2016年阿克陶MS6.7地震震源复杂性与烈度

2016年11月25日在我国新疆克孜勒苏州阿克陶县发生M_S6.7地震（阿克陶M_S6.7地震）.我们收集国内外地震资料,对主震及4级以上余震进行了重新定位和震源机制反演,对434次余震进行了双差定位,对主震震源过程进行了反演确定和复杂性分析,并基于反演确定的有限动态源模型估计了此次地震的烈度分布.结果表明：这次地震发生在当地一个近乎东西向展布的小型盆地内,很可能由一条新断层或隐伏断层的活动所致.发震断层近乎直立,近东西向展布,总体上表现为右旋走滑.破裂首先向西扩展,紧接着向东,随后向东西两个方向同时扩展,然后西侧破裂首先停止,东侧破裂继续,最后破裂在东侧停止,整个过程持续~20 s,释放地震矩1.08×10¹⁹N·m,相当于M_W6.6.破裂过程最终形成两个位错高值区,分别位于初始破裂点的东西两侧,西侧高值区规模较小,东侧区规模较大.根据烈度估计,烈度椭圆长轴方向与主震破裂方向以及余震展布方向一致,最大烈度约为Ⅸ度,主要集中在震中以东很小的区域,Ⅷ度区呈纺锤形,分布于震中东西两侧,Ⅴ至Ⅶ度区呈椭圆形,总体上东侧烈度大于西侧.

     

2014年新疆于田MS7.3地震序列重定位及其发震构造初步研究

2014年2月12日在新疆于田县发生了M_S7.3地震,主震前一天在震区发生了M_S5.4前震,震后余震活动频繁,由于震区台站十分稀疏和不均匀、地壳速度结构复杂,台网常规定位结果精度有限,很难从中获得序列的空间分布特征和活动趋势的正确认识.本文首先利用位于震区附近的于田地震台5年记录的远震波形数据,采用接收函数方法研究了震区附近的地壳结构,建立了震源区的地壳速度模型.在此基础上,联合震相到时和方位角对2014年于田M_S7.3地震序列(从2014年02月11日-2014年04月30日,共计577次地震)进行了重新绝对定位.结果显示,(1) 重定位后的前震和主震震中位置明显向地表破裂带及其附近的阿尔金分支断裂(南肖尔库勒断裂和阿什库勒-肖尔库勒断裂)靠近,两者相距5.4 km,主震位置为36.076°N、82.576°E,震源深度为22 km, 前震位置为36.055°N、82.522°E,震源深度为19 km;(2) 本文重定位结果显示,余震序列沿NEE-SWW展布,优势分布长度约73 km、宽度约16 km,平均震源深度为14.8 km,其中77%的余震分布在地表破裂带的西南端,这部分余震中少数沿阿什库勒-肖尔库勒断裂分布,绝大多数沿北东东向的南肖尔库勒断裂分布,位于地表破裂带东北端的余震沿阿什库勒-肖尔库勒断裂分布,但发生在地表破裂带的余震极少;重定位后,位于地表破裂带西南侧的震中分布由台网目录的近南北向变为北东向,与地表破裂带、南肖尔库勒断裂和阿什库勒-肖尔库勒断裂走向一致;(3) 沿重定位剖面的地震分布,可推断位于地表破裂带西南段的南肖尔库勒断裂与位于北东段的阿什库勒-肖尔库勒断裂倾向反向,南肖尔库勒断裂的倾向为SE,阿什库勒-肖尔库勒断裂的倾向为NW,这与本次地震野外考察得到的断裂性质一致.综合重定位结果、地表破裂带分布、震源机制解、南肖尔库勒断裂和阿什库勒-肖尔库勒断裂的性质认为,2014年于田M_S7.3地震的发震构造为阿尔金断裂西南尾段的两条分支断裂——南肖尔库勒断裂和阿什库勒-肖尔库勒断裂.     

