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为了取得邢台地震区地壳细结构,对该区进行了综合地球物理方法探测,其中电磁阵列剖面法（EMAP）测量在我国尚属首次．EMAP剖面穿过邢台7．2级地震区,经过EMAP阻抗求取、空间滤波处理和二维反演解释,剖面显示出清晰的地壳电性细结构特征：4km以上电性简单,4-20km深度电性复杂;震源区电性复杂,非源区简单;发震深度变化复杂;震源区电性突变,显示隐伏高角度断裂,高寻层不连续部位为发震部位．其观测结果对于了解该区的构造背景、发震构造和深部构造的关系有重要意义． 相似文献
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用电磁阵列剖面法 (EMAP)、大地电磁测深方法 (MT) ,沿三河 -平谷 8级大震震源区 ,作了 31 8km长的EMAP探测和两条总长 150 0 5km共 36个点的MT探测。获得了研究范围内的地壳上地幔电性结构、高导层特征和陡变带、高导异常体、断裂展布、岩石圈结构等结果 ,为搞清地震危险区的深浅构造关系、从电性结构特征推测发震模式和预测未来强震的可能地点提供了介质电性的多种参数 相似文献
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基于新疆区域数字地震台网震相观测报告, 采用双差定位方法对2019年新疆疏附MS5.1地震序列ML≥1.0地震进行重定位, 采用CAP波形反演方法, 获得了主震的震源机制解和震源矩心深度, 进而综合分析了本次地震可能的发震构造。 结果表明, 疏附5.1级地震震源位置为39.59°N, 75.57°E, 初始破裂深度为18 km, 震源矩心深度为18 km。 重定位后的地震序列呈两个优势方向展布, 分别为NEE向和NE向分支, NEE向为主要的余震优势分布区域, 呈长约13 km窄带状分布在喀什断裂附近。 另一条优势分布为沿NE向长度约9 km, 这可能与喀什断裂阶区有关。 深度剖面显示, 地震震源深度主要集中分布在8~20 km。 沿NEE走向深度剖面显示, 疏附5.1级地震破裂于深部, 余震沿优势分布的震源深度自SWW向NEE呈现逐渐加深的变化特征。 垂直于震中优势分布的深度剖面显示, 本次地震发震断层面倾向为N倾。 震源机制解显示本次地震断错类型为逆冲型, 结合震源深度剖面特征推断节面Ⅰ为本次地震的发震断层面。 综合地震序列空间分布特征、 震源机制以及震源区地质资料, 推测此次地震的发震构造可能为喀什断裂, 余震向浅部扩展。 相似文献
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基于区域地震台网观测数据,采用近震波形反演方法,确定2018年2月12日河北永清M4.3地震的最佳双力偶源震源机制解为:节面Ⅰ走向297°,倾角58°,滑动角-32°;节面Ⅱ走向45°,倾角63°,滑动角-144°;是一个略带正断分量的右旋走滑地震.结合近震转换波测定主震的震源深度在19km附近.地震序列的双差定位结果显示:永清地震序列震中呈北东向窄带展布,表明此次地震主要向北东向破裂;深度集中分布在17～19km,整体形态近于铅直,显示发震断裂具有走向北东、倾向南东、倾角陡立的特征,与节面Ⅱ的性质比较吻合,推测节面Ⅱ为发震断层面.将发震断层面参数与震源区附近断裂性质进行对比分析,形成了关于廊固凹陷附近区域地震构造的一些认识:(1)推测永清地震的发震构造不是地壳浅部发育的先存正断裂,而是震源区下方一条地壳尺度的深断裂,该深断裂为新生断裂,具有右旋走滑正断性质,倾角陡峭、近于直立、宽度较大,向上与夏垫断裂相通.(2)综合震源区附近多条深地震反射剖面探测结果,推测永清地震的发震断裂与新夏垫断裂同属一条断裂,称为:新夏垫深断裂.该断裂从夏垫向西南方向延伸至文安,并可能与霸县—束鹿—邯郸断裂带相联系,总长度超过150km.(3)基于2006年文安M5.1地震与2018年永清M4.3地震在震源机制上的相似性及震源位置上的关联性,结合区域构造条件,认为两次地震的发震构造均为新夏垫深断裂.(4)根据研究区几次显著地震的震源深度分布特征,参考区域断层构造、电性结构和流变学模型,推测活化克拉通块体新生断裂的脆韧性转换界面深度在15km附近. 相似文献
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基于新疆区域数字地震台网震相观测报告,采用HypoDD方法精确定位了精河MS6.6地震序列ML≥1.0地震的震源位置,综合分析了此次地震序列的空间分布特征和可能的发震构造。结果显示,主震震中为44.2639°N、82.8294°E,震源初始破裂深度为17.6km;地震序列总体沿近EW（273°）向单侧扩展,展布长度约20km;震源深度优势分布范围为7～17km;沿余震走向的深度剖面显示,主震向西10km范围内,余震震源有逐渐变浅的趋势,余震序列中尾端向SW方向偏转的地震震源较深;垂直于地震序列的深度剖面显示,地震序列自北向南呈现逐渐加深的变化特征,表明发震断层面倾向为S倾。综合考虑中国地震局地球物理研究所给定的震源机制解以及震源区地质构造情况推测,精河MS6.6地震发震构造可能为库松木契克山前断裂东段。 相似文献
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本文提出并试验了一种基于接收函数建立区域模型进行震源机制反演的方法.选取四川地震台网记录的M≥3且信噪比高的近震波形资料,反演得到了芦山地震序列中74个地震的震源机制.通过对震源深度和震源机制的综合分析,探讨了芦山地震的发震构造和区域应力场状态.采用接收函数方法反演获取了26个台站下方的S波速度结构,对不同区域的台站反演结果进行叠加平均,以此区域平均S波速度作为本文震源机制反演使用的区域模型的S波速度;区域模型的P波速度由经验公式给出.反演稳定性测试表明,使用不同模型或对原始波形记录加入随机噪声的反演结果与原始反演相比,震源深度最大误差为1km,断层面各参数误差水平也很低,且显示的发震类型是一致的,其中随机噪声带来的误差小于模型带来的误差.主震反演得到的震源机制解为:震源深度17km,矩震级6.47;节面Ⅰ走向213°,倾角51°,滑动角98°;节面Ⅱ走向20°,倾角40°,滑动角80°;显示芦山主震可视为纯逆冲型地震,发震构造可能是某个具有较大倾角的逆冲断层,而不是低缓的推覆构造的基底滑脱面.同时本文反演获取的73个M≥3余震的震源机制绝大多数也显示了类似的发震类型,逆冲型地震为67个,占92%,具有绝对优势;走滑型地震为5个,正断型地震为1个.其中5个走滑型地震中的4个均分布在震源区的东北端.整个芦山地震序列深度集中在12~20km,且沿震源区短轴的余震深度剖面有自西向东呈逐步变浅的趋势,呈现清晰的铲形断面结构,结合本地地质构造,可以推断芦山地震序列主要发生在龙门山前山断裂以东的逆冲推覆体内的一个隐伏断裂上.P轴方位角优势方位与区域应力场及汶川震源区南段的相一致,表明芦山序列地震活动主要受区域应力场控制,且汶川震后该区应该不存在应力场变化.P轴仰角随深度分布则显示了孕震层在浅部为脆性上地壳,而深部已经进入了中地壳低速层.断层面的几何形态简单,倾角均值在不同深度保持稳定在55°左右,与主震倾角接近,这与汶川震源区南段的研究结果明显不同,揭示了龙门山断裂带南段与此次芦山发震断裂在断层面几何形态上的明显差异. 相似文献
