Boreal temperature variability inferred from maximum latewood density and tree-ring width data, Wrangell Mountain region, Alaska   总被引：3，自引：0，他引：3  

Nicole K. Davi  Gordon C. Jacoby  Gregory C. Wiles 《Quaternary Research》2003,60(3):252-262

Variations in both width and density of annual rings from a network of tree chronologies were used to develop high-resolution proxies to extend the climate record in the Wrangell Mountain region of Alaska. We developed a warm-season (July–September) temperature reconstruction that spans A.D. 1593–1992 based on the first eigenvector from principal component analysis of six maximum latewood density (MXD) chronologies. The climate/tree-growth model accounts for 51% of the temperature variance from 1958 to 1992 and shows cold in the late 1600s–early 1700s followed by a warmer period, cooling in the late 1700s–early 1800s, and warming in the 20th century. The 20th century is the warmest of the past four centuries. Several severely cold warm-seasons coincide with major volcanic eruptions. The first eigenvector from a ring-width (RW) network, based on nine chronologies from the Wrangell Mountain region (A.D. 1550–1970), is correlated positively with both reconstructed and recorded Northern Hemisphere temperatures. RW shows a temporal history similar to that of MXD by increased growth (warmer) and decreased growth (cooler) intervals and trends. After around 1970 the RW series show a decrease in growth, while station data show continued warming, which may be related to increasing moisture stress or other factors. Both the temperature history based on MXD and the growth trends from the RW series are consistent with well-dated glacier fluctuations in the Wrangell Mountains and some of the temperature variations also correspond to variations in solar activity.  相似文献   

Geoid determination using adapted reference field, seismic Moho depths and variable density contrast   总被引：4，自引：0，他引：4  

H. A. Abd-Elmotaal  N. Kühtreiber 《Journal of Geodesy》2003,77(1-2):77-85

 The traditional remove-restore technique for geoid computation suffers from two main drawbacks. The first is the assumption of an isostatic hypothesis to compute the compensation masses. The second is the double consideration of the effect of the topographic–isostatic masses within the data window through removing the reference field and the terrain reduction process. To overcome the first disadvantage, the seismic Moho depths, representing, more or less, the actual compensating masses, have been used with variable density anomalies computed by employing the topographic–isostatic mass balance principle. In order to avoid the double consideration of the effect of the topographic–isostatic masses within the data window, the effect of these masses for the used fixed data window, in terms of potential coefficients, has been subtracted from the reference field, yielding an adapted reference field. This adapted reference field has been used for the remove–restore technique. The necessary harmonic analysis of the topographic–isostatic potential using seismic Moho depths with variable density anomalies is given. A wide comparison among geoids computed by the adapted reference field with both the Airy–Heiskanen isostatic model and seismic Moho depths with variable density anomaly and a geoid computed by the traditional remove–restore technique is made. The results show that using seismic Moho depths with variable density anomaly along with the adapted reference field gives the best relative geoid accuracy compared to the GPS/levelling geoid. Received: 3 October 2001 / Accepted: 20 September 2002 Correspondence to: H.A. Abd-Elmotaal  相似文献   

大地测量数据接口技术与接口标准   总被引：5，自引：0，他引：5  

吕志平赵冬青  张西光李健 《测绘学院学报》2003,20(2):89-92,95

建立了由接口文件、接口文件处理器和共享信息模型组成的大地测量数据接口体系结构，划分了大地测量数据服务的3类不同接口类型。在建立了面向对象的接口数据模型的基础上，讨论了面向传统用户的控制点数字化成果格式、面向生产过程的大地控制网统一数据结构和面向GIS的大地测量数据交换格式。  相似文献   

正常椭球内部场的内蕴几何与密度分布     

黄金水 《武汉大学学报(信息科学版)》1997,(4)

将重力场内蕴几何结构的研究引入到正常椭球内部场的研究中，深入探讨了内蕴几何量及其与内部物理量之间的关系，并据此建立了弱平衡条件下的基本微分方程，进而给出确定椭球内部内蕴几何量与场源密度分布的方法。研究表明，平衡形状理论中的Ｗａｖｒｅ公式和Ｃｌａｉｒａｕｔ方程可由内蕴几何与内部物理量之间的关系导出，它们是在平衡假设下取椭球近似的结果。  相似文献   

