Seismic stratigraphy and subsidence analysis of the southern Brazilian margin (Campos,Santos and Pelotas basins)

The Campos, Santos and Pelotas basins have been investigated in terms of 2D seismo-stratigraphy and subsidence. The processes controlling accommodation space (e.g. eustacy, subsidence, sediment input) and the evolution of the three basins are discussed. Depositional seismic sequences in the syn-rift Barremian to the drift Holocene basin fill have been identified. In addition, the subsidence/uplift history has been numerically modeled including (i) sediment flux, (ii) sedimentary basin framework, (iii) relation to plate-tectonic reconfigurations, and (iv) mechanism of crustal extension. Although the initial rift development of the three basins is very similar, basin architecture, sedimentary infill and distribution differ considerably during the syn-rift sag to the drift basin stages. After widespread late Aptian–early Albian salt and carbonate deposition, shelf retrogradation dominated in the Campos Basin, whereas shelf progradation occurred in the Santos Basin. In the Tertiary, these basin fill styles were reversed: since the Paleogene, shelf progradation in the Campos Basin contrasts with overall retrogradation in the Santos Basin. In contrast, long-term Cretaceous–Paleogene shelf retrogradation and intense Neogene progradation characterize the Pelotas Basin. Its specific basin fill and architecture mainly resulted from the absence of salt deposition and deformation. These temporally and spatially varying successions were controlled by specific long-term subsidence/uplift trends. Onshore and offshore tectonism in the Campos and Santos basins affected the sediment flux history, distribution of the main depocenters and occurrence of hydrocarbon stratigraphic–structural traps. This is highlighted by the exhumation and erosion of the Serra do Mar, Serra da Mantiqueira and Ponta Grossa Arch in the hinterland, as well as salt tectonics in the offshore domain. The Pelotas Basin was less affected by changes in structural regimes until the Eocene, when the Andean orogeny caused uplift of the source areas. Flexural loading largely controlled its development and potential hydrocarbon traps are mainly stratigraphic.     

塔里木盆地玉北地区埋藏史及热史分析

根据地层分层数据和古热流分析,对塔里木盆地玉北地区的5口代表性钻井进行了埋藏史、热史的模拟与分析,探讨了研究区烃源岩的热演化成熟过程,初步划分了烃源岩的成熟阶段和生烃期次。研究结果认为：玉北地区寒武系－泥盆系沉积时期,具有多次沉积埋藏和隆升剥蚀的交替;泥盆系沉积之后,石炭－二叠系呈现沉积埋藏的特征;中生代在玉北地区东部少量沉积三叠系,随后被剥蚀,而在中西部发生沉积间断;进入新生代,地层持续沉积,且沉积速率呈现增大趋势。研究区寒武系烃源岩自沉积以来成熟度演化相对连续,奥陶纪时进入生烃门限,成熟时期较早;志留－泥盆纪,受海西早期运动的影响,发生隆升剥蚀作用,烃源岩演化变缓;石炭－二叠纪受控于区域上持续稳定的地层沉积与广泛发育的火山活动,研究区寒武系烃源岩进入中高成熟阶段;由于喜马拉雅造山运动的远程效应,新生代研究区持续沉降,形成巨厚沉积,烃源岩成熟度达到高－过成熟,为天然气生成阶段     

速度误差对时间偏移和深度偏移的影响分析

地震数值计算表明:地震速度模型出现误差,对时间偏移和深度偏移有不同的影响,且深度偏移结果的误差往往大于时间偏移的误差,影响了深度偏移方法的广泛应用。根本原因在于时间偏移使用的是均方根速度,而深度偏移使用的是层速度,因此在速度模型相同的情况下,层速度的变化远大于均方根速度的变化。地震数值模拟分析同时说明,深度偏移结果的误差还取决于地下介质的结构和岩性。当界面二边速度差异比较大时,速度摄动值δ引起深度偏移结果的误差,远大于界面二边速度平缓变化的情况。深度成像的误差等于速度摄动值δ和界面二边速度对比度vi+1/vi的乘积。     

融合航空影像的LiDAR地物点云分类

点云滤波分类是LiDAR后续应用的基础工作,在点云滤波的基础上,以航空影像为辅助条件,结合点云高程信息,设计一套地物点云的分类方法。该方法首先融合航空影像与LiDAR数据,将对应RGB值赋予每个点,根据植被的光谱特征提取出部分植被点云;然后再根据文中定义的点云高程纹理,在剩余地物点云中提取出建筑物点,最后根据回波次数信息分离出剩余植被点,完成地物点云的分类。采用北京凤凰岭地区一组机载LiDAR数据进行实验。实验结果表明,该方法能够有效地将地物点云进行分类并且满足一定的精度要求,具有一定的实用价值。     

基于二维三次卷积插值算法的辛几何射线追踪

射线追踪是地震波走时层析成像的基础,射线空间位置的准确性及射线走时的精度决定了层析成像的可靠性.本文根据哈密尔顿系统可以有效提高程函方程解稳定性的特性,采用辛几何算法（SAM-Symplectic Algorithm Method）及二维三次卷积插值技术进行地震波射线追踪.由于采用了SAM算法,保证了地震波波前精度,提高了射线空间位置的准确性.数值模拟结果表明SAM既能保证哈密尔顿系统的稳定性又具有运算速度快的特点,提高了射线追踪的计算精度.     

