共查询到20条相似文献，搜索用时 156 毫秒
1.
本文根据某些调查和实验观察资料,对震前动物行为异常的地区分布与某些其他可能性短临前兆的关系进行了分析研究。结果表明,震前动物异常不仅主要集中分布在沿未来地震的发震构造和某些活动断裂的条带区和极震区或高烈度区,而且与这些地区的地质条件有关。同时,前震和某些其他前兆(声发射、地气、地下水组分、电场等)的临震变化在这些地区也较为集中,即这些可能性短临前兆因素构成了激起震前动物行为异常的地球物理背景。这些结果有助于揭示动物异常与其他前兆因素的关系,并可为判断动物异常与未来地震的关系和合理选择动物观察点提供一定的依据。 相似文献
2.
3.
通过强震震例阐述了重力观测在地震预测中的作用,分析了强震震间期与同震及震后重力场变化特征、区域重力场变化及其与强震活动的关系。强震前区域重力场出现大范围的有序性变化,震源区附近产生与地震孕育发生有关的局部重力异常区,并沿区域主要发震构造断裂带出现显著的重力变化梯度带;强震一般发生在重力变化高梯度带转弯附近或重力变化四象限分布特征中心附近;重力场动态变化图像能够较清晰地反映强震孕育、发展、调整过程的重力变化信息,并基于震例提出了强震震前重力变化的“场-源-带”基本模式。最后,提出我国重力监测预报发展中仍存在的问题,并对利用重力监测资料开展地震预测预报研究进行了展望。 相似文献
4.
5.
利用甘肃岷县漳县6.6级地震区所在的青藏块体东北缘地区的区域水准、GPS、流动重力和跨断层短测线等地形变监测资料,结合地质构造、动力环境和已往的研究结果,分析了不同类型资料反映的震前区域性地壳变形背景、断层形变异常特征和可能的机理.结果认为：（1）岷县漳县6.6级地震前西秦岭、六盘山等构造区不同程度地存在着GPS水平挤压闭锁高应变积累、垂直隆升异常高梯度带和重力升、降差异剧烈变化等中长期背景;（2）震前到震时发震断裂附近及其外围相关构造区域断层形变异常在空间和时间上的起伏波动变化显著,尤其是汶川地震以来的波动变化在一定程度上反映了与本区构造比邻的龙门山断裂带剧烈右旋错动对本区的影响,与本次岷县6.6级地震过程有关;（3）本区有地形变监测资料积累以来缺乏6级以上震例,虽然存在不同程度的中长期形变背景异常,但何时进入短期-短临阶段确实很难把握,需要不断积累总结和探索提高. 相似文献
6.
泾阳4.8级地震前后重力变化探析 总被引：2，自引：0，他引：2
系统分析了泾阳Ms4．8地震前后陕西关中地区流动重力观测资料，探讨了重力场的时空变化及其映震特征。结果表明：①震前在震中区附近形成较显著地重力负异常区，且与沉降区基本吻合。②泾阳地震震中区既是重力变化梯度带，也是重力异常的正值区到负值区的过度带。③由于震源区应力作用方式是以水平为主的左旋走滑运动，震前局部重力异常不显著。 相似文献
7.
8.
对2012年3月9日新疆洛浦MS6.0地震前陆态网络GPS连续跟踪站数据与喀什—伽师2010年7月～2012年3月期间重力复测数据进行计算分析。结果表明：（1）断层两端运动速率不同,为应力积累创造条件;（2）地震发生前监测区出现区域性的重力异常变化高值区,区域重力场等值线与发震断裂走向平行;震前区域重力场出现增强—减弱—增强过程。 相似文献
9.
10.
11.
本文根据近十年来我国地声观测的某些结果, 分析了地声的时-空分布特点, 并估计了透入基岩面上和水面中的声压.同时与震前动物异常特点, 以及与人和某些动物的听觉和振动感受器的敏感阈值进行了比较.最后, 对唐山余震期间同时段内鱼和地声活动的观察结果, 进行了相关分析.其结果如下:1.地声和动物异常的时-空分布图式基本相似, 并可认为都是临震前兆.2.三级左右地震震中附近地区, 地声透入基岩面上和水面中的声压, 在150——250赫芝频段内, 分别为23——19分贝和90——86分贝.由此可见, 人耳是不可能感觉到的, 但是通常在地面上栖息的猫、狗、雉和穴居的鼠是可能觉察到的, 而骨鳔鱼类可能优先于这些陆生动物觉察到水中的地声信息.同时, 基岩面位移的垂直振幅约为10-7厘米.这虽比某些动物的振动感受器的阈振幅约低3个数量级.但可推测, 在强烈地震前的地面位移的垂直振幅可达到或超过微米量级.这就可能为这些动物的振动感受器觉察到.3.相距约20公里的鱼和地声活动观察点, 同期内的观察结果表明, 它们共同反映了同一地区内的唐山余震活动.同时, 鱼和地声活动的日频度序列之间具有一定的互相关性. 相似文献
12.
资料表明某些强地震前中小地震的地震非均匀度（GL值）参数在强地震孕育进入中期或短期阶段出现明显异常变化, 显示出区域中小地震活动状态发生变化. 本文通过对含有障碍体的平直断层、 挤压型雁列式断层及Ⅲ型剪切裂纹等3种类型的岩石样本变形破坏过程声发射事件时间序列的分析, 讨论了GL值变化的物理意义. 计算结果表明, 这3种标本变形破坏过程中, 在应力应变处于非弹性阶段前夕或在岩石整体破裂失稳前破裂成核期间, GL值出现持续大于１的异常变化. 表明GL值能较好地刻画受压岩石破坏前的应变的非弹性变化, 具有一定的标本破裂指示意义. 相似文献
13.
