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1.
We consider the methods and results of magnetotelluric sounding in the AMTS and MTS modifications. Audiomagnetotelluric sounding (AMTS) was carried out for the first time in the area of a recent Tolbachik eruption. The results from our analysis of the magnetotelluric parameters show that the geoelectric medium involving a regional fault can be fitted by a 2D inhomogeneous model. The longitudinal and transverse sounding curves were assumed as the leading elements for interpretation. A joint analysis of these curves and of pseudo-sections of impedance phases provides evidence of a geoelectric inhomogeneity in the area where the Naboko Vent is situated. A bimodal inversion of the AMTS curves yielded a geoelectric section that contains a conductive inhomogeneity that is possibly related to a fault that carried fluids up to the ground surface. Along with AMTS, we used MTS curves in a broader range to identify a crustal conductive anomaly at depths of 15–35 km. The data from AMTS, MTS, and other geological and geophysical information were used to develop a conceptual model for the area of study that characterizes a possible origin of the anomalous zones. We obtained approximate estimates of rock porosity in the fault zone that transported magma melts upward into the overlying rocks in the area of the Naboko Vent. 相似文献
2.
This paper reports the results of magnetotelluric sounding (MTS) in the area where the Bol’she-Bannyi hydrothermal springs are discharged. The MTS curves were inverted on the assumption of a twodimensional inhomogeneous model using longitudinal and transverse curves of apparent resistivity. It was found that the geoelectric section contains a nearly vertical anomaly of high electrical conductivity at depths of 5.5–8 km, which is the signature of a deep-seated fault. The resulting geoelectric section for the upper crust and data from regional magnetotelluric soundings were used as a basis for developing a conceptual deep model of the Bol’she-Bannyi hydrothermal system. We quote an approximate estimate of rock porosity. According to the model, deep fluids come from a crustal layer into the subvertical deep-seated fault then penetrate via fissures into the sedimentary–volcanogenic cover, and finally arrive at the ground surface in zones of high rock permeability. We provide a recommendation for drilling a deep well in order to determine the potential of the Bol’she-Bannyi hydrothermal field. 相似文献
3.
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
4.
This paper is concerned with the Earth’s electromagnetic field, a deep geoelectrical section, and the dynamics of earth conductivity.
This analysis is based on MTS curves along directions that to a first approximation go along and across southern Kamchatka.
It is shown that the longitudinal and transverse MTS curves are subject to the influence of local and regional geoelectrical
inhomogeneities. The coast effect was studied by 3-D numerical modeling. The patterns we have found were used for interpretation
of generalized MTS curves. The resulting parameters of the geoelectrical section were refined by reducing the longitudinal
curve to the standard curve of apparent resistivity. The results from this interpretation are to be refined as more geoelectrical
information is forthcoming. The dynamics of lithospheric conductivity were studied from data acquired during the 2005–2008
monitoring of magnetotelluric impedance in the range of periods between several hundred and several thousand seconds. The
basis for the analysis was assumed to be the transverse impedance and its phase. The latter was found to exhibit anomalous
bay fluctuations that might have been related to earthquakes. A possible origin of these anomalies is discussed. 相似文献
5.
We consider the key features in the responses of magnetic tippers and MTS curves to the sharp contrast in electric conductivity at the interface between the land and the sea waters of the Sea of Okhotsk and the Pacific bounding Kamchatka. The zones with different intensity of the coast effect are revealed. Stronger manifestations of the effect are found to occur in the East Kamchatka, which is related to the induction effects of the electric currents concentrated in the Kuril-Kamchatka trench. Indentation of the coastline resulted in the appearance of three-dimensional (3D) effects in the magnetotelluric field of the eastern Kamchatka. These effects in the variations of the geomagnetic field are vanishing with an increasing period, giving room to low-frequency effects in the MT field, which are associated with the flow of electric currents around Kamchatka (the around-flow effect). It is shown that the transverse MTS curves over the entire region of Kamchatka suffer from the S effect at low frequencies and do not characterize the deep geoelectric structure. Only in the middle segments of the West and Central Kamchatka, the longitudinal MTS curves are weakly subjected to the induction effects and thus reflect the distribution of the deep electric conductivity. On the eastern coast of Kamchatka both the longitudinal and transverse MTS curves are strongly distorted by the 3D effects caused by the abundant capes and bays. The interpretation of MTS data in this region should necessarily invoke the 3D modeling of an MT field. 相似文献
6.