Patience,persistence and pre-signals: Policy dynamics of planned relocation in Austria

Within the wide array of adaptive responses to flood hazards, planned relocation of residents at risk is usually only taken into account if other responses are ineffective or unavailable. Residents targeted by planned relocation are confronted with radical changes in their livelihood; therefore, relocation is highly contested within public risk discourse. The present paper assesses dynamic processes in the design and implementation of voluntary planned relocation in the Austrian Danube catchment over five decades. Using the Multiple Streams Approach, the emergence of policy windows is mapped to developments in the problem, political, policy and population streams. A mixed-methods design combines semi-structured interviews of 88 affected households and 21 decision-makers with archival research. Repeated flood events underscored that standard protection did not suffice for all riverside communities. In consequence, national authorities acted as policy entrepreneurs to advocate planned relocation and direct the discourse; by contrast, local stakeholders and residents played a mostly passive role. The relocation policy developed from ad-hoc informal arrangements towards a formalised procedure. Relocation governance evolved as incremental change over a long time span instead of immediate, radical disruption. Policy acceptance by residents depended crucially on social learning and on coincidence with personal circumstances and biographical stages. Policy windows opened for several years, when pre-signals from ongoing public debate accumulated and the different timescales in the decision-making of public administrators, elected representatives and residents aligned. Key factors were long-term perspective, flexibility, engagement and social capacity at a local level to deal with and manage planned relocation.     

Tracking the North Korean nuclear explosion of 2006, using seismic data from Japan and satellite data from Taiwan

The location of the 2006 nuclear explosion in North Korea has been accurately imaged by back-projected regional Pn waves recorded by the Japanese Hi-net array. Based on the determined location, the nuclear explosion site can be identified from geo-referenced FORMOSAT-2 satellite images. The seismically determined epicenter is about 2.5 km northeast of the original estimate of its absolute location. Results indicate that a remote suspect event had been unambiguously detected and accurately located by a dense array within a regional distance. Employing ground truth correction, the satellite images can be referenced for shifting the array-determined epicenter to its absolute position. After correction, this event can be treated as a reference event for accurately locating future nuclear explosions. Our study utilizes public information from a dense seismic network and further demonstrates that commercial observation satellites can accurately monitor compliance with the Comprehensive Nuclear-Test-Ban Treaty, as well as earthquake and tsunami hazards almost in real time.     

利用和田地震台阵数据对2008年于田7.3级地震序列重新定位

利用新疆和田地震台阵数据,应用宽频F-K分析方法,结合新疆数字地震台网部分台站数据,通过震相到时、方位角和慢度的线形化反演地震定位方法对2008年3月21日新疆于田7.3级地震及2008年3月21日~2008年8月31日ML≥4.0的余震序列中119次地震进行重新定位,重新定位结果与新疆区域地震台网定位结果有明显差异。重新定位结果表明,于田7.3级地震序列呈近NS向条带分布,与野外考察发现地表破裂带基本一致。研究结果表明,利用地震台阵结合部分区域地震台网数据,可以对台网相对稀疏地区的地震进行较为精确的定位,可为基础研究和震情趋势判定提供基础资料。     

2009年4月19日新疆阿合奇5.4级地震

利用俄罗斯科学院比什凯克科学站地震台网中3个台站资料和新疆地震台网12个台站资料,分别用不同地震定位方法,对2009年4月19日中国新疆阿合奇5.4级地震和其3个余震震源参数进行重新定位。并且将其结果与新疆地震目录、中国地震台网统一地震目录进行了比较,对其宏观震中、发震构造、震源机制及地震类型等进行了分析与讨论。     

山西地震带中小震精确位置及其显示的山西地震构造特征

利用山西1981—2001年模拟观测台网和2002—2008年间数字地震台网的震相数据,采用绝对定位方法和双差相对地震定位方法对山西及其周边地区中小地震进行了精确重新定位.结果表明: (1) 重新精确定位后,震中水平误差≤5 km的地震由原来65.8%提高到86.2%;7498次原始无震源深度的地震取得了深度结果.(2)精确定位后震中分布格局与原始结果相比变化不大,绝大多数地震集中在中部断陷盆地带内,两侧隆起区则相对较少,与山西地质构造的区域性和成带性相吻合;震源深度北浅南深,存在由北向南逐渐加深的特点. (3)重定位结果可以大致勾勒出各构造盆地发震层下界,较清晰地分辨出断陷盆地、盆间隆起的位置.(4)地震深度分布与盆山构造形态有较好的相关性.