鲁甸M_S 6.5地震前昆明地震台定点形变观测异常分析

2014年8月3日鲁甸MS 6.5地震前,昆明地震台形变观测4个分量出现短临异常,排除降雨干扰,结合发震断裂性质及相关研究,分析定点形变异常与该地震前地壳活动的内在联系。分析认为,鲁甸6.5级地震前1—2个月,昆明地震台定点形变观测资料异常较为显著,洞体应变NS分量异常突出,是定点形变投入观测以来的显著异常;形变观测资料异常特征与鲁甸地震发震断裂性质吻合较好;NS分量和EW向分量较好记录了此次鲁甸地震NNW—SSE向包谷垴—小河左旋走滑断裂和NEE—SWW向破裂断层的震前活动过程。     

云南耿马7.2级地震地表破裂带研究

根据野外考察的实际资料,本文介绍了耿马7.2级地震地表破裂带的展布,结构要素及组合、位移分布等情况。同时依据位错资料对破裂带的应力活动及断裂两盘的运动状态进行了初步分析。认为本次地震发震构造以右旋走滑为主兼具张性,主压应力优势方位为N5°—10°E。断层两盘相对运动的总体方向为N55°W左右,断层运动的滑移角在30°—40°之间     

2021年青海玛多M7.4地震发震断裂的典型同震地表变形与晚第四纪断错累积及其区域构造意义

发震断裂的最新一次地震同震变形和晚更新世以来的变形历史是约束发震断裂强震变形行为的基础数据,是认识发震断层上地表破裂型地震的复发特征、评估地震危险性的关键数据,对深刻理解发震断裂演化历史和区域构造空间演化与动力学具有重要意义.2021年玛多M 7.4地震为青藏高原内巴颜喀拉块体活动构造及其强震研究提供了一个机会.本文利用大疆M300RTK无人机搭配P1相机对5个典型观测点进行厘米级分辨率和精度的航空摄影测量和野外调查,详细定量解析了典型破裂特征,通过地貌填图和变形地貌测量分析了晚第四纪以来断错地貌记录的位移累积特征.根据破裂组合特征、同震变形量变化和几何结构,2021年玛多M 7.4地震发震断裂江错断裂同震破裂分为朗玛加合日段、野马滩段、拉木草—东湖段和朗玛哦尔—昌麻河段,整个地震事件是一次跨越四个断裂段的级联破裂过程.朗玛加合日段以左旋走滑变形位移为主兼具正断倾滑,倾滑量可达0.61±0.03 m.野马滩段以左旋走滑变形为主兼具逆断倾滑,在野马滩西观测点倾滑量可达0.31±0.04 m,左旋走滑量达到2.83±0.13 m,江错西观测点仍然有1.97±0.08 m的左旋水平位移.朗玛...     

根据波速比变化预报地震的一个实例

1976年11月7日,我国川滇两省交界处昀盐源、宁蒗一带发生6.7级走滑断层型地震。震前约一年,作者根据附近约2万平方公里范围内的波速比普查结果,对未来主震的震级和地点作了比较符合实际的预报。发震时间的预报是后来根据其它前兆观测结果的综合分析作出的。 本文可以作为走滑断层型地震前观测到波速变化的一个新的实例。根据剪切破裂和粘滑运动之间的差别以及膨胀造成的各向异性,对有关结果作了初步讨论。     

2022年四川马尔康6.0级震群序列震源机制特征分析

采用近震全波形矩张量方法反演了2022年四川马尔康6.0级震群序列22次地震的震源机制解,结果显示：这22次地震全部为走滑型,断层面走向呈NNW和NE两个优势方向,断层面倾角近似直立,滑动角分布在0°和180°附近,P轴优势方位为NWW-SEE向,倾伏角接近水平,表明此次地震事件主要受区域NWW-SEE向水平挤压应力场控制。3次5级以上地震震源机制均与序列其他地震的总体震源机制差异较小,说明序列震源机制较为一致。结合精定位结果综合分析认为：马尔康震群属于多断层面触发性震群,3次5级以上地震是不同断裂的破裂事件,其中5.8级和6.0级地震发震断层面走向为NNW,为左旋走滑破裂事件;5.2级地震发震断层面走向为NE,为右旋走滑破裂事件,3个发震断层均以走滑错动为主,断层面近似直立。     

