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地震前,地壳变形引起地球密度重新分布,从而使地球重力场发生某些特征变化。本文对1990年7月菲律宾8级、台湾6.1级两个强震前后的广州重力资料进行了调和分析及高、低频滤波等处理,并对提取出的重力前兆进行了可信度检验。结果表明强震前广州地区的重力变化具有O_1等主波潮汐因子波形畸变,量值下降至最低值然后在回升阶段发震的前兆异常特征。非潮汐重力变化在临震前3天开始出现明显的高频脉冲式异常信息,作者认为这是一种可信的具有清晰物理意义的地震短临前兆。 相似文献
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STUDY ON DYNAMIC CHANGE OF GRAVITY FIELD IN XIANSHUIHE FAULT ZONE AND THEIR RELATION TO THE OCCURRENCE OF MS ≥ 5.0 EARTHQUAKES 
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下载免费PDF全文 Xianshuihe Fault, a main strong earthquake activity belt in southwest China, begins from Ganzi in the northwest, passes through Luhuo, Daofu, and Kangding, and then extents along the Dadu River valley. The fault is divided into two parts at Shimian, one part turns to south and converses to Anninghe Fault extending further to south, the other part, continuing to extend to southeast, cutting through Xiaoxiangling and then changing to Daliangshan Faults in the north of the Yuexi Basin, has the length of about 400km. Since 1700AD, there have happened 22 earthquakes larger than magnitude 6.0 and 8 earthquakes larger than magnitude 7.0. In this paper, we systematically collated and computed the gravity repetition measurement data along the Xianshuihe fault zone since 1988, and by referring to the anomaly index of gravity field of the predecessor achievements, analyzed the spatial-temporal variation of the regional gravity field and the relation to the occurrence of ≥ MS5.0 earthquakes. The mechanism of the regional gravity changes is further studied, and also the implication of strong earthquake risk because of the dynamic variation of gravity field in the near future is discussed.The results show that:1)The mobile gravity observation has the ability to detect crustal activity and MS ≥ 5.0 earthquake events. 2)There is definite correspondence between interannual gravitational field change and the 8 earthquakes among the 13 MS ≥ 5.0 earthquakes occurring in the surveying area since 1988, which can be determined according to the change of interannual gravitational field. Three M ≥ 6.0 earthquakes occurred 3~4 years after the abnormal image was developed, 4 earthquakes that occurred in the region of no data available were not determined. 3)A significant feature of the spatial-temporal variation of the regional gravity is a north-south run-through image before 2004, and characterized by the alternatively positive or negative variation in different year, the earthquakes of MS ≥ 5.0 occurring in this period were not distributed along the fault. Gravity variation magnitude indicates that there were two similar crustal material movement waves before 2004, corresponding to the course of earthquake space-time distribution from strong to weak in the study area. After 2010, the variation image shows that the local positive and negative zones are concurrent within a year, different from the image before 2004, and earthquakes of MS ≥ 5.0 basically occurred on the fault. It is believed that the variation of gravity field since 1988 and the seismic distribution fit with the geodynamic mode of strong and weak stages of the northeast motion of Indian plate. According to the conclusion we can try to optimize gravity anomaly index. After the Kangding earthquake in 2014, the north segment of Moxi Fault was still subject to negative high value changes till 2017 and then the gravity variation was further developed to a four quadrant distribution image. Based on the analysis of this paper and the previous variation trend of gravity field, we believe that the north segment of Moxi Fault has the background of medium-long term, strong or large earthquake risk. 相似文献
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1976年唐山地震前的重力位二次微商变化 总被引：1，自引：2，他引：1
