On the relation of moderate-short term anomaly of earth resistivity to earthquake

IntroductionMany anomalies due to earthquake have been recorded in observation of earth-resistivity for30 years and over, which showed that there objectively existed the anomalies of each-resistivity.The crustal strUcture and medium conditions are quite complex, so the complexity of the temporal,spatial and intensive development of the anomalies is inevitable. Both of time and amplitUde ofanomalies among some stations near an epicenter are different (even among different observational directi…     

Hierarchical properties of a stress field and its relation to fault displacements

The structure of the stress field is studied around a frictional shear fault on the basis of a theoretical solution. The hierarchical properties of tectonic stress fields are discussed. A method is proposed for the separation of fields of different ranks. It is shown that displacements of sides are dependent on the fault-plane orientation in the initial stress field and the type of that field; and on the coefficient of friction. These displacements are the greatest on planes that make angles below 45° with the compression axis of the initial field.     

A possible change in stress field orientation due to the 1976 Tangshan earthquake

Two techniques are used to study the stress field in the Tangshan region. First, the mean directions of principal stress axes in three subregions of the Tangshan aftershock region are determined from 29 focal mechanism solutions. In doing so a slip-fitting technique is applied which determines the mean stress tensor by minimizing the angle between the observed slip direction on every fault plane and the calculated shear stress resolved onto the fault planes. Each of the two nodal planes of the focal mechanism solutions are alternately considered as a possible fault plane. Second, by making a grid search over all possible orientations of stress axes, the meanP,B andT axes in the Tangshan region, both before and after the Tangshan mainshock, are found on the basis of firstP-wave polarity readings from a number of small earthquakes. The results indicate that there is a possible azimuthal change of the principal stress axes in the focal region due to the occurrence of the mainshock.     

利用小震分布和区域应力场确定磁县1830年7.5级强震断层面参数

对邯郸地震台网1984-2008年记录的磁县小地震,作双差定位,然后根据定位结果,对磁县历史强震断层参数作反演计算,求解磁县历史强震断层走向、倾角等特征参数,根据当地应力场来估算磁县历史强震断层的滑动角.     

Short-term and imminent anomalies of earthquake of load and unload response ratio of the well level to earth tides

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汶川8.0级地震前发震断裂带地震活动特征研究

设定两个不同研究区域,分别就汶川8.0级地震前地震活动特征进行研究,得出以下结论：①至少在2008年5月11日之前的38年时间中,龙门山断裂带中段出现M5.0以上地震空段,汶川巨大地震就发生在这一空段;②第一研究区域强震释放能量出现阶段性梯次减少现象;③至2008年初,估算出第一研究区域地应力积累量已达5.0136×1016J,相当于一次M7.9强震所能释放的能量;④第二研究区域中小地震在龙门山断裂带中段的南端形成了几乎垂直相交的两条地震带,小震活动明显增多.     

川滇地区长波辐射场变化与地震活动关系研究

2007年6月3日宁洱6.3级地震发生之前, 在川滇地区(20°～35°N, 95°～110°E)出现了一次显著的OLR短期和临震的异常增强现象。 对该区多年来OLR场的连续变化分析表明, 这种增强现象在强震多发年与平静年有明显的差异, 其中在地震多发年OLR数值场不仅为正距平, 而且震前短期大多增强幅度大; 而在地震平静年OLR数值场变化则多为负距平且波动小。 上述结果对今后应用卫星遥感长波辐射信息跟踪监视和预测强震有启示性意义。     

引起大地电场变化的一些因素

对河北省4个电场台站3年多的大地电场资料进行了全面的分析、整理,总结出引起大地电场变化的一些因素,这对我们认识资料有所帮助。对分析和利用大地电场资料有一定意义。     

The pattern characteristics of the tendency variations of earth resistivity and its relation to earthquakes

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利辛ML4．6地震与蒙城地电阻率变化特征

以消除年变化等短周期变化后的数据做为当月正常值,利用实测的月均值与正常值之比即月干扰比率、偏差等指标,突出反映月观测值在当月受到综合干扰因素影响的大小。从而突出地震前短临地电阻率异常。     

不同测向地电阻率测值及映震能力初探

对南京地震台、新沂地震台和郫县地震台地电阻率观测资料变化特征及邻区4次MS 5．0以上地震反应进行研究,发现：同一台站、不同测向地电阻率的测值大小可能存在较大差异,测值大的测道地电阻率年变化较规则,往往具有更强的映震能力。     

东昆仑断裂滑动速率变化及其对2017年九寨沟地震的应力加载

为了解东昆仑断裂活动对2017年8月8日九寨沟M_S7.0地震的影响,本文选取1999-2007年、2013-2017年GPS速度场作为约束,基于块体-位错模型反演计算东昆仑断裂两个时间段的块体运动速率、断裂滑动速率和滑动亏损率,并进一步研究青藏高原东缘最大剪应变率场和九寨沟震区的震间库仑应力累积速率.结果显示,东昆仑断裂中西段左旋走滑速率较高,东段走滑速率较低,自西向东逐步递减,存在明显的梯度.在两个时间段,阿坝块体刚性运动的方向顺时针偏转0.2°,运动速率由12.22 mm·a^-1增大到15.96 mm·a^-1;东昆仑断裂左旋走滑速率升高,其中西段较为明显（升高约1.2±0.3 mm·a^-1）;东昆仑断裂东段闭锁深度和闭锁程度增加;2013-2017年,东昆仑断裂滑动引起的九寨沟震区库仑应力累积速率是1999-2007年的3倍,最大剪应变率也明显升高.因此本文认为：2008年汶川地震和2013年芦山地震后,龙门山断裂部分解锁,阿坝地块活动性增强,东昆仑断裂滑动速率增大,导致九寨沟震区库仑应力加载速率增加,加速了九寨沟地震的孕育过程.

