2022年9月5日四川泸定MS6.8地震舆情分析

2022年9月5日12时52分,四川省甘孜州泸定县发生 M_S6.8地震,造成重大人员伤亡,引起社会公众的广泛关注。突发事件的信息发布和舆情引导越来越受到党和政府的高度重视,相关信息公开效率的影响甚至决定了事件处置的舆情发展。本研究以中国地震台网中心为舆情引导主体,对四川泸定 M_S6.8地震舆情进行分析研究,总结舆情引导经验,探讨突发地震舆情引导对地震部门有效开展震后应急的促进作用,以期为今后的防震减灾新闻宣传工作带来启示和思考。     

基于开源GIS的地震灾情速报信息收集与处置研究

针对河南省灾情获取效率低的现实问题,设计基于QGIS的微信小程序,实现灾情速报员属性数据空间化,并自动分配拨打电话任务,灾情调查人员及时将通过拨打电话获取的灾情信息快速上报,实时动态展布,并快速统计灾情速报信息,生成地震有感范围图和地震灾情信息汇总报告,为地震抗震救灾指挥部决策提供支持,满足河南及邻区小震、弱震较多地区地震应急、应急演练工作需求,也为其他应急系统建设提供参考。     

Rapid report of the 8 January 2022 ​MS 6.9 Menyuan earthquake,Qinghai, China

The M_S 6.9 Menyuan earthquake in Qinghai Province, west China is the largest earthquake by far in 2022. The earthquake occurs in a tectonically active region, with a background b-value of 0.87 within 100 ?km of the epicenter that we derived from the unified catalog produced by China Earthquake Networks Center since late 2008. Field surveys have revealed surface ruptures extending 22 ?km along strike, with a maximum ground displacement of 2.1 ?m. We construct a finite fault model with constraints from InSAR observations, which showed multiple fault segments during the Menyuan earthquake. The major slip asperity is confined within 10 ?km at depth, with the maximum slip of 3.5 ?m. Near real-time back-projection results of coseismic radiation indicate a northwest propagating rupture that lasted for ～10 ?s. Intensity estimates from the back-projection results show up to a Mercalli scale of IX near the ruptured area, consistent with instrumental measurements and the observations from the field surveys. Aftershock locations (up to January 21, 2022) exhibit two segments, extending to ～20 ?km in depth. The largest one reaches M_S 5.3, locating near the eastern end of the aftershock zone. Although the location and the approximate magnitude of the mainshock had been indicated by previous studies based on paleoearthquake records and seismic gap, as well as estimated stressing rate on faults, significant surface-breaching rupture leads to severe damage of the high-speed railway system, which poses a challenge in accurately assessing earthquake hazards and risks, and thus demands further investigations of the rupture behaviors for crustal earthquakes.     

Temporal evolution of the focal mechanism consistency of the 2021 Yangbi MS 6.4 earthquake sequence in Yunnan

Using the Cut And Paste (CAP) method, we invert the focal mechanism of 38 moderate earthquakes (M_S ≥ 3.0) recorded by Yunnan seismic network and analyze the corresponding focal mechanism consistency based on the minimum spatial rotation angle. Our results indicate that the M_S 6.4 mainshock is induced by a lateral strike slip fault (with a rake angle of ～ ?165°) and a little normal-faulting component event along a nearly vertical plane (dipping angle～ 79° and strike ～138°). Combining our results with high resolution catalog, we argue that the seismogenic fault of this earthquake sequence is a secondary fault western to the major Weixi-Qiaohou-Weishan fault. The focal mechanism evolution can be divided into three periods. During the first period, the foreshock sequence, the focal mechanism consistency is the highest (KA<36°); during the second period which is shortly after the mainshock, the focal mechanism shows strong variation with KA ranging from 8° to 110°; during the third period, the seismicity becomes weak and the focal mechanism of the earthquakes becomes more consistent than the second period (18°<KA<73°). We suggest that the KA, to some extent, represents the coherence between local tectonic stress regime and the stress state of each individual earthquake. Furthermore, high focal mechanism consistency and high linearity of seismic distribution may serve as indicators for the identification of foreshock sequence.     