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综合利用区域台站和流动台站(近台)的记录,基于初至P震相重新测定了2017年九寨沟序列M_S7.0主震和M_L≥3.0余震的震源位置,并利用较高精度的定位结果分析余震分布与地震构造的关系,解释发震断裂带的结构.获得的新认识有:(1)九寨沟主震震源深度为16km,位于余震带中段的南缘;余震主要分布深度为4～17km.(2)沿余震带的走向,余震分布与主震同震位错大小的分布明显相关.余震带中段8～16km深度存在的余震稀疏区与同震位错的高值区相吻合,应是发震断裂带主凹凸体的部位,也是主震时应变释放较充分的部位;余震带南东段10～18km深度的余震密集区对应了同震位错的亏损区之一,三次M_L≥5.0余震都发生于此;余震带西北段在5～10km之下既缺少余震,又属同震位错的亏损区,可能与那里多条断裂的交汇或合并造成的构造复杂性有关;余震带中-北西段3～5km深度的也缺少余震,也对应了浅部的同震位错亏损区.(3)证实了九寨沟地震的发震构造为虎牙断裂带北段,同时新揭示出发震断裂带表现为由主断裂和分支断裂构成的、向上分叉的花状结构,尺度约为4.5km宽(最大)、35km长,主断裂朝SW陡倾.这些反映主震破裂可能不只受控于单一的断裂,而有可能是沿主断裂发生主破裂,而沿分支断裂发生次要破裂.另外,本文对发震断裂带结构的分段解释,是遵循构造地质学原理去综合震源排列、震源机制解、地表断层已知位置、相邻剖面断层解释结果等信息的分析结果,而不仅仅依据余震的密集分布进行推断. 相似文献
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THE SOURCE PARAMETERS AND SEISMOTECTONIC IMPLICATIONS OF THE SEPTEMBER 4, 2017 ML4.4 LINCHENG EARTHQUAKE 
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下载免费PDF全文 LI He XIE Zu-jun WANG Yi-xi WANG Xiao-shan DONG Yi-bing ZHANG Hui PENG Zhao LIU Wen-bing GAO Ye WANG Li-xia 《地震地质》2019,41(3):670-689
At 3:05, September 4, 2017, an ML4.4 earthquake occurred in Lincheng County, Xingtai City, Hebei Province, which was felt obviously by surrounding areas. Approximately 60km away from the hypocenter of Xingtai MS7.2 earthquake in 1966, this event is the most noticeable earthquake in this area in recent years. On the one hand, people are still shocked by the 1966 Xingtai earthquake that caused huge disaster, on the other hand, Lincheng County is lack of strong earthquakes. Therefore, this quake has aroused widespread concerns by the government, society and seismologists. It is necessary to clarify whether the seismogenic structure of this event is consistent with the previous seismicity and whether it has any new implications for the seismic activity and seismic hazard in this region. Therefore, it is of great significance to study its seismogenic mechanism for understanding the earthquake activity in Xingtai region where a MS7.2 earthquake had occurred in 1966.
In this study, the Lincheng earthquake and its aftershocks are relocated using the multi-step locating method, and the focal mechanism and focal depth are determined by the "generalized Cut and Paste"(gCAP)method. The reliability of the results is analyzed based on the data of Hebei regional seismic network. In order to better constrain the focal depth, the depth phase sPL fitting method is applied to the relocation of focal depth. The inversion and constraint results show that aftershocks are mainly distributed along NE direction and dip to SE direction as revealed by depth profiles. Focal depths of aftershocks are concentrated in the depths of 6.5~8.2km with an average of about 7km. The best double-couple solution of the mainshock is 276°, 69° and -40° for strike, dip and slip angle for nodal plane I and 23°, 53° and -153° for nodal plane Ⅱ, respectively, revealing that it is a strike-slip event with a small amount of normal-fault component. The initial rupture depth of mainshock is about 7.5km obtained by the relocation while the centroid depth is 6km derived from gCAP method which was also verified by the seismic depth phase sPL observed by several stations, indicating the earthquake is ruptured from deep to shallow. Combined with the research results on regional geological structure and the seismic sequence relocation results, it is concluded that the nodal plane Ⅱ is the seismogenic fault plane of this earthquake.