     

ZD8仪地电阻率整点值短临异常研究

高精度的地电阻率测量其观测资料中有否短临地震前兆信息, 为此分析处理了宝坻台ZD8地电仪自1987年5月至2001年3月的地电阻率整点值观测资料, 分别对发生在宝坻台附近的中等地震和华北北部5级以上地震前该项资料的短临前兆变化的对应情况和异常形态特征进行了全面的分析研究, 结果表明该项资料的短临异常指标分别为0. 5%和1. 0%, 其预报效能的R值分别为0. 4和0. 373。     

山东及附近区域地震断层错动性质与地壳应力场特征

利用P、SH、SV波的初动及振幅比获得2001年4月至2012年8月山东及附近区域132次地震震源机制解,对该区域地震断层的错动性质及地壳应力场特征进行分析.结果表明,山东及附近区域地震断层错动的基本方向为北东向和北西向,错动方式以走向滑动为主,部分为斜向滑动.分区研究表明：聊考断裂带附近区域所受挤压作用相对较强,逆断型地震破裂较多;胶东半岛及北侧海域所受拉张作用略占优势,逆断型地震破裂较少;沂沭断裂带南部附近区域逆断型与正断型的地震破裂所占比例差别不大.     

Bayesian analysis on earthquake magnitude related to an active fault in Taiwan

It is understood that sample size could be an issue in earthquake statistical studies, causing the best estimate being too deterministic or less representative derived from limited statistics from observation. Like many Bayesian analyses and estimates, this study shows another novel application of the Bayesian approach to earthquake engineering, using prior data to help compensate the limited observation for the target problem to estimate the magnitude of the recurring Meishan earthquake in central Taiwan. With the Bayesian algorithms developed, the Bayesian analysis suggests that the next major event induced by the Meishan fault in central Taiwan should be in M_w 6.44±0.33, based on one magnitude observation of M_w 6.4 from the last event, along with the prior data including fault length of 14 km, rupture width of 15 km, rupture area of 216 km², average displacement of 0.7 m, slip rate of 6 mm/yr, and five earthquake empirical models.     

昆仑山口西8.1级地震前库尔勒测区相对应力场变化

2001年昆仑山口西MS8.1地震震前,库尔勒台站钻孔应变仪记录到了特大应变变化,经多次异常落实、实地调查并进行了多次论证,确认异常是可靠的。根据库尔勒台记录资料计算了相对应力场并对其进行了分析、讨论。结果表明,昆仑山口西MS8.1地震前主应力方向出现偏转变化,最大偏转量达83°。主应力值变化达1400kPa,剪应力增大了523kPa。研究了相对应力场的基本特点,并讨论了有关问题。     

广州地区活动断裂的特征及其与工程抗震的关系

根据第四纪地质、地球化学、地壳形变和地震活动资料,论述了晚第四纪广州地区主要断裂的活动特征。认晚更新世以来,广从断裂、清泉街断裂、瘦狗岭断裂和文冲断裂发生过拉张式活动,但活动较弱,对工程地震未构成较严重危害,但在这些断裂所通过的地了在砂土液化、淤泥塌陷等潜在地质灾害。     

The seismicity and tectonic stress field characteristics of the Longmenshan fault zone before the Wenchuan M_S8.0 earthquake

The seismicity of Longmenshan fault zone and its vicinities before the 12 May 2008 Wenchuan MS8.0 earthquake is studied.Based on the digital seismic waveform data observed from regional seismic networks and mobile stations, the focal mechanism solutions are determined.Our analysis results show that the seismicities of Longmenshan fault zone before the 12 May 2008 Wenchuan earthquake were in stable state.No obvious phenomena of seismic activity intensifying appeared.According to focal mechanism solutions of ...     

华北地区成组地震前后的地电阻率异常特征

分析了自有地电阻率观测资料以来华北地区发生的三次成组地震前后的异常特征,其中包括1976年唐山地震组、1989年大同地震组和1998年张北地震组.结果发现(1)成组地震的地电阻率异常持续时间都比较长,主震发生后异常一般会继续下降或维持低值异常不恢复,整个成组地震的趋势背景非常清楚;(2)主震前异常台站范围比较广,异常台站数目比较多,后续地震的异常多集中在震源区;(3)成组地震结束后,异常一般都很快恢复.最后探讨了成组地震的地电阻率异常发展特征与孕震机理的关系.