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本文研究了我国大陆部分中、强地震前地电阻率变化,得到地电阻率临震突变是我国大陆中、强地震前能观测到的一种客观电现象;讨论了地电阻率临震突变的变化特点、变化形态和时、空间分布特征。 本文认为地电阻率临震突变主要是临震前震源区孕震造成地电台勘探体介质湿度发生变化而引起的。 相似文献
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景泰6.2(Ms)级地震地电阻率变化特征 总被引:4,自引:0,他引:4
本文讨论了景泰6.2级地震,400km范围内有关11个地电台震前地电阻率变化,得到如下结论:1)武威、定西和水丹地电台在本次地震前观测到地电阻率临震突变;2)中、强地震前地电台能否观测到地电阻率临震突变与分布于震源区内、外的深大活断裂、强烈活断层以及发震应力场有关;3)临震前地电阻率变化时-空特征表明本次地震可能是NNW向(或与该方向大致相同)应力场短期内作用增强诱导发生的,并且震源断层北盘起了主导作用。 相似文献
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本文分析了内蒙古地区四个地电台站附近二十一次地震发生前后视电阻率的变化特征,并对视电阻率法预报地震的效果问题进行了讨论。尽管各台站的观测条件不尽相同,但可以看出视电阻率法对我区台站周围150公里范围内 Ms≥4.7级的地震具有一定监测能力。 相似文献
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最佳地电台台址条件与环境条件的讨论 总被引:3,自引:0,他引:3
地电台观测地电阻率及其变化以研究地震活动规律,首要的问题是如何选择或评估其台址的优劣,选取最佳地电台台址。文中讨论了地电台台址的地质构造条件、测区地下介质结构条件、介质水文条件、地形地貌条件、电磁干扰等对地电台站观测效能的影响,为选建和评估地电台台址提供较全面、系统的依据。 相似文献
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为了研究地电阻率和电场的变化与地震活动性之间的关系,近年来苏联在中亚地震预报试验场进行了实地测量和多方面的探讨,现将其观测结果介绍如下。 一、地电阻率的变化与地震活动性关系的观测结果 1.1偶极电测深 1983年,苏联科学院高温研究所电磁方法试验考察队在伏龙芝地震预报试验场用偶极测深法,采用AB=620m的供电极距,对地壳上部岩层电阻率的变化进行了研究。 相似文献
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南京台旧地电场地震例总结 总被引:3,自引:0,他引:3
根据南京台旧地电场地的十余年电阻率资料,讨论了电阻率变化与这一期间江苏发生的中强地震间的可能关系,分析了震前电阻率异常变化的主要特征。同时,对该台断、旧地电场地电阻率观测资料进行了对比分析,其结果也可供其他地电台参考。 相似文献
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本文重点讨论了某些强震和中等地震前有代表性的地电阻率临震突变现象。研究了地电阻率临震异常的时空展布特征,并将这些现象与地震活动性、应变资料、地下水位及水温等资料作了对比。还讨论了地电阻率临震异常与震源机制解、发震断裂等的关系。阐明这些事实与地电阻率临震异常在时间上的同步性,在空间上的一致性,从而对地电阻率临震现象作了某些解释,认为地电阻率临震异常的原因有待进一步研究,它们可能是构造应力场迅速变化及由应力变化而引起的地下水的组分和状态变化综合影响的结果。同时指出,由于强震前地电阻率临震异常分布的不均匀性,能记录到异常的台站仅仅是一部分,这就给捕捉临震异常增加了难度,必须建立一定密度的台网进行长时间连续的观测。至于中等强度地震的临震信息,只有在某些特定的地震前,且在靠近震中的特定台站才可能记录到。 相似文献
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强震前地电阻率异常的模糊识别 总被引:2,自引:0,他引:2
本文用模糊集从属函数方法,对1976年唐山7.8级地震和宁河河6.9级地震前华北地区20多个台站的地电阻率观测数据和1988年澜沧——耿马7.6级地震前腾冲台地电阻率观测数据以及1989年巴塘6.7级地震前甘孜台地电阻率观测数据进行了计算,共计处理5500多个数据,从中提取了中期趋势与短临异常,并对唐山地震前地电阻率异常进行了概略分析。 相似文献
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STUDY ON THE ELECTRICAL STRUCTURE OF THE ANQIU AND JUXIAN ELECTROMAGNETIC STATIONS IN THE TANLU FAULT ZONE 下载免费PDF全文
ZHANG Ji-hong ZHAO Guo-ze DONG Ze-yi WANG Li-feng HAN Bing WANG Qing-lin TANG Ting-mei WANF Mei 《地震地质》2019,41(5):1239-1253
The Yishu fault zone is one of the branch faults of the Tanlu fault zone in its central part. Moderate and strong earthquakes occurred in the Yishu fault zone repeatedly. Due to its complex structure, the Yishu fault zone attracts much attention from earthquake researches. The Anqiu and Juxian electromagnetic stations in Shandong Province locate near the Anqiu-Juxian Fault and Changyi-Dadian Fault, which are branches of the Yishu fault zone, respectively. Geoelectric field and geomagnetic field observation were carried out in these two stations. The Wudi electromagnetic station is in the west of Tanlu fault zone in the Jidong-Bohai block and 230km from Anqiu electromagnetic station. This paper firstly describes the crustal structure near the electromagnetic stations by using magnetotelluric(MT)method. By processing the data carefully, we obtain the MT data in good quality near the stations. The MT data of each electromagnetic station and its nearby area suggests that the electrical structure and geological structure of the