汶川Ms 8.0级地震余震重新定位及其空间分布特征研究

对南四川台网提供的2008年5月12日至2008年12月31日期间发生的地震观测报告资料进行了整理,并根据研究需要从中挑选出了2957次地震事件用于地震定位研究.然后,采用双差定位方法对汶川Ms 8.0级地震及挑选出的余震进行了重新定位,得到2678个地震的震源位置,重新定位后走时均方根残差由重新定位前的1.01s降到了0.20s,水平和垂直方向标准差分别为±0.85km和±1.3km.余震震中沿走向分布的总长度约为350km,震源深度优势分布为5～20km,平均震源深度为11.4km.文章结合地表考察破裂、震源机制解等研究结果,对余震空间分布进行了更为详细的分段和讨论,提出以下3点认识:1)余震震中沿主破裂带表现出明显的空间分段活动特征,根据余震空间分布特征和震源机制解可推测断层运动方式由一开始的逆冲为主,经过渡段最终转换为以右旋走滑为主;2)沿小鱼洞-棉篪-理县和青川-文县方向延伸的北西向余震带存在两个与龙门山构造带走向近似垂直的捩断层;3)龙门山构造带的北段(水观乡以北),存在一个斜跨北川-映秀断裂和青川-平武断裂的隐伏断层,并且该隐伏断层参与了北段余震的发震过程.     

龙门山地震带5.12汶川地震余震空间分布特征

2008年5月12日14时28分至10月12日12时,四川省汶川发生Ms8.0级地震后共记录到余震33 308次,Ms≥ 4.0级余震268次.采用GIS技术,对龙门山地震带上汶川、北川、青川3个县从2008年5月12日~10月12日12时发生的156次Ms≥ 4.0级余震的空间分布进行了研究.结果显示:在汶川、北川、青川3个县境内:①在东西方向上,若干余震点位的连线与纬线平行,Ms≥ 4.0级余震呈现纬向地带性特征;②Ms≥4.0级余震亦呈现经向地带性特征;③Ms≥4.0级余震点位在南北方向与东西方向的连线形成了经纬交织的网格,在空间上呈现等间距网络状分布现象;④Ms≥4.0级的156次余震均发生在经纬交织的网络节点处及其附近,在空间上具有原地复发性的特点.研究结果对于该地震带的趋势分析和震情监视有一定的意义.     

2013年四川芦山7.0级地震发震构造机理及青衣江上游流域地貌的响应

2013年4月20日发生在四川芦山的7.0级地震位于龙门山断裂带南段,文中通过分析震区青衣江上游流域地貌的构造响应与典型的震灾特征,研究此次地震的发震构造机理。对穿越龙门山断裂带南段的青衣江上游水系地貌特征及流域盆地面积高程积分的分析结果表明：该地区流域地貌发育对龙门山断裂带的新活动具有明显的反馈作用。在芦山地震中,遭受严重破坏的建筑物呈条带状分布,并产生大量次生地表张性地裂缝、串珠状砂土液化等地表破坏现象,其展布方向均与震区中的主断裂和背斜隆起相平行。余震分布表明,芦山地震与本区的双石-大川断裂、新开店断裂和大邑断裂的新活动有关。龙门山断裂带为典型的逆冲推覆构造,具有前展式发育特征,芦山地震的发震构造就具有该特征。综合龙门山南段的地貌响应过程、芦山地震的地表破坏及余震分布特征,认为芦山7.0级地震应为龙门山断裂带持续向SE逆冲扩展、地壳挤压缩短的产物。     

