THE APPLICATION OF IMAGE-BASED MODELING IN PALEOEARTHQUAKE TRENCH STUDY

The geological structure exposed by paleoearthquake trenches is the key material to the right cognition of fault activity and paleoearthquake. However, paleoearthquake trenching inevitably destroys active tectonic geomorphic evidence and trench exposures are usually difficult to reserve. The conventional process of recording the delicate geological information, manually constructing photomosaics by image-editing software, is time-consuming and produces undesirable artificial distortions. Herein, we explored the process of constructing trench orthophotomosaics and the 3D image model using the Image-based Modeling technology and applied it to the Liutiaohe trench across the Tianqiaogou-Huangyangchuan Fault, Gansu Province. Based on the 3D image modeling and orthophotomosaic, we firstly constructed the control points and scale bars on cleaned trench walls and collected photos of all sections of the trench with a digital camera in the field, and then reconstructed the 3D model of the trench through the Agisoft PhotoScan, an efficient image-based modeling software, and finally yielded the 3D image model of the trench and othophotomasaics of the trench exposures. The results show that the automated workflow can produce seamless, sub-millimeter-level high-resolution photomosaics more quickly, with precision in the centimeter range, and the 3D image model is of great help to identify strata and geological structures in trenches with much lower capital and labor costs and low expertise levels compared with LiDAR, meanwhile, the 3D archive benefits the share and communication and even allows future reinterpreting the site using new insights.     

A new Lower Triassic (Induan) Jerus Limestone locality in northwest Pahang,Peninsular Malaysia: Conodont fauna,depositional and tectonic settings

Limestones exposed north of Raub, Pahang, Malaysia, and sandwiched between the Bentong‐Raub Suture Zone and the westernmost margin of the Sukhothai Arc terrane, yield a late Dienerian (late Induan) conodont fauna. The co‐occurrence of Neospathodus dieneri Sweet (morphotypes 1, 2 and 3) and Neospathodus pakistanensis Sweet represents the Neospathodus dieneri morphotype 3 sub‐zone of the Neospathodus dieneri Zone. The sampled limestones are interpreted as the northwards extension of the Jerus Limestone which crops out near Cheroh and Jerus villages, significantly extending the known outcrop of the Jerus Limestone northwards. The Jerus Limestone is interpreted as hemipelagic and formed in a foredeep or forearc setting on top of the accretionary complex formed by eastwards subduction of the Palaeo‐Tethys during the Lower to Middle Triassic.     

利用混合法构建三维数字岩心(英文)

在弹性波有三维数字岩心描述了岩石的微观孔隙结构。X射线CT扫描是获取三维数字岩心最准确和直接的方法,但实验成本高。本文结合沉积过程模拟和模拟退火算法,提出了重建三维数字岩心的混合法,基于岩石二维图像重建三维数字岩心。利用岩石颗粒沉积算法构建初始数字岩心,作为模拟退火算法的初始状态。运用模拟退火算法调整岩石颗粒和孔隙的相对位置,使三维数字岩心与岩心二维图像具有相似的自相关函数,从而建立三维数字岩心。与传统模拟退火算法相比,该方法计算时间明显减小。运用局部孔隙度理论定量比较了重建数字岩心和岩心X射线微CT图像,两种数字岩心具有相似的均质性和孔隙连通性。利用有限元方法和格子玻尔兹曼方法分别模拟了重建三维数字岩心的地层因素和渗透率,数值模拟结果与实验结果相符。相比传统模拟退火算法,混合法重建数字岩心的传导特性更接近真实岩心的传导特性。     

基于新型单相MICP技术改性黏性土力学特性的试验研究

微生物诱导碳酸钙沉积(MICP)是一种绿色低碳的新型土体改性技术.该技术当前主要适用于渗透性较好的砂土,普遍使用两相处理方法,即菌液和胶结液分开施用.然而,对于渗透性相对较差的黏性土,传统的两相处理方法难以适用.为此,引入新的单相胶结方法,即菌液和胶结液混合施用,通过调节溶液的初始pH值为细菌水解作用提供窗口期,避免微生物絮凝阻塞孔隙,使混合液均匀分布于土体一定深度范围内,从而达到显著提升胶结效果的目的.利用喷洒法将混合液喷洒至土体表层进行MICP处理,处理完成后使用超微型贯入仪SMP-1测试土体表层不同深度处的结构强度,分析土体力学特性的空间差异,对土体的胶结效果进行定量评价.此外,探究了胶结液浓度(0.2M、0.5M和1.0M)及胶结方法(调节pH与否)对于土体结构强度及MICP改性效果的影响.结果表明:采用单相MICP技术对黏性土进行改性,能够显著提高其结构强度,具有较好的适用性;在不高于1.0 M的胶结液浓度范围内,黏性土的胶结效果随着胶结液浓度增加而提升;相比较而言,调节pH的单相胶结方法对于提升土体胶结的深度和均匀性有明显积极作用.新型单相MICP技术简单易行,能够节约成本,在黏性土表层加固方面具有潜在推广应用价值.     