日喀则蛇绿岩研究中的几个问题

日喀则蛇绿岩是中国最著名的蛇绿岩,但是,许多问题存在争论,许多现象没有搞清楚。文中讨论了日喀则蛇绿岩中一些重要的现象以及对目前发现的许多矛盾如何考虑的问题。例如,(1)日喀则蛇绿岩中是否存在席状岩墙群?是否存在席状岩床群?本文认为,席状岩墙群应当是存在的,因为有不对称冷凝边出现。而席状岩床群可能是有问题的,岩床作为侵入体可以出现在许多地方,但是,蛇绿岩中不可能出现席状岩床群,尤其还把它作为蛇绿岩岩石组合的一个单元。笔者认为,所谓的席状岩床群可能是席状岩流群,它不是一个独立的单元,是玄武岩单元下部的成员。(2)日喀则蛇绿岩是否统统是蛇绿岩是一个需要考虑的问题,雅鲁藏布江东西两段出现的岩石组合及其产出背景与日喀则地区的蛇绿岩明显不同,其中有些可能未必是蛇绿岩。(3)自1972年彭罗斯会议以来,蛇绿岩研究发展到现在,可能已经进入了一个关键时期。文中回顾了蛇绿岩的定义及其构造意义,指出1972年彭罗斯会议关于蛇绿岩的定义仍然是适用的。蛇绿岩可以概括为洋壳+地幔,这个洋壳来自板块扩张脊,是年轻的;这个地幔是大洋岩石圈地幔,也可能保留有古老岩石圈地幔的印记。蛇绿岩产于板块扩张脊,这是蛇绿岩构造含义的唯一解,蛇绿岩不存在多解性。(4)日喀则蛇绿岩的许多基本观点主要是法国学者提出来的,如关于岩床群的见解,慢速扩张的见解等。但是,上述见解是否都是对的是需要思考的。日喀则蛇绿岩具有得天独厚的条件,我们应当很好利用这个条件,努力把我们的研究做好,为全球蛇绿岩研究贡献我们的一份力量。     

2008年汶川地震(Ms8.0)非对称同震破碎带的确定:来自WFSD-1随钻流体的证据

地震过程中相当可观的一部分能量消耗于裂隙的活化与形成,来自汶川地震断裂带科学钻探一号孔(WFSD-1)的随钻流体表明,地震新形成的裂隙对应有较强的流体异常,它们为流体的入侵提供了良好的通道。随钻流体呈非对称性分布于主滑移面的两侧,主要的流体异常带集中在主滑移带下方须家河组顶部120 m范围内,该带中气体的含量以及变动的频率明显高于上部相同的宽度范围以及下部沉积岩层,来自地球物理测井的资料同样显示这一带破碎严重并伴随有大量水的侵入,暗示汶川地震形成的裂隙具有非对称性分布的特征。这一特征可能同时受控于断裂上盘彭灌杂岩与下盘须家河组岩层的力学性质差异以及地震破裂过程中形成的非对称性应力分布。     

Wavelet Analysis of Earthquake Activity in the West of the Chinese Mainland and Its Adjacent Area

INTRODUCTIONWiththedevelopmentofsocietyandquickurbanizationfeaturedbyacentralizationofpopulationsandeconomies ,itisverylikelythatastrongearthquakewillcausethedeathofhundredsandthousandsofpeopleandhugelossofproperty .Forexample ,intheepicenterareaoftheBame…     

中国大陆7级强震前地下流体前兆时空特征

对中国大陆1969年以来11次7级强震前地下流体前兆观测资料分阶段进行统计分析,并选用雷达图描述了中国大陆7级强震前地下流体前兆异常的时空特征,认为其特征主要表现在：异常出现时间上的阶段性与不均匀性,中长期趋势性异常分散,短临异常相对集中,且各占总异常比例的50％左右;震前异常集中在一定的范围内,并沿活动断裂呈现出一定的集中性;中长期趋势异常较早出现在震源区附近,并呈现出由震源区向外围扩散-收缩-扩散-收缩的过程,特别是进入短临阶段后,异常向震源区收缩的趋势更为明显;在震源区(或在距震源较近的范围内)异常所占的比例大,远离震源区所占比例小,且有由震源区向外围逐渐减小的趋势。     

Stress Changes Modelled for the Sequence of Strong Earthquakes in the South Iceland Seismic Zone Since 1706

The South Iceland seismic zone is, roughly speaking, situated between two sections of the mid-Atlantic ridge, i.e., the Reykjanes Ridge southwest of Iceland and the Eastern Volcanic Zone on the island. It is a transform zone, where earthquakes are expected to occur on E-W-trending left-lateral shear faults, equivalent to conjugate, N-S-oriented right-lateral, rupture planes. In fact, earthquakes take place on en-échelon N-S-oriented faults, which is indicated by the distribution of main shock intensities, aftershocks as well as by surface fault traces. The stress field continuously generated in the fault zone by opening of the adjacent ridges is computed and superimposed on the stress field changes induced by a series of 13 earthquakes (M 6) between 1706 and 2000. The level of the pre-seismic stress field is analysed as well as the size of the area under high stress. Finally, the post-seismic stress field of June 2000 is analysed, to see where high stresses might have accumulated. The modelling indicates that the rupture planes located on separated parallel N-S-striking zones are dense enough to lead to an area-wide stress release by the series of events. The obtained pre-seismic stress level for most events is high and stable with the exception of situations when several strong shocks occur over a time span of several days, i.e., display typical main shock-aftershock patterns. The size of areas under high stress aside from of the rupture plane, i.e., where no event occurs at the specific time, is of medium to small size.