2011年9月10日瑞昌—阳新4.6级地震的震源破裂特征与区域强震危险性

基于区域数字地震台网记录,采用HYPODD方法精确定位了2011年9月10日瑞昌—阳新地震序列的震源位置,采用CAP方法反演得到了4.6级主震的震源深度和震源机制解,并结合区域深度震相sPg、PmP和sPmP对主震震源深度进行了进一步确定,随后探讨了这次地震的震源破裂特征和所在区域的强震危险性.结果显示:瑞昌—阳新4.6级地震的震源深度为15±2 km,震源机制解为节面Ⅰ走向30°,倾角86°,滑动角-169°,节面Ⅱ走向299°,倾角79°,滑动角-4°,发震构造为郯城—庐江断裂带往震区延伸隐伏的瑞昌—武穴断裂;本次地震发生在长江中下游断块东部,所在区域的5.5级以上地震具有明显的成组活动特征,近期显著地震集中发生在郯城—庐江断裂带南段及其分支断裂上,地震能量有加速释放的趋势,未来十年左右该区域存在发生6级左右强震的可能性.     

2011年9月10日瑞昌、阳新间M4.6地震序列特征分析

2011年9月10日瑞昌、阳新间M4.6地震之后,震中区附近发生一系列余震活动.从序列特征、小震震源机制解、余震活动的时空分布特征以及震区地质构造情况等方面,对该地震序列进行初步研究,结果显示:M4.6地震序列中较强的地震活动主要沿NE走向的枫林桥断裂分布,ML2.0以下的微弱地震活动主要沿NW向的襄樊—广济断裂带武穴段分布,M4.6主震可能由NE向的枫林桥断裂所控制.     

用CAP方法反演2010年6月5日山西阳曲M_S4.6地震震源机制解

利用CAP方法反演了2010年6月5日阳曲MS4.6地震震源机制解,得到震级MW为4.5,节面I走向213°、倾角47°、滑动角-161°,节面II走向109°,倾角76°,滑动角-44°,属于倾滑型;精确定位显示震中处于石岭关隆起区,CAP反演和精定位结果推断本次地震的震源深度为17～20km。震源机制解节面参数与震中附近的山根底断裂和系舟山西麓断裂产状存在差异,这两条断裂不是阳曲地震的发震断裂,由于现场野外地质考察未发现地表断裂,不排除本次地震为隐伏断层活动的结果。     

2011年Ms4.6瑞昌-阳新地震的震源机制及发震构造探讨

2011年Ms4.6瑞昌-阳新地震是瑞昌地区继2005年M5.7地震后的又一中等强度地震,文中从多角度对此次地震的发震构造进行了探讨.利用双差定位法进行的地震精定位结果显示,主震发生在NE向断裂的西南端,余震的分布则呈现出沿NNE和NW两个方向展布的特征.野外考察发现,等震线长轴方向为NE,沿此方向烈度衰减较慢.考虑震源时间函数的影响,采用波形反演方法得到了此次地震的震源机制解.节面Ⅰ走向302.2°,倾角68.2°,滑动角-3.8°;节面Ⅱ走向33.6°,倾角86.5°,滑动角-158.1°.综合分析认为,NNE向郯庐断裂的南端隐伏段(瑞昌-武穴断裂)为此次地震的发震构造,而与NW向断裂的共轭作用造成了部分余震沿着NW向分布的特征.     

采用CAP方法反演2016年广西苍梧M_S 5.4地震震源机制解

北京时间2016年7月31日广西梧州市苍梧县发生M_S 5.4地震,基于海南地震台网数字波形资料,采用CAP方法反演震源机制解。结果显示,此次M_S 5.4地震震源深度较浅,最佳深度为5.1 km,其中节面Ⅰ参数为:走向340°,倾角37°,滑动角-18°;节面Ⅱ参数为:走向85°,倾角79°,滑动角-125°。初步推断苍梧M_S 5.4地震破裂面运动以走滑为主,兼有正断性质,反演参数与中国地震台网中心结果较为一致。     

利用FOCMEC方法计算震源机制解的影响因素分析——以九江—瑞昌Ms5.7地震为例

应用Snoke最新发展的利用P波、SV波和SH波的初动和振幅比联合计算震源机制解的方法(FOCMEC),以2005年11月26日九江—瑞昌MS5.7地震为例,分析速度结构模型、震源定位误差、初动与振幅比资料和台站分布等对计算震源机制解的影响.结果表明,FOCMEC方法应采用研究区内的精细速度结构模型,各层速度误差在5％...     