近场动力学理论在区域地面沉降建模中的应用研究

地面沉降是由自然和人类活动共同作用导致的缓变性地质灾害,是区域可持续发展的重要影响因素。以往地面沉降在建模时需要地裂缝等不连续结构的位置、走向、深度等信息,在构建微分方程模拟时需假设模型连续,这对开展地面沉降-地裂缝-地面塌陷一体化模拟带来一定的局限性。于2000年出现的近场动力学理论提出以积分形式描述材料受力过程,方法具有无需先验知识与连续性假设的优点,在材料的疲劳、损伤、断裂等模拟研究中展现出良好的应用前景。本文综述了其在岩石水力压裂、滑坡、饱水岩土材料等领域的研究进展;提出了应用近场动力学进行区域地面沉降建模求解的一般方法;结合InSAR技术获取的沉降信息、三维地震频谱谐振勘探技术获取的地下结构与密度信息等,提出了模型的反演调参与优化方法。以北京东部梨园-台湖镇-张家湾镇区域为实验区,建立了其4 km×6 km范围、0.2 km深度的近场动力学地面沉降模型,以实验区地下水位月均下降速率为边界条件,对2007—2010年地面沉降过程进行模拟。模拟结果与实测值的平均绝对误差为18 mm,表明近场动力学在地面沉降建模中有较好的适用性。     

Reflected and transmitted waves in a channel with side porous mattresses

The problem of wave propagation and wave damping in a channel with side porous mattresses of arbitrary shape protruding from the walls is studied. The solution was achieved by applying 3-D boundary element method and was employed to study wave field in the channel and to analyze the effect of the geometry of the mattresses and physical and hydraulic properties of porous material on wave damping. The results show that wave damping in the channel strongly depends on wave parameters, especially, on the wave number. Wave reflection and transmission decrease with increasing the wave number. The results also show that the wave field in the channel strongly depends on the geometry of the mattresses as well as on physical and hydraulic properties of porous material used to build these wave dampers. The geometry of the mattresses and physical and hydraulic properties of porous material have a moderate effect on wave reflection and a significant effect on wave transmission. The results show that wave transmission down the channel decreases with increasing the length and thickness of the mattresses. Moreover, wave transmission decreases with increasing the porosity and damping properties of porous media used to build the mattresses. The analysis shows that porous mattresses protruding from the channel walls are very efficient in damping water waves propagating down the channel and may be built in channels to reduce high waves and achieve desired wave conditions. Theoretical results are in reasonable agreement with experimental data.     

基于ArcEngine的虚拟校园信息管理系统的设计与实现

阐述基于组件式GIS的开发方式,结合3维建模技术、数据库技术开发虚拟校园信息管理系统的基本思路,重点研究了3维模型的入库方法,以及基于GeoDatabase的数据库设计。以VirtualCampus系统开发为例,介绍了利用Visual C++与ArcEngine开发虚拟校园信息管理系统的方法。     

Detection of free vertical convection and double-diffusion in groundwater monitoring wells with geophysical borehole measurements

Two algorithms for in-situ detection and identification of vertical free convective and double-diffusive flows in groundwater monitoring wells or boreholes are proposed. With one algorithm the causes (driving forces) and with the other one the effects (convection or double-diffusion) of vertical transport processes can be detected based on geophysical borehole measurements in the water column. Five density-driven flow processes are identified: thermal, solutal, and thermosolutal convection leading to an equalization, as well as saltfingers and diffusive layering leading to an intensification of a vertical density gradient. The occurrence of density-driven transport processes could be proven in many groundwater monitoring wells and boreholes; especially shallow sections of boreholes or groundwater monitoring wells are affected dramatically by such vertical flows. Deep sections are also impaired as the critical threshold for the onset of a density-driven flow is considerably low. In monitoring wells or boreholes, several sections with different types of density-driven vertical flows may exist at the same time. Results from experimental investigations in a medium-scale testing facility with high aspect ratio (height/radius = 19) and from numerical modeling of a water column agree well with paramters of in-situ detected convection cells.     

海岛(礁)、滩涂和水下地形矢量数据融合方法研究与实现

海岛(礁)、滩涂和水下地形DLG数据库是重要的测绘成果,为开展海洋综合调查工作提供了数据基础。然而,现有的三库测绘成果是分阶段采集的,数据精度和数据模型不一致,且存在大量重复采集的情况,最终成果也是分库存储的,这使其无法进行统一管理和更新。为此,本文对多源海洋基础空间要素数据的融合方法进行了研究,首先采用矢量数据匹配技术获取对应实体,然后通过本文提出的属性融合技术和基于中误差与对应点的几何信息融合技术对三库DLG数据进行融合,以实现三库数据的属性共享、几何精度的改进和数据冗余的减少。最后,我们还基于.NET和Arc GIS Engine组件开发了海洋基础空间要素数据融合系统,用于浙江省海岛(礁)、滩涂和水下地形基础空间要素数据的融合。