北京天文台的WET三通道高速光度计

对北京天文台新近改造成的三通道高速光度计的结构和性能进行介绍,并给出了在兴隆站85公分望远镜的一些实测结果.     

Stable carbon isotope variations in northwest Europe during the last glacial–interglacial transition

Stable carbon isotope data that span part of the last glacial–interglacial transition (ca. 14-9 ka ¹⁴C BP; ca. 15–11 ka cal. BP), and which derive from organ-specific plant macrofossils recovered from two lake sediment profiles in the UK and one in Norway, are compared. The recorded temporal variations show similar trends, which, over a millennial time-scale appear to parallel the main drift in δ¹⁸O as determined for the GRIP ice-core. It is postulated that some smaller scale variations in the δ¹³C profiles may reflect the shorter term oscillations in δ¹⁸O values evident in the GRIP record, although this is less certain. Overall, however, the results suggest that stable carbon isotope measurements based on organ-specific terrestrial plant macrofossils may provide (i) a means for establishing correlations between terrestrial successions and (ii) additional paleoenvironmental information, as the apparent ‘shadowing’ of the GRIP record indicates a common forcing mechanism for both Greenland δ¹⁸O and northwest European δ¹³C variations. From the evidence available we suggest that the recorded δ¹³C variations reflect fluctuations in air temperature and/or changes in water vapour pressure in the atmosphere. © 1997 John Wiley & Sons, Ltd.     

月面形貌的3维可视化算法

基于大范围地形可视化算法研究的基础上,对平面geometry clipmaps算法进行改进,利用GPU的顶点着色器实现平面地形向球面地形的投影变换,并综合利用球面视域裁剪、球面视点控制等技术,使geometry clipmaps算法适用于球面海量地形数据的3维可视化;收集处理月球全球影像和形貌高程数据,对算法进行验证,实现月球表面形貌的实时动态3维可视化.试验表明:绘制算法可不受数据量大小的限制、绘制效率高、效果逼真,但存在两极变形较大的缺点.

Abstract：

Based on the study of visualization arithmetic of large area terrain, plane geometry clipmaps algorithm is improved. Projection transformation from plane landform to sphere landform was realized by using GPU vertex shader. In that improved algorithm, methods such as sphere vision field culling and sphere viewpoint control are used.That makes geometry clipmops algorithm more effective in 3D visualization of massive sphere terrain data. The whole moon image and DEM data are collected and disposed, which are used to verify the capability of that algorithm, realizing dynamic and real time 3D visualization of moon surface. The experiments show that the graphic algorithm isn't limited by data quantity, which is of high efficiency and reality simulation, but the two-pole distortion is serious.     

0302号(鲸鱼)台风降水和水粒子空间分布的三维结构特征

由于缺乏关于台风结构信息的高分辨率资料,即探测台风云系内部结构特征的技术限制,造成了进一步理解台风的动力传送特征的困难.作者用热带测雨卫星(TRMM,Tropical Rainfall Measuring Mission)的测雨雷达(PR,Precipitation Radar)和TRMM微波图像仪(TMI,TRMM Microwave Imager)资料详细研究了"鲸鱼"台风(0302号)于2003年4月16日1105 UTC的降水和降水云系中各种水粒子的三维结构特征.通过分析发现该时刻:(1)台风降水中大部分区域为层性降水(占总降水面积的85.5%),对流性降水占总降水面积的13.1%,但对流性降水的贡献却达到41.8%,所以,虽然对流性降水所占面积比例很少,但是它对总降水量的贡献却很大.(2)60%降水主要集中在距离台风中心100 km以内的区域,约占总降水量的60%.(3)各种水粒子含量随着与台风中心距离的增加而减少.降水云系中水粒子最大含量出现高度与水粒子的种类和与台风中心的距离有关.最后,分析了台风降水和降水云系中三维分布的成因.     

基于多源数据的三维城市建模方法

以天津新港三维城市建模为例,介绍了基于二维数据、DEM和3D模型等多源数据的三维城市建模的方法和关键技术。为有效利用现有数据资源快速、准确建立三维城市模型提供了一种经济、灵活、省时、高效的方法。