用双差地震定位法再次精确测定1998年张北-尚义地震序列的震源参数

1998年1月10日北京时间11时50分（03时50分UTC），在北京西北约180 km的河北省张北县与尚义县交界地区发生的ML=6.2地震. 该地震是近年华北地区的重要地震事件. 由于地表未见明显的活动断裂展布，震后的野外考察未给出任何优势走向的地表破裂资料，余震分布也没有显示出优势的展布方向，因此发震构造不清楚.笔者曾应用主事件相对定位方法，对张北——尚义地震序列的主震和ML3.0余震重新精确定位，得出结论:张北——尚义地震序列的主震震中位置为41.145N、114.462E，位于宏观震中的北东方向约4km处，震源深度15 km; 余震震源分布在走向180～200、接近于竖直的平面内及其附近. 这一重新精确定位的结果表明，张北——尚义地震的发震构造是一北北东向的断层. 文中作者应用另一相对定位方法——双差地震定位法，对张北——尚义地震序列的主震和ML3.0余震再度进行精确定位. 双差地震定位法重新定位后，得出结论:张北——尚义地震序列的主震震中位置为41.131N、 114.456E，位于宏观震中的北东方向约2.5 km处，震源深度12.8 km; 余震震源也分布在走向N10E的接近于竖直的平面内及其附近. 这一重新精确定位的结果，再次表明张北——尚义地震的发震构造是一北北东向的断层.      

小净距隧道施工小导管注浆效果的数值模拟分析

利用有限差分法,对软弱围岩小净距隧道进洞施工中两种小导管注浆加固范围的加固效果进行了对比分析,揭示了施工过程中两种加固范围对隧道周边变形和应力的影响.研究结果表明增加对雁形部上部范围加固的方案较仅加固中间岩柱的方案有利于施工的安全.     

动力打桩一维波动方程的改进及其工程应用

对桩的可打入性进行准确的分析和预测是打桩施工的关键环节,同时也关系到整个工程的进度与成败.近年来,在海洋工程和港口工程中都出现了大直径、超长桩,由于这种桩的重量大对桩的可打入性有显著影响,考虑桩身自重和桩周土阻力,对打桩分析的一维应力波动方程进行改进、推导.采用有限差分法求解波动方程,编制计算程序结合实际工程进行打桩分析,分析结果与实测数据吻合较好,表明经改进的动力打桩一维波动方程能很好的预测桩的可打入性及打桩过程中桩身应力分布情况.     

Three-dimensional numerical modelling of wind-driven circulation in a homogeneous lake

A three-dimensional numerical model has been developed to study wind-induced circulation patterns in a shallow homogeneous lake with a complex bathymetry. The governing equations are the unsteady Reynolds-Averaged Navier–Stokes equations in which the non-hydrostatic pressure distribution has been included. The model was tested against analytical solutions and laboratory data for wind-induced currents and then applied to Esthwaite Water, a small lake in Cumbria, UK. The model was used to study the main model parameters and to generate typical circulation patterns for a variety of conditions in the lake. Simulations showed that a non-hydrostatic pressure distribution did not have any noticeable influence on the overall circulation pattern in the lake. However, comparisons with field data at some measurement stations in the near-shore region with sharply varying bottom topography showed that the hydrodynamic pressure component had some influence on the vertical velocity profile.     

水平磁场台际转换函数C_u的大小——有限差分法模型计算研究

计算的几种模型表明，用改进的三维有限差分法程序计算的异常体中心点上的水平磁场实部可达 1.53，这就意味着水平场转换函数 Cu也可达 1.53，与单台垂直磁场的转换函数有相同量级的大小。     

浅析山西临汾中心地震台定点水准测段高差的变化特征

叙述了山西临汾中心地震台定点水准观测场地及所跨断层的简况，利用1987年至2000年的观测资料对跨断层的2个测段高差变化进行了分析，结果表明，BM4-BM1测段能反映所监测断层的变化。     

Arbitrary Difference Precise Integration Method for Solving the Seismic Wave Equation

Wave equation migration is often applied to solve seismic imaging problems. Usually, the finite difference method is used to obtain the numerical solution of the wave equation. In this paper, the arbitrary difference precise integration (ADPI) method is discussed and applied in seismic migration. The ADPI method has its own distinctive idea. When dispersing coordinates in the space domain, it employs a relatively unrestrained form instead of the one used by the conventional finite difference method. Moreover, in the time domain it adopts the sub-domain precise integration method. As a result, it not only takes the merits of high precision and narrow bandwidth, but also can process various boundary conditions and describe the feature of an inhomogeneous medium better. Numerical results show the benefit of the presented algorithm using the ADPI method.     

Generation of thermal inertia image over a part of Gujarat: A new tool for geological mapping

Thermal inertia is a volume property and can be used to detect the subsurface features in an alluvium-covered area. A thermal inertia image has been generated over a part of Gujarat using consecutive day and night NOAA-AVHRR data. Gujarat contains two important rift basins in the western margin of India, namely, Cambay and Kutch basins. Major land covers exist in this region are alluvium, continental sediments, various rocks of Mesozoic and Cenozoic origin followed by Deccan Volcanics, tertiary and quaternary deposits. Validation of thermal inertia parameters with existing values obtained from literature indicates the efficacy of the developed technique. The study indicates that thermal inertia image can be used as a new method for geologic mapping/basin delineation where exposure is less or contrast is negligible between litho-units using traditional photography/sensing techniques.     

川滇地区现今块体水平运动变形特征分析

依据川滇地区1991，1999和2001年GPS测量数据，利用DDA正分析基本原理，结合现有的地质资料，对该地区近年来的水平构造运动特征进行了模拟分析，认为川滇地区水平运动整体速率在1999～2001年期间明显减弱；川滇决体主压应变以顺时针旋转为主，方向为SE—SEE；其南部是运动变形相对剧烈、易于积累能量的区域；未来一两年内，该地区地震活动水平不会太高。     

Simulating strong ground motion from complex sources by reciprocal Green functions

We have developed a method to calculate site and path effects for complex heterogeneous media using synthetic Green’s functions. The Green’s functions are calculated numerically by imposing body forces at the site of interest and then storing the reciprocal Green’s functions along arbitrary finite-fault surfaces. By using reciprocal Green’s functions, we can then simulate many source scenarios for those faults because the primary numerical calculations need be done only once. The advantage of the proposed method is shown by evaluation of the site and path effects for three sites in the vicinity of the Los Angeles basin using the Southern California Velocity Model (version 2.2, Magistrale et al., 2000). In this example, we have simulated 300 source scenarios for 5 major southern California faults and compared their responses for period longer then 3 seconds at the selected sites. However, a more detailed comparison with strong motion records will be necessary before a particular hazard assessment can be made. For the tested source scenarios the results show that the variations in the peak velocity amplitudes and durations due to a source scenarios are as large as variations due to a heterogeneous velocity model.