芦山Mw6.6地震序列的震源机制及震源区应力场

为研究2013年4月20日芦山M_w6.6地震的发震构造及孕震机理, 基于4月20日—6月1日地震序列中114次M≥3.0余震震源机制解, 深入分析了余震震源机制及震源区应力场的时空分布特征, 获得的主要认识如下: (1)芦山M≥3.0余震以逆冲型为主, 走滑型次之, 正断型最少, 震源机制P轴方位一致性较好, 以近NWW-SEE为优势方向, 倾角分布在0~30°, 表明余震活动主要受龙门山断裂所在的区域应力场控制; (2)芦山余震区压应力S1方位存在明显的局部空间分区差异, 以主震震中为界, 余震区南边S1方向总体呈NWW方向, 而余震区北边S1方向表现出由NW经EW向NE的逆时针旋转, 可能反映了余震区北边发震断层错动以逆冲为主兼有一定的走滑分量; (3)压应力S1方位随时间的变化不明显, 呈近NWW方向, 但其倾角逐渐变水平, 应力张量方差逐渐变大, 震源机制错动类型始终以逆冲为主, 随时间变的相对紊乱, 反映了震源区应力场随时间的调整变化特性; (4)深度剖面结果显示压应力方位与发震断层走向的夹角在80°~120°, 即近乎垂直, 震源断层面向NW倾斜, 芦山余震活动受控于近垂直发震断裂的挤压作用, 属于典型的逆冲断层.      

芦山地震发震构造及其与汶川地震关系讨论

芦山地震发生在巴彦喀拉块体与华南块体之间龙门山推覆构造带南段。野外考察表明,芦山地震在震中区没有形成具有构造地质意义的地震地表破裂带,仅在各山前陡坡地带出现平行于山麓陡坡的张性地裂缝、山地基岩崩塌、滑坡等边坡震动失稳现象和震动引起的砂土液化现象。重新定位的芦山地震余震分布、震源机制解和地表构造地质等分析表明,芦山地震的发震断层为一条现今尚未出露地表、其上断点仍埋藏在地下9 km以下地壳中的一条盲逆断层,走向212°,倾向NW,倾角38°±2°,上断点以上至地表的构造变形符合断层扩展背斜模型。根据汶川地震和芦山地震的余震空间分布、地震破裂过程、深浅构造关系等差异反映出它们是分别发生在龙门山推覆构造带中段和南段的两次独立地震破裂事件。     

芦山地震发震构造及其与汶川地震关系讨论

芦山地震发生在巴彦喀拉块体与华南块体之间龙门山推覆构造带南段。野外考察表明,芦山地震在震中区没有形成具有构造地质意义的地震地表破裂带,仅在各山前陡坡地带出现平行于山麓陡坡的张性地裂缝、山地基岩崩塌、滑坡等边坡震动失稳现象和震动引起的砂土液化现象。重新定位的芦山地震余震分布、震源机制解和地表构造地质等分析表明,芦山地震的发震断层为一条现今尚未出露地表、其上断点仍埋藏在地下9 km以下地壳中的一条盲逆断层,走向212°,倾向NW,倾角38°±2°,上断点以上至地表的构造变形符合断层扩展背斜模型。根据汶川地震和芦山地震的余震空间分布、地震破裂过程、深浅构造关系等差异反映出它们是分别发生在龙门山推覆构造带中段和南段的两次独立地震破裂事件。     

广西典型岩溶区土壤水分含量空间自相关分析

以广西壮族自治区马山县为研究区,在野外调查、室内实验测试获取182个土壤水分含量数据的基础上,采用半方差函数和Moran’s I统计量对研究区域土壤水分含量的空间自相关关系、空间相关尺度和空间分布规律进行了研究。结果表明:(1)研究区域土壤水含量平均值为16.97%,受结构性因素和随机因素共同作用,土壤水分含量具有中等强度的空间异质性;(2)研究区域土壤水分含量Moran’s I指数为0.423,表明研究区内土壤水分含量存在空间自相关性,在0~21 km和31~34 km范围内土壤水分含量自相关性为正,在21.7~31 km和34~45 km范围内自相关性为负;(3)Lisa聚类图表明,土壤水分含量空间聚集区和空间孤立区相伴存在,其中“高—高”空间聚集主要分布在马山县东北部,“低—低”聚集区主要分布在东南部。“低—低”聚集区和“高—低”孤立区土壤水分含量缺乏风险大。      

