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2008年5月12日四川汶川8.0级地震与部分余震的震源机制解 总被引：4，自引：0，他引：4
采用区域和远台Pn或Pg初至波初动符号, 利用下半球等面积投影, 求解了2008年5月12日四川汶川8.0级地震和截止到2008年12月10日发生的部分4级以上余震的震源机制解。 汶川8.0级地震的震源机制为: 节面Ⅰ的走向为5°, 倾角为48°, 滑动角为39°; 节面Ⅱ的走向为247°, 倾角为62°, 滑动角为131°。 P轴方位角为309°, 仰角为8°, T轴方位角为208°, 仰角为54 °, B轴方位角为44°, 仰角为35°。 结合地质构造和余震空间分布, 可以确定节面Ⅱ为发震断层面。 根据震源机制解, 引发本次地震的断层活动主要表现为逆冲, 主破裂面为S67°W与该地震所在断层的走向基本一致(断裂总体走向N45°E)[1]; 主压应力轴P轴为N51 °W, 主压应力轴P轴方位与该区域构造应力场方向基本一致。 根据余震震源机制解结果, 龙门山断裂带南段发生的余震与北段发生的余震的震源机制都具有优势分布, 且两者差异明显。 早期发生在南段的余震的破裂是以逆倾滑动为主, 兼有走向滑动; 而随着时间的推移, 余震向北段迁移, 在龙门山构造的北段地震震源的破裂方式以走向滑动为主, 兼有一定的逆倾滑动; 龙门构造带南段震源应力场受主震应力场的控制, 而龙门构造带北段震源应力场不仅受区域应力场的影响, 还受主震应力场的影响。 相似文献
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利用中国区域台网地震波形记录,采用CAP方法反演了香格里拉德钦(位于云南省)—得荣(属于四川省)2013年8月28日MS5.1、8月31日MS5.9地震及8次MS4余震的震源双力偶断层面解和震源质心深度.结合震区地质构造、余震分布、烈度分布、动力学背景等资料,分析了此次地震序列的震源机制和应力场特征.反演结果表明,此次地震序列为节面倾角倾斜的正断层型地震,发震断层为NWW向活动构造带.序列中最大地震MS5.9和次大地震MS5.1地震的破裂节面分别为走向299°、倾角53°、滑动角-73°;走向290°、倾角55°、滑动角-72°.震源区受到强烈的水平拉张力、垂直挤压力作用.MS5.9地震后续余震T、P轴方位角随时间变化强烈,表明MS5.9地震后震源区应力调整作用明显.震源区应力场反演结果显示,地震发生的构造带上最大主拉应力为NNE-SSW向,最大主压应力为NW-SE向,与GPS观测所反映的地表最大主应力分布方向基本一致,表明震源区的应力状态可能主要受到背景大尺度构造应力场的控制.此次地震序列填充了川滇地区震源机制及应力场的空间分布图像,1976年以来可靠的震源机制解资料表明香格里拉次级块体是川滇块体及周边区域显著的拉张作用区域.香格里拉次级块体和保山次级块体正断层地震的断层节面及震源应力轴分布的空间变化,与GPS观测反映的地表最大主拉应力分布较一致,其空间分布特征反映了在青藏高原物质挤出背景下,块体之间相互作用、地势差异等作用对构造活动的影响. 相似文献
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从IRIS全球数字地震台网长周期记录中, 选取震中距位于30deg;~90deg;的垂直向远震P波资料, 反演了2003年9月27日中、 俄、 蒙边界MS7.9地震及10月1日MS7.3强余震的地震矩张量解, 研究了MS7.9地震的时空破裂过程. 参考余震的空间分布及周围断层走向, 确定MS7.9地震发震断层走向127deg;、倾角为79deg;、滑动角为171deg;. MS7.9地震震源破裂过程反演结果表明,整个破裂过程持续了37 s,释放标量地震矩0.97times;1020 Nmiddot;m. 破裂主要发生在长110 km, 宽30 km的中地壳以上,最大位错3.6 m. 起始破裂处不是滑动量最大的地方. 断层面上显示出两个显著的、滑动量超过2.0 m的破裂区. 破裂传播至MS7.3震源区附近时, 滑动量迅速减小,显示出破裂传播过程的受阻停止, 反映了障碍体引起的破裂过程的不均匀性. 相似文献
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本文分别以地震破裂长度和余震区分布长度作为地震时断层的破裂长度,从而建立了我国东部、西部和全国范围内的震级与断层破裂长度以及断层破裂长度与震级之间的两种回归关系式,以供有关部门预报地震震级和评定场地影响烈度时参考。但在场地的地震危险性概率计算中,本文建议采用由余震区分布长度所确立的震级之间的关系式较为合适。 相似文献
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基于中国国家和四川区域数字地震台网记录,采用HypoDD方法精确定位了四川芦山ML2.0级以上地震序列的震源位置,采用CAP方法反演了36次ML4.0级以上地震的最佳双力偶震源机制解,并利用小震分布和区域应力场拟合了可能存在的发震断层面参数,从而综合分析了芦山地震序列的震源深度、震源机制和震源破裂面特征,探讨可能的发震构造.结果显示,7.0级主震的震源位置为30.30°N、102.97°E,初始破裂深度为15 km左右,震源矩心深度为14 km左右,最佳双力偶震源机制解的两组节面分别为走向209°/倾角46°/滑动角94°和走向23°/倾角44°/滑动角86°,可视为纯逆冲型地震破裂,绝大多数ML4.0级以上余震的震源机制也表现出与主震类似的逆冲破裂特征.ML2.0级以上余震序列发生在主震两侧,集中分布的长轴为30 km左右,震源深度主要集中在5～27 km,ML3.5级以上较大余震则集中分布在9～25 km的深度上,并揭示出发震断层倾向北西的特征.利用小震分布和区域应力场拟合得到发震断层参数为走向207°/倾角50°/滑动角92°,绝大多数余震发生在断层面附近10 km左右的区域.综合地震序列分布特征、主震震源深度和已有破裂过程研究结果,可以推测主震破裂过程自初始点沿断层的两侧扩展破裂,南侧破裂比北侧稍长,滑动量主要集中在初始破裂点附近,可能没有破裂到地表.综合本文研究成果、地震烈度分布和现有的科学考察结果,初步推测发震构造为龙门山山前断裂,也不排除主震震中东侧还存在一条未知的基底断裂发震的可能性. 相似文献
