城市模拟目标的3维热辐射方向性模型

以城市3维结构场景为研究目标,考虑其光影遮蔽关系,模拟传感器视场内目标的可见表面,实现视场尺度内城市模拟目标方向亮温的准确模拟。利用地面试验观测数据对3维热辐射方向性模型进行验证。结果表明,该模型对城市3维结构目标的方向亮温具有较好的模拟精度,均方根误差为0.7K,能够描述微观尺度下城市3维模拟目标的热辐射方向性。利用该热辐射方向性模型对城市区域物理模型的方向亮温进行模拟,发现城市区域物理模型热辐射存在显著的方向差异,并伴有热点效应产生。     

Deformation fabrics of glaucophane schists and implications for seismic anisotropy: the importance of lattice preferred orientation of phengite

ABSTRACT

Strong seismic anisotropy is observed in many subduction zones. This effect is attributed partly to subducting oceanic crust that is transformed into blueschist facies rocks. Because blueschist facies constituents such as glaucophane, epidote, and phengite show strong anisotropic elasticity, seismic anisotropy in subducting oceanic crust can be attributed to the lattice preferred orientation (LPO) of these minerals. We studied the deformation fabrics and seismic properties of phengite-rich epidote–glaucophane schists from the Franciscan Complex of Ring Mountain, California. The samples are composed mainly of glaucophane, epidote, and phengite. Some samples contain abundant phengite, the maximum being 40%. The LPOs of glaucophane showed that the [001] axes are aligned subparallel to lineation, and both (110) poles and [100] axes are aligned subnormal to foliation. The epidote [001] axes are aligned subnormal to foliation, with both (110) and (010) poles aligned subparallel to lineation. The LPOs of phengite are characterized by the maxima of [001] axes subnormal to foliation, and both (110) and (010) poles and [100] axes are aligned in a girdle subparallel to foliation. The phengite showed substantially strong seismic anisotropy (AV_P = 42%, max.AV_S = 37%). The glaucophane schist with abundant phengite showed significantly stronger seismic anisotropy (AV_P = 30%, max.AV_S = 23%) than the epidote–glaucophane schist (AV_P = 13%, max.AV_S = 9%). When the subduction angle of phengite-rich glaucophane schist is considered, the polarization direction of the fast S-waves for vertically propagating S-waves changed to a nearly trench-parallel direction for the subduction angle of 45?60°, and the S-wave anisotropy became stronger for vertically propagating S-waves with increasing subduction angles. Our data showed that phengite-rich blueschist facies rock can therefore contribute to the strong trench-parallel seismic anisotropy occurring at the subducting oceanic crust and at the slab–mantle interface in many subduction zones.     

The high‐K calc‐alkaline Alagoinhas pluton: anisotropy of magnetic susceptibility,geochemistry, emplacement setting,and implications for the evolution of Borborema Province,NE Brazil

The Alagoinhas pluton is a member of the widespread high‐K calc‐alkaline association of northeastern Brazil. Some authors suggest that this region represents an amalgamation of distinct tectonic terranes assembled during the Brasiliano (Pan‐African) orogeny. Our work compares geochemical data (major, trace and REE) of the Alagoinhas with other plutons of same petrotectonic association (Caruaru‐Arcoverde batholith). These plutons apparently intrude several distinct tectonic terranes, separated by a major E‐W dextral transcurrent system, the East Pernambuco shear zone (EPSZ). Anisotropy of magnetic susceptibility and structural data for the Alagoinhas pluton are used to compare tectonic regimes across the EPSZ. The results indicate that the Caruaru‐Arcoverde batholith and the Alagoinhas pluton evolved from similar sources and were subjected to the same tectonic regime during emplacement, placing severe restrictions on use of the EPSZ as a suture zone between distinct tectonic terranes.     

Magnetic Characterization of Amphibolites from the Fomopéa Pluton (West Cameroon): Their Implication in the Pan-African Deformation of the Central African Fold Belt

The Fomopea granitic pluton is emplaced in gnessic and amphibolitic basement.These gneissic and amphibolitic basement rocks are represented in the pluton's body as sub-rounded,elongated or stretched xe...     

