Thermal and rheological structures of the Xisha Trough, South China Sea   总被引：8，自引：0，他引：8  

Xiaobin Shi  Di Zhou  Xuelin Qiu  Yixiang Zhang 《Tectonophysics》2002,351(4)

The Xisha Trough, located in the northwest of the South China Sea (SCS) mainly rifted 30 Ma ago, has been a failed rift since the cessation of the seafloor spreading of the NW subbasin. Based on the velocity–depth model along Profile OBH-4 across the Xisha Trough, a seven-layer density–depth model is used to estimate density structure for the profile. The relationship between seismic velocity and radiogenic heat production is used to estimate the vertical distribution of heat sources in the lower crust. The 2-D temperature field is calculated by applying a 2-D numerical solution of the heat conduction equation and the thermal lithosphere thickness is obtained from the basalt dry solidus (BDS). The rheology of the profile is estimated on the basis of frictional failure in the brittle regime and power-law steady-state creep in the ductile regime. Rheological model is constructed for a three-layer model involving a granitic upper crust, a quartz diorite lower crust and an olivine upper mantle. Gravity modeling supports basically the velocity–depth model. The Moho along Profile OBH-4 is of relatively high heat flow ranging from 46 to 60 mW/m² and the Moho heat flow is higher in the trough than on the flanks. The depth of the “thermal” lithospheric lower boundary is about 54 km in the center, deepens toward two sides, and is about 75 km at the northern slope area and about 70 km at the southern Xisha–Zhongsha Block. Rheological calculation indicates that the two thinnest ductile layers in the crust and the thickest brittle layer in the uppermost mantle lie in the central region, showing that the Xisha Trough has been rheologically strengthened, which are mainly due to later thermal relaxation. In addition, the strengthening in rheology during rifting was not the main factor in hampering the breakup of the Xisha Trough.  相似文献   

Computational modeling of cyclic mobility and post-liquefaction site response   总被引：3，自引：0，他引：3  

Ahmed Elgamal  Zhaohui Yang  Ender Parra 《Soil Dynamics and Earthquake Engineering》2002,22(4)

Under seismic excitation, liquefied clean medium to dense cohesionless soils may regain a high level of shear resistance at large shear strain excursions. This pattern of response, known as a form of cyclic mobility, has been documented by a large body of laboratory sample tests and centrifuge experiments. A plasticity-based constitutive model is developed with emphasis on simulating the cyclic mobility response mechanism and associated pattern of shear strain accumulation. This constitutive model is incorporated into a two-phase (solid–fluid), fully coupled finite element code. Calibration of the constitutive model is described, based on a unique set of laboratory triaxial tests (monotonic and cyclic) and dynamic centrifuge experiments. In this experimental series, Nevada sand at a relative density of about 40% is employed. The calibration effort focused on reproducing the salient characteristics of dynamic site response as dictated by the cyclic mobility mechanism. Finally, using the calibrated model, a numerical simulation is conducted to highlight the effect of excitation frequency content on post-liquefaction ground deformations.  相似文献   

Simulation of individual particle movement in a gravel streambed     

J. Mikael Malmaeus  Marwan A. Hassan 《地球表面变化过程与地形》2002,27(1):81-97

A two‐dimensional simulation model of travel distances of individual particles in a gravel‐bed river is presented. The model is based on a number of rules, which include particle size, entrainment, trajectory, distance of movement and entrapment. Particle interactions are controlled by resistance fields defined about each obstacle and critical elevation defined in the model. Resistance fields, particle dropping and critical elevation rules control particle interactions. The interaction rules cause the particles to develop pebble clusters, stone cells and transverse structures (transverse ribs). The simulated travel distances of individual particles are consistent with reported field results. Individual particle travel distances were simulated using two different models; one without interactions between the individual particles and the stationary bed and one with interactions. The case without interactions demonstrates the random nature of sediment transport, and narrow ranges of travel distances. Wider ranges of travel distances, similar to those for natural situations, were obtained for the cases with interactions. The more intense the interaction between the mobile stones and the stationary ones, the wider the range of distances of travel for a given particle size. Modelling the mean travel distance yielded a result similar to that published previously, which was based on empirical data. Well developed bed‐surface structures were obtained for relatively poorly sorted sediment with intense interactions between particles. Transverse structures developed when relatively large particles were allowed to move. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Improved treatments for evaluating horizontal magnetic components through the 3-D FDM in E -polarization induction problems     