A method of approximate magnetotelluric sounding (MTS) data inversion is developed on the basis of the representation of the inverse operator by an artificial neural network in classes of geoelectric structures. A methodology of the neural network inversion of magnetotelluric data is proposed for a family of classes of geoelectric structures and the uncertainty of the inferred results is estimated. A neural network algorithm of MTS data inversion is tested using synthetic 2-D data. 相似文献
7.
Yu. F. Moroz G. A. Karpov T. A. Moroz A. G. Nikolaeva V. A. Loginov 《Journal of Volcanology and Seismology》2013,8(5):294-306
The results of magnetotelluric and magnetovariational studies in the Uzon caldera are considered. An analysis of magnetotelluric parameters yielded the required method of interpretation. The MTS curves were interpreted in the framework of a 2D model using the REBOCC program. Geoelectric cross sections of the caldera were constructed along two orthogonal lines. Anomalies of high electrical conductivity were identified in the sediments and in the basement and were found to be confined to the locations of geothermal springs. The higher conductivity of these anomalies is here related to the presence of highly mineralized hydrothermal solutions. Electrical conductivity was used for an approximate estimation of porosity in the sediments and basement. A subvertical zone of higher porosity was identified at depths of 1.5–3.5 km in the caldera with a connection to the channelways of fluids rising into the sediments. It is hypothesized that highly mineralized solutions are diluted with vadose water in that zone and come through fissures onto the ground surface in the form of hot springs. The totality of these data suggested a conceptual model to characterize the main features in the generation of hydrothermal springs in the Uzon caldera. 相似文献
8.
The MTS data acquired in Kamchatka during the last 30 years have been analyzed and summarized. Our interpretation is based on curves oriented along and across Kamchatka. Longitudinal and transverse curves can be affected by local geoelectric inhomogeneities. These were suppressed by conformal averaging. A bimodal interpretation of average longitudinal and transverse curves yielded a deep geoelectric model, which can be adopted as a starting point to be subsequently refined by 3D numerical modeling. The model involves a crustal conductive layer extending along central Kamchatka. In the east of the peninsula this layer is connected with crustal transverse conductive zones as wide as 50 km. Those zones have extensions toward the Pacific Ocean. Major centers of present-day volcanism occur in the transverse zones. The upper mantle contains an asthenospheric conductive layer forming an uplift beneath the present-day volcanic belt of Kamchatka. 相似文献
9.
利用GMS-06电磁观测系统对上海奉城—浙江湖州剖面进行了大地电磁数据采集,获得了超过4000 s的高质量长周期观测数据,为沪浙地区深部电性结构研究提供了有利条件.通过反演处理,综合倾子解释结果和重磁资料以及最新的地震解释结果,在电性和断裂结构上获得了新的认识,对湖州—苏州、乌镇—马金、枫泾—川沙以及太仓—奉贤这几条深大断裂带的展布以及对区域构造格架的控制作用进行了新的评价,其中枫泾—川沙断裂是上海断隆和湖州—南通台拱之间推覆构造过渡带的控制断裂,太仓—奉贤断裂带的主体位置推断在亭林附近.同时,对高阻基底以上电性层进行了解释,揭示了岩石圈底界面的结构和构造形态,推断湖州—苏州断裂西侧存在壳内高导层. 相似文献
10.