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2013年4月20日在四川省雅安市芦山县发生M7.0级地震.根据四川省台网资料和收集的国内外相关资料,我们分析了芦山地震的基本参数、余震分布、序列衰减等特征.结果表明:芦山地震位于龙门山断裂南段,其震源力学机制显示为纯逆冲性质,与龙门山断裂构造特征相符合;芦山地震的余震较丰富,震后15天震区已发生7800多次余震,其中,5级以上余震4次,最大余震是4月21日17时5分芦山、邛崃交界M5.4级地震;余震分布形成的图形显示其长轴走向与龙门山断裂构造走向一致,余震分布显示密集区长轴约40 km,短轴约20 km.与汶川M8.0级地震在震源力学机制、破裂过程、余震空间展布以及地表破裂等对比分析后表明:芦山地震与汶川地震的震源错动类型、破裂过程、地表破裂以及余震活动等特征存在明显差异;芦山地震与汶川地震震中位置相距90 km,两次地震的余震密集区相距50 km;汶川8.0级地震造成龙门山断裂中北段较充分破裂,芦山7.0级地震则展布于龙门山断裂南段且破裂尺度有限;两者有发震构造上的联系,但两次地震是相对独立的地震事件. 相似文献
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山西大同-阳高地震的震源机制及发震模式 总被引：2，自引：0，他引：2
根据全国地震台网的记录资料及前人对山西大同-阳高地震的研究结果，通过对大同-阳高地震震源机制及大同遥测地震台网的单（多）台小震综合断层面解的研究，结合当地地质构造条件，推断出大同-阳高地震的震源应力场及前震、主震、最大余震的发震断层。通过对大同-阳高地震中余震随时间分布、烈度等震线分布和构造裂缝的研究，给出了大同-阳高地震中几次主要地震的破裂方向、破裂长度等。 相似文献
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宁洱地震序列的震源机制解分析 总被引：1，自引：1，他引：0
利用云南数字地震台网资料得到宁洱地震序列的主震、5.1级强余震和52个余震震源机制解.分析表明,该地震序列的发震断裂呈NW走向,倾角陡立.在接近水平的近南北向压应力作用下,断裂具有右旋走滑的错动性质.主震、强余震和众多的余震都发生在同一发震断裂上.大量的余震震源机制解结果与主震一致,是地震序列的主要破裂类型,但还存在与主要类型不一致的倾向滑动类型,这可能与余震破裂起始点的微构造控制作用有关,但是它们呈水平向的应力轴与主震的主应力轴一致.NW向断层作右旋走向错动,滑动断层推挤的象限都是逆冲类型的余震,而拉张的象限都是正断层类型的地震.宁洱地震序列的震源机制和周围4次5级以上地震的震源机制相同,表明震源区应力场和区域应力场完全一致,宁洱地震的孕育和发生受区域应力场的控制. 相似文献
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基于首都圈数字地震台网的宽频带资料，首先采用CAP方法确定了永清MS4.3地震和廊坊MS3.0地震的震源机制解:永清地震节面Ⅰ的走向、倾角和滑动角分别为52°，62°和?140°，节面Ⅱ的走向、倾角和滑动角分别为300°，55°和?35°；廊坊地震节面I的走向、倾角和滑动角分别为48°，57°和?147°，节面Ⅱ的走向、倾角和滑动角分别为299°，63°和?38°。两次地震的震源机制解较为一致，推测它们可能具有相同的发震断层。利用近震转换波获得两次地震的震源深度，分别为19 km和13 km。利用双差法对两次地震的主余震进行重新定位，结果显示:两个地震序列的震中均呈NE向分布，余震震源深度均浅于主震震源深度，震源深度分别集中在17—20 km和12—13 km范围内，两个序列的短轴剖面揭示了震源分布均呈现倾向SE，倾角陡立的特点。将地震序列的分布与震源机制解的结果进行对比，认为两个序列的水平展布方向与其对应的主震震源机制解中节面Ⅰ的走向比较接近，深度分布的高倾角特征也与节面Ⅰ比较相似，因此认为发震断层面均为节面Ⅰ。通过将震源机制解中节面Ⅰ的参数和地震序列的分布与区域活动断层的产状性质进行比较，取得了一些关于发震构造和地震成因的重要认识:① 永清MS4.3地震和廊坊MS3.0地震的发震构造不是上地壳的先存正断裂?河西务断裂，不排除与中下地壳的新生构造或深大断裂有关；② 永清、廊坊地震发生在13—19 km深度上，结合地壳结构、断裂构造以及区域流变结构等资料，推测该深度范围可能是廊固凹陷的壳内脆性?韧性转换区域，是地震孕育和发生的有利构造部位。 相似文献
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STUDY ON THE SEISMOGENIC FAULT AND DYNAMICS PARAME-TERS OF THE 2014 MS6.6 JINGGU EARTHQUAKE IN YUNNAN 
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下载免费PDF全文 On October 17, 2014, a MS6.6 earthquake occurred in Jinggu, Yunnan. The epicenter was located in the western branch of Wuliang Mountain, the northwest extension line of Puwen Fault. There are 2 faults in the surrounding area, one is a sinistral strike-slip and the other is the dextral. Two faults have mutual intersection with conjugate joints property to form a checkerboard faulting structure. The structure of the area of the focal region is complex. The present-day tectonic movement is strong, and the aftershock distribution indicates the faulting surface trending NNW. There is no obvious surface rupture related to the known fault in the epicenter, and there is a certain distance from the surface of the Puwen fault zone. Regional seismic activity is strong. In 1941, there were two over magnitude 7.0 earthquakes in the south of the epicenter of Jinggu County and Mengzhe Town. In 1988, two mainshock-aftershock type earthquakes occurred in Canglan-Gengma Counties, the principal stress axes of the whole seismic