大地震震级测定及速报

为了研究在强烈地震发生时,记录图最大振幅出格,如何决速测定强震震级这一实用化很强的问题,在用面波持续时间及测定体波震级方法的基础上。本文用云南1988年11月发生在澜沧、耿马地区的两次M_S≥7.0的地震资料(由全国基准台网SK仪器记录的地震图),进一步研究用这两种方法快速测定大地震震级作为速报方法的可能性。研究结果表明,用归算的面波持续时间测定M_S作为大震速报,一般需要等待从地震图初至后延10—20分钟的时间,而用体波测定震级m_B作为大震速报仅需要等待从初至后延数秒至5分钟左右。因此,是最为实用的大震速报方法。其优点在于图上最先到达的总是体波,对于M_S≥7.0的地震,体波振幅往往不限幅,这种特征满足强震测定和大震速报的需要。本文用澜沧、耿马两次大震的资料,对这两种方法作了较好的比较和检验。用收集到的约1500多个中强地震的面波震级和体波震级数据,经验统计给出两者之间的线性关系为M_S=1.55mg-3.47。     

基于状态转移矩阵的Hilbert码快速生成算法

空间填充曲线的空间排列码可实现多维空间到一维空间的线性映射,广泛应用于空间查询、空间索引、空间划分及影像编码等领域。Hilbert是一种优秀的空间填充曲线,具有非常好的空间聚集性。传统的Hilbert排列二进制循环位操作算法的算法复杂度为O(n²)。本文首先分析了Hilbert的分形自相似特性,推导并归纳出Hilbert状态转移矩阵,按位编码顺序定义了空间划分中的象限顺序,将Hilbert状态转移矩阵转换为C++中的数组运算,减少了Hilbert码计算过程中的嵌套循环及迭代处理,将算法复杂度降为O(n)。其次,采用位域共用体以数值计算替代了传统计算过程中的数值与字符串间类型转换,提高了Hilbert码生成算法的性能。最后,在C++环境下实现了Hilbert码快速生成算法的相关代码,并完成算法的正确性验证实验和性能对比实验。实验结果表明,本文提出的算法计算结果与二进制循环位算法的结果一致,在性能上本文算法与二进制循环位算法及空间层次分解算法相比有明显的优势。     

山东泗水双震叠加快速定位浅议

以2007年11月15日6时5分23秒和37秒在山东泗水接连发生的ML3.1和ML3.3两次地震为例,分析研究了地震叠加如何快速定位的问题。研究结果表明,在大震速报中,可以根据测定的第1个地震的三要素参数,直接确定后一次地震的震中经、纬度,第2个地震的发震时刻等于第1个地震测定的发震时刻加两PG到时差,第2个地震震级等于第1次地震多台测定的震级加上任一单台测定两次地震震级差。     

基于IE的羊八井中子监测器数据实时发布系统

介绍了基于IE(Internet Explorer)浏览器的西藏羊八井中子监测器数据发布系统, 具体描述了系统结构和工作界面、 网络服务器的工作原理、 快视图输出界面和数据输出界面运行的流程, 以及这两种输出界面在网络服务器中所涉及到的参数设置和数据库访问, 相关shell文件及快视图生成软件的编制。     

中国地质科学院对5.12汶川地震的快速反应与调查研究

面对5.12汶川8级地震突发灾害,中国地质科学院组织专家,科学分析发震动力学背景,第一时间奔赴震中地区开展地表破裂变形与地震地质灾害调查,随后系统开展地震科学钻探选址、活动断裂与地震变形观测、地应力测量、地质灾害地面调查、堰塞湖与水工环综合评价。6位专家参加国家汶川地震专家委员会,编辑出版《汶川地震灾区地震—地质灾害图集》,组织召开汶川地震动力学分析研讨会,2位专家参加国土资源部抗震救灾前方指挥部工作。在第33届国际地质大会期间,组织汶川地震大型展览,应邀作汶川地震、地震科学钻、地表破裂等学术报告,受到国际同行的高度关注。组织申报汶川地震断裂带科学钻探工程,2008年11月第一口地震科学钻开工;组织落实国家专项、973课题、地质调查项目等科研任务,有效地调整了面向地质灾害的学科结构和人才布局。     

基于Quick Shift算法的高光谱影像分类

论述了面向对象分类方法处理高光谱高空间分辨率影像的优势与流程;分析了快速漂移(Quick Shift)算法的原理,该算法在进行模式搜索时具有可控制模态选择和平衡过分割与欠分割的特点。将该算法应用于高光谱影像分割,可得到面向对象分类所需的较理想的同质影像对象。为提高影像分割的效率,提出了一种基于灰度共生矩阵的自适应核带宽确定方法,能够兼顾影像空间特征和光谱特征。最后采用最小距离分类法、支持向量机分类法与提出的分类方法进行了对比试验,实验结果表明了该方法的有效性。     

