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1.
穿过郯庐断裂带中段（沂沭断裂带,36°N）所做的大地电磁测深（MT）剖面长约150km.使用Robust技术和远参考道大地电磁方法处理观测数据.通过分析视电阻率、阻抗相位、Swift二维偏离度和区域走向,定性确定测区的电性结构.二维反演解释中选择非线性共轭梯度（NLCG）方法,使用TE、TM两种模式资料联合反演,沿剖面的二维电性结构显示：自西向东,鲁西隆起、郯庐断裂带、胶莱坳陷及鲁东隆起4个电性区块分别对应,鲁东和鲁西隆起区为高阻,郯庐断裂带电性结构复杂,高、低阻相间,胶莱坳陷为低阻（高导）区.沿MT剖面附近曾发生3个地震,其震源区处在电性变化剧烈部位,并在震源区附近存在高导体. 相似文献
2.
APPLYING 3D INVERSION OF SINGLE-PROFILE MAGNETOTELLURIC DATA TO IDENTIFY THE SHADE AND YUNONGXI FAULTS 
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下载免费PDF全文 JIANG Feng CHEN Xiao-bin DONG Ze-yi CUI Teng-fa LIU Zhong-yin WANG Pei-jie 《地震地质》2019,41(6):1444-1463
Many synthetic model studies suggested that the best way to obtain good 3D interpretation results is to distribute the MT sites at a 2D grid array with regular site spacing over the target area. However, MT 3D inversion was very difficult about 10 years ago. A lot of MT data were collected along one profile and then interpreted with 2D inversion. How to apply the state-of-the-art 3D inversion technique to interpret the accumulated mass MT profiles data is an important topic. Some studies on 3D inversion of measured MT profile data suggested that 2D inversions usually had higher resolution for the subsurface than 3D inversions. Meanwhile, they often made their interpretation based on 2D inversion results, and 3D inversion results were only used to evaluate whether the overall resistivity structures were correct. Some researchers thought that 3D inversions could not resolute the local structure well, while 2D inversion results could agree with the surface geologic features much well and interpret the geologic structures easily. But in the present paper, we find that the result of 3D inversion is better than that of 2D inversion in identifying the location of the two local faults, the Shade Fault(SDF)and the Yunongxi Fault(YNXF), and the deep structures.
In this paper, we first studied the electrical structure of SDF and YNXF based on a measured magnetotelluric(MT) profile data. Besides, from the point of identifying active faults, we compared the capacity of identifying deep existing faults between 2D inversion models and 3D models with different inversion parameters. The results show that both 2D and 3D inversion of the single-profile data could obtain reasonable and reliable electrical structures on a regional scale. Combining 2D and 3D models, and according to our present data, we find that both SDF and YNXF probably have cut completely the high resistivity layer in the upper crust and extended to the high conductivity layer in the middle crust. In terms of the deep geometry of the faults, at the profile's location, the SDF dips nearly vertically or dips southeast with high dip angle, and the YNXF dips southeast at depth. In addition, according to the results from our measured MT profile, we find that the 3D inversion of single-profile MT data has the capacity of identifying the location and deep geometry of local faults under present computing ability. Finally, this research suggests that appropriate cell size and reasonable smoothing parameters are important factors for the 3D inversion of single-profile MT data, more specifically, too coarse meshes or too large smoothing parameters on horizontal direction of 3D inversion may result in low resolution of 3D inversions that cannot identify the structure of faults. While, for vertical mesh size and data error thresholds, they have limited effect on identifying shallow tectonics as long as their changes are within a reasonable range. 3D inversion results also indicate that, to some extent, adding tippers to the 3D inversion of a MT profile can improve the model's constraint on the deep geometry of the outcropped faults. 相似文献
3.
在青藏高原东北缘至鄂尔多斯地块沿玛沁—兰州—靖边剖面进行62个测点的大地电磁观测,采用Robust技术对观测数据进行了处理和张量阻抗分解.分析了视电阻率和阻抗相位曲线、二维偏离度、区域走向.采用RRI二维反演技术进行了资料的反演解释,二维剖面的电性结构显示：（1）玛沁断裂带、兰州深断裂带、马家滩—大水坑断裂带将剖面分为4个电性区块：巴颜喀拉地块、秦祁地块、边界带和鄂尔多斯地块.（2）区块1、2和4的地壳电性结构有类似特点：上地壳为高阻层,下地壳上部为低阻带,下地壳下部到上地幔电阻率随深度逐渐升高.区块3电性成层性差、结构复杂,是现今构造活动较强烈的地区.（3）玛沁断裂带、海原断裂带和罗山—云雾山断裂带为较陡立的超壳断裂带;西秦岭北缘断裂带为壳内断裂带. 相似文献
4.