area is in the direction of NNE. Geological method can be adopted to clarify the distribution of surficial fracture caused by active faults, and high-precision seismic positioning and spatial distribution characteristics of seismic sequences can contribute to understand deep seismogenic faults and geometric features. Thus, we can better analyze the three-dimensional spatial distribution characteristics of seismotectonics and the deep and shallow tectonic relationship. The focal mechanism reveals the property and faulting process to a certain extent, which can help us understand not only the active property of faults, but also the important basis for deep tectonic stress and seismogenic mechanism. In order to study the fault characteristic of the Jinggu earthquake, the stress field characteristics of the source area and the geometric parameters of the fault plane, this paper firstly uses the 15 days aftershock data of the Jingsuo MS6.6 earthquake, to precisely locate the main shock and aftershock sequences using double-difference location method. The results show that the aftershock sequences have clustering characteristics along the NW direction, with a depth mainly of 5~15km. Based on the precise location, calculations are made to the focal mechanisms of a total of 46 earthquakes including the main shock and aftershocks with ML ≥ 3.0 of the Jinggu earthquake. The double-couple(DC)component of the focal mechanism of the main shock shows that nodal plane Ⅰ:The strike is 239°, the dip 81°, and the rake -22°; nodal plane Ⅱ, the strike is 333°, the dip 68°, and the rake -170.31°. According to focal mechanism solutions, there are 42 earthquakes with a focal mechanism of strike-slip type, accounting for 91.3%. According to the distribution of the aftershock sequence, it can be inferred that the nodal plane Ⅱ is the seismogenic fault. The obtained focal mechanism is used to invert the stress field in the source region. The distribution of horizontal maximum principal stress orienation is concentrated. The main features of the regional tectonic stress field are under the NNE-SSW compression(P axis)and the NW-SE extension(T axis)and are also affected by NNW direction stress fields in the central region of Yunnan, which indicates that Jinggu earthquake fault, like Gengma earthquake, is a new NW-trending fault which is under domination of large-scale tectonic stress and effected by local tectonic stress environment. In order to define more accurately the occurrence of the fault plane of the Jinggu earthquake, with the precise location results and the stress field in the source region, the global optimal solution of the fault plane parameters and its error are obtained by using both global searching simulated annealing algorithm and local searching Gauss-Newton method. Since the parameters of the fault plane fitting process use the stress parameters obtained by the focal mechanism inversion, the data obtained by the fault plane fitting is more