and palaeo oceanographic significance of Botryocyrtis scutum in the three cylindrical samples that have occurred in the South China Sea since the Pleistocene. The relative abundances of the radiolarian Botryocyrtis scutum in the three cylindrical samples in the South China Sea since the Pleistocene are correlated with oxygen isotopic records, indicating that the relative abundance of the Botryocyrtis scutumv corresponds well to the oxygen isotopic records since the MIS 18. The abundance of B. scutum fluctuated during the glacial and interglacial periods, with its high abundance during the interglacial period and the low one during the glacial period. Just like the oxygen isotopic records, the abundance changes of B. scutum indicate the glacial and interglacial cycle and at the same time can be considered as a tool for the stratigraphic classification and correlation.
This paper presents the discussion of the stratigraphic and palaeo oceanographic significance of Botryocyrtis scutum in the three cylindrical samples that have occurred in the South China Sea since the Pleistocene. The relative abundances of the radiolarian Botryocyrtis scutum in the three cylindrical samples in the South China Sea since the Pleistocene are correlated with oxygen isotopic records, indicating that the relative abundance of the Botryocyrtis scutumv corresponds well to the oxygen isotopic records since the MIS 18. The abundance of B. scutum fluctuated during the glacial and interglacial periods, with its high abundance during the interglacial period and the low one during the glacial period. Just like the oxygen isotopic records, the abundance changes of B. scutum indicate the glacial and interglacial cycle and at the same time can be considered as a tool for the stratigraphic classification and correlation.
2000, 25(6): 557-563.
Abstract:
Structural and petrological research combined with the geological analysis of the isotopic dating references available now is used in this paper to demonstrate that the present day observed tectonic framework of the ultrahigh pressure (UHP) metamorphic belt in the Dabie Sulu region was formed dominantly in an extensional process at 200-170 Ma, on amphibolite facies conditions, following the Triassic collision between the Sino Korean and Yangtze cratons. The relic syn collision and UHP structures are preserved in the relatively large eclogite and other UHP metamorphic rock masses. Examples of the eclogite drawn from the Chengmagang and Hejiawan in Hubei Province, the Bixiling in Anhui Province, and Donghai in Jiangsu Province, are used to analyze and describe such relic UHP structures as the massive eclogite with weak foliations, the UHP shear zones and A type folds. It is stressed in the paper that only early UHP relic structural records may reflect the tectonic environment in the continental collision stage, and the corresponding relative dynamic features. On this basis, a kinematic model is proposed to represent the dynamic framework of the northward subduction of the Triassic (240-210 Ma) Yangtze craton under the Sino Korean craton and of their corresponding oblique collision.
Structural and petrological research combined with the geological analysis of the isotopic dating references available now is used in this paper to demonstrate that the present day observed tectonic framework of the ultrahigh pressure (UHP) metamorphic belt in the Dabie Sulu region was formed dominantly in an extensional process at 200-170 Ma, on amphibolite facies conditions, following the Triassic collision between the Sino Korean and Yangtze cratons. The relic syn collision and UHP structures are preserved in the relatively large eclogite and other UHP metamorphic rock masses. Examples of the eclogite drawn from the Chengmagang and Hejiawan in Hubei Province, the Bixiling in Anhui Province, and Donghai in Jiangsu Province, are used to analyze and describe such relic UHP structures as the massive eclogite with weak foliations, the UHP shear zones and A type folds. It is stressed in the paper that only early UHP relic structural records may reflect the tectonic environment in the continental collision stage, and the corresponding relative dynamic features. On this basis, a kinematic model is proposed to represent the dynamic framework of the northward subduction of the Triassic (240-210 Ma) Yangtze craton under the Sino Korean craton and of their corresponding oblique collision.
2000, 25(6): 565-572.