Svetlana Kováčiková Igor Logvinov Andriy Nazarevych Lesya Nazarevych Josef Pek Victor Tarasov Pavel Kalenda 《Studia Geophysica et Geodaetica》2016,60(2):280-296
We present results of a study of the seismicity and the geoelectric structure of the Eastern Carpathians. After the evaluation of the seismicity, new methods of processing and analyzing seismic data are developed, which allow constructing an averaged horizontal-layered velocity model of the crust in the Carpathian region of Ukraine, tracing the seismic active faults and localizing the seismic events both in horizontal and in vertical direction with a better precision. For the study of the conductivity structure beneath the Eastern Carpathians, the collected magnetovariation and magnetotelluric data are used. The depth of electrical conductivity anomalies are estimated and the resulting quasi-3D model of the conductivity structure beneath the Carpathians is compared with the seismicity in the depth range of 10 ± 2.5 km. The comparison suggests possible geological mechanisms: the seismic events occur mainly in resistive solid rock domains which surround aseismic high-conductivity zones, consisting of at least partially melted material. Aqueous fluids, or a joint effect of several mechanisms, may also play an active role in this distribution. 相似文献
11.
Yu. F. Moroz T. A. Moroz V. A. Loginov A. G. Nurmukhamedov D. A. Alekseev 《Izvestiya Physics of the Solid Earth》2016,52(1):29-44
The results of the magnetotelluric (MT) soundings before and after an earthquake are analyzed. The interpretation is based on the longitudinal and transverse MT curves (along and across the strike of the main tectonic elements, respectively). The MT curves are distorted by the ρ- and coast effect. The distortions due to the coast effect are estimated by the testing three-dimensional (3D) model. It is established that the coast effect distortion at the periods up to 1000 s is small and can be disregarded. The divergence of the longitudinal and transverse MT curves, which points to the presence of the deep faults, is thoroughly studied. The inversion of the MTsounding curves is carried out by the REBOCC program of the numerical two-dimensional modeling. This program implements the procedures of elimination of the ρ-effect and the joint inversion of the longitudinal and transverse MT sounding curves. The obtained geoelectrical cross sections provide an insight into the structure of electrical conductivity of the lithosphere before and after the earthquake. The more intense variations in the electric conductivity are observed in the zone of the deep faults. These variations are related to the changes in the porosity and saturation of the rocks by the highly mineralized fluids. 相似文献
12.
A procedure for the simultaneous interpretation of magnetotelluric and near-field transient electromagnetic sounding (MTS and NF TEMS, respectively) data is proposed. The advantages of the complex interpretation are demonstrated by specific examples. In accordance with the interpretation of the field data, geoelectrical sections of the lithosphere in the western part of the Chuya Depression are constructed. A reduction in the depth to the conductive crustal layer in the epicentral zone is found, and the geoelectrical boundary in the upper part of the paleozoic basement is revealed. 相似文献
13.
V. K. Khmelevskoy B. P. Petrukhin P. Yu. Pushkarev 《Izvestiya Physics of the Solid Earth》2010,46(9):735-738
The plane harmonic electromagnetic fields are considered in the theory of magnetotelluric methods in the range of frequencies
from 0.0001 Hz to 20 kHz. These fields are natural by their origin and contain information on the depths from tens of meters
up to 100 km and more. The magnetotelluric soundings, which use the fields of radio stations, expand the frequency band almost
up to 1 MHz and make it possible to study the depths from the first few meters. The method of radio-wave interference sounding
supplements geoelectric prospecting on plane waves into the range of even higher frequencies (up to 100 MHz). In this case,
the conduction and displacement currents become comparable, which makes it possible to distinguish objects both by their electrical
conductivity and by their dielectric permittivity. For the two-layered model of a medium, there exist simple kinematic methods
of data interpretation of a radio-interferometry sounding. Within multilayer, and especially horizontally heterogeneous, media,
methods for solving equations of electrodynamics and inverse problems of geophysics are required. In the present paper, the
foundations of the theory of radio-interferometry sounding, the methodology, its role in geoelectric prospecting, and the
opportunities for the solution of geological problems are discussed. 相似文献
14.
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
15.
16.
We measured and interpreted 30 physical magnetotelluric sounding sites using an SGS-E station and 20 km of electrical profiling
observations using SDVR-4M instrumentation. We constructed a map of seismicity, an interpretation map, and four geoelectric
sections, which give an idea of the deep structure for the Kulu earthquake-generating zone. A general geoelectric upper crustal
model was developed for the zone down to depths of 20–22 km. Three nearly vertical conductive volumes were identified (thickness
3–5 km, depth 10–22 km), which provide the positions of seismically active deep-seated faults that pinpoint the Kulu earthquake-generating
zone. The preliminary boundary of the zone was determined. It was found that earth-quake epicenters are confined to lithosphere
volumes with increased concentrations of conductive layers and zones. 相似文献
17.