Study on the S-wave Splitting Characteristics in the Longtan Reservoir Area,Guangxi,China

In this paper,the shear wave splitting features of the Longtan reservoir area are studied by adopting the traditional cross-correlation coefficient method and polarization analysis,using the data recorded by the seismic network founded by a project under the National Science and Technology Pillar Program from April 2009 to April 2010.We found that most of polarization directions at seismic stations are consistent with the direction of the overall regional stress field,but local structures and faults may con...     

Seismic characterization of reservoirs with multiple fracture sets using velocity and attenuation anisotropy data

Knowledge about the spatial distribution of the fracture density and the azimuthal fracture orientation can greatly help in optimizing production from fractured reservoirs. Frequency-dependent seismic velocity and attenuation anisotropy data contain information about the fractures present in the reservoir. In this study, we use the measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuths to infer information about the multiple fracture sets present in the reservoir. We consider a reservoir model with two sets of vertical fractures characterized by unknown azimuthal fracture orientations and fracture densities. Frequency-dependent seismic velocity and attenuation anisotropy data is computed using the effective viscoelastic stiffness tensor and solving the Christoffel equation. A Bayesian inversion method is then applied to measurements of velocity and attenuation anisotropy data corresponding to different seismic frequencies and azimuth to estimate the azimuthal fracture orientations and the fracture densities, as well as their uncertainties. Our numerical examples suggest that velocity anisotropy data alone cannot recover the unknown fracture parameters. However, an improved estimation of the unknown fracture parameters can be obtained by joint inversion of velocity and attenuation anisotropy data.     

S波分裂在皖北地震中的研究应用

利用S波分裂方法的基本理论及计算方法,重点研究了皖北地区具有代表性的利辛张村附近周边地区25 km内,自1999年蒙城地震台数字化测震仪器正式记录以来至2010年9月,ML2.0及以上地方震的单台地震波形,利用有关S波分裂方法进行处理,得到该地区不同时段的S波的偏振方向及延迟时间,为皖北地区地震活动性研究及应力活动状态...     

Fabric evolution within shear bands of granular materials and its relation to critical state theory

In an effort to study the relation of fabrics to the critical states of granular aggregates, the discrete element method (DEM) is used to investigate the evolution of fabrics of virtual granular materials consisting of 2D elongated particles. Specimens with a great variety of initial fabrics in terms of void ratios, preferred particle orientations, and intensities of fabric anisotropy were fabricated and tested with direct shear and biaxial compression tests. During loading of a typical specimen, deformation naturally localizes within shear bands while the remaining of the sample stops deforming. Thus, studying the evolution of fabric requires performing continuous local fabric measurements inside these bands, a suitable task for the proposed DEM methodology. It is found that a common ultimate/critical state is eventually reached by all specimens regardless of their initial states. The ultimate/critical state is characterized by a critical void ratio e which depends on the mean stress p, while the other critical state fabric variables related to particle orientations are largely independent of p. These findings confirm the uniqueness of the critical state line in the e ? p space, and show that the critical state itself is necessarily anisotropic. Additional findings include the following: (1) shear bands are highly heterogeneous and critical states exist only in a statistical sense; (2) critical states can only be reached at very large local shear deformations, which are not always obtained by biaxial compression tests (both physical and numerical); (3) the fabric evolution processes are very complex and highly dependent on the initial fabrics. Copyright © 2010 John Wiley & Sons, Ltd.     

气煤孔隙度与Thomsen各向异性参数高阶交错网格数值模拟

对气煤煤样孔隙率测试的基础上,讨论了各向异性系数与孔隙率的关系,表明各向异性的大小与孔隙率之间有一定的关系。应用高阶交错网格差分算法,对一阶速度-应力弹性波方程进行模拟,分析了其稳定性和边界条件。通过对Thomsen各向异性参数的模拟表明,主要控制的是P波的各向异性强弱,δ主要控制水平垂直正交方向上的各向异性强弱。对煤田各向异性研究具有重要意义。     

各向异性介质转换波速度逐层单参数分析方法

转换波的时距曲线是非双曲线方程,由于介质的各向异性,使得转换波在实际地层中的传播更为复杂。针对各向异性介质中PSV转换波的速度分析展开讨论,鉴于各向异性介质的PSV波速度分析不能脱离PP波数据而单独进行,在学习前人研究成果的基础上,充分利用PP波速度分析的有效信息,对PSV转换波进行逐层单参数分析,在一定程度上简化了速度分析的程序,提高了速度分析的精度,并通过理论模型试算,验证了方法的正确性和可行性。