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991.
Yuan Gao Jing Wu Jin-An Cai Yu-Tao Shi Shu Lin Ting Bao Zu-Ning Li 《Journal of Seismology》2009,13(2):267-275
This study is focused on Fujing Province in China, southeast of Cathaysia block (SECB). The present work benefits from the
data provided by the Fujian Seismic Network (FJSN) to study the seismic anisotropy in the crust. By means of a systematic
analysis and adequate software package, we examine shear-wave splitting from data recorded at ten FJSN stations during the
period January 1999 to December 2003. The results demonstrate that the average fast wave polarization is N109.4° E ± 42.6°,
corresponding to the horizontal principal compressive stress in the test zone, and the average normalized slow wave time delay
is 2.5 ± 1.5 ms/km. The predominant polarizations at stations in the eastern part of SECB are in the N–W direction, which
suggests that they are related to the regional horizontal principal compressive stress and also to the strikes of faults.
In contrast, the predominant polarizations at two stations in the western part of SECB are in the N–E direction. This polarization
direction does not coincide with the direction of the horizontal principal compressive stress, but it follows the strikes
of near faults, thus suggesting the influence of the local tectonics and a change in the stress field. The results prove that
the predominant polarizations are parallel to the strikes of faults whenever the stations are on active faults. At a few stations
near the coastal line, some polarizations show a certain amount of scatter which may be caused by crossing faults and irregular
topography. Finally, the spatial distribution of time delays depicts strong lateral variations near the coast just where the
seismic activity is comparatively bigger, so that the magnitude of anisotropy seems to be consistent with the most seismically
active area. 相似文献
992.
光弹颗粒材料的直剪实验研究 总被引:1,自引:0,他引:1
对颗粒材料中的力链分布特征的了解,有助于从根本上了解颗粒材料基本性质。借助光弹实验,对两种直径混合的颗粒材料在二维直剪作用下的平均强度力链分布和几何结构变化进行了初步的探索。光弹实验方法是目前能够直观观察到力链分布的唯一有效的实验方法,在进行光弹实验前,设计研制了光弹直剪仪并进行了多次光弹圆盘颗粒材料退火实验。利用数字图像技术对光弹实验结果进行处理,并尝试用彩色梯度算法表征颗粒材料的平均受力情况,并获得平均强度力链。结果表明,二元颗粒材料集合体的几何结构具有各向异性。对力链方向统计分析表明,平均强度力链出现了局部化。 相似文献
993.
利用断层带特有震相通过观测模拟可以得到断层带介质的性质。本文回顾了地震学领域中断层带震相研究的发展历程,对断层带首波、断层带围陷波的国内外研究现状进行了综述,并结合国际上有关断层带震相研究的最新进展,对基于地震波形研究断层性质的前景进行了展望。 相似文献
994.
云天地表总辐射和净辐射瞬时值的计算方法 总被引:1,自引:0,他引:1
为减少计算机时,满足实时预报要求,全球数值预报模式中的辐射计算频率通常设定为三小时。这样处理会大大减少计算量,但也同时导致较大辐射日变化偏差,并影响模式对地面能量平衡,对流及降水的模拟。为改进这一缺陷,我们开发了一种辐射快速计算方案,可用于计算瞬时地面太阳总辐射和净辐射,使到达地面的太阳辐射计算可与模式积分同步进行,从而改善地面太阳辐射日变化模拟。本文介绍云天的计算方法。该方案所用的输入变量均为预报模式或卫星观测所能提供的量。结果表明:该方案既可用于数值预报模式也可利用观测资料独立计算地面太阳辐射。经与美国能源部大气辐射观测资料检验,该方案的精度很高,地面总辐射瞬时值的平均计算误差小于7%。 相似文献
995.
This paper proposed a method to retrieve the land surface reflectance from the HJ-1A/B CCD data. The aerosol optical depth(AOD), the most important factor affecting the atmospheric correction of CCD images at all bands, is proposed to retrieve from the CCD imagery by the approach of dense dark vegetation(DDV) method. A look-up table in terms of the transmittances, the path radiances and the atmospheric spherical albedo as functions of the AOD was established for a variety of sun-sensor geometry and aerosol loadings. The atmospheric correction is then achieved with the look-up table and the MODIS surface reflectance output(MOD09) as the priori datasets. Based on the retrieved AOD and the look-up table of atmospheric correction coefficients, the land surface reflectance was retrieved for the HJ-1A/B data according to the atmospheric radiative transfer equation. Some in-situ measurement Data for Yanzhou of Shandong province in East China and MODIS land surface reflectance products MOD09 are used to preliminarily validate the proposed method. The results show that the proposed method can remove effectively the atmospheric contributions, and the overall accuracy of the retrieval land surface reflectance can be improved substantially. 相似文献
996.
