复杂地表低信噪比地震数据处理研究

焉耆盆地地质条件复杂,侏罗纪末燕山运动和第三纪喜山运动的挤压推覆作用在焉耆盆地南缘霍拉山前形成一系列推覆构造.由于地形起伏大,近地表结构复杂,采集的地震资料信噪比较低;以推覆构造为主体的地下地质复杂性给地震成像造成极大的困难.针对该复杂地区低信噪比地震资料,在偏移前资料预处理中,通过采取一系列旨在提高信噪比、重建反射信号的技术,为后续的复杂构造成像处理奠定基础.针对断裂交错的复杂推覆构造成像,采用增强高波数波场成像的半解析Fourier地震偏移方法,能很好地成像强速度对比下的陡倾角大断裂地质构造,有效突出推覆体构造的空间形态,改善推覆体下的成像效果.     

基于局地集合变换卡尔曼滤波的全球海洋资料同化系统设计及算法加速

通过对局地集合变换卡尔曼滤波(LETKF)算法的计算时间复杂度的完整分析,发现计算集合空间分析场误差协方差的逆矩阵这一过程计算量最大,耗时最长。且在并行计算环境下,该步骤CPU计算量分配不均是影响计算效率的直接原因。为解决这一问题,采用“贪心算法”设计了一套新的负载均衡策略,并使用该策略开发了一个基于LETKF和并行海洋模块2(POP2)的高性能并行海洋资料同化系统。将2004年1~2月日平均的最优插值海表温度资料(OISST)和同时期的Argo温盐剖面资料同化进入POP2。结果表明,同化有效降低了温度和盐度的均方根误差。同时,在不改变计算结果的前提下,相比原始同化系统,新系统计算性能提升1倍。在更高分辨率(0.1°×0.1°)下,该系统的计算性能仍然可以提升1倍,说明新设计的负载均衡方案稳定可靠。该方案具有很强的可扩展性和移植性,在业务预报中有广泛的应用前景。     

Temporal variations in the abundance and sinking flux of diatoms under fast ice in summer near Syowa Station, East Antarctica

To investigate the fate of ice algae released from sea ice, we investigated the abundance, species composition, and sinking flux of diatoms in the water column under fast ice near Syowa Station, Antarctica during the summer of 2005/2006. The diatom assemblage in the water column consisted of chain-forming planktonic species, in contrast to the under-ice assemblage dominated by pennate species reported from this site in the past; this dissimilarity suggests the presence of an unconsolidated platelet ice layer under the congelation ice, within which planktonic species can bloom. Among the dominant diatoms, Porosira pseudodenticulata and Pseudo-nitzschia cf. turgiduloides were dominant in the water column, and their water column stocks were higher than their mass sedimentation. These species apparently maintain their populations in the surface layer, as their production remains in the water column. In contrast, Fragilariopsis kerguelensis and Thalassiosira australis were scarce in the water column but rich in the flux, indicating active sinking and export of their production to the benthic ecosystem. This distinction in buoyancy control and sinking characteristics of the dominant diatoms on release from the fast ice influences the diatom species composition and carbon flow under the ice.     

Eurasian Arctic shelf hydrography: Exchange and residence time of southern Laptev Sea waters

The hydrography of the Laptev Sea is significantly influenced by river water and sea-ice processes, which are highly variable over the annual cycle. Despite of an estuarine structure the inner and outer shelf regions are decoupled at times as documented by the stability of a warm intermediate layer formed during summer below the Lena River plume. We demonstrate that a remnant of this warm layer is preserved below the fast ice until the end of winter, while only slightly farther to the north, offshore of the landfast ice in the polynya region, the pycnocline is eroded and no signature of this layer is found. The warm intermediate layer (WIL) formed during summer can be used as tracer for Laptev Sea shelf waters throughout the winter. Thereby, residence times of southern Laptev Sea waters can be estimated to be at least from summer to the end of winter/spring of the following year.     