运用GIS探讨中国铜矿床空间分布及其与断裂带的关系

本文从中国铜矿的地理分布出发,通过对矿点密度和断裂密度等值线的相关性分析,探讨了铜矿的空间分布及其与断裂带的关系,得出：断裂密度在（60,220）区间的铜矿点占总数的81.9%;在距断裂带20.76假定单元内（实际距离为86km）集中了大约83%的铜矿点。由此可见,断裂带与铜矿区带的展布有关,对铜矿床分布的控制作用明显。     

基于关联维数的地质灾害空间分布特征分析

通过分形理论中关联维数及其动态变化来揭示黑水河流域地质灾害的时空分布特征,并探讨了影响区内地质灾害空间分布的相关因素。研究表明:区内不同规模地质灾害点系统空间分布具有分形特征,崩塌灾害点的分布最为集中,滑坡次之,泥石流则最为分散;近十年来区内每年所发生灾害的空间分布集中程度变化剧烈,呈现强集中、弱分散的特点;近五年来每年所发生的灾害呈逐渐分散趋势,但灾害的累积却有逐渐集中的趋势;影响区内地质灾害空间分布异同的主要因素为地形坡度、地层岩性、河流、降雨、人类工程活动、高程、断裂。     

豫西熊耳山Ag、Ag-Pb、Au、Mo及Pb矿床 (点)的空间分布特征及找矿启示

对豫西熊耳山121个Ag、Ag-Pb、Au、Mo及Pb矿床(点)的空间分布特征进行了分析,并在此基础上探讨了熊耳山地区找矿潜力区。在经度方向上,它们集中于熊耳山的东、西两端,而在中部(111.45°~111.50°和111.60°~111.65°)出现两个矿床频数低值;在纬度方向上,矿化主要集中分布于34.10°~34.25°的中部地带。121个矿床(点)的高程(采矿平硐海拔高度)集中分布于600~750 m、800~1 050 m和1 100~1 200 m三个高程区间内,熊耳山东、西两端大型Ag-Pb、Au和Mo矿床的高程大致相当。121个矿床(点)组成了6条矿化种类各异和走向不同的矿化条带,分别为近NW向的Ag及Ag-Pb矿化条带(M1)和Au(Mo、Pb)矿化条带(M3)、近NE向的Au(Mo、Pb)矿化条带(M2)、近EW的Pb-Au(Mo)矿化条带(M4)、近NNW向的Au矿化条带(M5)和近NS向的Au(Mo、Pb)矿化条带(M6),其走向均与区域以及矿床控矿构造的走向大致相当。121个矿床(点)在空间三个投影面中均遵循分形丛集分布,并且存在两个无标度网格区,显示了多重分形的特征,发现熊耳山矿集区的分布具有约10 km等间距的特征,并结合透岩浆流体成矿理论对熊耳山地区进一步的成矿潜力区进行了分析。     

汶川8．0级地震序列时空分布研究

基于四川防震减灾信息网以及中国地震台网中心、中国地震信息网、国家地震科学数据共享中心提供的汶川8．0级地震目录资料,对2008年S月12日至2010年3月1日共1613次3．0级及以上余震的地震序列进行了时空分布分析。结果表明：汶川8．0级地震的余震大致可分为7个阶段,主震后18天应列为大地震强余震发生的警戒时间;地震序列的b值为0．751,印证了在类型相同的情况下主震震级越大b值越高的观点;地震序列的P值为1．117,与全球地震衰减速率相当;汶川地震的余震分布主要沿龙门山断裂走向北东向扩展,且具有明显分区性,自南向北分为南、中、北3区段,南区为地震起始破裂段,地震后期余震则主要分布在北区;震源深度分布在10～40km,集中在10～20km,表明龙门山断裂主要发生在中上地壳,且震源深度由南向北呈现逐渐变浅的趋势;震源深度扩展,南区呈明显脉冲状,中区主要是依次由15、30、25km深度向深、浅层同时扩展,北区余震深度分布呈“乙”字型,最后稳定在15km左右。     