station are comparable. This paper applied 1-D and 2-D inversion for MT data and obtained the crustal electrical structure model beneath the Anqiu and Juxian seismic station. The shallow electrical structure from the MT method was compared with the results of symmetrical quadrupole electrical sounding. The model suggests that the electrical structure beneath the Anqiu and Juxian electromagnetic stations is complex and shows the feature of block boundary. The Wudi electromagnetic station is located inside a basin, the crustal structure shows layered feature typical for the stable blocks. Beneath the Anqiu electromagnetic station, there is a 1km-thick relative low resistivity layer in the shallow crust and a high resistivity body beneath it with a depth of 13km. There is a high resistivity structure in the crust beneath the Juxian electromagnetic station. The crustal structures are divided into two different parts by Anqiu-Juxian Fault and Changyi-Dadian Fault, respectively. More conductive layers appear to the west of the two faults. Plenty of fluid possibly exists within the conductive body to the west of Changyi-Dadian Fault, which plays important role in the earthquake generation. There is a relative low resistivity layer in the crust within 1~2km beneath the Wudi electromagnetic station. Beneath the relatively low resistivity layer, a relatively high resistivity layer extends to a depth of around 15km, and the resistivity value decreases with the increase of depth. The electrical resistivity model suggests the seismic activity of the Yishu fault zone around the Anqiu and Juxian electromagnetic stations should be taken into account seriously, and monitoring and research on it need to be strengthened. The results of this paper provide a certain reference value for the crustal structure research to similar stations. 相似文献
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观测地壳浅层电阻率随时间变化以寻找地震信息是地电阻率方法的目的。实际工作中,在保证观测精度的前提下,发现正常(无震)情况的地电阻率仍然存在着复杂的变化,给定量和定性分析地震异常带来相当大的困难。 本文分析了一些台站正常地电阻率的变化规律,并在此基础上提出“变化电性剖面模式”,来阐明一些台站正常地电阻率变化的复杂过程及其产生的可能原因。从此观点出发,导出以二层电性剖面为特征的台站正常地电阻率相对似年变化幅度公式。通过典型计算,提出获取平稳的正常原始资料是解决上述困难问题的方向,并指出了获取平稳正常变化资料的具体途径。 相似文献
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DIFFERENTIATION DIRECTION OF TELLURIC CURRENTS IN THE SOUTHERN SECTION OF THE TANLU FAULT ZONE 下载免费PDF全文
The Tancheng-Lujiang Fault is an important tectonic boundary in eastern China. The southern part of the Tancheng-Lujiang Fault is located south of Baohai Bay, which is an area with a dense population and frequent economic activities. It is worth conducting an in-depth study on the southern section of the fault, especially in the aspect of geophysical exploration and seismicity analysis. Electrical structure detection is an important way to interpret the structural activity of the fault. It can also analyze and explore the influence of the fault on the physical properties of both sides of the fault based on the geoelectrical observation data. In the study area, there are densely distributed stations of geoelectrical observation, including 27 fixed stations distributed along the fault zone from the southern Baohai Bay to Nanjing, Jinagsu Province. The continuous observations and recording of these stations provide a favorable condition for studying the tectonic activity of Tancheng-Lujiang Fault.
