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怀 4井为国家重点观测井,在多次地震前都有明显的异常出现,对监视北京西北地区的地震起着重要的作用。文中分析了 5次中强地震前怀 4井地下流体测项的异常情况。统计了自 1998年以来周围 300km范围内 4级以上地震前怀 4井流体测项的映震情况。认为怀 4井对其周围 260km范围内≥4 0级的地震反应比较灵敏。并归纳出怀 4井流体测项前兆异常的如下特征: 1)水汞前兆异常形态为突跳型,异常结束后发震; 2)断层气二氧化碳前兆异常形态为多点高值起伏型,异常转折下降中发震; 3)水氡前兆异常形态为阶变型,异常中发震; 4)氢气前兆异常形态为突跳型,异常结束后发震。通过本研究,有助于今后对怀 4井流体异常的识别,根据怀 4井各测项对地震孕育各阶段反映的差异,更容易判定未来地震的发震时刻 相似文献
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依据 《中国震例》 资料,统计分析了云南地区1966—2006年MS≥5.0地震的地下流体测项异常,结果表明:超过70%的水位和水温震前异常表现为上升,水氡和水位异常出现时间最早;震级越大相应的流体异常范围就越大;大多数震前流体异常会持续到地震发生,说明流体异常与震前地壳活动有关,并据此得出云南地区地震发生时间及异常检测井至震中距离的经验性边界方程。分类汇总云南地区地下流体测项的异常形态,识别出该地区地下流体异常的5种主要异常形态,即趋势转折类、周期类、突变类、阈值类和综合类,并举例阐明了各种异常形态的特征及其可能的成因。本文研究结果对于认识云南地区流体异常特征以及提升流体异常应用水平具有一定的参考意义。 相似文献
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分析了泉州四至村井1984年至1987年地下水化学组份的变化特点后,发现Cl~-、Ca~(++)Mg~(++)、水电导率在寻乌5.5级地震前,Rn、PH值在台湾7.6级地震前均有明显的异常。认为这些异常可能是地震前兆异常。 相似文献
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2002年8月3日沙城ML4．4地震是该年7个月以来，首都圈地区发生的显著地震，虽然该地震震级不大，但怀来台体应变的短临异常十分显著。作者主要介绍了该地震前体应变异常特征，同时介绍了地下流体测项阳原三马坊数字气氡异常和怀4井水汞异常及预报情况。 相似文献
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从《中国震例》中选取1976～1998年川滇地区发生的15次MS≥6地震作为震例,依据图形对比和统计的方法,分析了不同震级的地震前水位(流量)、温度及水氡异常变化的协调性特征,结果显示,无论是在时间演化方面还是在空间演化方面,这3个流体测项之间都具有协调性演化关系,震级不同,异常的表现形式也不同,并且7级以上地震的异常的协调性特征明显好于6.0～6.9级地震。 相似文献
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根据前人对西秦岭北缘断裂带上历史地震及古地震复发周期和离逝时间等的综合研究,得出该断裂存在发生强震的较大潜在风险,因此加强对该断裂现今构造活动的定点监测和地震预测预报具有重要现实意义。据此,根据断裂逸出气体测项剖面浓度分布（变化）特征,在西秦岭北缘断裂带（天水段）上新建3个断层土壤气连续观测站,开展断层气（H2、CO2、Rn、CH4）浓度观测,分析断裂带不同段深部气体特征的空间差异及其随时间的变化特征,监测甘东南地区应力调整与地震活动。初步观测资料分析表明：在正常情况下其背景值比较稳定,且同一测项在不同测点变化形态具有相似性、同步性,说明观测资料真实可靠,并具有可比性。各测点出现测项同步异常变化时,可能反映了区域应力调整及变化状态,对震情跟踪和地震预测提供参考判据。 相似文献
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Electrical conductivity anomalies in the earth 总被引：1，自引：0，他引：1
Yoshimori Honkura 《Surveys in Geophysics》1978,3(3):225-253
Anomalies of short-period geomagnetic variations have been found in various regions over the world. It is known that such anomalies arise from electromagnetic induction within an electrical conductivity anomaly or from local perturbation of induced electric currents by a conductivity anomaly. In order to investigate a regional electric state in the Earth, conductivity anomaly (CA) studies based on anomalous behaviors of geomagnetic variations have been extensively undertaken, as well as studies based on magnetotelluries in which induced currents are directly used.Some of the geomagnetic variation anomalies, however, turned out to be caused by surface conductors, such as sea water and sediments. Anomalies of this sort have been intensively studied and classified into coast, island, peninsula, and strait effects in the case of sea effects. Three-dimensional conduction or channelling of induced electric currents is sometimes observed in the cases of sediments and some crustal conductivity anomalies. However, anomalies of such surface origins often provide some information of the underground conductivity structure.Electrical conductivity anomalies can be classified into two types: anomalies originating in the crust and in the upper mantle. Many of crustal anomalies are well correlated with metamorphic belts, fracture zones, and hydrated layers, and magnetic and gravity anomalies are also often found over the conductivity anomalies. Most of mantle anomalies have been interpreted mainly in terms of high temperature and partial melting, since conductivity anomalies coincide well with anomalies in heat flow and seismic wave velocities. 相似文献
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Detection of preferential infiltration pathways in sinkholes using joint inversion of self-potential and EM-34 conductivity data 总被引：2，自引：0，他引：2
The percolation of water in the ground is responsible for measurable electric potentials called self‐potentials. These potentials are influenced by the distribution of the electrical conductivity of the ground. Because sinkholes are associated both with self‐potential and electrical conductivity anomalies, a joint inversion of EM‐34 conductivity and self‐potential data is proposed as a way of delineating the location of these features. Self‐potential and EM conductivity data were obtained at a test site in Normandy (France) where sinkholes and crypto‐sinkholes are present over a karstic area in a chalk substratum overlain by clay‐with‐flint and loess covers. The presence of sinkholes and crypto‐sinkholes is associated with negative self‐potential anomalies with respect to a reference electrode located outside the area where the sinkholes are clustered. The sinkholes also have a conductivity signature identified by the EM‐34 conductivity data. We used the simulated‐annealing method, which is a global optimization technique, to invert jointly EM‐34 conductivity and self‐potential data. Self‐potential and electrical conductivity provide clear complementary information to determine the interface between the loess and clay‐with‐flint formations. The sinkholes and crypto‐sinkholes are marked by depressions in this interface, focusing the groundwater flow towards the aquifer contained in the chalk substratum. 相似文献