14.
本文在研究宝坻地声序列特点的基础上,进一步探讨了地声序列在短临预报中的应用和意义。结果表明,宝坻地声现场观测结果与地震活动性和岩石力学实验结果非常一致。 相似文献
15.
THE COMPREHENSIVE ANALYSIS AND RESEARCH OF RECENT GRAVITY AND CRUSTAL DEFORMATION IN NORTHEASTERN EDGE OF THE TIBETAN PLATEAU 
下载免费PDF全文
下载免费PDF全文 ZHU Yi-qing LIANG Wei-feng HAO Ming ZHAO Ling-qiang HAO Qing-hua ZHANG Guo-qing LIU Lian 《地震地质》2017,39(4):768-780
In this study, we systematically analyzed the relationship between regional gravity changes, 3D crustal deformation, regional tectonic environment and strong earthquakes based on the relative gravity measurements(2011-2014), GPS data and the background vertical deformation from the leveling measurements conducted from 1970 to 2011. Subsequently, we further characterized the temporal-spatial patterns and discussed the mechanism of regional gravity changes and the crustal deformation. The results can be summarized as follows:1)The regional gravity changes, the GPS-derived horizontal deformation and the vertical deformational obtained from leveling data showed a close spatial relationship:The gravity increased along with the direction of horizontal movement, and the gravity decreased with the crustal uplift and vice versa, which reflects the inherited characteristics of neotectonic activities. 2)The crustal deformation was closely related to the active faults. The contour lines of gravity changes and vertical deformation were generally along with the Qilian-Haiyuan Fault(the strike is NWW), and the crustal horizontal deformation showed left-lateral strike slip motion near the Qilian-Haiyuan Fault. 3)The strong earthquakes usually occur in the active faults where intensive gravity change and vertical and/or horizontal deformation occurred. The extrusion deformation, surface compression rate and gravity changes were obvious near the epicenter of 2016 Menyuan earthquake. The 2013 Minxian-Zhangxian MS6.6 earthquake occurred in the direction-turning area of intense gravity gradient zone and the transitional area of surface compression and vertical deformation. The first author of this paper has made a medium-term forecast before the Minxian and Menyuan earthquakes, especially the location of the earthquake. Based on the above understandings, we emphasized that:there are still possibilities of strong or huge earthquakes within medium-long term in the areas of crustal deformation anomalies in the study region. 相似文献
16.
Introduction The study of acoustic emission evidenced by rock fracture experiments is the most important field of seismology. By means of the rock fracture technique system, many researchers tried to prove the possible relationship between some parameters such as b value and the stress variation prior to rock fracture using the acoustic emission results from different types of rock fracture ex-periments (MA et al, 2004a, b; Lockner, 1993; JIANG and ZHANG, 1998). In order to investigate th… 相似文献
17.
对几种不同结构的岩石标本在变形过程中声发射b值和频谱随时间的变化特征进行了对比研究 ,其中包括完整花岗岩标本、含有天然愈合节理的花岗岩标本、含有拉张型和挤压型雁列式断层以及平直断层的标本等。研究表明 ,声发射b值和频谱的特征不仅会受标本结构的影响 ,而且在同一标本的不同变形阶段也可能表现出不同的特征 ,其机制与变形方式以破裂为主或以摩擦为主有关。当变形以破裂为主时 ,声发射b值和频谱在失稳前会出现明显的下降 ;当变形以摩擦为主时 ,声发射b值和频谱在失稳前变化相对较小 ,且上升或下降均可能出现。实验结果意味着b值和频谱特征作为失稳前兆 ,在不同的构造环境下可能会有不同的特征 ,而强震孕震区内不同断裂构造的存在会造成前兆时空分布的非均匀性 相似文献
18.
19.
STUDY ON DYNAMIC CHANGE OF GRAVITY FIELD IN XIANSHUIHE FAULT ZONE AND THEIR RELATION TO THE OCCURRENCE OF MS ≥ 5.0 EARTHQUAKES 下载免费PDF全文
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
20.
Acoustic Emission Experiments of Rock Failure Under Load Simulating the Hypocenter Condition 总被引：3，自引：0，他引：3
Hui-hui Zhang Xiang-chu Yin Nai-gang Liang Huai-zhong Yu Shi-yu Li Y. C. Wang C. Yin Victor Kukshenko Nikita Tomiline Surguei Elizarov 《Pure and Applied Geophysics》2006,163(11-12):2389-2406
A series of acoustic emission (AE) experiments of rock failure have been conducted under cyclic load in tri-axial stress tests. To simulate the hypocenter condition the specimens are loaded by the combined action of a constant stress, intended to simulate the tectonic loading, and a small sinusoidal disturbance stress, analogous to the Earth tide induced by the Sun and the Moon. Each acoustic emission signal can indicate the occurrence time, location and relative magnitude of the damage (micro-crack) in the specimen. The experimental results verified some precursors such as LURR (Load/Unload Response Ratio) and AER (Accelerating Energy Release) before macro-fracture of the samples. A new parameter, the correlation between the AE and the load, has been proposed to describe the loading history. On the eve of some strong earthquakes the correlation between the Benioff strain and the Coulomb failure stress (CFS) decreases, similar to the variation of LURR prior to strong earthquakes. 相似文献