A worldwide test of three long-term premonitory seismicity patterns—a review

Worldwide analysis of the clustering of earthquakes has lead to the hypothesis that the occurrence of abnormally large clusters indicates an increase in probability of a strong earthquake in the next 3–4 years within the same region. Three long-term premonitory seismicity patterns, which correspond to different non-contradictory definitions of abnormally large clusters, were tested retrospectively in 15 regions. The results of the tests suggest that about 80% of the strongest earthquakes can be predicted by monitoring these patterns.Most of results concern pattern B (“burst of aftershocks”) i.e. an earthquake of medium magnitude with an abnormally large number of aftershocks during the first few days. Two other patterns, S and Σ often complement pattern B and can replace it in some regions where the catalogs show very few aftershocks.The practical application of these patterns is strongly limited by the fact that neither the location of the coming earthquake within the region nor its time of occurrence within 3–4 years is indicated. However, these patterns present the possibility of increasing the reliability of medium and short-term precursors; also, they allow activation of some important early preparatory measures.The results impose the following empirical constraint on the theory of the generation of a strong earthquake: it is preceded by abnormal clustering of weaker earthquakes in the space-time-energy domain; corresponding clusters are few but may occur in a wide region around the location of the coming strong earthquake; the distances are of the same order as for the other reported precursors.     

Time-dependent analysis of aftershock events and structural impacts on intraplate crustal seismicity of the Van earthquake (Mw 7.1, 23 October 2011), E-Anatolia

The Van earthquake (M _W 7.1, 23 October 2011) in E-Anatolia is typical representative of intraplate earthquakes. Its thrust focal character and aftershock seismicity pattern indicate the most prominent type of compound earthquakes due to its multifractal dynamic complexity and uneven compressional nature, ever seen all over Turkey. Seismicity pattern of aftershocks appears to be invariably complex in its overall characteristics of aligned clustering events. The population and distribution of the aftershock events clearly exhibit spatial variability, clustering-declustering and intermittency, consistent with multifractal scaling. The sequential growth of events during time scale shows multifractal behavior of seismicity in the focal zone. The results indicate that the extensive heterogeneity and time-dependent strength are considered to generate distinct aftershock events. These factors have structural impacts on intraplate seismicity, suggesting multifractal and unstable nature of the Van event. Multifractal seismicity is controlled by complex evolution of crustal-scale faulting, mechanical heterogeneity and seismic deformation anisotropy. Overall seismicity pattern of aftershocks provides the mechanism for strain softening process to explain the principal thrusting event in the Van earthquake. Strain localization with fault weakening controls the seismic characterization of Van earthquake and contributes to explain the anomalous occurrence of aftershocks and intraplate nature of the Van earthquake.     

Earthquake Modelling at the Country Level Using Aggregated Spatio-Temporal Point Processes

The goal of this paper is to derive a hazard map for earthquake occurrences in Pakistan from a catalogue that contains spatial coordinates of shallow earthquakes of magnitude 4.5 or larger aggregated over calendar years. We test relative temporal stationarity by the KPSS statistic and use the inhomogeneous J-function to test for inter-point interactions. We then formulate a cluster model, and de-convolve in order to calculate the hazard map, and verify that no particular year has an undue influence on the map. Within the borders of the single country, the KPSS test did not show any deviation from homogeneity in the spatial intensities. The inhomogeneous J-function indicated clustering that could not be attributed to inhomogeneity, and the analysis of aftershocks showed some evidence of two major shocks instead of one during the 2005 Kashmir earthquake disaster. Thus, the spatial point pattern analysis carried out for these data was insightful in various aspects and the hazard map that was obtained may lead to improved measures to protect the population against the disastrous effects of earthquakes.     