A. G. Nurmukhamedov I. I. Chernev D. A. Alekseev A. G. Yakovlev 《Izvestiya Physics of the Solid Earth》2010,46(9):739-750
The article discusses the results of the interpretation of magnetotelluric sounding (MTS) data generated in the vicinity of
the Mutnov steam hydrothermal deposit during the period from 2004 to 2006. Approaches to an interpretation of magnetotelluric
(MT) data in a situation characterized by significant 3D distortions and the coastal effect phenomenon are discussed. The
resulting 3D geoelectric model is presented. Based on analysis of the created geoelectric model, the principal geoelectric
horizons are characterized, which includes the parameters of the integral conductivity and the morphology of the geoelectric
boundaries. Zones of the highest values of the electrical conductivity of the watered tuffaceous sediment horizon have been
identified, as well as zones of the maximum lateral electrical conductivity contrasts that are interpreted as discharge zones
of hydrotherms. The results of the drilling carried out based on MTS data are presented. 相似文献
5.
稀疏测线大地电磁资料三维反演研究:合成算例(英文) 总被引：2，自引：1，他引：1
受勘探成本和工区环境等因素的影响,当前大多数大地电磁实际工作采取布置稀疏测线采集数据和使用二维反演方法解释这些稀疏测线数据的方式。然而,二维反演方法在解释三维地电构造数据时存在局限性,有时甚至做出错误的地质解释。本文尝试了使用三维反演方法对大地电磁稀疏测线数据进行反演解释。使用大地电磁全信息资料三维共轭梯度反演程序对理论模型合成稀疏测线数据进行了三维反演。结果表明:这种反演方案是可行与有效的。同时,我们发现在不同数据的三维反演结果中,四个张量阻抗元素和两个倾子数据同时反演的结果相对更为准确,更接近理论模型。 相似文献
6.
对穿过宁夏海原大震区西安州(N36.5°,E105.5°)北至同心县韦州(N37.28°,E106.48°)的大地电磁测深剖面，采用远参考道大地电磁方法进行测量和资料处理，得到高精度的数据如视电阻率、阻抗相位、二维偏离度、最佳主轴方位角等. 依据这些数据，对测区的电性结构进行了定性分析和二维定量反演解释. 结果表明，沿剖面可以分成5个电性区块，与西、南华山隆起(Ⅰ)、兴仁堡—海原盆地(Ⅱ)、中卫—清水河盆地(Ⅲ)、中宁—红寺堡盆地(Ⅳ)和鄂尔多斯西缘带(Ⅴ)对应，各区块的边界由大断裂构成. 地表到深度10km左右，西、南华山隆起和鄂尔多斯西缘带呈高阻特性，兴仁堡—海原、中卫—清水河、中宁—红寺堡三个盆地的电阻率较低且呈盆地凹陷形状，盆地基底显示为西南深东北浅的簸箕状起伏形态，基底最深约为8km. 西、南华山隆起、中卫—清水河盆地和鄂尔多斯西缘带的下地壳为“正常”电阻率结构. 兴仁堡—海原和中宁—红寺堡盆地的下地壳上部为“异常”低电阻率带. 1920年的海原大震区存在明显的电性结构差异，震区西南侧和上部区域为相对高阻，东北侧和下部区域为相对低阻. 相似文献
7.
大地电磁资料的灵敏度研究 总被引：2，自引：0，他引：2
本文研究了大地电磁资料对地球电性结构模型参数的灵敏度,它在反演解释中具有重要意义.通过研究均匀半空间中视电导率资料的灵敏度函数与计算分析实际观测资料的Fréchet导数和斜率表明,视电导率资料的灵敏度在地表最大,从地表向下呈指数衰减,频率愈高,电导率愈大,衰减也愈快.视电阻率资料和阻抗相位资料对高频、浅层和低阻层具有更高的灵敏度,几何参数的平均灵敏度高于电性参数的平均灵敏度,通常阻抗相位资料比视电阻率资料更灵敏.同时,根据阻抗实部定义的视电阻率与Kunetz定义的时间域大地电磁响应,反映地层电性差异的灵敏度最高. 文章还指出,在实际的反演解释中,如何正确有效地应用阻抗相位资料,提高分辨能力,仍是急待解决的问题. 相似文献
8.
