山东地区地壳速度与中强地震的关系

利用山东区域地震数字台网提供的数据,通过三维层析成像方法结合山东地质构造实际情况,对山东区域进行联合走时反演地壳速度结构,获得该区分辨率较高的三维速度结构图像。结果表明：不同深度上的速度分布反映出山东地区深部构造的某些重要信息,为进一步研究该区的活动构造及地震参数计算提供科学依据。在地壳速度结构与中强地震活动的关系上,再次显示出中强震多发生在速度结构高速单元与低速单元的过渡带附近,说明中强震的孕育与震源区周围介质的不均匀性有关。     

平顶山地区爆破识别判据分析

对2008年1月1日-2012年12月31日河南数字地震台网记录的平顶山地区的地震与爆破事件,从初动方向、振幅比、周期比和记录波形对比等进行分析,结果表明：振幅比和记录波形对比可以作为平顶山地区爆破识别判据,初动方向可以作为该地区爆破识别的辅助判据.     

山东及附近海域构造环境剪应力场分析

利用山东数字地震台网的地震波形记录,选取2007年以来台网记录清晰的ML≥2．0数字地震波形资料,计算每次地震的环境剪应力值τ0和矩震级MW,并分析其相关关系;结合山东地区地质构造和地震活动性特点,对胶东半岛及北部海域、南黄海北部地区、沂沭带地区、冀鲁豫交界地区应力场分布和时空变化进行细致分析,并探讨其区域特征及与地震活动性的关系。     

基于OpenSees的混凝土结构连续倒塌分析中的从属节点建模技术

对重大工程结构进行强地震作用下的连续倒塌全过程分析并建立相应的设计与控制方法,已成为当前地震工程领域的发展趋势。目前,由于数值求解方面的困难,绝大多数针对极端作用下的结构连续倒塌的研究止步于数值临界状态的界定,在分析过程中不能实时地对结构构件的损伤状态进行监测并根据构件的损伤状态对分析模型进行修改。为了实现连续倒塌过程中构件的逐步失效,在OpenSees程序中,基于Beam with Hinges Element构建了端部带附属节点的Beam with Hinges Element,并根据构件失效情况对附属节点的多点约束进行控制。采用三次静力凝聚方法和Newmark-beta法,给出了对此改进建模技术可信的理论背景,方法的准确性通过一个简单框架算例得到了验证。     

长乐-南澳构造带白垩纪“片麻状”浆混杂岩的成岩机制研究——以泉州肖厝岩体为例

闽东南长乐南澳构造带沿线出露大面积白垩纪花岗岩岩基,普遍存在岩浆混合现象,肖厝侵入岩是其中的代表性岩体.野外观察和化学分析表明,肖厝侵入岩由二长花岗岩和辉长闪长岩、以及该两种混合端员岩浆混合形成的闪长质-花岗闪长质-花岗质过渡岩类组成;岩石总体富碱、富LREE和LILE、贫HFSE; A/CNK=0.82～1.05,属准铝质微过铝质钙碱性系列,部分受流体交代的岩石A/CNK值可升高至1.69;岩浆混合过程中发生了元素的选择性富集/亏损和同位素组成的均一化,（87Sr/86Sr）为0.7055～0.7061,εNd（t）为-1.9～-3.0.锆石年代学研究表明,肖厝侵入岩的岩浆混合开始于约136Ma,于121Ma时初始侵位于下地壳.结合区域地质特征,分析了肖厝侵入岩的成岩机制,提出岩体侵位早于长乐-南澳构造带的变质变形作用,两者不存在成因上的联系;118～～100Ma时该构造带曾发生过深层次地壳逆冲推覆,使形成于中—下地壳的韧性剪切带和肖厝侵入岩共同快速上升至地表.     

Identifying spatio-temporal variation and controlling factors of chemistry in groundwater and river water recharged by reclaimed water at Huai River,North China

Reclaimed water is efficiently used to recover the dry river, but river water and groundwater may be impacted considering the water quality. Thus, it is critical to study the factors controlling water chemistry. Samples of reclaimed water, river and groundwater were collected monthly from January to September in 2010, in Huai River (North China). And samples were analyzed for major 15 physio-chemical parameters. Using hierarchical cluster analysis, 9 months are divided into two distinct groups, which show the clear temporal variation. In reclaimed water and river water, one group includes February, while the other includes other months. In shallow and deep groundwater, one group includes months from January to April, while the other encompasses others. Monitoring stations are classified into three groups. Group A with high value of ions and nitrogen (order: NH₄-N > NO₃-N > NO₂-N) includes reclaimed water and river water. Group B with moderate concentration and nitrogen (order: NO₃-N > NH₄-N > NO₂-N) includes all shallow groundwater and one deep groundwater. Group C with the low value and nitrogen (order: NO₃-N > NO₂-N > NH₄-N), includes two deep groundwater. Using multivariate analysis and ionic relationships, river water chemistry is found to be controlled by reclaimed water and evaporation process; chemistry in shallow groundwater and one deep groundwater, with type of Na–Ca(Mg)–HCO₃–Cl, is controlled by dissolution of calcite, carbonate weathering. Additionally, reactions of nitrification, denitrification and cation exchange occur in the infiltration of reclaimed water; chemistry in the other deep groundwater, with type of Ca–Mg–HCO₃–Cl, is controlled by dissolution of calcite, carbonate weathering and denitrification.     