Abstract:
A series of experiments on the transfer between the brittle and ductile properties of the Maryland diabase was performed, with natural pyrophyllite as the medium for the pressure transfer, at the temperature ranging from 800 to 1 000 ℃, at the confining pressure ranging from 0.6 GPa to 1.0 GPa, and at the strain rate ranging from 10-4 to 10-5 s-1. The experiment results show that the rock is deformed into typical brittle fractures at the strain rate ranging from 10-4 to 10-5 s-1, at the confining pressure of 1.0 GPa, and at the temperature lower than 800 ℃. At the temperature higher than 1 000 ℃, the rock is deformed dominantly into the metastable creep. At the temperature ranging from 800 to 950 ℃, the deformation of the rock turns from the brittle fractures to the pseudo ductile flow. Therefore, the sensitive effect of the temperature change on the rock transfer between brittle and ductile properties is greater than that of the pressure change. The micro structural observation shows that the transfer between the brittle and ductile properties in the diabase is dominated by the conjugated ductile flow network in the form of the rarefaction and diffusion.
A series of experiments on the transfer between the brittle and ductile properties of the Maryland diabase was performed, with natural pyrophyllite as the medium for the pressure transfer, at the temperature ranging from 800 to 1 000 ℃, at the confining pressure ranging from 0.6 GPa to 1.0 GPa, and at the strain rate ranging from 10-4 to 10-5 s-1. The experiment results show that the rock is deformed into typical brittle fractures at the strain rate ranging from 10-4 to 10-5 s-1, at the confining pressure of 1.0 GPa, and at the temperature lower than 800 ℃. At the temperature higher than 1 000 ℃, the rock is deformed dominantly into the metastable creep. At the temperature ranging from 800 to 950 ℃, the deformation of the rock turns from the brittle fractures to the pseudo ductile flow. Therefore, the sensitive effect of the temperature change on the rock transfer between brittle and ductile properties is greater than that of the pressure change. The micro structural observation shows that the transfer between the brittle and ductile properties in the diabase is dominated by the conjugated ductile flow network in the form of the rarefaction and diffusion.
2000, 25(6): 573-578.
Abstract:
This paper presents a comprehensive geochemical study of rocks from the cross section of Sidaohe quarry in Macheng, one of the representative outcrops of eclogite and its host rocks in Dabie UHPM belt. It is revealed in this paper that the eclogite shares the geochemical features with N MORB, and its felsic host rocks can be categorized as TTG gneiss and garnet bearing granite. Evidences from REE and w (Nb) / w (Ta) ratios, Sm Nd isotopes and U Pb zircon dating favor the scenario that TTG gneiss originated from the partial melting of eclogite during the process of subduction, therefore, a special allochthonous relationship in tectonics arises between TTG gneiss and eclogite, the origin of TTG gneiss, while the garnet bearing granite would have resulted from the partial melting of eclogite during its exhumation, but the V type REE pattern denotes that HREE enriched mineral (s) was crystallized when the granite was forming, and the garnet would have been the most favorable candidate of these minerals. Low w (Nb) / w (Ta) ratios of garnet bearing granite indicate that the melting occurred in some extent due to fluid metasomatism, a product of the retrograde metamorphism of UHPM rocks. Therefore, the garnet bearing granite and eclogite would have been in a sub in situ relationship, as the granite may have occurred in the depth where garnet was stable.
This paper presents a comprehensive geochemical study of rocks from the cross section of Sidaohe quarry in Macheng, one of the representative outcrops of eclogite and its host rocks in Dabie UHPM belt. It is revealed in this paper that the eclogite shares the geochemical features with N MORB, and its felsic host rocks can be categorized as TTG gneiss and garnet bearing granite. Evidences from REE and w (Nb) / w (Ta) ratios, Sm Nd isotopes and U Pb zircon dating favor the scenario that TTG gneiss originated from the partial melting of eclogite during the process of subduction, therefore, a special allochthonous relationship in tectonics arises between TTG gneiss and eclogite, the origin of TTG gneiss, while the garnet bearing granite would have resulted from the partial melting of eclogite during its exhumation, but the V type REE pattern denotes that HREE enriched mineral (s) was crystallized when the granite was forming, and the garnet would have been the most favorable candidate of these minerals. Low w (Nb) / w (Ta) ratios of garnet bearing granite indicate that the melting occurred in some extent due to fluid metasomatism, a product of the retrograde metamorphism of UHPM rocks. Therefore, the garnet bearing granite and eclogite would have been in a sub in situ relationship, as the granite may have occurred in the depth where garnet was stable.