Behrooz Oskooi Mahmoud Mirzaei Behnam Mohammadi Mohammad Mohammadzadeh-Moghaddam Feridon Ghadimi 《Studia Geophysica et Geodaetica》2016,60(1):141-161
Magnetotelluric (MT) and ground magnetic surveys were conducted on the Mahallat geothermal field situated in Markazi province, central Iran, as a primary part of the explorations and developments of a geothermal energy investigation program in the region. Mahallat region has the greatest geothermal fields in Iran. MT survey was performed in November 2011 on an 8 km profile crossing the hot springs with a total of 17 stations. The 2D inversion of the determinant MT data was performed using a 2D inversion routine based on the Occam approach. The 2D resistivity model obtained from the determinant data shows a low resistivity zone at 800-2000 m depth and a higher resistivity zone above the low resistivity zone, interpreted as geothermal reservoir and cap rock, respectively. It also revealed two major concealed faults which are acting as preferential paths for the circulation of hydrothermal fluids. To obtain more geophysical evidence, a ground magnetic survey with 5000 stations was also performed over an area of 200 km2 around the MT profile. Magnetic measurements show a main positive anomaly of about +1000 nT over the study area, which could be interpreted as an intrusive body with the high magnetic susceptibility (i.e. mafic and ultramafic rocks) into the sedimentary host rocks. We interpret the body as the heat source of the geothermal system. Structural index and depth estimation of the anomaly indicate that the intrusive body is similar to a cylinder extending from about one kilometer depth down to greater depths. The results of MT and magnetic investigations indicate a geothermal reservoir which proves the preliminary geological observations to a great extent. 相似文献
9.
The Magnetotelluric Phase Tensor: A Critical Review 总被引：1，自引：0，他引：1
John R. Booker 《Surveys in Geophysics》2014,35(1):7-40
10.
The palaeotectonic models of the North American continent have been deeply influenced by the concept of a North American Central Plains conductivity anomaly (NACPCA) which was postulated as a result of large area, wide-spaced, array studies, using the Magnetic Deep Sounding (MDS) method.
A recent closely spaced magnetotelluric (MT) survey across this proposed anomaly near the Canadian-U.S. boundary by Jones and Savage (1986) failed to detect the NACPCA at the location suggested by the MDS. However, this survey did verify a conductivity anomaly discovered by Rankin and Kao (1979) and a new anomaly 75 km east of NACPCA. Our present study verifies this latter anomaly and quantitative results are presented. The striking isotropy in apparent resistivity does not prevent the interpretation of anomalous resistivity distributions. This is discussed in the text.
The failure of the MDS array studies to detect our anomaly is readily explainable by the wide station spacing; however, the failure of the MT survey to detect the NACPCA leads us to the conclusion that it may not be a continuous feature. 相似文献
11.
印度板块北部地形起伏较大的喜马拉雅山地区由几个构造互异的地质单元组成,依地形高、低把喜马拉雅碰撞带分成低喜马拉雅和高喜马拉雅.为了研究与主要逆冲带（含主缝合带MCT和主边界带MBT）有关的地壳电性结构,沿Rohtangpass (海拔4000 m) 到Mandi (海拔400 m)剖面进行了MT探测.通过对16个测点观测资料的分析和考虑地形的二维反演,获得了沿剖面的二维电性结构.电性结构显示,在Chail和主逆冲边界带下方,东西走向的缝合带突然转向北.在下喜马拉雅的Rampur 区段的元古代基底为范围较大的高阻体,而浅部地壳被逆冲带分成向北倾的电导性块体和电阻性块体.Chail 逆冲带东侧低喜马拉雅Rampur 区段的推挤和它西侧的基底脊柱体导致主边界带及相关的逆冲带（Kangra 拐角）向北转弯,Kangra拐角处的应力可能是由于西侧基底脊柱体进入到Kangra 区引起的. 相似文献
12.
13.
O. L. Poltaratskaya E. B. Fainberg B. Sh. Singer 《Izvestiya Physics of the Solid Earth》2006,42(1):51-59
Analysis of magnetotelluric (MT) sounding studies in western Yakutia showed that amplitude curves are strongly affected by the regional distribution of electrical conductivity heterogeneities of the sedimentary cover, while phase curves are distorted to a lesser extent. The distribution of the longitudinal conductance in the sedimentary cover is constructed, and MT fields and resistivity and phase curves are modeled. Based on combined analysis of experimental and model data and results of inversion of corrected curves, an interpretation of main anomalies of MT fields is given and a regional crustal anomaly of the electrical conductivity is discovered. 相似文献
14.