There are several active faults around the hypocenter of Lincheng earthquake sequence, however, none of the known faults on the current understanding is completely consistent with the seismogenic fault. To determine the seismogenic mechanism, the lucubrated research of the MS7.2 Xingtai earthquake in 1966 could provide a powerful reference. The seismic tectonic characteristics of the 1966 Xingtai earthquake sequence could be summarized as follows:There are tensional fault in the shallow crust and steep dip hidden fault in the middle and lower crust, however, the two faults are not connected but separated by the shear slip surfaces which are widely distributed in the middle crust; the seismic source is located between the hidden fault in the lower crust and the extensional fault in the upper crust; the earthquake began to rupture in the deep dip fault in the mid-lower crust and then ruptured upward to the extensional fault in the shallow crust, and the two fault systems were broken successively. From the earthquake rupture revealed by the seismic sequence location, the Lincheng earthquake also has the semblable feature of rupturing from deep to shallow. However, due to the much smaller magnitude of this event than that of the 1966 earthquake, the accumulated stress was not high enough to tear the fracture of the detachment surface whose existence in Lincheng region was confirmed clearly by the results of Lincheng-Julu deep reflection seismology and reach to the shallower fault. Therefore, by the revelation of the seismogenic mechanism of the 1966 Xingtai earthquake, the seismogenic fault of Lincheng earthquake is presumed to be a concealed fault possessing a potential of both strike-slip and small normal faulting component and located below the detachment surface in Lincheng area. The tectonic significance indicated by this earthquake is that the event was a stress adjustment of the deep fault and did not lead to the rupture of the shallow fault. Therefore, this area still has potential seismic hazard to a certain extent. 相似文献
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RELOCATION OF THE HUTUBI MS6.2 EARTHQUAKE SEQUENCE ON 8 DECEMBER 2016 AND ANALYSIS OF THE SEISMOGENIC STRUCTURE 下载免费PDF全文
下载免费PDF全文 Based on the digital waveforms of Xinjiang Seismic Network, the Hutubi MS6.2 earthquake sequence (ML ≥ 1.0) was relocated precisely by HypoDD.The best double-couple focal mechanisms of the main shock and aftershocks of ML ≥ 4.0 were determined by the CAP method. We analyzed the characteristics of spatial distribution, focal mechanisms and the seismogenic structure of earthquake sequence. The results show that the main shock is located at 43.775 9°N, 86.363 4°E; the depth of the initial rupture and centriod is about 15.388km and 17km. The earthquake sequence extends unilaterally along NWW direction with an extension length of about 15km and a depth ranging 5~15km. The characteristics of the depth profiles show that the seismogenic fault plane dips northward and the faulting is dominated by thrusting. The nodal planes parameters of the best double-couple focal mechanisms are:strike 292°, dip 62° and rake 80° for nodal plane I, and strike 132°, dip 30° and rake 108° for nodal plane Ⅱ, indicating that the main shock is of thrust faulting. The dip of nodal planeⅠis consistent with the dip of the depth profile, which is inferred to be the fault plane of seismogenic fault of this earthquake. According to the comprehensive analysis of the relocation results, the focal mechanism and geological structure in the source region, it is preliminarily inferred that the seismogenic structure of the Hutubi MS6.2 earthquake may be a backthrust on the deeper concealed thrust slope at the south of Qigu anticline. The earthquake is a "folding" earthquake taking place under the stress field of Tianshan expanding towards the Junggar Basin. 相似文献