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Data on fluorine concentration in water in the Middle Klyaz’ma Basin during summer low-water period have been obtained. Fluorine background concentration has been determined in streams (Klyaz’ma R., small rivers, and creeks), water bodies (drainage ditches, lakes), and subsoil waters. Anthropogenic fluorine hydrochemical anomalies have been determined and localized with respect to urbanized industrial areas. An assumption has been made and experimentally substantiated, according to which fluorine concentration in subsoil water is governed by the processes of its distribution between water and host rocks. It has been established that the interaction of soils with snowmelt water and alluvial deposits with river water in neutral and acid media is accompanied by fluorine removal from solution, while in a weakly alkaline medium, fluorine passes from solid phase into solution. The effect of dissolved organic matter on the process of fluorine leaching from rock minerals also depends, primarily, on the equilibrium pH value: in weakly alkaline media, the presence of organic acids contributes to fluorine mobilization, while in weakly acid media, it reduces mobilization rate. 相似文献
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林国元 《地震地磁观测与研究》2010,31(4):57-60
2008年3—7月福建地区共发生4次中等地震,福建地下流体氟离子有多孔观测井,在震前或震后出现高值突跳的现象;2008年9-11月福建地下流体氟离子又有多孔观测井出现高值异常。本研究通过实验提出:该氟离子高值异常为非地震前兆异常,建议准备一支氟离子选择性电极作为备用电极,用于对比观测,以提高氟离子观测数据异常的判别。 相似文献
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The data of long-term electromagnetic monitoring are used for studying the dynamics of electric conductivity of the medium
and the electric field of the terrestrial sources. The electric conductivity of the medium is estimated from the magnetotelluric
transfer functions (impedance tensor and telluric tensor). The electric field of terrestrial sources is identified by filtering
the variations of the observed electric field of the Earth. The magnetotelluric parameters and the electric field of terrestrial
sources feature anomalous changes of supposedly earthquake-related origin. The anomalies associated with the same earthquake
are not simultaneous. It is shown that these anomalies are generated by processes occurring at different depths. The strong
earthquake is preceded by the appearance of surface anomalies several months before the event and accompanied by a deep coseismic
anomaly. The probable nature of the recognized anomalies is discussed. 相似文献
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Common studies on the static electric field distribution over a conductivity anomaly use the self-potential method. However, this method is time consuming and requires nonpolarizable electrodes to be placed in the ground. Moreover, the information gained by this method is restricted to the horizontal variations of the electric field. To overcome the limitation in the self-potential technique, we conducted a field experiment using a non conventional technique to assess the static electric field over a conductivity anomaly. We use two metallic potential probes arranged on an insulated boom with a separation of 126 cm. When placed into the electric field of the free air, a surface charge will be induced on each probe trying to equalize with the potential of the surrounding atmosphere. The use of a plasma source at both probes facilitated continuous and quicker measurement of the electric field in the air. The present study shows first experimental measurements with a modified potential probe technique (MPP) along a 600-meter-long transect to demonstrate the general feasibility of this method for studying the static electric field distribution over shallow conductivity anomalies.Field measurements were carried out on a test site on top of the Bramsche Massif near Osnabrück (Northwest Germany) to benefit from a variety of available near surface data over an almost vertical conductivity anomaly. High resolution self-potential data served in a numerical analysis to estimate the expected individual components of the electric field vector.During the experiment we found more anomalies in the vertical and horizontal components of the electric field than self-potential anomalies. These contrasting findings are successfully cross-validated with conventional near surface geophysical methods. Among these methods, we used self-potential, radiomagnetotelluric, electric resistivity tomography and induced polarization data to derive 2D conductivity models of the subsurface in order to infer the geometrical properties and the origin of the conductivity anomaly in the survey area. The presented study demonstrates the feasibility of electric field measurements in free air to detect and study near surface conductivity anomalies. Variations in Ez correlate well with the conductivity distribution obtained from resistivity methods. Compared to the self-potential technique, continuously free air measurements of the electric field are more rapid and of better lateral resolution combined with the unique ability to analyze vertical components of the electric field which are of particular importance to detect lateral conductivity contrasts. Mapping Ez in free air is a good tool to precisely map lateral changes of the electric field distribution in areas where SP generation fails. MPP offers interesting application in other geophysical techniques e.g. in time domain electromagnetics, DC and IP.With this method we were able to reveal a ca. 150 m broad zone of enhanced electric field strength. 相似文献
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大气电场异常作为地震短临预报标志研究进展 总被引：5，自引：0，他引：5
通过对华北地地区进行震前大气电场异常观测研究的较为全面分析和总结,验证和论述了震前大气电场异常的基本特征,用大量的震例证实了在每次较大的近场地震发生前都能观测到该类异常现象,以及当较长一段时间内观测不到该类异常时,近场近期也不会有较大地震发生的可能。 相似文献