2021年5月22日青海玛多Ms7.4地震发震构造分析

精确的余震序列定位及震源机制反演能够提供强震破裂尺度、发震断层面和区域应力场等信息,为震后应急决策和分析发震构造提供科学依据.本研究采用双差定位方法对2021年5月22日 青海玛多Ms7.4地震序列进行精定位,得到震后9天内共1055个事件的精定位结果;同时,利用青海、西藏、四川和甘肃台网记录的波形数据,采用近震全波形矩张量反演方法得到了玛多Ms7.4地震15次中等余震(Ms≥4.0)震源机制解,并进一步反演得到震源区构造应力场.地震定位结果显示,玛多主震位于玛多—甘德断裂与甘德南缘断裂之间,发震断层面较为陡立,余震序列在时间上呈现出不对称的双侧破裂模式,且沿主破裂面的两端均表现出分支破裂特征,说明本次地震触发了分支断层;震源机制结果显示15次中等余震包含12次走滑型和3次逆冲型地震,暗示主断层破裂受到局部异常结构的影响;另外,应力场反演表明震源区为近EW向挤压特征,与该区域最大水平主压应力优势取向一致.结合上述结果以及周边地质构造背景,我们认为玛多地震发震构造为位于巴颜喀拉地块内部一条NWW向的高倾角左旋走滑断裂,主破裂触发了东西两端分支断层活动,断层面的非均匀性控制了余震序列时空分布的差异性.     

根据波速比变化作出中期地震预报的一个实例

1976年11月7日,我国川滇两省交界处的盐源、宁蒗一带发生6.7级走滑断层型地震.震前约一年,作者根据附近约二万平方公里范围内的波速比普查结果,对未来主震的震级和地点作了比较符合实际的中期预报.发震时间的预报是后来根据其它前兆观测结果的综合分析作出的.本文可以作为走滑断层型地震前观测到波速比变化的一个新的实例.根据剪切破裂和粘滑运动之间的差别以及膨胀造成的各向异性,对有关结果作了初步讨论.      

GNSS观测的2021年5月22日玛多MS7.4地震同震位移及其约束反演的滑动破裂分布

2021年5月22日青海省果洛州玛多县发生M_W7.4地震,此次地震产生的地表破裂在空间上表现出明显的分段特征.本文基于不同来源的GNSS连续观测网数据获取了此次地震的精细三维同震形变场,结果显示:观测到的最大水平位移量达到280 mm,最大垂直形变量仅为25 mm,暗示此次地震的逆冲分量较小;此次地震具有较为明显的左旋走滑特征,同震形变基本对称,在NW-SE向的影响范围更广,该方向上水平同震形变大于3 mm的震中距范围超过500 km.进而,本文以余震精定位结果和GNSS观测到的三维同震形变场为约束,构建了地表破裂线为折线、倾角为85°、倾向西南的断层模型,反演了滑动破裂分布.结果显示:滑动破裂分布在震中两侧不均匀,均破裂到地表,破裂深度达到15 km左右,最大滑移量为4.73 m,计算的矩震级为M_W7.37.该结果与余震精定位结果具有很好的一致性,破裂的极值区正好位于早期余震空区,推测该余震空区未来的发震风险性较低.最后基于反演结果模拟计算了震中区域形变和应变场,结合应变值在断层地表迹线东南侧呈现挤压特征和已有的研究成果,推测此次地震增强了巴颜喀拉块体在东部地区挤压应力的积累特征,导致东部地区发震危险性增强,值得后续跟踪研究.     

2014年云南鲁甸M_W6.1地震:一次共轭破裂地震

烈度与余震分布显示2014年云南鲁甸MW6.1(MS6.5)地震的发震构造较复杂.为深入了解鲁甸地震的发震断层与破裂特征,本文考虑了单一断层破裂和共轭断层破裂的情况,对震中距250km范围内的近震资料(宽频带资料和强震资料)和远震体波资料进行了反演,得到了鲁甸地震的破裂过程,探讨了滑动分布与余震分布之间的关系.根据反演得到的滑动分布、震源时间函数和波形拟合,认为鲁甸地震是一次在北西向主压应力与北东向主张应力的统一应力场下发生的两条共轭断层先后破裂的一次复杂地震事件.在破裂开始后0~2s,破裂主要发生在ENE—WSW向(近东西向)的断层上,随后NNW—SSE向(近南北向)断层开始破裂,释放了大部分的地震矩.由于近南北向断层南段(即震中以南)的破裂规模较大,且以左旋走滑为主,对近东西向断层的西段起到了一定程度的解锁作用,可能是震中以西无明显主震破裂但存在密集余震分布的主要原因.     