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本文利用邢台地震台网资料研究了1966年3月邢台地震强震活动期间地震位置的空间分布随时间变化的过程。给出了一系列反映邢台地震序列强震孕育、破裂、应力场调整及地震构造的立体图象。进一步探讨了震区地壳介质中存在的障碍体与地震发生的关系。认为这种震区介质的非均匀构造所导致的邢台地震的破裂是一个沿北北东方向的断断续续的发展过程。较好地解释了几个六级以上强震的发生以及强震期后出现的中强余震两头跳现象。本文还对六级以上强震的破裂过程进行了讨论,并与已有结果作了对比,还考察了强震活动期间震源深度随时间变化与大震发生的关系。 相似文献
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We select the Xiluodu-Wudongde reservoir area in the downstream of Jinsha River as the research area, and use the CAP and GPAT method to obtain focal mechanisms of ML ≥ 2.0 earthquakes from 2016 to 2017 in this region. Then, we analyze the spatial distribution characteristics of focal mechanism solutions in each local region and investigate the relationship between seismicity and regional structures. According to 414 focal mechanism solutions we get following conclusions:1)The Xiluodu dam began to impound water on May 4, 2013, and seismicity increased significantly after impoundment. We get 49 focal mechanisms in the Xiluodu dam and its adjacent area which are dominated by thrust faulting and next by strike-slip faulting, which are mainly distributed near the middle section of the Ebian-Jinyang fault zone. The distribution of nodal planes striking in NNW to NE direction is consistent with that of regional faults, and some large earthquakes are controlled by regional structures. 2)There are 39 and 24 focal mechanisms obtained in the unimpounded Baihetan and Wudongde dams and adjacent areas, and the spatial distribution of focal mechanism solutions are relatively consistent, dominated by strike-slip faulting with a small amount of thrust and normal faulting. The sinistral strike-slip earthquakes are consistent with the activity of Xiaojiang fault zone and Puduhe-Xishan Fault. The strikes of the nodal planes are distributed discretely, and many groups of faults intersect with each other in the area, suggesting that the seismogenic environment is relatively complex. 3)The seismicity in Ludian continues to be active after the Ludian M6.5 earthquake. By the end of 2017, we got 260 focal mechanism solutions in the aftershock area of the Ludian MS6.5 earthquake of Aug 3rd, 2014, which show an "L-shape" in distribution and are dominated by thrust and strike-slip faulting. The long axis is distributed in EW direction, and the short axis is distributed in near NNW direction. The strikes of nodal planes are mainly near EW and near NE, and the nodal planes in the NW direction are less. According to characteristics of a large number of focal mechanism solutions, we deduce that there may exist a buried structure in the EW direction, the seismicity is controlled by different types of faults and the seismogenic structure is very complex. 4)The centroid depth in each region is concentrated in the range of 5~15km, indicating that the seismogenic layer in the study area is 5~15km deep in the middle and upper crust. 相似文献