The physics of gas chimney and pockmark formation,with implications for assessment of seafloor hazards and gas sequestration

Pockmarks form where fluids discharge through seafloor sediments rapidly enough to make them quick, and are common where gas is present in near-seafloor sediments. This paper investigates how gas might lead to pockmark formation. The process is envisioned as follows: a capillary seal traps gas beneath a fine-grained sediment layer or layers, perhaps layers whose pores have been reduced in size by hydrate crystallization. Gas accumulates until its pressure is sufficient for gas to invade the seal. The seal then fails completely (a unique aspect of capillary seals), releasing a large fraction of the accumulated gas into an upward-propagating gas chimney, which displaces water like a piston as it rises. Near the seafloor the water flow causes the sediments to become “quick” (i.e., liquefied) in the sense that grain-to-grain contact is lost and the grains are suspended dynamically by the upward flow. The quickened sediment is removed by ocean-bottom currents, and a pockmark is formed. Equations that approximately describe this gas–piston–water-drive show that deformation of the sediments above the chimney and water flow fast enough to quicken the sediments begins when the gas chimney reaches half way from the base of its source gas pocket to the seafloor. For uniform near-surface sediment permeability, this is a buoyancy control, not a permeability control. The rate the gas chimney grows depends on sediment permeability and the ratio of the depth below seafloor of the top of the gas pocket to the thickness of the gas pocket at the time of seal failure. Plausible estimates of these parameters suggest gas chimneys at Blake Ridge could reach the seafloor in less than a decade or more than a century, depending mainly on the permeability of the deforming near-surface sediments. Since these become quick before gas is expelled, gas venting will not provide a useful warning of the seafloor instabilities that are related to pockmark formation. However, detecting gas chimney growth might be a useful risk predictor. Any area underlain by a gas chimney that extends half way or more to the surface should be avoided.     

ESTIMATION OF SCOUR HOLE PROPERTIES AROUND VERTICAL PILE USING ANNs

Correct estimation of the scour around vertical piles in the field exposed to oscillatory waves is very important for many offshore structures and coastal engineering projects. Conventional predictive formulas for the geometric properties of scour hole, however, are not able to provide sufficiently accurate results. Artificial Neural Networks (ANNs) are simplified mathematical representation of the human brain. Three-layer normal feed-forward ANN is a powerful tool for input-output mapping and has been widely used in civil engineering problems. In this article the ANNs approach is used to predict the geometric properties of the scour around vertical pile. Two different ANNs including multilayer perceptron (with four different learning rules) and radial basis functions neural networks are used for this purpose. The results show that a three-layer normal feed-forward multilayer perceptron with quick propagation (QP) learning rule can predict the scour hole properties successfully.     

Displacement properties of landslide masses at the initiation of failure in quick clay deposits and the effects of meteorological and hydrological factors

This study aimed to identify displacement properties of landslide masses at the initiation of failure and factors that affect the landslides activities in areas where quick clay is found. We set up a research site in a quick clay deposit area in Norway and monitored the displacements of landslide masses and meteorological and hydrological factors for a long period of time using an automatic monitoring system. The system collected data for two landslides that occurred at the site from the start of their movement until their ultimate collapse.

The two landslides that were monitored showed definite secondary and tertiary creep stages before they collapsed. One of the landslides moved from the secondary stage to the tertiary creep stage when another landslide occurred nearby. The tertiary stage of this landslide showed reconstruction of short primary, secondary, and tertiary creep stages. These phenomena suggested that (1) the stress at the end of the landslide mass was released during the nearby landslide, and (2) a new stress distribution was formed in the landslide mass. The critical strain differed for 14 times between the two landslide masses we monitored. The difference was likely attributable to the difference in the contents of quick clay, which shows small critical stress against slope failure, as well as topological factors.

Our analyses of the effects of hydrological and meteorological factors on landslides showed that the precipitation of 3 and 10 days before six slope failures as the final stages of the landslides that had occurred in the research area was no different from the mean precipitation of periods that showed no slope failure, suggesting that precipitation had no direct effects on the collapse of the landslide masses. On the other hand, the traveling velocities of the landslide masses during the secondary creep stage, which was prior to their collapse, were affected by the water content of the soil and precipitation (and the amount of snowmelt water), but was little correlated with the pore-water pressure of the quick clay layer. We also found that the presence of snow cover scarcely affected landslide movements.     

Quick Bird遥感数据在龙羊峡库区白刺滩滑坡调查中的应用

应用具高分辨率、高清晰度、信息量丰富及数据时效性强等特点的QuickBird遥感数据,对龙羊峡库区白刺滩特大型滑坡进行遥感调查,利用先进的遥感数据处理技术,综合地质学、灾害学原理和地理空间信息技术,分析了白刺滩滑坡的形成条件、成因机理,认为龙羊峡库水强烈侵蚀和降雨综合作用是促进滑坡发生的主要诱发因素。