2000, 25(6): 579-585.
Abstract:
The geological metadata can be classified, on the basis of the difference in objects described by the geological metadata, as the metadata for the database, the metadata for the data set and the metadata for the data element layer. A certain difference arises in the management and the metadata in different layers. The most essential element in the research into the geological metadata is to formulate and utilize the metadata standard. In this paper, a three layer geological metadata system consisting of a basic metadata set, a summary metadata set and a detailed metadata set, is presented for the practical application and in line with the geological metadata standard available now. Each layer of metadata is appropriate to its corresponding user group. In this paper, is finally summarized the patterns for the utilization and management of several metadata, on the basis of the present successful experience on the utilization of the metadata.
The geological metadata can be classified, on the basis of the difference in objects described by the geological metadata, as the metadata for the database, the metadata for the data set and the metadata for the data element layer. A certain difference arises in the management and the metadata in different layers. The most essential element in the research into the geological metadata is to formulate and utilize the metadata standard. In this paper, a three layer geological metadata system consisting of a basic metadata set, a summary metadata set and a detailed metadata set, is presented for the practical application and in line with the geological metadata standard available now. Each layer of metadata is appropriate to its corresponding user group. In this paper, is finally summarized the patterns for the utilization and management of several metadata, on the basis of the present successful experience on the utilization of the metadata.
2000, 25(6): 587-591.
Abstract:
The palaeo desert is a special aeolian depositional system. Because of the difference in mechanism between the aeolian and the hydatogenous depositions, the principle presently applied to the sequence stratigraphic research into the continental lacustrine basins in line with the lake flooding surface, is not perfectly appropriate for the research into the palaeo desert strata. This paper is focused on the palaeo desert depositional process and controlling factors with the underground water surface as the depositional base level. In addition, this paper also deals with the construction and unit classification of the palaeo desert sequence stratigraphy, and introduces concepts and methods for the research into the palaeo desert genetic strata and sedimentology.
The palaeo desert is a special aeolian depositional system. Because of the difference in mechanism between the aeolian and the hydatogenous depositions, the principle presently applied to the sequence stratigraphic research into the continental lacustrine basins in line with the lake flooding surface, is not perfectly appropriate for the research into the palaeo desert strata. This paper is focused on the palaeo desert depositional process and controlling factors with the underground water surface as the depositional base level. In addition, this paper also deals with the construction and unit classification of the palaeo desert sequence stratigraphy, and introduces concepts and methods for the research into the palaeo desert genetic strata and sedimentology.
2000, 25(6): 592-598.
Abstract:
Mafic ultramafic rock blocks, consecutively distributed in Kuhai Saishitang region, are closely associated with each other in origin, as shown by their different geological features. These rock masses constitute the oceanic crust vestiges that once existed but later were broken. The petro geochemical features show that the rock masses originating from the enrichment mantle source similar to that of OIB or E MORB, may have occurred in the region above the initial spreading small oceanic basin or subduction zone. The isotope dating references show that the initial spreading of the oceanic basin may have occurred in D 3, and the subduction may have occurred in P1-P2.
Mafic ultramafic rock blocks, consecutively distributed in Kuhai Saishitang region, are closely associated with each other in origin, as shown by their different geological features. These rock masses constitute the oceanic crust vestiges that once existed but later were broken. The petro geochemical features show that the rock masses originating from the enrichment mantle source similar to that of OIB or E MORB, may have occurred in the region above the initial spreading small oceanic basin or subduction zone. The isotope dating references show that the initial spreading of the oceanic basin may have occurred in D 3, and the subduction may have occurred in P1-P2.
2000, 25(6): 599-603.