运用尾波干涉技术监测瑞昌—阳新MS4.6地震后地壳介质变化

基于2011年瑞昌—阳新M_S4.6地震序列事件波形及其观测报告,采用双差重定位法、波形互相关法和尾波干涉法,筛选出了同时被黄梅台和九江台记录且波形互相关系数≥0.920的两组重复地震对:D₁（2011-09-11 05:44 M_L2.3和2011-10-24 08:06 M_L2.2）和D₂（2011-09-18 07:06 M_L2.8和2011-10-2408:06 M_L2.2）,发现瑞昌—阳新M_S4.6地震后1.5个月内（2011-09-11—10-24）震源区S波早期尾波波速增加。      

渤海海域地震震源机制解与现今应力场特征

渤海地区是我国东部地震较为活跃的地区之一,历史上强震频发,曾被列为地震重点危险区,其震情备受关注。近期该地区有感地震多发,因此有必要深入了解这些地震的震源破裂性质,同时探究渤海地区现代构造应力场分布,以期为后续判识地震危险性研究工作提供科学参考。本文基于前人对渤海地区震源机制解的研究结果,采用波形反演方法计算并补充完善了2010—2022年M≥3.5地震的震源机制解,使用MSATSI软件包反演计算区域构造应力场。结果表明,渤海海域近期地震事件以走滑型为主,其次为正断型,与地震事件附近主要断裂带的运动学特征具有较好的一致性;区域构造应力场的优势方位为NEE向,与华北地区构造应力场基本一致,整体相对稳定,局部存在一定差异,这与海域地震数量较少且分布不均有关,另外应力形因子R值相对较小,区域地壳应力以张应力为主。     

2011年6月8日新疆托克逊MS5.3地震震源机制解反演

2011年6月8日9时53分,新疆维吾尔自治区吐鲁番地区托克逊县发生Ms5.3地震.据新疆自治区民政厅报告,截至6月9日7时,地震造成托克逊县1241人受灾,324户1335间房屋不同程度受损,其中50户168间农牧民住房成为危房、无法居住,274户1135间房屋墙体开裂,博斯坦乡中学24间教室房屋开裂,伊拉湖乡医院8间病房开裂,无人员伤亡报告.     

靖字——抚松Ms4．6级地震序列特征

2008年8月5日靖宇-抚松发生Ms4．6级地震。本文对这次地震的区域地质构造、震源机制、地震序列特征等进行了分析。结果表明,此次地震的发震构造是浑江断裂带;震前地震活动呈现“稀疏-密集-平静”特征,余震衰减正常;序列空间位置变化不大,相对集中在北东向条状分布,走向与浑江断裂带一致。     

河南及邻区地震的震源机制

汇编了河南及邻区1965－2000年共52次ML≥3.5地震的震源机制。分析表明：震源机制两组节面的走向为北北东向和北西西向；P轴多为北东江向；T轴大都为北北西向；地震断层主要为走滑类型，菏泽5.9级地震前P轴方向呈现出由紊乱到趋向一致的特征。     

2013年1月29日中哈交界Ms6．1地震震源机制解与发震断层研究

针对2013年1月29日发生在中哈交界Ms6．1地震,基于新疆数字台网中心宽频带波形记录,采用CAP方法反演了其震源机制解。结果显示：该次地震震源深度为27km,其中一个节面走向161°,倾角76°,滑动角-164°,与哈佛大学计算结果一致;结合余震空间分布和GPS观测结果,判定该节面为破裂面,同时推断该处有一发震断层,其走向NWW、倾角较大、断错性质为右旋走滑型。     

FOCAL MECHANISM AND SEISMOGENIC STRUCTURE OF THE M5.0 YUEXI EARTHQUAKE ON 1 OCT. 2014, SOUTHWESTERN CHINA

The Oct.1,2014 M5.0 Yuexi earthquake occurred on the Daliang Shan fault zone where only several historical moderate earthquakes were recorded.Based on the waveform data from Sichuan regional seismic network,we calculated the focal mechanism solution and centroid depth of the M5.0 Yuexi earthquake by CAP (Cut and Paste) waveform inversion method,and preliminarily analyzed the seismogenic structure.We also calculated the apparent stress values of the M5.0 earthquake and other 14 M_L≥4.0 events along the Shimian-Qiaojia fault segment of the eastern boundary of the Sichuan-Yunnan block.The result indicates that the parameters of the focal mechanism solution are with a strike of 256°,dip of 62°,and slip of 167° for the nodal plane Ⅰ,and strike of 352°,dip of 79°,and slip of 29° for the nodal plane Ⅱ.The azimuth of the P axis is 121° with dip angle of 11°,the azimuth of T axis is 217° with dip angle of 28°,and the centroid depth is about 11km,and moment magnitude is M_W5.1.According to the focal mechanism solution and the fault geometry near the epicenter,we infer that the seismogenic fault is a branch fault,i.e.,the Puxiong Fault,along the central segment of the Daliang Shan fault zone.Thus,the nodal plane Ⅱ was interpreted as the coseismic rupture plane.The M5.0 Yuexi earthquake is a strike-slip faulting event with an oblique component.The above findings reveal the M5.0 Yuexi earthquake resulted from the left-lateral strike-slip faulting of the NNW Dalang Shan fault zone under the nearly horizontal principal compressive stress regime in an NWW-SEE direction.The apparent stress value of the Yuexi earthquake is 0.99MPa,higher than those of the M_L ≥ 4.0 earthquakes along the eastern boundary of the Sichuan-Yunnan block since 2008 Wenchuan M8.0 earthquake,implying a relatively high stress level on the seismogenic area and greater potential for the moderate and strong earthquake occurrence.It may also reflect the current increasing stress level of the entire area along the eastern boundary,and therefore,posing the risk of strong earthquakes there.     