局部畸变问题曾经困扰大地电磁资料反演解释几十年,大地电磁三维数值模拟技术的发展为剖析局部畸变特点和得到可靠的反演成像结果提供了技术基础。本文采用三维数值模拟成像方法对典型三维局部畸变模型进行模拟分析。三维数值模拟结果显示:电场分量垂直电性分界面的极化模式视电阻率曲线(对应二维情况下TM模式)在穿越低阻异常体界面时,曲线会先上移后下移,而在穿越高阻异常体界面时,曲线会先下移后上移,这与电性分界面处积累面电荷产生的二次电场有关。三维模型中XY模式、YX模式视电阻率和相位在三维异常体附近的水平变化是呈现近似垂向对称的,该现象与电场垂直跨越电性界面时视电阻率的变化规律是吻合的,当测线分别沿X方向和Y方向展布时,三维情况下的XY和YX模式分别对应二维情况下的TM模式。低阻小异常体对区域构造响应的畸变影响比高阻小异常体要严重。低阻小异常体对二维区域响应的两种极化模式视电阻率和相位都有非常明显的畸变影响,相比较而言对TE模式的畸变要大于TM模式,因此我们在做二维反演解释时,可优先考虑拟合TM模式数据。位于小异常体中心上方测点的三维畸变响应虽然与对应真实二维区域响应的差异比较大,但可以等效于某种二维模型响应,这种由局部畸变造成的假二维响应在实际野外数据的解释中是需要注意的。 相似文献
15.
佳木斯地块及东缘是中国东北地区的重要地质构造单元. 为探测该地区地壳深部结构与构造关系，沿桦南—饶河实施了240 km的大地电磁测深的探测研究. 采用光滑模型二维反演方法对桦南—饶河大地电磁剖面的探测数据进行了二维反演和综合地球物理解释. 研究结果揭示了研究区断面域的电性结构：(1)剖面西段具有稳定的高阻特征且具有稳定的岩石圈厚度（约90km），在十几公里深度范围存在壳内高导层，该区段对应佳木斯地块. (2)剖面中部具有明显的电性梯度带，该梯度带反映了佳木斯地块的东界位置及其深部的结构形态. (3)剖面东段电性特征揭示了佳木斯地块以东区段浅部为逆冲推覆体，深部为多个高阻块体和低阻条带相间的电性结构，这些高阻块体可能为早期俯冲的岩石圈残片. 相似文献
16.
17.
G. Michael Hoversten 《Geophysical Prospecting》1996,44(6):935-961
Hydrocarbon exploration in the Papuan fold belt is made extremely difficult by mountainous terrain, equatorial jungle and thick karstified Miocene limestones at the surface. The high-velocity karstified limestones at or near the surface often render the seismic technique useless for imaging the subsurface. In such areas magnetotellurics (MT) provides a valuable capability for mapping subsurface structure. The main structural interface which can be mapped with MT, due to the large electrical contrast, is the contact between the resistive Darai limestone and the underlying conductive sediments of the Ieru Formation. In some areas the base of the Darai can be mapped with reasonable accuracy by fitting 1D models to the observed MT data. However, in many cases where 2D and 3D effects are severe, 1D interpretations can yield dramatically incorrect results. Numerical and field data examples are presented which demonstrate the severity of the 1D errors and the improvements in accuracy which can be achieved using a 2D inverse solution. Two MT lines over adjacent anticlines, both with well control and seismic data, are used to demonstrate the application of 1D and 2D inversions for structural models. In both cases the seismic data provide no aid in the interpretations. The example over the Hides anticline illustrates a situation where 1D inversion of either TE or TM mode provides essentially the same depth to base of Darai as 2D inversion of both TE and TM. Both models provide base Darai depth estimates which are within 10% of that measured in the well. The example over the Angore anticline illustrates the inadequacy of 1D inversion in structurally complex geology complicated by electrical statics. The TE mode fits a 1D Darai thickness of 800 metres while the TM mode fits a 1D Darai thickness of 3500 metres, bracketing the thickness of 2450 metres observed in the well. The final 2D inversion model provides a depth estimate of 2250 metres. Four MT lines along the Angore anticline have been interpreted using 2D inversion. A high degree of correlation exists between lineaments observed on an airborne radar image and zones of low resistivity within the high-resistivity material interpreted as Darai limestone. These low-resistivity zones are interpreted as fault zones. Three-dimensional modelling has been used to simulate 3D statics in an otherwise 2D earth. These data were used to test the Groom-Bailey (GB) decomposition for possible benefits in reducing static effects and estimating geoelectric strike in the Papua New Guinea (PNG) field data. It has been found that the GB decomposition can provide improved regional 2D strike estimates in 3D contaminated data. However, in situations such as PNG, where the regional 2D strike is well established and hence can be fixed, the GB decomposition provides apparent resistivities identical to those simply rotated to strike. 相似文献
18.