representative of the rupture plane, that is, the strike 332.75°, the dip 89.53°, and the rake -167.12°. The buried depth of the rupture plane is 2.746km, indicating that the source fault has not cut through the surface. Based on the stress field characteristics and the inversion results of the fault plane, it is preliminarily believed that the seismogenic structure of the Jinggu earthquake is a newly generated nearly vertical right-lateral strike-slip fault with normal component. The rupture plane length is about 17.2km, which does not extend to the Puwen fault zone. Jinggu earthquake occurred in Simao-Puer seismic region in the south of Sichuan-Yunnan plate. Its focal mechanism solution is similar to that of the three sub-events of the Gengma earthquake in November 1988. The seismogenic structure of both of them is NW-trending and the principal stress is NE-SW. The rupture plane of the Jinggu main shock(NW direction)is significantly different from the known near NS direction Lancang Fault and the near NE direction Jinggu Fault in the study area. It is preliminarily inferred that the seismogenic structure of this earthquake has a neogenetic feature. 相似文献
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Seismogenic mechanism of the Lancang and Gengma earthquakes 总被引：1，自引：0，他引：1
Ｓｅｉｓｍｏｇｅｎｉｃ ｍｅｃｈａｎｉｓｍ ｏｆ ｔｈｅ Ｌａｎｃａｎｇ ａｎｄ Ｇｅｎｇｍａ ｅａｒｔｈｑｕａｋｅｓ（俞维贤）（周瑞琦）（候学英）（周光全）ＳｅｉｓｍｏｇｅｎｉｃｍｅｃｈａｎｉｓｍｏｆｔｈｅＬａｎｃａｎｇａｎｄＧｅｎｇｍａｅａｒｔｈ... 相似文献
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STUDY ON SOURCE PARAMETERS OF THE 8 AUGUST 2017 M7.0 JIUZHAIGOU EARTHQUAKE AND ITS AFTERSHOCKS,NORTHERN SICHUAN 下载免费PDF全文
下载免费PDF全文 WU Wei-wei WEI Ya-ling LONG Feng LIANG Ming-jian CHEN Xue-fen SUN Wei ZHAO Jing 《地震地质》1979,42(2):492-512
On August 8, 2017, a strong earthquake of M7.0 occurred in Jiuzhaigou County, Aba Prefecture, northern Sichuan. The earthquake occurred on a branch fault at the southern end of the eastern section of the East Kunlun fault zone. In the northwest of the aftershock area is the Maqu-Maqin seismic gap, which is in a locking state under high stress. Destructive earthquakes are frequent along the southeast direction of the aftershocks area. In Songpan-Pingwu area, only 50~80km away from the Jiuzhaigou earthquake, two M7.2 earthquakes and one M6.7 earthquake occurred from August 16 to 23, 1976. Therefore, the Jiuzhaigou earthquake was an earthquake that occurred at the transition part between the historical earthquake fracture gap and the neotectonic active area. Compared with other M7.0 earthquakes, there are few moderate-strong aftershocks following this Jiuzhaigou earthquake, and the maximum magnitude of aftershocks is much smaller than the main shock. There is no surface rupture zone discovered corresponding to the M7.0 earthquake. In order to understand the feature of source structure and the tectonic environment of the source region, we calculate the parameters of the initial earthquake catalogue by Loc3D based on the digital waveform data