共查询到20条相似文献，搜索用时 125 毫秒
1.
2.
1999年11月29日的岫岩5.4级地震,发生在一直被列为年度重点地震危险区的北侧,此次地震是1979年以来该区发生的最大、具有前震性质的震群型地震。5.4级地震的发生,是该区地震危险程度的缓解,还是标志着地震危险性继续增强,或者说是标志着该区地震活动将进入一个新的阶段?本文选取渤海、北黄海及附近地区(36°～41°N,119°～124.5°E)为研究区,以中国地震局分析预报中心编制的中国地震目录和日报目录以历史地震目录为基础资料(中国地震简目汇编组,1988),对上述几个问题进行研究。1 与渤海、黄海及附近地区地震趋势关系1.1 历史地震活动时… 相似文献
3.
海域活动断裂探测和古地震研究 总被引：8，自引：0，他引：8
我国地震活动强烈 ,不仅在陆域的不同地震区带内有强烈的地震活动 ,而且在不同海域也有强震发生 ,如在渤海、南黄海、台湾海峡和北部湾等海区均发生过多次 6～ 7 级地震 ,有的海域地震的重复性很高 ,如渤海及邻近海域自公元 1 54 8年以来已先后发生过 4次 7级以上地震 ,南黄海在最近 50 0年内已发生过 1 0次以上 6～ 7级地震 ,台湾海峡在 1 7世纪和2 0世纪先后发生过多次 7级以上地震。近 40年来 ,我国对陆域活动构造和地震构造的调查和研究取得了很大进展 ,尤其是最近 2 0年来 ,由于定量活动构造学的发展 ,对陆域大地震发生的构造条件及… 相似文献
4.
5.
1991年11月5日在江苏射阳发生了4．7级地震，1992年1月23日在南黄海北部发生了5．3级地震，10月22日射阳东海域发生了4．8级地震，11月4日南黄海北部发生了4．6级地震，对上述4次地震笔者等曾作出了一定程度的年度中期预报。本文对该地震震前的预报概况，预报基本思路和主要科学依据作了概述，并讨论了给予的启示。认为在一定条件下对某些地震作出某种程度的科学预报还是可能的。 相似文献
6.
长江中下游—南黄海地震带地震活动趋势分析 总被引：6，自引：0，他引：6
对长江中下游－南黄海地震带地震活跃期,幕划分及其发展趋势进行了研究,对江苏及其邻区今后几年地地震在形势及重点危险区进行了判定,分析认为：长南带从１９７１年以来进入第二活跃期的第３幕,该幕地质活动将持续到２０１０年前后,最高活动水平为６．５级左右,今后几年江苏东部至南黄海海域发生５－６级或６级以上地震的可能性较大。 相似文献
7.
小金6.6级地震发生在鲜水河断裂带与龙门山断裂带之间一个地震活动水平较低的地区.根据该地区近10多年来中小地震活动的频度～震级统计关系,计算得到这一地区7级地震复发周期为435～523年;6级为58～69年;5级为10.1～11.7年.对该区及附近地震活动分析表明,小金地震前6年左右震中附近出现4级背景性地震空区;1989年3月1日小金5.0级地震为空区内逼近地震。小金地震前1年多四川西部曾出现背景性地震条带;震中附近曾出现弱震空区。b 值的时空扫描显示这次地震前2年多附近地区 b 值存在一个由高值到低值的变化过程.对周围4°×4°范围2.5级以上地震活动归一化熵计算结果,断层面总面积熵有下降异常,反映地震时间间隔及单位面积地震频度的熵无变化. 相似文献
8.
9.
通过对黄海北部海域近几年来地震空间活动特征和幕式活动特征的分析讨论,认为该区域大震前小震空间活动征兆明显;此区域仍然处于高应力水平,存在发生Ms≥5．0级地震的可能。 相似文献
10.
江淮地震区的地震活动性研究 总被引：3，自引：0，他引：3
江淮地震区是以５－６级地震为主的中强地震活动区,其地震活动存在百年尺度和数十年尺准周期性,中强地震活动存在东移和逆时针迁移二种运动,１９９０年以来本区与华北及华南地区的交界带地震活跃。根据以上分析贝斯估计、地震复发的条件概率预测、下世纪初可能发生６级左右地震,位置估计在本区东部的南黄海海域,苏、皖交界也有发生中等以上地震的可能。 相似文献
11.