Deep structure of the northeastern margin of the Parnaiba Basin, Brazil, from magnetotelluric imaging 总被引：1，自引：0，他引：1
The magnetotelluric (MT) method has been applied to the determination of the deep resistivity structure of the northeastern margin of the Parnaiba Basin. Transient electromagnetic (TEM) and MT data were collected in early 1999 along a 95 km long N–S line, extending from the coast across the projected subcrop position of a discontinuous fault found to the west of the study area that is believed to be a possible basin‐bounding fault. The MT data were processed to yield the TE‐ and TM‐mode responses and then corrected for static shift using central‐loop and single‐loop TEM data, respectively. Regularized 2D MT inversion was subsequently undertaken using a structured initial model with the near‐surface constrained by TEM inversion results. As a consistency check, we performed another set of 2D inversions using different smooth initial models. The various optimal 2D inversion models show clearly the presence of a major basement trough, over 2 km deep, located about 70 km from the coast. We interpret it as possibly marking the main basin margin and suggest that it may have implications for groundwater resource development in the area. 相似文献
19.
Since the true Earth is 3-D in nature, a three-dimensional (3-D) inversion has clear advantages over lower dimensional inversions. We utilized a 3-D magnetotelluric (MT) inversion code, WSINV3DMT, to obtain a realistic resistivity model using a long period MT data set collected in the Northwest Sabalan geothermal field in Ardabil, Iran. The apparent resistivity and phase curves, the magnetic induction vectors, the impedance polar diagrams and the rotational invariant of impedance tensor, indicate a complex 3-D conductivity structure. After setting up the model parameters and designing the appropriate block discretization, we performed the 3-D inversions for two sets of observed data; one set includes the full MT impedance tensor and another set contains only off-diagonal elements of the MT impedance. The final model was selected according to the relative magnitude of the data misfit and the model norm with respect to various Lagrangian multipliers. The results of this study illustrate the 3-D inversion of the off-diagonal elements of MT impedance tensor is precisely enough to explain the structures related to the geothermal source. The obtained results were compared with the results of available 2-D models and they are then interpreted using all of the geological and drilling data of the area. The main outcome of this study is the precise delineation of the geometry of geothermal source that is located at the center of the study area with a surface coverage of about 7 km2. 相似文献
20.
Yanling Shi Zhanxiang He Zuzhi Hu Qiang Wei Dechun Li Cuixian Meng Liansheng Ji Sheng Zhang 《Studia Geophysica et Geodaetica》2018,62(1):167-185
Mapping deep geological hydrocarbon targets is of significant importance in basin exploration. In areas lacking reliable seismic data, magnetotelluric (MT) and gravity explorations are helpful to delineate the distribution of potential deep geological hydrocarbon targets. Here we investigate the effectiveness of the integrated 3D MT and gravity explorations for mapping the potential deep hydrocarbon source rocks. The result based on the data from the W Basin (part of the Ordes Basin) of China demonstrates that the method is efficient and economical for basin exploration. The method is particularly useful in target areas which are of great interest for oil and gas exploration but lack high quality seismic data. In our method, we first use the high-precision 3D small-bin MT data acquisition to improve the data accuracy. Then we perform datum static correction method and apply 3D inversion to obtain the3D resistivity distribution. We also develop a layered resistivity model based on resistivity logging to assist the interpretation of the inverted 3D resistivity data so as to derive an initial 3D geological model. Starting from the initial model, we use 2D gravity data to update the model via 2D inversion line by line, and then pass the updated model for the next round of the 3D MT inversion. The integrated inversion is implemented iteratively so the model converges to satisfy the need of final geological analysis. The application to the W Basin shows that we could successfully delineate the geological distribution of the potential deep hydrocarbon source rocks within the basin and map the thickness of the upper Paleozoic. 相似文献