Structural modal parameter identification and damage diagnosis based on Hilbert-Huang transform

Traditional modal parameter identifi cation methods have many disadvantages,especially when used for processing nonlinear and non-stationary signals.In addition,they are usually not able to accurately identify the damping ratio and damage.In this study,methods based on the Hilbert-Huang transform(HHT) are investigated for structural modal parameter identifi cation and damage diagnosis.First,mirror extension and prediction via a radial basis function(RBF) neural network are used to restrain the troublesome end-effect issue in empirical mode decomposition(EMD),which is a crucial part of HHT.Then,the approaches based on HHT combined with other techniques,such as the random decrement technique(RDT),natural excitation technique(NExT) and stochastic subspace identifi cation(SSI),are proposed to identify modal parameters of structures.Furthermore,a damage diagnosis method based on the HHT is also proposed.Time-varying instantaneous frequency and instantaneous energy are used to identify the damage evolution of the structure.The relative amplitude of the Hilbert marginal spectrum is used to identify the damage location of the structure.Finally,acceleration records at gauge points from shaking table testing of a 12-story reinforced concrete frame model are taken to validate the proposed approaches.The results show that the proposed approaches based on HHT for modal parameter identifi cation and damage diagnosis are reliable and practical.     

Dynamic analysis of slab track on multi-layered transversely isotropic saturated soils subjected to train loads

The dynamic responses of a slab track on transversely isotropic saturated soils subjected to moving train loads are investigated by a semi-analytical approach. The track model is described as an upper Euler beam to simulate the rails and a lower Euler beam to model the slab. Rail pads between the rails and slab are represented by a continuous layer of springs and dashpots. A series of point loads are formulated to describe the moving train loads. The governing equations of track-ground systems are solved using the double Fourier transform, and the dynamic responses in the time domain are obtained by the inverse Fourier transform. The results show that a train load with high velocity will generate a larger response in transversely isotropic saturated soil than the lower velocity load, and special attention should be paid on the pore pressure in the vicinity of the ground surface. The anisotropic parameters of a surface soil layer will have greater influence on the displacement and excess pore water pressure than those of the subsoil layer. The traditional design method taking ground soil as homogeneous isotropic soil is unsafe for the case of RE 1 and RG 1, so a transversely isotropic foundation model is of great significance to the design for high train velocities.     

Spectral-element simulations of elastic wave propagation in exploration and geotechnical applications

We apply the spectral-element method (SEM), a high-order finite-element method (FEM) to simulate seismic wave propagation in complex media for exploration and geotechnical problems. The SEM accurately treats geometrical complexities through its flexible FEM mesh and accurately interpolates wavefields through high-order Lagrange polynomials. It has been a numerical solver used extensively in earthquake seismology. We demonstrate the applicability of SEM for selected 2D exploration and geotechnical velocity models with an open-source SEM software package SPECFEM2D. The first scenario involves a marine survey for a salt dome with the presence of major internal discontinuities, and the second example simulates seismic wave propagation for an open-pit mine with complex surface topography. Wavefield snapshots, synthetic seismograms, and peak particle velocity maps are presented to illustrate the promising use of SEM for industrial problems.     

RZB型深井宽频带地形变综合观测系统的垂向应变测量单元

目前钻孔应变观测一般为水平应变,使用无限岩石平板中的钻孔应力集中模型,可反演出水平应力场分布及变化.如果在此基础上加上垂向应力测量,就可反演出三维应力场分布.本文介绍的RZB型深井宽频带地形变综合观测系统的垂向应变测量单元,外钢筒为波纹管结构,并通过螺旋刻丝、热处理等技术,其垂向等效弹性模量比耦合水泥低一个数量级,同时垂向应变钢筒的水平向等效弹性模量高于垂向弹性模量一个数量级.垂向应变探头的力学结构可以被形象地看成是一个螺旋柱形弹簧,其轴向极易产生弹性形变,而水平向的硬度却得到了极大的加强,因此可在竖井中较为准确地测量轴向应变.