recorded by Sichuan seismic network and seismic phase data collected by the China Earthquake Networks Center. Smaller events in the sequence are relocated using double-difference algorithm; source mechanism solutions and centroid depths of 29 earthquakes with ML≥3.4 are obtained by CAP method. Moreover, the source spectrum of 186 earthquakes with 2.0≤ML≤5.5 is restored and the spatial distribution of source stress drop along faults is obtained. According to the relocations and focal mechanism results, the Jiuzhaigou M7.0 earthquake is a high-angle left-lateral strike-slip event. The earthquake sequence mainly extends along the NW-SE direction, with the dominant focal depth of 4~18km. There are few shallow earthquakes and few earthquakes with depth greater than 20km. The relocation results show that the distribution of aftershocks is bounded by the M7.0 main shock, which shows obvious segmental characteristics in space, and the aftershock area is divided into NW segment and SE segment. The NW segment is about 16km long and 12km wide, with scattered and less earthquakes, the dominant focal depth is 4~12km, the source stress drop is large, and the type of focal mechanism is complicated. The SE segment is about 20km long and 8km wide, with concentrated earthquakes, the dominant depth is 4~12km, most moderate-strong earthquakes occurred in the depth between 11~14km. Aftershock activity extends eastward from the start point of the M7.0 main earthquake. The middle-late-stage aftershocks are released intensively on this segment, most of them are strike-slip earthquakes. The stress drop of the aftershock sequence gradually decreases with time. Principal stress axis distribution also shows segmentation characteristics. On the NW segment, the dominant azimuth of P axis is about 91.39°, the average elevation angle is about 20.80°, the dominant azimuth of T axis is NE-SW, and the average elevation angle is about 58.44°. On the SE segment, the dominant azimuth of P axis is about 103.66°, the average elevation angle is about 19.03°, the dominant azimuth of T axis is NNE-SSW, and the average elevation angle is about 15.44°. According to the fault profile inferred from the focal mechanism solution, the main controlling structure in the source area is in NW-SE direction, which may be a concealed fault or the north extension of Huya Fault. The northwest end of the fault is limited to the horsetail structure at the east end of the East Kunlun Fault, and the SE extension requires clear seismic geological evidence. The dip angle of the NW segment of the seismogenic fault is about 65°, which may be a reverse fault striking NNW and dipping NE. According to the basic characteristics of inverse fault ruptures, the rupture often extends short along the strike, the rupture length is often disproportionate to the magnitude of the earthquake, and it is not easy to form a rupture zone on the surface. The dip angle of the SE segment of the seismogenic fault is about 82°, which may be a strike-slip fault that strikes NW and dips SW. The fault plane solution shows significant change on the north and south sides of the main earthquake, and turns gradually from compressional thrust to strike-slip movement, with a certain degree of rotation. 相似文献