永善－大关7．1级地震序列震源区应力场分析

由云南永善－大关Ｍｓ７．１级地震序列中的１１个Ｍｓ≥４级地震的震源机制解和９８个小震震源机制解，分析了震源区应力场的基本图象和变化形态。结果表明，震源区应力场的基本图象和构造应力场的方向相符。Ｍｓ７．１级主震未对震源区应力场的方向产生可觉察的改变。大量小震机制解的空间取向的优势方向与主震机制解一致。取向离散的小震机制解多出现在序列的前期，至序列末期则很少发现。小震机制解由较离散向集中过渡，显示了震源区应力场动态调整的过程。因此，小地震在强震序列中也做出不可忽略的贡献。     

川滇次级地块震源机制解类型与一致性参数

根据P波、S波的振幅并结合部分记录清晰的P波初动资料,求得1994——2005年川滇地区4个次级地块,即川青地块、雅江地块、川中地块和滇中地块2.5级以上有良好地震波记录的925次地震的震源机制解. 结合已取得的中强地震的震源机制解资料,研究了上述4个次级地块的应力场特征及震源断层的错动类型. 其P轴优势方位分布:川青地块为EW方向,雅江地块、川中地块、滇中地块为ESE或SE方位. 根据大量震源机制解资料, 编程计算了各地块的平均应力张量, 即主应力sigma;1, sigma;2, sigma;3的方向. 定义了单个震源机制解的力轴与平均应力张量的差异, 或称震源机制解的一致性参数, 进而分析了川滇4个次级地块的值和震源断层错动类型的分布及随时间的变化. 通过次级地块大量区域小震震源机制解的测定,可以给出动态应力场和震源断层错动方式的变化信息.      

STUDY ON THE SEISMOGENIC FAULT AND DYNAMICS PARAME-TERS OF THE 2014 MS6.6 JINGGU EARTHQUAKE IN YUNNAN

On October 17, 2014, a M_S6.6 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 M_S6.6 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 M_L ≥ 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.     

DETERMINATION OF FAULT PLANE PARAMETERS IN THE LONGTAN RESERVOIR BY USING PRECISELY LOCATED SMALL EARTHQUAKE DATA AND REGIONAL STRESS FIELD

The Longtan reservoir is located in Tian'e County, Guangxi Zhuang Autonomous Region, southwestern China on the upper reaches of Hongshui River, the main stream of the Pearl River. The dam of the reservoir is 200m high, and the maximum water depth can be up to 194m as the water level reaches 400m. The reservoir storage capacity is 27.3 billion cubic meters, so it is a typical high-dam reservoir with large storage capacity. Terrain of the reservoir is high in the west and low in the east. The reservoir is located at the confluence of the Hongshui River, Buliu River, Nanpan River, Beipan River, Mengjiang River and Caodu River. The construction of Longtan hydropower station officially started in July 2001, and the reservoir impoundment was on September 30, 2006. The power station is equipped with 9 sets of 700 000kW water turbine generator units, with a total installed capacity of 6.3 million kW and an average annual generating capacity of 18.7 billion kW·h. So its storage and hydropower capacity rank third only to the world-famous Three Gorges hydropower project and the ultra-large hydropower project in Xiluodu of Jinsha River in China. Seismicity enhanced rapidly in the reservoir area after the impoundment. More the 5 000 earthquakes have been recorded so far, with the maximum magnitude of M_L4.8, which occurred on September 18, 2010. The earthquakes are mainly concentrated in the deep water area where fault zones run through. Assuming the seismogenic fault can be simulated by a plane and most small earthquakes occur nearby the fault plane, the information of seismogenic fault can be obtained by the hypocenter location parameters of small earthquakes.     

阿尔金断裂带中东段地震活动特征及危险性讨论

讨论了阿尔金断裂带1900年以来的5级以上地震活动,结果显示空间上地震活动具有分段性,其中在青海段出现5级地震填空性空段,并形成5级地震的平静区,时间上具有平静和活跃交替的特征。进一步分析阿尔金断裂带青海段(茫崖北—肃北)现代小震活动,结果显示:茫崖以西震源深度约40 km以内,青海段(茫崖北—肃北)震源深度约10 km范围内,超过10 km较少,肃北—黑崖子以东约100 km处震源深度由浅逐渐变深,从10 km左右逐渐变化到40 km左右。与此同时,依据上述资料探讨了阿尔金断裂带青海段的强震危险性。     

2003年9月27日中、俄、蒙边界Ms7.9地震震源机制及破裂过程研究

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.