Abstract:
In this paper, the occurrence features and patterns of the sapphire in Shandong Province are introduced by field investigation, drilling prospecting and indoor sample analysis. In addition, the paper presents the direction of the future mineral exploration, the factors that may affect the quality of the sapphire, and the ways to utilize the sapphire in the future.
In this paper, the occurrence features and patterns of the sapphire in Shandong Province are introduced by field investigation, drilling prospecting and indoor sample analysis. In addition, the paper presents the direction of the future mineral exploration, the factors that may affect the quality of the sapphire, and the ways to utilize the sapphire in the future.
2000, 25(6): 604-611.
Abstract:
The petroleum system, actually a petroleum pool forming dynamic system, is a product of the combination of petroleum natural gas geology and system science, and a new type hierarchical geological entity, a composite between the research objective and abstract model, if it is viewed from the system science by the petroleum geologists. Therefore, the petroleum system should be appropriate to the whole petroleum gas geological unit sequence instead of only to a certain unit in a certain structural layer. The research method for the petroleum system is defined to be a systematic method characterized by the qualitative and quantitative processes. In view of the nonlinear feature of the petroleum pool forming process and also of the defects that are present in many current basin simulations and petroleum pool forming simulations, the authors attempt to introduce the logical reasoning and method for the system dynamics, to propose the concept of petroleum system dynamics and to reiterate their basic principle, and to establish a primary methodological system for the petroleum gas system dynamics. The result of the system dynamic simulation can be used to forecast and evaluate the petroleum resources in the basins and depressions.
The petroleum system, actually a petroleum pool forming dynamic system, is a product of the combination of petroleum natural gas geology and system science, and a new type hierarchical geological entity, a composite between the research objective and abstract model, if it is viewed from the system science by the petroleum geologists. Therefore, the petroleum system should be appropriate to the whole petroleum gas geological unit sequence instead of only to a certain unit in a certain structural layer. The research method for the petroleum system is defined to be a systematic method characterized by the qualitative and quantitative processes. In view of the nonlinear feature of the petroleum pool forming process and also of the defects that are present in many current basin simulations and petroleum pool forming simulations, the authors attempt to introduce the logical reasoning and method for the system dynamics, to propose the concept of petroleum system dynamics and to reiterate their basic principle, and to establish a primary methodological system for the petroleum gas system dynamics. The result of the system dynamic simulation can be used to forecast and evaluate the petroleum resources in the basins and depressions.
2000, 25(6): 613-616.
Abstract:
The occurrence state, trapping pattern and heterogeneity characteristic of the coalbed methane pool contribute to the important role of the coalbed methane pool analysis in the coalbed methane exploration and development. The conditions of the coalbed methane pool and the heterogeneity of the rock in the coal reservoir are both important aspects of the coalbed methane pool analysis. The analysis and assessment of the coalbed methane pool should meet the needs of the progress of coalbed methane exploration and development. In the initial exploration, the evaluation of the chosen exploration region should be dominated by the analysis of the geological conditions of the coalbed methane pool. However, the sampling drilling of the well network should be dominated by the analysis, especially by the heterogeneous analysis, of the coalbed methane pool.
The occurrence state, trapping pattern and heterogeneity characteristic of the coalbed methane pool contribute to the important role of the coalbed methane pool analysis in the coalbed methane exploration and development. The conditions of the coalbed methane pool and the heterogeneity of the rock in the coal reservoir are both important aspects of the coalbed methane pool analysis. The analysis and assessment of the coalbed methane pool should meet the needs of the progress of coalbed methane exploration and development. In the initial exploration, the evaluation of the chosen exploration region should be dominated by the analysis of the geological conditions of the coalbed methane pool. However, the sampling drilling of the well network should be dominated by the analysis, especially by the heterogeneous analysis, of the coalbed methane pool.
2000, 25(6): 617-623.