本文对辽东半岛南部及东侧海域的地震活动背景及特征作了分析。研究结果表明未来该区周围有发生中强地震的危险性。该区位于华北强震二维破裂网格分布的结构点附近、中强地震带空段的交汇部位;发生在1988年辽宁及其邻区有两条4级地震条带在其附近交汇;本区还存在着地震活动空区、空带和低b值异常;全国地震综合预报专家系统和综合模式识别两种方法确定该区为全国Ⅱ类地震危险区;极值分析结果也表明该区周围处于缺震状态,5—6级地震具有较高的发震概率。 相似文献
12.
渤海海域地震震源深度的分布特征 总被引：3，自引：1，他引：2
震源深度的研究对于探索地震孕育和发生的深部环境,地震能量集结、释放的活动构造背景,以及地壳内部构造变形及其力学属性等都有非常重要的意义。本文选择渤海海域内观测精度相对较高的地震资料作为样本,统计分析了不同震级档、不同空间范围的震源深度分布特征,并初步探讨了震源深度与地震构造、地壳结构的关系。结果表明,渤海海域内中小震的震源深度在空间上的分布是不均匀的,发生在渤中断陷内的地震,其震源深度一般较深;而发生在山东半岛北部沿海与辽东半岛沿海的地震,其震级较低且震源一般较浅。但总体上,渤海海域内的地震多发生在10-20km的地壳中、上部,属浅源地震。 相似文献
13.
14.
在确定潜在震源区中如何应用地震和地质资料是编制中国地震烈度区划图(1990)的关键问题,包括如何利用地震和地质资料来勾划地震带和潜在震源区的范围和方向,以及确定本底地震和潜在震源区的震级上限 相似文献
15.
QU Jun-hao WANG Chang-zai LIU Fang-bin ZHOU Shao-hui ZHENG Jian-chang LI Xin-feng ZHANG Qin 《地震地质》2019,41(1):99-118
Since the earthquake of ML3.8 occurring on October 1, 2013 in Ruishan, Weihai City, Shandong Province, the sequence has lasted for about 4 years(Aug. 31, 2017). Seismicity is enhanced or weakened and fluctuated continuously. More than 13250 aftershocks have been recorded in Shandong Seismic Network. During this period, the significant earthquake events were magnitude 4.2(ML4.7)on January 7, 4.0(ML4.5)on April 4, M3.6(ML 4.1)on September 16 in 2014 and M4.6(ML5.0)on May 22, 2015. The earthquake of ML5.0 was the largest one in the Rushan sequence so far. In order to strengthen the monitoring of aftershocks, 18 temporary stations were set up near the epicenter at the end of April, 2014(official recording began on May 7)by Shandong Earthquake Agency, which constitutes an intensified network in Rushan that surrounds the four quadrants of the small earthquake concentration area together with 12 fixed stations nearby, and provides an effective data foundation for the refinement of Rushan earthquake sequence.
The velocity structure offers important information related to earthquake location and the focal medium, providing an important basis for understanding the background and mechanism of the earthquake. In this paper, double-difference tomography method is used to relocate the seismic events recorded by more than six stations of Rushan array from May 7, 2014 to December 31, 2016, and the inversion on the P-wave velocity structure of the focal area is conducted. The Hyposat positioning method is used to relocate the absolute position. Only the stations with the first wave arrival time less than 0.1 second are involved in the location. A total of 14165 seismic records are obtained, which is much larger than that recorded by Shandong Seismic Network during the same period with 7708 earthquakes and 2048 localizable ones. A total of 1410 earthquakes with ML ≥ 1.0 were selected to participate in the inversion. Precise relocation of 1376 earthquakes is obtained by using double-difference tomography, in which, there are 14318 absolute traveltime P waves and 63162 relative travel time P waves. The epicenters are located in distribution along NWW-SEE toward SEE and tend to WS, forming a seismic belt with the length about 3km and width about 1km. The focal depths are mainly concentrated between 4km and 9km, occurring mainly at the edge of the high velocity body, and gradually dispersing with time. It has obvious temporal and spatial cluster characteristics. Compared with the precise relocation of Shandong network, the accuracy of the positioning of Rushan array is higher. The main reason is that the epicenter of Rushan earthquake swarm is near the seaside, and the fixed stations of Shandong Seismic Network are located on the one side of the epicenter. The nearest three stations(RSH, HAY, WED)from the epicenter are Rushan station with epicentral distance about 13km, the Haiyang station with epicentral distance about 33km, and Wendeng station with epicentral distance about 42km. The epicentral distance of the rest stations are more than 75km. In addition, the magnitude of most earthquakes in Rushan sequence is small. The accuracy of phase identification is relatively limited due to the slightly larger epicentral distance of the station HAY and station WED in Shandong Seismic Network. Furthermore, the one-dimensional velocity model used in network location is simple with only the depth and velocity of Moho surface and Conrad surface. The epicentral distances of the 18 temporary stations in Rushan are less than 10km, and the initial phase is clear. The island station set up on the southeast side and the Haiyangsuo station on the southwest side form a comprehensive package for the epicenter. Compared with the double-difference algorithm method, the double-difference tomography method used in this paper is more accurate for the velocity structure, thus can obtain the optimal relocation result and velocity structure.