本文介绍了唐山大地震前在北京通县西集地震台用扭秤观测的重力位二次微商变化。这个资料与唐山地震前的重力异常符合得比较好。扭秤测量精度较高，仪器性能稳定，两秤臂的一致性好，它对唐山地震前观测的重力异常是一个很好的旁证和补充。说明唐山地震前的重力变化，尤其是１９７５年的加速上和临震前的得力下降是可信的。西集台第一次观测到与地震孕育过程有关的重力位二次微商异常，这对研究唐山地震的前兆，特别是重力场的变化原 相似文献
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利用青藏高原东北缘2011-2015年期间的流动重力观测资料,系统分析了区域重力场变化及其与2016年1月21日青海门源MS6.4地震发生的关系,结合GNSS、水准观测成果和区域地质构造动力环境,进一步研究了区域重力场变化的时空分布特征及其机理.结果表明：（1）测区内重力场异常变化与祁连山断裂带在空间上关系密切,反映沿祁连山断裂带（段）在2011-2015年期间发生了引起地表重力变化效应的构造活动或变形.（2）门源MS6.4地震前,测区内先出现了较大空间范围的区域性重力异常,到临近发震前显示出相对闭锁的现象,且围绕震中区周围出现四象限分布特征的局部重力变化,地震发生在重力反向变化过程中,并出现显著的四象限分布特征的重力异常变化,其中,青海门源与甘肃天祝一带重力差异变化达100×10-8m·s-2以上.（3）区域重力场动态演化大体反映了青藏高原东北缘物质北东流的动态效应,门源震中附近区域地壳受挤压变形显著、面压缩率和重力剧烈变化的特征最为显著.（4）重力场的空间分布及其随时间变化与地壳垂直与水平运动及地质构造活动等观测结果有一定的对应关系,强震易发生在重力变化四象限分布中心地带或正、负异常区过渡的高梯度带上. 相似文献
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绘制了重力的时序变化曲线和空间等值线,从动态的角度分析了1998年张北6.2级地震和1999年大同5.6级地震前后的流动重力异常的演化及特征。结果显示,地震的孕育过程与重力场变化有关,地震发生在重力下降的异常时段,震中位于重力变化高梯度区。 相似文献
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唐山及大同－阳高地震大地形变与重力前兆综合研究 总被引：1，自引：0，他引：1
本大概还了近年来利用大地形变及重力复测资料研究唐山及大同－阳高地震的丰富成果，对这２次地震震前大地形变及重力前兆综合研究认为：震中区震前呈现闭锁状态；断层蠕滑及深部物质的运移，是震前的显著标志；地震成因的组合模式可以较好地解释唐山及大同一阳高地震的机制；跟踪监测形变场、重力场及断层活动时空演化特性，是利用大地形变及重力测量手段进行地震预测的基本出发点。 相似文献
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CHARACTERISTICS OF MULTI-SCALE GRAVITY FIELD VARIATION AND SEISMOGENIC MECHANISM ANALYSIS IN THE SOUTHEASTERN TIBETAN PLATEAU 下载免费PDF全文
下载免费PDF全文 CHEN Zhao-hui MENG Xiao-hong ZHANG Shuang-xi LIU Jin-zhao WANG Tong-qing ZHANG Pin WEI Shao-gang 《地震地质》2019,41(3):690-703
As the most basic geophysical field, the earth gravity field has achieved wide attention, and its spatial anomaly characteristics and dynamic variation can provide important scientific basis for studying the internal structure and dynamics of the Earth. Based on the mobile gravity observation data of the southeastern Tibetan plateau from 2013 to 2016, the dynamic variation tendency and anomaly characteristics of the regional gravity field in different temporal resolutions are obtained before and after the Ludian and Jinggu earthquakes in the study area respectively. The method of wavelet multi-scale decomposition is used to analyze the relationships of gravity field variation with the earth movement, material density change, and strong earthquake preparation. The deep material variation, dynamic process and the mechanism of earthquake inoculation in the southeastern Tibetan plateau are further discussed. Results indicate that the gravity field variation in the source region before the Ludian and Jinggu earthquake respectively is characterized by obvious positive and negative anomalous transition zone and gradient zone that are consistent with the direction of fault tectonics, suggesting the strong crustal movement and mass migration during the earthquake incubation period. The result of wavelet multi-scale decomposition of the gravity field during the period from September 2013 to April 2014 shows that the gravity field variation at different depth and space scale in the crust and upper mantle of the southeastern Tibetan plateau is significantly correlated with seismic distribution and the location of active fault zone. This indicates that the earthquake inoculation in the study area is closely related to the fault movement and the distribution of material density in the crust and upper mantle, which may be affected by the complex deep dynamic process of the material migration in the crust and mantle. The characteristic that strong earthquakes always occur near positive and negative anomaly transition zones and gradient zones of gravity field change is preliminarily explained, based on the dynamic process of material migration in the crust and upper mantle of the southeastern Tibetan plateau. The research results of this paper have some reference value to the study on the earth movement and seismogenic mechanism. 相似文献
