2018年5月6日称多5.3级地震序列重定位及发震构造分析     

李启雷  李玉丽  刘文邦 《地震地磁观测与研究》2019,40(3):1-6

采用双差定位法对2018年5月6日称多5.3级地震及其余震序列进行重新定位,至2018年7月15日共获取129个地震的重新定位结果。结果显示,称多5.3级地震序列主要呈NWW或NNW向分布,其中长轴沿NWW向展布,长约11 km,震源深度主要分布在6-12 km范围内,优势分布为8-11 km。此次地震的震源机制解为走滑型,最佳波形拟合深度为10.1 km。结合精定位、震源机制等综合分析,认为主破裂面走向呈NNW向,发震构造应为巴颜喀拉山主峰断裂。  相似文献   

STUDY ON RELATIONSHIP BETWEEN SEISMIC DISTRIBUTIONOF RUSHAN SEQUENCE AND VELOCITY STRUCTURE     

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 M_L3.8 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(M_L4.7)on January 7, 4.0(M_L4.5)on April 4, M3.6(M_L 4.1)on September 16 in 2014 and M4.6(M_L5.0)on May 22, 2015. The earthquake of M_L5.0 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 M_L ≥ 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   

龙门山断裂带最新地震活动特征及其意义   总被引：1，自引：0，他引：1       下载免费PDF全文

刘小梅  吴晶  梁春涛  钱旗伟  杜培笑 《地球物理学报》2019,62(4):1312-1322

综合最新布设的龙门山断裂带地震空段台阵(LmsSGA)与四川省地震局固定地震台网数据,对龙门山断裂带新近一年(2016年11月21日到2017年10月28日)的23479个地震事件开展双差定位工作,共获取包括汶川地震余震和芦山地震余震在内的6111个重定位地震事件.在此基础上,分别与汶川地震和芦山地震的早期余震空间分布特征进行比较.研究发现在汶川地震发生近十年后,其余震活动依旧活跃.汶川地震现今余震活动主要分布在10~25km的深度区间,震源深度呈现西南段较东北段偏深的特征.此外,汶川近年余震分布相比早期余震偏深,破裂带西南段的余震活动有向深部迁移的趋势.对于芦山地震,其近期余震活动较弱,余震主要分布在10~15km的深度区间,比早期余震的分布区间偏浅.龙门山断裂带最新余震活动分布特征表明,余震活动随着时间的推移有迁移的现象.考虑到距离主震事件已分别有5~10年的流逝时间,余震迁移现象可能由以流体扩散方式为主的准静态应力机制触发.  相似文献   

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魏贵春  陈俊华  廖武林  张文娟 《大地测量与地球动力学》2009,29(6):56-59

???????λ?????????????????ML3.8???????и?????????????????λ?????113?ε???λ????????????????????м??з????????ML3.8??????????????????????????????7km?????????о????????????????λ????λ????????????????С?в???????????з?????????????棬??????????λ????н???????  相似文献   

2019年6月17日四川长宁Ms6.0地震震源区三维速度结构   总被引：1，自引：0，他引：1       下载免费PDF全文

孙权  裴顺平  苏金蓉  刘雁冰  薛晓添  李佳蔚  李磊  左洪 《地球物理学报》2021,64(1):36-53

四川盆地南部地区自2015年以来地震活动性持续增长,并相继发生了数次M5.0及以上的中强地震.2019年6月17日的长宁Ms6.0地震则是其中震级最大的一次强震,且震后相继发生了一系列M5.0及以上的中强地震,给当地的生命和财产安全造成了极大危害.研究此次大震的地下结构和发震机制有助于理解该区地震异常活跃的机理,并为今...  相似文献   

东昆仑断裂玛沁-玛曲段断层结构和应力场特征研究     

周琳  李君  张佩  靳源 《大地测量与地球动力学》2021,41(1):62-66

为研究东昆仑断裂玛沁-玛曲段的活动特征,利用双差定位法对东昆仑断裂玛沁-玛曲段2009-01～2018-09中小地震进行重新定位,并基于CAP(cut and paste)方法反演研究区域3.5级以上地震的震源机制解.结果显示,地震活动沿断裂带分段特征明显,在101°E附近地震沿阿万仓断裂分布,近10 a来玛沁至若尔盖...  相似文献   