the velocity structure shows that there are three distinct regions with different velocities in the vicinity of the focal area. The earthquakes mainly occur in the intersection of the three regions and on the side of the high velocity body. With the increase of depth, P wave velocity increases gradually and there are two distinct velocity changes. The aftershock activities basically occur near the dividing line to the high velocity side. The south side is low velocity abnormal body and the north side is high velocity abnormal body. High velocity body becomes shallower from south to north, which coincides with the tectonic conditions of Rushan. Considering the spatial relationships between the epicenter distribution and the high-low velocity body and different lithology of geological structure, and other factors, it is inferred that the location of the epicenter should be the boundary of two different rock bodies, and there may be a hidden fault in the transition zone between high velocity abnormal body and low velocity abnormal body. The interface position of the high-low velocity body, the concentrating area of the aftershocks, is often the stress concentration zone, the medium is relatively weak, and the intensity is low. There is almost no earthquake in the high velocity abnormal body, and the energy accumulated in the high velocity body is released at the peripheral positions. It can be seen that the existence of the high-low velocity body has a certain control effect on the distribution of the aftershocks. 相似文献
16.
徐州是我国震害预测试点城市之一。影响城市震害的主要因素是城市所处的地质背景——地质因素和城市现状——社会因素。本文以现场调查资料为基础,以宏观震害经验为依据,考虑建筑物结构类型、建筑质量、建筑密度、人口、空旷场地、道路和危险工业等社会因素,运用多因素易损性(vulnerabiliy)分析法,完成了徐州市社会因素地震易损性分析,指出了该市抗震的薄弱环节和薄弱地区,为抗震防灾提供了依据。 地震易损性分析的结果是地震易损性分析图,总的易损性指数M是编制易损性分析图的依据。在总的易损性指数M中,建筑物易损性指数b占60—70%,其为建筑物易损性趋势矩阵A乘以建筑物组成矩阵B的转置阵矩阵BT所得矩阵C的迹。 相似文献
17.
使用皎口、海城、陡和、浑源等地震序列的地震波记录，研究了拐角频率随地震序列进程的变化特征。为了消除地震震级对拐角频率趋势性变化的影响，求得了每个地震的拐角频率与序列中同震级地震拐角频率的比值随地震序列发展而变化的曲线，较好地反映出该比值的发展进程；即在一个前一主一余地震序列中，同震级前震拐角频率高于余震拐角频率；而对震群地震序列则看不出这种变化。利用地震序列外围地区适当范围小震资料的拐角频率作为背景值，其比值曲线同样很好地反映出地震序列发展的规律。本方法可以作为对地震序列发展趋势进行较客观评估的新方法。 相似文献
18.
中国地震局地壳应力研究所科学技术处 《震灾防御技术》2006,1(3):283-284
2006年7月4日11时56分在河北省文安县(东经116.3°、北纬38.9°)发生5.1级地震,北京市、天津市、河北和山西均有震感。本文作者在地震现场调查的基础上,对比分析了我国其他大陆地区5级左右地震的人员伤亡和震害情况,探讨了此次地震未造成人员伤亡和较大损失的原因。 相似文献
19.
20.
1999年 1 1月 2 5日澄江发生 5.2级地震 ,2个月后的 2 0 0 0年 1月 2 7日在相邻的丘北 -弥勒地区发生了 5.5级地震 .分析了丘北—弥勒 5.5级地震的区域地震活动背景、地震孕育过程和地震活动性异常特征 ,为探讨在一次中强地震后如何预报后续地震提供了一个震例 . 相似文献