Abstract:
The isotopic composition of the natural gas is affected by such factors as the organic type of the source rock, the thermal evolutionary growth, and the secondary change after the pool formation. The isotopic distribution pattern of the unit hydrocarbon is used to differentiate between geochemical fingerprints affected by various factors. The isotope in the unit hydrocarbon of the natural gas often turns heavier with the increase of the number of the carbon. However, the isotopic reversal in the unit hydrocarbon of the natural gas is relatively universal in the deep strata of the Xujiaweizi depression, Songliao basin. The high geothermal gradient and bacterial biodegradation have a small effect on the formation of the isotopic reversal in this region. No sufficient geological evidence is available for the consequence of the mixing process of the oil type gas in the shallow layer or of the inorganic gas. The mixing of different types of gases in the organic materials in the same layer and the evaporative fractionation via the micro leaking of the gas in the cap rock may have been the major causes for the isotopic reversal of the natural gas in the deep strata of the Xujiaweizi depression, Songliao basin.
The isotopic composition of the natural gas is affected by such factors as the organic type of the source rock, the thermal evolutionary growth, and the secondary change after the pool formation. The isotopic distribution pattern of the unit hydrocarbon is used to differentiate between geochemical fingerprints affected by various factors. The isotope in the unit hydrocarbon of the natural gas often turns heavier with the increase of the number of the carbon. However, the isotopic reversal in the unit hydrocarbon of the natural gas is relatively universal in the deep strata of the Xujiaweizi depression, Songliao basin. The high geothermal gradient and bacterial biodegradation have a small effect on the formation of the isotopic reversal in this region. No sufficient geological evidence is available for the consequence of the mixing process of the oil type gas in the shallow layer or of the inorganic gas. The mixing of different types of gases in the organic materials in the same layer and the evaporative fractionation via the micro leaking of the gas in the cap rock may have been the major causes for the isotopic reversal of the natural gas in the deep strata of the Xujiaweizi depression, Songliao basin.
2000, 25(6): 624-628.
Abstract:
Gas hydrate, a kind of new type energy resources discovered over the past ten years, has aroused much attention from many countries around the globe, because of the very important role the gas hydrate has played in energy resource exploration, submarine geo hazards prevention, and change in global climate. This kind of compounds usually exists within the sediments from the continental margins and also within the permafrosts of the polar areas, but the amount of gas hydrates occurring in the continental margins exceeds 90% of the total amount of gas hydrates existing in the whole world. In this case, this paper presents a detailed discussion on the indirect indicators of gas hydrate occurrence within submarine sediments, for the purpose of rapid and accurate determination of the distribution of this kind of compounds without the sediment sampling or without the hydrate samples collected.
Gas hydrate, a kind of new type energy resources discovered over the past ten years, has aroused much attention from many countries around the globe, because of the very important role the gas hydrate has played in energy resource exploration, submarine geo hazards prevention, and change in global climate. This kind of compounds usually exists within the sediments from the continental margins and also within the permafrosts of the polar areas, but the amount of gas hydrates occurring in the continental margins exceeds 90% of the total amount of gas hydrates existing in the whole world. In this case, this paper presents a detailed discussion on the indirect indicators of gas hydrate occurrence within submarine sediments, for the purpose of rapid and accurate determination of the distribution of this kind of compounds without the sediment sampling or without the hydrate samples collected.
2000, 25(6): 629-632.
Abstract:
Measures for the increase in oil production in oil wells are of various types. Different measures may bring about different effects of the increase in oil production. However, they also have different cost combinations. In this paper, a method is proposed for the improvement in the economic evaluation of different measures for the increase in oil production. The first step of this method is to forecast the accumulated increase in oil production after the measure is adopted. The second step is to estimate the investments and costs. The final step is to make net benefit, economic limit, and sensitivity analyses of the measure adopted. Consequently, the actual evaluation result of a certain oil well is obtained to prove the effectiveness of this method.