3-D structural reconstruction of Moho in the Tangshan earthquake area by using inversion of curved interface     

赖晓玲  张先康  郑需要 《地震学报(英文版)》1997,10(5):625-637

３ＤｓｔｒｕｃｔｕｒａｌｒｅｃｏｎｓｔｒｕｃｔｉｏｎｏｆＭｏｈｏｉｎｔｈｅＴａｎｇｓｈａｎｅａｒｔｈｑｕａｋｅａｒｅａｂｙｕｓｉｎｇｉｎｖｅｒｓｉｏｎｏｆｃｕｒｖｅｄｉｎｔｅｒｆａｃｅＸＩＡＯＬＩＮＧＬＡＩ（赖晓玲）ＸＩＡＮＫＡＮＧＺＨＡＮＧ...  相似文献   

青藏高原及其邻区岩石层三维密度结构   总被引：17，自引：5，他引：17       下载免费PDF全文

方剑  许厚泽 《地球物理学报》1997,40(5):660-666

搜集了青藏高原及其邻近区域的S波速度三维层析成像结果和2万多个实测重力点资料，将重力资料进行各种改正并网格化为30′×30′的布格重力异常．首先采用密度差与S波速度差之间的经验关系式，建立青藏地区岩石层密度的初始模型，再利用布格重力异常进行阻尼最小二乘法反演，得到青藏地区岩石层三维密度分布结果．反演结果表明：（1）青藏高原岩石层密度分布不仅在纵向上不均匀，而且在横向存在明显的不均匀．在深度10－70km范围内，高原整体呈低密度特性，在50－70km深度范围内低密度特征更加突出，与周缘地区存在0，1g／cm³的密度差．而在90－110km深度范围内，高原岩石层地幔显示密度高．（2）岩层密度分布与大地构造有明显相关的分区性，显示出青藏块体、巴颜喀拉块体、塔里木块体和印度块体．  相似文献   

东北输油管道锦县,盖县,海城段地基土抗液化强度研究     

廖旭  高常波 《东北地震研究》1997,13(4):76-80

对东北输油管道锦县，盖县，海城段的粉土细砂，中砂，粉砂进行了振动液化试验，取得了和类土的τｄ－ｌｏｇＮｆ曲线，τｄ／σ′－ｌｏｇＮｆ曲线，为在以上地区进行液化判别提供了重要的基础资料，同时也为研究其它的地区相同土质的振动性能提供借鉴。  相似文献   

A mixed finite element method for Hele-Shaw cell equations     

J. M. Guevara-Jordan  J. Glimm 《Computational Geosciences》1997,1(1):35-58

A new numerical method to solve the system of equations describing two phase flow in a Hele-Shaw cell is presented. It combines a mixed finite element method, the method of subtraction of the singularity and a front tracking grid in a single computational strategy. This choice of discretization techniques is well motivated by the difficulties present in the system of equations and the physics of the problem. The new method was tested against analytical solutions and also by solving the Saffman–Taylor viscous fingering problem for finite and infinite mobility ratios. In both cases convergence under mesh refinement is achieved for the fingers developed from an initial sinusoidal interface. Finger splitting is observed for low values of the surface tension and high mobility ratio. Different explanations, based in our results, are provided for this phenomenon. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

洪泛平原农村居民地空间分布特征定量研究及应用探讨   总被引：23，自引：2，他引：23  

徐雪仁  万庆 《地理研究》1997,16(3):47-54

通过对影响居民地空间分布因素的分析,探讨了洪泛平原农村居民地空间分布特征;利用地理信息系统技术对不同高程带内居民地分布规模、等级和空间分布密度作了定量研究,得到了居民地空间分布密度和人口空间分布密度参数;并结合洪灾淹没区居民地损失的估算,对研究结果的应用作了探讨。  相似文献   

高温高压下水岩界面反应与金的迁移富集   总被引：1，自引：0，他引：1  

王玉荣  阚小凤  王志强 《矿物岩石地球化学通报》1997,(2)

高温高压下水岩界面反应与金的迁移富集王玉荣阚小凤王志强（中国科学院广州地球化学研究所，广州５１０６４０）关键词水岩界面反应自发电池实验地球化学本实验以哈达门沟［１］及东坪金矿［２］为地质背景，研究钾长石岩中金矿化富集的物理化学条件。该区金矿既与早期变...  相似文献