曲线箱梁桥地震反应的频域精细传递矩阵法

本文将高精度的精细积分法和力学概念清晰的传递矩阵法结合起来,以微分方程和矩阵分析理论为基础,提出了一种新的精细传递矩阵形式,在频域内对曲线箱梁桥地震反应进行分析. 与传统的传递矩阵法相比,无需对微分方程进行求解,只需按照迭代公式进行计算,就可以得到所需要的传递矩阵.这种方法公式简单,理论上可实现任意精度要求,而且计算效率较高.能够快速、高精度地进行曲线梁桥的地震反应分析.算例显示了精细传递矩阵法的有效性..     

Quantitative particle size,microtextural and outline shape analyses of glacigenic sediment reworked by paraglacial debris flows

Particle size analysis and scanning electron microscopy have been used with some success to differentiate sediments sampled from varying geomorphological environments. In the paraglacial environment, however, discrimination of paraglacially reworked deposits from in situ glacigenic deposits has proven to be problematic. We consider till sediments that have been reworked by paraglacial debris flows and in situ, unreworked parent material, and apply a series of quantitative techniques in an attempt to discriminate samples from each environment. Initial analysis of particle size suggests some eluviation of fines from the debris‐flow‐reworked deposits but is of insufficient significance to allow reliable differentiation of geomorphological environment. Similarly, although slight differences are identified in terms of quartz grain surface microtextures and quartz grain outline shape, subsequent PCA, cluster and Fourier analyses fail to reliably differentiate quartz grains from each geomorphological environment, owing to high levels of intra‐sample heterogeneity. This lack of apparent difference may arise from a lack of paraglacial process operation of significant magnitude or duration for a characteristic process imprint to emerge at this scale of observation. Accordingly, further assessment of particle‐size and microtextural characteristics of glacial and paraglacial sediments may be most fruitful where sediments have been reworked over long distances. Moreover, differentiating glacial from paraglacial deposits is likely to yield the most reliable results where rigorous statistical analyses are combined with a wide range of sedimentological and geomorphological techniques. Copyright © 2008 John Wiley and Sons, Ltd.     

一种适于震后快速评估的群体易损性分析方法

本文提出了一种适用于震后快速评估的群体易损性分析方法,将模糊数学中的熵权法确定权重和相似理论引入到群体易损性分析中,可快速准确地评估出群体建筑物的震害情况。本方法不需要详细调查城市所有房屋的结构力学参数,所采用的影响结构抗震能力的主要因素从房屋普查资料中即可获得,可作为将来震后快速评估系统的重要组成部分。同时,本方法还可以得到群体易损性曲线,可应用于预测城市震害、估计城市的综合抗震能力。本文以城镇中量大、面广的砌体结构为例,详细介绍了该方法的研究过程。最后,用算例证明了本方法的准确性和实用性。     

局部断层精确计算定理的证明

本文给出了局部断层图像重建精确计算定理的简单证明。局部断层图像重建是一类仅需较少的扫面数据的断层成像技术,可以有效降低扫面物体的辐射剂量,提高图像重建速度。文献[6]针对局部断层成像的概念提出了一种扇形束的一般扫描轨道的局部断层的精确图像重建方法。本文为文献[6]的定理提供了一个简捷的证明。     

Dynamic response of utility tunnel duringthe passage of Rayleigh waves

The modeling methodologies and calculation of dynamic response of underground structure under Rayleigh waves is investigated in this paper. First the free field responses under Rayleigh waves are analyzed and the numerical results agree well with the theoretical results. Then, the approximate Rayleigh waves are put forward based on the preliminary re-search, and Rayleigh wave field is obtained through fast Fourier transform technique. Taking a utility tunnel as an example, its dynamic responses under Raylei...     

山西长治测震台网速报地震震级误差初探

选取山西长治数字测震台网2006年10月至2009年12月记录到的301个ML≥2.0地震,对其震级等参数进行了重新计算、整理和统计分析,并与山西省测震台网所给出的震级参数进行了回归分析和曲线拟合,得到长治台网平均震级与省台网震级的线性和非线性回归公式、相关系数和均方根误差等。为震级测定提供参考,以减小速报地震震级误差。