Measures for the increase in oil production in oil wells are of various types. Different measures may bring about different effects of the increase in oil production. However, they also have different cost combinations. In this paper, a method is proposed for the improvement in the economic evaluation of different measures for the increase in oil production. The first step of this method is to forecast the accumulated increase in oil production after the measure is adopted. The second step is to estimate the investments and costs. The final step is to make net benefit, economic limit, and sensitivity analyses of the measure adopted. Consequently, the actual evaluation result of a certain oil well is obtained to prove the effectiveness of this method.
2000, 25(6): 633-637.
Abstract:
The authors of this paper advance, in terms of the evolution of the groundwater system, that the anomalous fluctuations and water quantity disequilibrium are present in any groundwater system where a large scale groundwater resources development is underway. The correct understanding of these phenomena is not only of theoretical significance to the further understanding of the attributes of groundwater resources, but also of important practical significance to the planning of the water resource development strategy reflecting the harmonious relationships among groundwater resources, economy and environment.
The authors of this paper advance, in terms of the evolution of the groundwater system, that the anomalous fluctuations and water quantity disequilibrium are present in any groundwater system where a large scale groundwater resources development is underway. The correct understanding of these phenomena is not only of theoretical significance to the further understanding of the attributes of groundwater resources, but also of important practical significance to the planning of the water resource development strategy reflecting the harmonious relationships among groundwater resources, economy and environment.
2000, 25(6): 638-641.
Abstract:
In this paper, the geological references of the Xi'an city are employed to make an detailed investigation into the geological environment of the Xi'an city. In addition, the corresponding model is employed to make a comprehensive evaluation of the land utilization capability, providing a scientific basis for the decision making of the controlling measures for urban land utilization projects.
In this paper, the geological references of the Xi'an city are employed to make an detailed investigation into the geological environment of the Xi'an city. In addition, the corresponding model is employed to make a comprehensive evaluation of the land utilization capability, providing a scientific basis for the decision making of the controlling measures for urban land utilization projects.
2000, 25(6): 642-646.
Abstract:
The artificial neural network (ANN) method is used to solve the puzzle that occur in the drilling: the identification of the lithology of the strata drilled. The drilling features are used to design the structure and output form of the ANN, to develop the ANN software for the identification of the strata drilled, to analyze various factors that affects the application of the ANN and to make a further research into the optimum design of the ANN. The research shows that the ANN perfectly matches the identification of the strata drilled. Various ANN parameters such as the training efficiency, the hidden layer number, the hidden layer unit number, and the data processing may affect the application of the ANN.
The artificial neural network (ANN) method is used to solve the puzzle that occur in the drilling: the identification of the lithology of the strata drilled. The drilling features are used to design the structure and output form of the ANN, to develop the ANN software for the identification of the strata drilled, to analyze various factors that affects the application of the ANN and to make a further research into the optimum design of the ANN. The research shows that the ANN perfectly matches the identification of the strata drilled. Various ANN parameters such as the training efficiency, the hidden layer number, the hidden layer unit number, and the data processing may affect the application of the ANN.
2000, 25(6): 647-650.
Abstract:
The quantitative relation between parameters and performance of the impregnated diamond bit has always been a weak research area in the study of the diamond bit. In this paper, the quantitative analysis, rigorous theoretical calculation and derivation are both employed to obtain the quantitative relation between the diamond bit efficiency and life span and the diamond bit parameters. The conclusion from the quantitative research is in perfect conformity with the qualitative results concerned, indicating that the research is feasible into the quantitative relation between the diamond bit performance and the diamond bit parameters. The result of the quantitative relation between the diamond bit performance and the diamond bit parameters can be applied to the guidance to the diamond bit parameter design that might be used to forecast the performance of the diamond bit.
The quantitative relation between parameters and performance of the impregnated diamond bit has always been a weak research area in the study of the diamond bit. In this paper, the quantitative analysis, rigorous theoretical calculation and derivation are both employed to obtain the quantitative relation between the diamond bit efficiency and life span and the diamond bit parameters. The conclusion from the quantitative research is in perfect conformity with the qualitative results concerned, indicating that the research is feasible into the quantitative relation between the diamond bit performance and the diamond bit parameters. The result of the quantitative relation between the diamond bit performance and the diamond bit parameters can be applied to the guidance to the diamond bit parameter design that might be used to forecast the performance of the diamond bit.