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On 16th September 2013, an M5.1 earthquake occurred in Badong County, Hubei Province, which is the biggest one since the first water impounding in 2003 in the head region of the Three Gorges Reservoir area. The crustal velocity information is needed to determine the earthquake location and focal mechanism. By comparison, the 1-D velocity structure model from Zhao was adopted in this study. Double difference location method was applied to determine the precise locations of the M5.1 earthquake sequence. Relocation results show that the dominant distribution of this sequence is along NEE direction. In order to understand its seismogenic structure, focal depth profiles were made. Profile AA' was along the sequence distribution, and the earthquake sequence extended about 12km. Focal depth of mainshock is deeper than that of aftershocks, and earthquake rupture propagated laterally southwestward. The seismic profile BB' and CC' were perpendicular to profile AA', which represent the dip direction. Both profiles show that the focal depth becomes deeper toward southeast, and dip angle is about 50°. It means that the possible seismogenic fault strikes NEE and dips southeast. Focal mechanism could provide more information for judging the seismogenic structures. Many methods could obtain the focal mechanism, such as P-wave first motion method, CAP method, and some other moment tensor methods. In this paper, moment tensor inversion program made by Yagi Y is adopted. 12 regional seismic stations ranging from 100~400km are picked up, and before the inversion, we removed the mean and trend. The seismic waveforms were band pass filtered between 0.05 and 0.2Hz, and then integrated into displacement. Green's functions were calculated using the discrete wavenumber method developed by Kohketsu. The focal mechanism of the M5.1 mainshock manifests that the NEE-striking fault plane probably is the possible seismogenic fault, which is consistent with the analysis of focal depth profiles. The focal mechanisms of the ML≥2.0 aftershocks are retrieved by P-wave first motion method, and the nodal plane I is in accordance with the earthquake sequence distribution and the fault plane of the mainshock. FMSI program was adopted to inverse the stress field in the earthquake area, and the results show that the earthquake sequence is under the control of the regional stress field. The earthquake sequence occurred on the stage of slow water unloading, and ETAS model was introduced to testify the influences of water level fluctuations on earthquakes. The results denote that the reservoir played a triggering role in the earthquake, however, the NEE-striking seismogenic fault is the controlling factor. 相似文献
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本文利用近年来地震及地壳结构资料,研究了震源深度分布。震源主要分布在4—20公里的深度范围内,称为地震活跃层,大多数地震又都集中于厚度为10—15公里的层内,称为地震密集层,密集层的深度因地而异,震源大多位于花岗岩质层。地震活跃层的分布由粘滑机制及脆性剪切破裂可能存在的范围决定,它的上界主要由稳定滑动—粘滑过渡区决定,下界由脆性—延性形变过渡区决定。地震活跃层及密集层的深度由地壳中的温度、压力及岩石条件决定。震源有成层分布的现象,可能与地壳中各界面的层间粘滑有关 相似文献
17.
晋冀鲁豫交界地区震源位置及震源区速度结构的联合反演 总被引：1，自引：0，他引：1
利用邯郸数字台网记录到的2001—2008年间460次ML≥1.0地震的1861条P波到时数据, 采用震源位置和速度结构联合反演方法确定晋冀鲁豫交界地区(35.0°~38.0°N, 113.0°~116.0°E)地震的震源位置分布和该区域的速度结构。 结果表明: ① 经过重新定位后, P波走时的均方根残差(RMS)由反演前的1.35 s降到反演后的0.45 s。 定位偏差在EW方向上平均为0.031 km, 在NS方向上平均为0.029 km, 在垂直方向上平均为0.060 km。 ② 邢台震区的中小地震明显呈NEE向分布, 深度主要集中分布在7~14 km范围内; 磁县震区中小震分布相对复杂, 具有NEE和NWW两个展布方向, 震源深度主要集中在8~18 km范围内, 总体上晋冀鲁豫交界地区中小地震深度呈现北部浅南部深的趋势。 ③ 反演得到了晋冀鲁豫交界地区的速度结构, 在邢台地震极震区下方7~14 km处存在低速层, 与1966年邢台7.2级地震的震源深度一致;在磁县地震极震区下方13~18 km处也存在低速层与1831年磁县7.5级地震震源深度一致, 且磁县震区下方的速度结构比邢台震区更为复杂。 相似文献
18.
１９６９年７月的１８日１３时２４分５０秒，渤海发生了一次７．４级地震，震源深度３５ｋｍ，从地壳厚度分布来看，震中区地壳厚度为２９ｋｍ。所以渤海地震很可能是一次地幔地震。本文从地震活动性、宏观特征分析开始，结合地壳厚度、居里等温面起伏以及地壳上地幔的电性结构和岩石实验材料，对这次地震的深部构造做了论述。 相似文献