龙门山断层破裂的频率非平稳特性

为研究地震过程中的频率非平稳特性,对近年来龙门山断层发生的两次大地震:汶川大地震和芦山大地震的近断层地震记录进行频谱分析。结果表明:相对于芦山地震有较大走向滑动分量的汶川地震,大多数位于汶川地震断层滑动前方的台站接收到更高的频率成分,位于断层滑动后方的台站接收到的地震波频率较低;尽管芦山地震断层相对汶川地震有较小的走向滑动分量,但仍然可以得出与汶川地震相同的结论,不同的是虽然芦山地震沿断层面向上方向分量大,但是其同一台站东西、南北、竖直三方向分量记录幅值相当。把芦山地震三分量记录变换到走向和沿断层面向上方向,证实了沿断层面向上方向高频成分更丰富。在断层滑动前方接收到的地震波频率较高,在断层滑动后方接收到的频率较低,这正是多普勒效应影响的结果。由于多普勒效应的客观存在,其对频率非平稳特性的影响与震源、传播路径和场地效应一样具有普遍性;所以,工程场地接收到的地震波的频率不仅取决于震源、传播路径、场地效应,还取决于断层滑动速度(多普勒效应)。     

青藏高原东南缘活动断裂地质灾害效应研究现状

青藏高原东南缘不同性质、不同类型、不同特点活动断裂发育且较为活跃,自2008年汶川地震发生以来,相继发生了玉树地震、庐山地震、鲁甸地震等。地震引发、触发、诱发产生了大量地质灾害,造成了惨重的生命财产损失。通过收集与分析相关资料,对青藏高原东南缘活动断裂地质灾害效应研究进展与取得成果进行了归纳总结,从活动断裂地质灾害主要控制因素,地质灾害发育特征、空间分布规律、演化模式、形成机制,不同性质断裂控制效应、断裂两盘差异效应、地震动参数效应、地形地貌效应等地质环境效应和地质灾害力学效应等方面进行了综述。在此基础上,对活动断裂地质灾害效应研究中存在的如不同类型活动断裂和不同震级地震与地震地质灾害相关性、以及地震地质灾害监测与风险评估等问题或重点研究方向进行了探讨,其研究结果为地震地质灾害致灾机理、风险评估、防灾减灾等研究提供参考。      

The progress of emergency response and rescue in China: a comparative analysis of Wenchuan and Lushan earthquakes

Earthquake emergency response and rescue (ERR) is a global challenge, but especially in developing countries. As a large earthquake-prone developing country, China’s experiences and lessons in ERR can provide a useful reference for other developing countries. In this article, China’s ERR progress is summarized by comparatively analyzing the Wenchuan and Lushan earthquakes, two major recent earthquake events in Sichuan Province. From a comprehensive investigation of the research, it can be concluded that emergency response speed, inter-organizational coordination, and relief resource mobilization are the three critical ERR indicators which can be further subdivided into sixteen sub-indicators. Using these indicators, the Wenchuan and Lushan earthquake ERR processes were comprehensively compared based on data collected from observations and interviews. The results showed that the response and rescue efforts at the Lushan earthquake were faster, more coordinated, and more orderly than those at the Wenchuan earthquake. In addition, the unified earthquake ERR system, the people-oriented principle, and the information disclosure mechanism were examined, which also revealed several major shortcomings, such as deficits in the adaptability to relief technologies, the lack of coordination between rescue organizations, and the lack of capabilities in the local communities. Finally, several recommendations are given for the practical improvement of and future research into the establishment of an effective ERR.     

Comparing the Hawkes and Trigger Process Models for Aftershock Sequences Following the 2005 Kashmir Earthquake

In an earlier study (Van Lieshout and Stein in Math Gesoci 44(3):309–326, 2012) we postulated the existence of two major earthquakes in the 2005 Kashmir disaster instead of a single one, based upon the pattern of aftershocks. In this study, we explore this hypothesis further by fitting several spatial point pattern models. In particular, we discuss the Hawkes and the trigger process models for earthquake aftershock sequences following the Kashmir catastrophe in 2005. The minimum contrast method is used for estimation of the parameters. The study shows that the trigger model fits better than the Hawkes model. The most likely number of main shocks is rounded to 2 generating the almost 200 aftershocks, whereas the Hawkes model would estimate a parent process of approximately 18 parents with on average about 10 descendants. We conclude that the spatial pattern of aftershocks can best be understood as a mixture of two bivariate normal distributions centered around two major shocks and estimate the parameters.