LI Jiandong Zhian SUN LIU Yimin Jiangnan LI Wei-Chyung WANG WU Guoxiong 《大气科学进展》2012,29(6):1185-1199
The direct radiative forcing(DRF) of sulfate aerosols depends highly on the atmospheric sulfate loading and the meteorology,both of which undergo strong regional and seasonal variations.Because the optical properties of sulfate aerosols are also sensitive to atmospheric relative humidity,in this study we first examine the scheme for optical properties that considers hydroscopic growth.Next,we investigate the seasonal and regional distributions of sulfate DRF using the sulfate loading simulated from NCAR CAM-Chem together with the meteorology modeled from a spectral atmospheric general circulation model(AGCM) developed by LASG-IAP.The global annual-mean sulfate loading of 3.44 mg m 2 is calculated to yield the DRF of 1.03 and 0.57 W m 2 for clear-sky and all-sky conditions,respectively.However,much larger values occur on regional bases.For example,the maximum all-sky sulfate DRF over Europe,East Asia,and North America can be up to 4.0 W m 2.The strongest all-sky sulfate DRF occurs in the Northern Hemispheric July,with a hemispheric average of 1.26 W m 2.The study results also indicate that the regional DRF are strongly affected by cloud and relative humidity,which vary considerably among the regions during different seasons.This certainly raises the issue that the biases in model-simulated regional meteorology can introduce biases into the sulfate DRF.Hence,the model processes associated with atmospheric humidity and cloud physics should be modified in great depth to improve the simulations of the LASG-IAP AGCM and to reduce the uncertainty of sulfate direct effects on global and regional climate in these simulations. 相似文献
997.
The Effects of Different HITRAN Versions on Calculated Long-Wave Radiation and Uncertainty Evaluation 总被引:1,自引:0,他引:1 下载免费PDF全文
Four editions of the High Resolution Transmission (HITRAN) databases (HITRAN96, HITRAN2K, HITRAN04, and HITRAN08) are compared by using a line-by-line (LBL) radiative model in the long-wave calculation for six typical atmospheres. The results show that differences in downward radiative fluxes between HITRAN96 and HITRAN08 at the surface can reach a maximum of 1.70 W m 2 for tropical atmospheres. The largest difference in heating rate between HITRAN96 and HITRAN08 can reach 0.1 K day 1 for midlatitude summer atmosphere. Uncertainties caused by line intensity and air-broadened halfwidths are also evaluated in this work using the uncertainty codes given in HITRAN08. The uncertainty is found to be 1.92 W m 2 for upward fluxes at the top of the atmosphere (TOA) and 1.97 W m 2 for downward fluxes at the surface. The largest heating rate caused by the uncertainty of line intensity and air-broadened half-width can reach 0.5 K day 1 . The differences in optical depths between 1300 and 1700 cm 1 caused by different HITRAN versions are larger than those caused by the uncertainties in intensity and air-broadened half-width. This paper suggests that there is inaccurate representation of line parameters over some spectral ranges in HITRAN and more attention should be paid to these ranges in fields such as remote sensing. 相似文献
998.
为研究原状马兰黄土的渗透各向异性,以延安削山造地重大工程开挖所揭露的完整黄土剖面中的马兰黄土层为研究对象,采用室内变水头渗透试验获取不同埋深不同渗流时长原状黄土垂直向和水平向的渗透系数,并对试验前后黄土试样垂直向和水平向SEM(scanning electron microscope)电镜扫描结果进行分析,从微观结构上揭示原状马兰黄土结构各向异性的原因。结果表明:原状黄土垂直向和水平向饱和渗透系数具有显著各向异性,且垂直向和水平向渗透系数都随渗流时间的持续而减小,各向异性渗透性能在时间尺度上具有某种衰减关系;同时,原状黄土各向异渗透性能随埋深的增大而逐渐减弱;土颗粒结构的接触、排列方式是导致黄土原生各向异性的根本原因,也是导致渗流初始阶段渗透系数各向异性的原因,而渗流作用产生的次生结构各向异性则使渗透系数各向异性在时间尺度上表现得更为明显。 相似文献
999.
1000.
The undrained stability of slopes in anisotropic fine-grained soils is studied in this paper using the finite element method (FEM). A constitutive model is presented, able to account for the observed variation of undrained strength with loading direction. The model is able to encompass the different strength distributions observed in normally, slightly overconsolidated and heavily overconsolidated soils. A series of stability analyses have been performed to explore the effect of the type of undrained strength anisotropy on the stability and failure mechanisms of slopes of different inclinations. In addition, a real case study of the failure of an underwater slope is analysed with the numerical approach presented. It suggests that, by considering undrained strength anisotropy, the failure can be satisfactorily explained. 相似文献