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利用双差定位方法对2018年松原MS5.7地震序列中ML≥1.0地震重新定位，之后使用CAP方法求解松原MS5.7地震序列中强地震的震源机制解，再借助MSATSI软件包反演得到松原地区的区域应力场。综合分析以上研究结果得到如下结论:① 松原MS5.7地震序列发生在NW走向的第二松花江断裂与NE走向的扶余—肇东断裂交会处，将地震精定位结果沿两条断层走向作剖面分析，NW向剖面主轴长度约为5 km，震中分布均匀，NE向剖面主轴长度亦约为5 km，震中呈倾向NE的高倾角分布；② 该序列中的4次ML≥3.7地震的震源机制解具有良好的一致性:节面Ⅰ走向为NE向，节面Ⅱ走向为NW向，均为高倾角走滑断层。中强地震的震源机制节面解与第二松花江断裂性质基本一致，由此推断第二松花江断裂是本次松原地震的发震断层；③ 松原地区的主压应力方位角为N86°E，倾角为7°，主张应力方位角为N24°E，倾角为71°。松原地区的区域应力场既受到大尺度的板块构造运动的控制，又受到区域构造运动的影响。在太平洋板块对北东亚板块向西俯冲作用下，东北地区产生了近EW向的主压应力，受周边地质构造控制，松辽盆地内NE向断裂与NW向断裂交会处易发生走滑型地震，2018年松原MS5.7地震正是在这种构造作用控制下发生的中强地震。 相似文献
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2006年6月21日文县5.0级地震发生在构造环境复杂的地区,该地区之前已有100多年没有发生过中强地震。该地震的发生说明该地区的地震活动开始增强。文县5.0级地震没有形成地表破裂带,给研究发震构造带来了一定的困难,通过1/20万地质图、遥感资料解译、震源机制反演以及地震序列精确定位的方法依然能够研究该地震的发震构造。为判定该地区未来的地震危险性,文中采用遥感资料解译、多种方法反演震源机制、双差法地震精定位的方法联合分析该地震的发震构造。1/20万地质图显示该区域存在多条断裂,遥感资料的解译结果表明石坊-临江断裂为较活动的断裂。2种方法所得震源机制结果表明该地震为左旋走滑兼有逆冲,主压应力方向为N60°E。双差法定位结果也支持该地震为走滑兼有逆冲,余震的分布与断裂的逆冲有关。结合多种结果联合分析认为该地震的发震构造为石坊-临江断裂,主压构造应力方向为N60°E 相似文献
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2014年3月27日和30日湖北秭归县发生了三峡水库蓄水以来该地区最大的2次地震,文中通过多种方法分析了2次地震的震源与发震构造特征。采用Kiwi方法反演2次地震的矩张量解,该方法中使用了湖北和重庆测震台网14个宽频带波形记录和6层地壳速度结构模型,反演结果显示,2次地震观测谱和波形与理论谱和波形拟合得比较好,非拟合误差数0.57,表明反演结果是可靠的。2次地震均为走滑兼少量逆冲错动,但前一地震为左旋走滑,后一地震为右旋走滑,矩张量解中DC成分偏少而ISO成分多可能是库水对地下介质物性影响的反映。同时也使用三峡台网15个子台记录的波形资料,采用双差定位法重新精定位了从3月27日至4月27日时段内超过500次地震序列事件,结果显示余震序列分布方向为NNW向和NE向,但主要集中在NE向,并分别沿NNW和NE向作了深度剖面,剖面显示震源深度为4.5~10.0km,余震在深部呈现2个较明显的断面,与震源机制解NE向节面产状一致。野外现场宏观烈度调查指出,Ⅴ度极震区等震线为一椭圆,长轴NWW向,短轴NE向,结合野外现场考察结果和震源区地质构造背景,综合推断仙女山断裂北端的NE向破裂面为2次地震的发震断面,余震序列的NE和NNW向分布、剖面上发震层的形态和深度特征表明,这次地震活动受到了仙女山断裂和九畹溪断裂活动的控制与影响。 相似文献
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The 2018,Songyuan,Jilin M_S5. 7 earthquake occurred at the intersection of the FuyuZhaodong fault and the Second Songhua River fault. The moment magnitude of this earthquake is M_W5. 3,the centroid depth by the waveform fitting is 12 km,and it is a strike-slip type event. In this paper,with the seismic phase data provided by the China Earthquake Network, the double-difference location method is used to relocate the earthquake sequence,finally the relocation results of 60 earthquakes are obtained. The results show that the aftershock zone is about 4. 3km long and 3. 1km wide,which is distributed in the NE direction. The depth distribution of the seismic sequence is 9km-10 km. 1-2 days after the main shock,the aftershocks were scattered throughout the aftershock zone,and the largest aftershock occurred in the northeastern part of the aftershock zone. After 3-8 days,the aftershocks mainly occurred in the southwestern part of the aftershock zone. The profile distribution of the earthquake sequence shows that the fault plane dips to the southeast with the dip angle of about 75°. Combined with the regional tectonic setting,focal mechanism solution and intensity distribution,we conclude that the concealed fault of the Fuyu-Zhaodong fault is the seismogenic fault of the Songyuan M_S5. 