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通过大理岩破裂实验,考察了典型构造中微裂纹的演化、集结的过程和特征．根据损伤理论,分析了构造对微破裂演化的控制作用．根据微破裂集结临界条件的相似原理,认为这些特征可以类推到公里尺度,它们有助于解释地震中短期阶段的前震或广义前震分布,作为地震前兆的一次效应．其它物理效应为二次或三次效应．微破裂集结时局部密度突然加大,有助于解释部分前兆记录突跳现象．非集结部分出现部分微裂纹愈合,密度反向变化,有助于解释一些前兆记录在短临阶段记录中出现反向的现象．考察了不同构造的不同部位微破裂萌生和演化的范围差异,这些差异有助于解释不同地质构造孕震区域的孕震过程,从而可解释板缘和板内地震前兆记录的差异．这种差异可能被不同观点学者分别引用,以论证地震是否有前兆记录的问题．然而,在考察不同地区的前兆记录时,必须注意不同地区的地质背景． 相似文献
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几次大地震前后地电场中长期变化分析与研究 总被引：1，自引：0，他引：1
地电场是地球表面天然存在的电场, 包括大地电场和自然电场。 利用“合成能量累加”方法, 分析处理了甘肃省、 青海省、 四川省、 重庆市所辖部分台站2007年7月至2017年12月的地电场观测数据, 研究和讨论了汶川8.0级地震等几次大地震前后地电场中长期异常变化特征。 研究结果显示, 几次MS7.0以上大地震前后, 均出现了地电场区域性准同步异常变化; 地电场异常变化经历了“震前—发震—震后”三个阶段, 震前和震后变化比较明显, 发震期变化相对平稳, 时间跨度达12个月以上; 地电场异常变化主要沿构造带分布, 变化强度随震中距的增加而减小。 相似文献
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利用川西地区2010-2012年期间的流动重力观测资料,系统分析了区域重力场变化及其与2013年4月20日四川芦山7.0级地震发生的关系.结果主要表明:①区域重力场异常变化与北东向龙门山断裂带南段和北北西向马尔康断裂带在空间上关系密切,反映沿该两断裂带(段)在2010-2012年期间发生了引起地表重力变化效应的构造活动或变形.②芦山7.0级地震前,测区内出现了较大空间范围的区域性重力异常,而震源区附近产生了局部重力异常,沿龙门山断裂带南段形成了重力变化高梯度带,其中,宝兴、天全、康定、泸定、石棉一带重力差异变化达100×10-8m·s-2以上;这些可能反映芦山地震前,区域及震源区附近均产生与该地震孕育、发生有关的构造运动或应力增强作用.③重力场差分动态演化图像和重力场累积变化动态图像均反映芦山7.0级地震孕育过程的最后2~3年出现较显著的流动重力异常变化,可视为该地震的中期前兆信息;本文第一作者等也曾基于该流动重力异常变化在芦山7.0级地震前做过一定程度的中期预测,尤其是地点预测.本文的例子再次证明流动重力观测能较好地捕捉到强震孕育发生过程中,特别是该过程最后阶段的重力异常变化信息.因此,区域流动重力场观测对未来强震的中-长期预测,尤其是在发震地点的判定上具有优势. 相似文献
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通过对1992~2008年间各期观测资料进行全时空扫描,分析华北地区网区重力场的演化特征,总结震前异常的形态、持续时间和变化幅度,指出重力场空间变化易于发生地震的部位,并对一些问题进行讨论。结果显示:华北地区重力场总体变化不具明确规律性;大量测点存在明显的背景性趋势性异常变化;重力场变化与网区及周边地区中强地震的活动联系密切,较明显的重力场异常反应多发生在震前2年左右时间,且常伴有大面积高值异常区出现。重力变化"0"线、高梯度带、异常中心(含极值)附近是重力场空间变化易于发震的部位。 相似文献
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１９７５￣１９９１年间,广东河源市新丰江水库区发生了５次ＭＬ４．７￣５．１级地震。距震中１０ｋｍ以内的河源黄子洞地电台记录到了震前不同程度的地电阻率异常变化。采用距平法消除年变干扰后异常延续时间一般为３个月左右,电阻率异常下降幅度在１％左右。利用《指南》中的震兆异常信度分析法确认其异常信度后,利用模糊信息处理法对异常判定地震三要素进行了计算,结果与实际基本符合。 相似文献
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Based on the mobile gravity observation data in 2014-2016 in Guangxi and its adjacent areas, this paper systematically analyzed the changes of regional gravity field and its relation to the MS5.4 Cangwu, Guangxi earthquake on July 31, 2016, and combined with GPS observation data and seismic geological survey results, discussed the temporal and spatial distribution characteristics of the changes of regional gravity field and its mechanism. The results show that:(1) Before and after the MS5.4 Cangwu earthquake, the gravity anomaly changes near the earthquake area were closely related to the major faults in space, which reflects the crustal deformation and tectonic activities that caused the surface gravity change along the seismogenic fault in the period of 2014-2016; (2) The gravity changes near the epicenter before and after the MS5.4 Cangwu earthquake showed an evolution process in which the positive gravity anomaly zone changed to the negative gravity anomaly zone, a gravity gradient belt appeared along NNE direction and the earthquake occurred in its reverse change process; (3) The epicenter of the MS5.4 Cangwu earthquake located both near the gravity gradient belt and in the zero transition zone of the surface strain gradient and the edge of the high maximum shear strain rate area, the observational fact further proved that the dynamic image of gravitational field and deformation field have important instruction significance to the location prediction of strong earthquakes; (4) in recent years, the gravity dynamic change in northwestern Guangxi presented a four-quadrant distribution pattern, and there is the risk of generating earthquake of magnitude about 5 in the center of the quadrants. 相似文献