In the long-term observation of geoelectric observation network, the geoelectric field measurements of long- and short-spacing measuring tracks in the same direction at the same station vary significantly because of the effect of long-term stability of the observation system and the environment near the electrodes. Also, the data curve changes complicatedly and seems to be in a mess. However, there are three basic facts of observation existing in the geoelectric field change: 1)The variation amplitude of the geoelectric field changes observed on the long- and short-spacing measuring tracks in the same direction at the same station(including tidal response changes and the rapid change events such as short periods or pulses)is the same or very close; 2)The Ex and Ey components at the same station always show the same variation in the same time period, or the opposite, which is related to the anisotropy of the medium under the station; 3)The rapid changes of the minute values of the geoelectric field observed at different stations are synchronous in a wide spatial area. In this study, in order to take full advantage of these basic facts, we only use the amplitude variation of geoelectric field with time.
Based on the data of 27 geoelectric field observation stations in the study area, we used the current density vector and streamline to characterize telluric current with its divergence and vorticity calculated in the southern Tancheng-Lujiang Fault in this paper. The results show that: 1)the telluric current shows the phenomenon of opposite directional differentiation in the southern part of the fault zone, the direction of the current vector is NE on the east side, while the direction is NW to SW on the west side; (2)The divergence and vorticity of telluric current also show the differentiation phenomenon along the fault, the positive/negative maximum of vorticity and divergence mainly occurs near the fault zone and the direction of alternating positive and negative gradient(or negative gradient)of vorticity or divergence is consistent with the strike of the fault zone. By analyzing the current superposition simulation results and comparing them with previous studies, an interpretation model of the above phenomenon is established in this paper. The results agree with previous studies on the electrical structure of this region. Besides, the results that telluric current differentiates along the fault zone may improve our understanding of the process of deep electrical and material migration. 相似文献
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应用吉林省内榆树、 四平两个地电阻率台站观测资料, 采用形态法、 归一化变化速率法和各向异性度法, 分析研究了1999年汪清MS7.0深震以及2006年乾安—前郭MS5.0浅源地震前的地电阻率异常变化. 结果表明, 震前地电阻率出现长趋势下降变化或短临异常变化, 表现为: ① 汪清MS7.0深震前, 榆树台和四平台地电阻率月均值曲线上均显示出震前持续2年尺度的中期下降异常; ② 汪清MS7.0深震以及乾安—前郭MS5.0浅源中强震前, 榆树台和四平台地电阻率变化速率均大于异常指标; ③ 乾安—前郭MS5.0地震前, 四平台地电阻率各向异性度曲线显示出明显的低值异常变化, 而榆树台各向异性度S曲线则出现破年变变化. 上述异常变化的原因可能为, 太平洋板块向NW方向挤压, 导致震源区及附近最大主压应力方位(或近于该方位)NW向的挤压作用突出, 引起介质内部导电流体快速进入或重新分布, 从而使地电阻率出现长趋势下降变化和各向异性变化. 相似文献
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结合我国实际,本文提出四类地电阻率季节变化的干扰模型.经模型理论计算及同有季节变化的四十多台站的实测资料对比得出:(1)地电阻率季节变化是探测深度偏浅时,地表层电性变化,特别是表层地下水水位年动态变化所引起的一种与地震无关的干扰变化.其变化形态与量级取决于干扰模型、地电断面类型以及探测深度.(2)通常地电阻率季节变化与浅层电阻率变化的符号一致,呈现出正常季节变化;但对 K,Q 型地电断面,当干扰层位于地表第一层时,将从某一供电极距开始,出现反常的季节干扰变化.(3)当探测深度大于300m 时,不论正常的还是反常的季节变化,其幅度都将小于2%.因此,只要适当选择台址或加大供电极距使探测深度足够大,便可排除或压低这种干扰. 相似文献