7 earthquake. This paper also relocates the earthquake sequence of the previous magnitude 5. 0 earthquake in 2017. Combined with the results of the focal mechanism solution,we believe that the two earthquakes have the same seismogenic structure,and the earthquake sequence generally develops to the southwest. The historical seismic activity since 2009 shows that after the magnitude 5. 0 earthquake in 2017,the frequency and intensity of earthquakes in the earthquake zone are obviously enhanced,and attention should be paid to the development of seismic activity in the southwest direction of the earthquake zone. 相似文献
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华北强烈地震深部构造环境的探测与研究 总被引：6，自引：1，他引：5
20世纪六七十年代以来, 华北地区发生了一系列强烈地震． 强烈地震的孕育、 发生和发展与深部构造密切相关． 近50年来, 我国地震科学领域在强烈地震的地震构造和深部环境方面开展了大量的研究． 深部地球物理探测和地震层析成像结果揭示了华北地区地壳结构的基本特征, 并在强烈地震发生的深部构造环境等问题上取得了重要进展． 本文在回顾华北地区地壳上地幔结构探测的基础上, 对1966年邢台MS7.2, 1976年唐山MS7.8, 1975年海城MS7.3和1679年三河—平谷M8.0地震的地震构造和深部构造环境进行评述． 深部地球物理数据的综合分析表明, 震源下方的低速异常带, 高角度超壳深断裂, 地壳深浅构造的不一致, 偏低的上地幔顶部速度和局部隆起的莫霍界面, 是华北伸展构造区深部孕震环境的共同特征． 相似文献
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On January 21, 2016, a M6.4 earthquake occurred in Menyuan county, Qinghai Province. Its epicenter is located in the Qilian-Hexi Zoulang tectonic zone, which records several moderate-large historical earthquakes. Previous studies on this event are based on geology, remote sensing data and focal mechanism solutions, lacking analysis on its seismogenic structure. In order to study seismogenic fault plane and seismoteconic style of the earthquake, this work uses data of seismic intensity, aftershocks, and geology to address this issue. Furthermore, we calculate Coulomb stress changes imposed by the 1927 Gulang M8 and 1986 Menyuan M6.4 earthquake on the fault plane of the 2016 Menyuan M6.4 earthquake. The results indicate the early two events have posed distinct impacts on two nodal planes:loading or triggering on nodal plane Ⅰ, and unloading or delay on Ⅱ. In some cases such triggering stress is approaching or up to the threshold value of 0.01 MPa. Combining isoseismals, aftershock distribution, geological structure and different Coulomb stress changes aforementioned, the nodal plane Ⅱ of the source model is considered the seismogenic feature. In conjunction with geophysical data, we establish the seismogenic model of the Menyuan earthquake, which is a positive flower structure in a profile, gentle in the upper and steep in the lower, characterized by thrusting in a strike slipping fault system. This is a possible model for thrusting earthquakes generated by strike-slip faults in a compressional tectonic regime. 相似文献