澜沧—耿马地震发震构造初步研究

本文根据澜沧—耿马地震形变带、极震区及余震序列分布特征,分析了7.6和7.2级地震的发震构造,认为北北西向旱母坝断层是7.2级地震的发震构造,7.6级地震的发震构造不是一条单一的断层,北西向木嘎断裂和北北西向澜沧—勐海断裂均有明显破裂表现,这一特点与震区复杂的地质构造背景有密切联系。     

澜沧—耿马地震带大震47年复发周期及其科学意义

在前人研究的基础上,利用自相关函数方法分别对云南各主要地震带大震复发周期分别进行了系统计算,发现云南各地震区大震复发周期随着各自与板块缝合线的距离增是呈现规律性增加：澜沧－耿马地震带,因东、西两邻区大震复发周期分别为４６－４７年,故确认其大震复发周期为４７年。该４７年大震复发周期的确定,超越了本带历史地震记载缺乏、近３０年来地震活动高度平静、前人经验和前兆台网十分薄弱等难以逾越的障碍,对１９８８－     

云南活动性断裂带的结构变异与孕震体构造的空间关系

中国的强震主要发生在一些板内大型走滑断裂带上,地震的破裂基本上是以走滑型破裂为特征。在这些活动性的走滑断裂带上形成的孕震体构造与该走滑断裂结构在空间的变化有关,并且表现出几种主要的变异形式。结合西南地区地震构造的实例,本文剖析了这几种结构变异形式,阐明了孕震体构造存在的空间机制。本文从地震与构造丛集相关及其所具有的分维特征入手,展开了对孕震区断裂结构变异特征的识别和孕震体空间机制的探讨,表述了一条活动性大断裂必须由若干次级断裂和无数中小断裂的空间组合,才能形成孕震体的必要条件。     

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.     

从高波速比试论云南丽江7级地震的孕震模式

利用震中周围多台地震波资料计算平均波速比, 并对计算误差作了统计和分析, 提出了在介质存在横向不均匀的情况下数据处理方法。在资料有相当可信度的基础上, 动态追踪了１９９６ 年２ 月３ 日云南丽江７ 级地震前滇西北地区波速比的十余年时空演化图象。显示出： 丽江地震孕震区的高波速比异常图象经历了由小到大、由大到小并再次扩大的过程;而低波速比的异常图象则由大到小、由小到大并再次缩小的过程; 地震发生在低波速比异常区包围的高波速比异常区的交汇部位。其时间进程的演化显示丽江地震的孕震区在１９８８年耿马—澜沧７６ 、７２ 级地震后进入非线性阶段, １９９５ 年孟连西中缅边境７３ 级地震前进入失稳阶段。结合滇西北地区地震垂直分布图象和对照含硬包体试样在破裂孕育过程中波速场的演化图象, 表明丽江地震的孕震区具备了坚固体孕震模式的高波速特征     

THE SOURCE PARAMETERS AND SEISMOTECTONIC IMPLICATIONS OF THE SEPTEMBER 4, 2017 ML4.4 LINCHENG EARTHQUAKE

At 3:05, September 4, 2017, an M_L4.4 earthquake occurred in Lincheng County, Xingtai City, Hebei Province, which was felt obviously by surrounding areas. Approximately 60km away from the hypocenter of Xingtai M_S7.2 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 M_S7.2 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 M_S7.2 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.     