2000, 25(6): 651-655.
Abstract:
The purpose of this paper is to inverse directly the multi layer density interface by means of genetic algorithms, one of the global optimization methods. At first, this paper presents the improvement of the genetic algorithm in line with the gravity inversion for the combination of the determination of the exchange positions with the fitting of the gravity anomaly during the exchange of the genes in the genetic algorithm. In this case, the genetic algorithm appropriate to the gravity inversion can be obtained. Then, this paper presents the direct inversion of the multi layer density interface using this improved GA. The results of the theoretical model and field section show that this kind of improvement is effective.
The purpose of this paper is to inverse directly the multi layer density interface by means of genetic algorithms, one of the global optimization methods. At first, this paper presents the improvement of the genetic algorithm in line with the gravity inversion for the combination of the determination of the exchange positions with the fitting of the gravity anomaly during the exchange of the genes in the genetic algorithm. In this case, the genetic algorithm appropriate to the gravity inversion can be obtained. Then, this paper presents the direct inversion of the multi layer density interface using this improved GA. The results of the theoretical model and field section show that this kind of improvement is effective.
2000, 25(6): 656-662.
Abstract:
The 2 dimensional forward calculation for time spectral resistivity (TSR) is to compute the electric field transient response caused by a 3-D electric current dipole on the 2-D polarizable earth surface. As part of the so called 2.5-D numerical simulation for time domain electromagnetic field, this 2 dimensional forward calculation is still a difficult problem in geophysics. In this paper, a new algorithm is established for this problem with the following four features: (1) A 2-D finite element method is adopted to subdivide a triangular lattice by adding two diagonal lines in the rectangular lattice, and at the same time to eliminate unknown variables to be calculated at the central node of the rectangular lattice by using the Gauss elimination. Therefore, this method can be used not only to simulate accurately any complex 2-D geoelectric section, but also to save the calculation load. (2) A new algorithm for the computation of the secondary field is directly employed to compute only a primary field of the two components of electric and magnetic fields along the geoelectric structure. Such a method is advantageous not only in the relatively high computation precision, but also in the absence of much increase in calculation load. (3) The new G-S transformation method is used to make the inverse Laplace transformation, and, at the same time, the delay theorem of the Laplace transformation is used to calculate the interpolation at the intervals of the multiplication time, resulting in the rapid calculation of the transient electromagnetic responses to the dense samples. (4) This algorithm can be used to compute the transient electromagnetic response to the polarizable and conductive earth (including the IP and EM effects).
The 2 dimensional forward calculation for time spectral resistivity (TSR) is to compute the electric field transient response caused by a 3-D electric current dipole on the 2-D polarizable earth surface. As part of the so called 2.5-D numerical simulation for time domain electromagnetic field, this 2 dimensional forward calculation is still a difficult problem in geophysics. In this paper, a new algorithm is established for this problem with the following four features: (1) A 2-D finite element method is adopted to subdivide a triangular lattice by adding two diagonal lines in the rectangular lattice, and at the same time to eliminate unknown variables to be calculated at the central node of the rectangular lattice by using the Gauss elimination. Therefore, this method can be used not only to simulate accurately any complex 2-D geoelectric section, but also to save the calculation load. (2) A new algorithm for the computation of the secondary field is directly employed to compute only a primary field of the two components of electric and magnetic fields along the geoelectric structure. Such a method is advantageous not only in the relatively high computation precision, but also in the absence of much increase in calculation load. (3) The new G-S transformation method is used to make the inverse Laplace transformation, and, at the same time, the delay theorem of the Laplace transformation is used to calculate the interpolation at the intervals of the multiplication time, resulting in the rapid calculation of the transient electromagnetic responses to the dense samples. (4) This algorithm can be used to compute the transient electromagnetic response to the polarizable and conductive earth (including the IP and EM effects).