经过半个多世纪的发展,国内外利用大地电磁法研究地球内部电性结构取得了令人瞩目的成就,这些研究成果多数是基于电性各向同性理论.然而地球内部普遍存在电性各向异性现象,地壳和上地幔中存在的电性各向异性是地电模型、地下结构和构造模型间一个重要的联系因素.本文首先由麦克斯韦方程出发,引入张量电导率,根据二维电性各向异性结构的特点,得到一组关于平行走向的电场分量Ex和磁场分量Hx的偏微分方程.使用有限差分法求解偏微分方程,求出Ex和Hx的近似解,并以此求得其它场分量;随后,通过对普通及特殊的二维电性各向异性结构做正演模拟,研究其对观测大地电磁场的影响,从而认识在普通及某种特定地质条件下的电磁传播特性,为其后对大地电磁实测资料的处理解释奠定理论基础;最后,以本文的研究成果为基础,将电性各向异性理论引入对实测大地电磁资料的处理解释中,通过对新疆某地的大地电磁资料做二维正演拟合解释,说明了电性各向异性现象的普遍存在,也验证了理论的正确性及算法的实用性,为今后分析解释大地电磁资料中的电性各向异性现象提供理论依据和技术指导,并开拓了对大地电磁实测资料处理的思路和方法. 相似文献
18.
本文对大地电磁观测阻抗实施一种数学变换--"共轭阻抗变换",发现转换后的观测阻抗和区域阻抗之间存在特定的关系,这种特定关系不受电场局部畸变的影响,而且同样不需要关于地下区域结构维性的假设,在区域结构是三维的情况下也是成立的.对转换后的观测阻抗采用已有的Swift旋转方法即可求得区域主轴方位角,然后采用最优化方法求取区域阻抗相位、振幅以及畸变因子.同时根据转换后的观测阻抗重新定义了不受电场局部畸变影响的构造维性参数.采用合成理论数据验证了新算法的正确性,和Swift、Bahr、GB、相位张量、WAL方法进行了对比分析,并将新方法应用于实测资料的解释,发展了一套消除局部畸变和进行构造维性分析的MT精细资料处理技术.进一步的工作是将新算法推广到多点多频,并采用最优化技术分解,发展一种稳定性好、多测点多频点的阻抗张量分解技术. 相似文献
19.
Studies of the relationships between ground-water systems and surface-water systems (lakes) generally require knowledge of the hydrogeologic properties of lakebed materials. Direct measurement of these properties may be prohibitively expensive or difficult in an offshore environment. A correlation between longitudinal conductance, a geoelectric parameter, and lakebed leakance (vertical hydraulic conductivity divided by thickness) may provide a rapid and inexpensive method for estimating lakebed hydrogeological properties using data collected by offshore seismic and electrical surveys. A test of the method at three study sites in Lake Michigan shows a positive linear relationship between the logarithm of longitudinal conductance and the logarithm of lakebed leakance at the three sites. 相似文献
20.
O. K. Zakharova V. V. Spichak A. K. Rybin V. Yu. Batalev A. G. Goidina 《Izvestiya Physics of the Solid Earth》2007,43(4):297-303
The paper analyzes the correlation between the electrical conductivity and temperature in the upper crust of the Bishkek geodynamic research area (the Northern Tien Shan). Electrical conductivity profiles constructed from magnetotelluric data and thermograms from the boreholes near magnetotelluric sounding (MTS) points are used for estimations. The correlation analysis of conductivity and temperature profiles to depths of 3–4 km showed that, first, the correlation coefficients do not depend on the distance between the borehole and the nearest MTS point; second, the good correlation between the conductivity and temperature observed for the majority of borehole-MTS point pairs is accounted for by the fact that the study parameters vary with depth in a manner normal for laminated sedimentary rocks; and, third, a low correlation is due to specific features of the geological structure between the borehole and MTS point under consideration. 相似文献