2009年云南姚安6.0级地震震源机制与发震构造的分析研究

利用P波、SV波、SH波初动及其振幅比联合反演震源机制解的方法,计算了2009年7月9日发生在云南姚安6.0级地震余震序列的震源机制解,同时结合地震序列的空间分布,对姚安6.0级地震的发震断层性质和震区应力场特征进行综合分析。结果分析表明：（1）姚安6.0级地震发震断层为NWW—SEE向的直立右旋走滑断层,与美国哈佛大学的主震CMT解节面基本一致,也与余震优势方向分布一致,证明结果可靠;（2）震区主压应力场优势方向为NNW—SSE向,与其现今区域构造应力场主压应力NNW—SSE向一致,表明主震应力场主要受到现今区域构造应力场的控制,同时还有一些小的余震与主震应力场不同,表明震区应力场的多样性和复杂性;（3）结合本次地震序列的空间分布、震源机制解特征、震区断裂构造特征综合分析,综合判定姚安6.0级地震的发震构造属于马尾箐断裂。     

走滑断层地表位移动态演化特征研究

在经典走滑断层位移公式基础上引入时间变量, 研究断层运动中地表位移与时间的动态变化关系, 得到走滑断层地表位移时空动态演化公式。 当观测点处于断层近、 中场或者孕震阶段处于孕震中、 晚期时, 地表位移近似正比于时间对数函数。 得到以下结果: ① 走滑断层随时间的位移是不收敛的, 但发散速度十分缓慢。 ② 目前多数GPS水平方向的时间序列良好的线性特征为时间对数函数的局部线性近似。 ③ 在孕震中、 晚期的任意时刻, 断层近、 中场的地表任意一点的位移与其距断层的距离成正比, 即垂直于断层方向的地表位移曲线近似一条直线。 ④ 从震前的某个时刻开始计时, 震前距断层远的站点产生的位移比距断层近的站点产生的位移大; 震后距断层近的站点产生的位移比距断层远的站点产生的位移大。 走滑断层地表位移动态演化公式适用于断层的近中场, 孕震的中晚期, 可为断层地震危险性的判定提供理论支持。     

Andaman-Sumatra island arc: II. The December 26, 2004 earthquake as one of the key episodes in seismogenic activation of the arc in the beginning of XXI century

The interpretation of the nature and parameters of the source for the earthquake that occurred in Sumatra on December 26, 2004 is suggested. Our study relies on a variety of data on the geological structure of the region, long-term seismicity, spatial distribution of the foreshocks and aftershocks, and focal mechanisms; and the pattern of shaking and tsunami, regularities in the occurrence of the earthquakes, and the genetic relationship between the seismic and geological parameters inherent in various types of seismogenic zones including island arcs. The source of the Sumatran earthquake is a steep reverse fault striking parallel to the island arc and dipping towards the ocean. The length of the fault is ～450 km, and its probable bedding depth is ～70–100 km. The magnitude of this seismic event corresponding to the length of its source is 8.9–9.0. The vertical displacement in the source probably reached 9–13 m. The fault is located near the inner boundary of the Aceh Depression between the epicenter of the earthquake and the northern tip of the depression. The strike-slip and strike-slip reverse the faults cutting the island arc form the northern and southern borders of the source. The location and source parameters in the suggested interpretation account quite well for the observed pattern of shaking and tsunami. The Aceh Depression and its environs probably also host other seismic sources in the form of large reverse faults. The Sumatran earthquake, which was the culmination of the seismogenic activation of the Andaman-Sumatra island arc in the beginning of XXI century, is a typical tsunamigenic island-arc earthquake. By its characteristics, this event is an analogue to the M _W = 9 Kamchatka earthquake of November 4, 1952. The spatial distribution of the epicenters and the focal mechanisms of the aftershocks indicate that the repeated shocks during the Sumatran event were caused by the activation of a complex system of geological structures in various parts of the island arc and Andaman Sea instead of the slips on a single rupture (a subduction thrust about 1200–1300 km in length).     

鲁甸6.5级地震发震断层判定及其构造属性讨论

鲁甸6.5级地震是川滇菱形块体南南东向运动在青藏高原东缘与华南地块相互作用边界变形带上发生的一次中等强度地震.尽管野外应急科学考察没有发现明显的地震地表破裂带,但云南昭通防震减灾局局域地震台网记录到的余震条带状分布、震后科学考察获得的地震烈度长轴方位和极震区地震裂缝等显示出发震断层为NW向包谷垴-小河断裂,左旋走滑性质,属大凉山断裂南端部组成部分;库仑应力计算表明,鲁甸地震可对周边活动断层系历史地震空段产生应力加载作用,其地震危险性不容忽视.