唐山及邻区双差层析成像研究          下载免费PDF全文

郭蕾  张素欣  王宁  周依 《地震工程学报》2021,43(2):287-295

收集唐山及邻区2010—2018年76个固定地震台站的震相数据,采用双差层析成像的方法,联合反演了唐山及其邻区中上地壳的震源位置和P波三维速度结构。结果表明:在浅层研究区P波速度的变化特征与地表地质构造和活动断裂的展布具有较好的一致性。唐山断裂两侧速度差异明显,其附近P波速度结构横向不均性显著;中地壳存在明显的低速异常,推测可能与幔源物质侵入有关。重新定位后震中位置更加集中,M_L3.0以上地震主要位于P波高、低速变化较强烈的区域。  相似文献   

晋冀豫交界地区地壳三维速度结构与地震分布特征          下载免费PDF全文

刘巧霞  徐志萍  邱勇  段永红  姜磊  莘海亮  赵延娜  贾宇鹏  张丹 《地震工程学报》2021,43(6):1251-1262,1279

利用区域双差层析成像方法,基于2008年10月—2018年6月近震资料,对晋冀豫交界地区记录到的地震事件进行震源位置与P波、S波三维速度结构的联合反演。重新定位后,地震空间位置得到明显改善,浅部的速度结构与地形及沉积层厚度对应较好,研究区内控制性断裂和地震多分布在太行山隆起区的高、低速变化梯级带上。对比分析研究区内不同构造单元及同一构造单元不同深度的P、S波速度异常特征及其与中小地震和历史强震的分布关系,结合研究区内历史强震和现今中、小震分析发震构造及深部孕震环境,为该区未来强震危险区判定提供科学依据。  相似文献   

2017年3月渤海地震序列微震检测与发震构造分析     

马婷  邓莉  王晓山  宋程  谭毅培 《中国地震》2021,37(2):415-429

地震序列发震构造研究是区域地震活动性和地震危险性分析的重要基础。2017年3月渤海海域发生地震序列活动,该序列发生在郯城-庐江断裂带与张家口-渤海地震带的交汇部位,区域构造较为复杂。然而在渤海海域,连续运行的固定地震监测仪器难以布设,导致地震监测能力相对较弱。本文首先采用模板匹配方法对序列遗漏地震进行检测,再使用波形互相关震相检测进行震相校正,基于校正后的震相到时数据对序列进行精定位,并计算序列中2次最大地震的震源机制解。通过计算共检测到目录遗漏地震32个,约为台网目录中地震数量的1.8倍。根据波形互相关聚类分析发现渤海地震序列可分为2组,一组为M_L4.4地震及其余震序列,一组为最大震级M_L3.5的震群,另有一个M_L1.6地震与其他地震波形相似度较低,可能为一个孤立的地震事件。精定位和震源机制结果显示,2组地震均为NE走向,M_L4.4地震发生在低倾角正断层,M_L3.5地震发生在高倾角走滑断层。最后结合区域地质构造相关研究成果,认为M_L4.4地震及其余震序列发震构造为渤中凹陷内NE向低倾角的伸展性正断层,M_L3.5震群发震构造为NE向倾角较陡的次级走滑断层。  相似文献   

基于手机信令数据的深圳市二元居住空间迁居模式研究     

易行  仝德  吴雅莹  沈月  储君  吕婷苗 《地理研究》2023,42(1):137-155

迁居是城市空间重构的基础动力,了解其行为机制对改善住房结构、优化空间组织具有重要意义,然而目前针对大城市内部、正规与非正规二元居住空间并存的迁居研究仍较薄弱。本文基于生命历程理论与家庭迁居理论,利用2018年12月至2019年12月的手机信令等多源数据,识别深圳市二元居住空间分布和迁居流样本,从迁居流特征、邻里属性和二元空间类型三方面选取指标开展基于主成分分析的K-means聚类,探究迁居模式、结构特性与形成原因。结果表明：(1)非正规内部、正规与非正规交互、正规内部三层次迁居类型间存在年龄和居住质量递增的趋势,但均呈现通勤导向;(2)二元迁居的主体是短距离迁移,形成了4个大规模迁居网络集群,总体方向表现出郊区化趋势;(3)迁居模式可聚类为社区型、改善型、家庭型、事业型4类,结合二元空间分异影响呈现出8亚类,不同类型迁居群体属性和动因存在显著差别,总体反映出人们在不同生命历程下的迁居过程。最后,文章针对不同迁居模式提出差异化空间治理政策建议。  相似文献