Chen Po-fang 《地震学报(英文版)》2002,15(5):519-525

To improve the accuracy of the numerical evaluation through the 3-D finite difference method, the surface boundary conditions are added to modify the old program. The author has tested the new program by making calculations for the model constructed by Wanamaker, et al (1984). The comparison between the numerical results obtained from this paper and those by Wannamaker, et al (1984) indicates that a pronounced improvement is realized in the evaluation of the horizontal magnetic components. Moreover, better calculations for the vertical magnetic components are also obtainable by using the new program.  相似文献   

用ANSYS模拟结构-地基动力相互作用振动台试验的建模方法   总被引：37，自引：6，他引：37  

陈波  吕西林  李培振  陈跃庆 《地震工程与工程振动》2002,22(1):126-131

本文以结构－地基动力相互作用振动台模型试验为基础，结合通用有限元软件ANSYS，对结构－地基动力相互作用体系进行有限元计算建模的一些问题作了研究，主要包括柔性土容器的模拟、土体动力本构模型的选用、土体与结构交界面上的状态非线性模型、网格划分、重力的考虑、结构中钢筋的处理以及对称性的应用等。文中给出了利用上述建模方法对结构－地基动力相互作用体系进行计算的一些加速度时程结果，并与试验结果相对照，吻合较好。通过计算分析，验证了简化处理方法的合理性和计算模型的可行性。  相似文献   

An oases dynamics model and its application in the Manas oasis     

CHEN Zhengjiang  SHI Wenzhong  HUI Yanghe 《地理学报》2002,12(3):348-356

This study applies theories of systems and system dynamics to ecological economic systems in the oasis environment, with the intention of finding the basic characteristics of the oasis environment and its feedback structures. This study explores the inner mechanisms of economic development in the oasis environment and its relationship to policy variables. This model is applied to economic development in the Manas oasis of the Xinjiang Uygur Autonomous Region of China. System dynamics method starts from studying feedback structure within the system study and then searches for the best solution through identifying the right "policy point" and through model simulation in the computer. It embodies the cream of "systems cybernetics theory". This study is justified because the nature of the oasis system and the simulation results are scientifically sound and practically feasible.  相似文献   

GRAPHER、Surfer32与CorelDRAW1O在物探成图中的应用   总被引：1，自引：0，他引：1  

刘川宁 《矿产与地质》2003,17(1):62-64

用GRAPHER、Surfer32软件作出给定数据的曲线图、平剖图、平面等值线图和立体曲面图后，再用CorelDRAW10来编辑，可快速做出一张满意而又少占存储空间的图件。  相似文献   

基于OpenGL的多层三维空间实体叠加建模     

田静  陈圣波  胡卓伟  赵灵军  阎雨 《世界地质》2003,22(4):404-407

多层三维空间实体普遍存在于现实生活中。借助于目前国际最广泛应用的三维图形接口OpenGL将其真实地显示出来，具有重要的现实意义。其中多层三维空间实体建模技术是显示过程的关键步鼻。在实现单层空间实体三维建模的基础上，利用OpenGL实现了多层三维空间实体叠加建模，叠加实现的过程及其属性数据的表示方法。  相似文献   

地球化学样品分析质量管理系统   总被引：3，自引：5，他引：3       下载免费PDF全文

胡建平  郑存江 《岩矿测试》2003,22(3):211-216

利用VFP6．0强大的数据计算和管理功能，设计了对地质调查样品分析数据的实验室质量管理系统。该系统不仅可以同时管理多个图幅样品的数据，还可以自动实现样品编码、内检样品按指定比例随机生成、一级和二级标样质量汇总、内检合格率和报出率计算、二级标样质量监控图绘制以及按选定格式进行分析数据和内检数据的导入和导出，可以根据用户的需要输出美观的表格。该系统适用于不同比例尺化探数据的实验室质量管理。  相似文献   

不同电阻率测深方法对旁侧不均匀体的反映   总被引：2，自引：0，他引：2  

强建科  阮百尧 《物探与化探》2003,27(5):379-382

利用三维有限元数值模拟,重点研究了旁侧三维不均匀体所产生的视电阻率的影响问题,展示了4种常规电阻率测深法在旁侧不均匀体上的异常分布特点;探讨了测深点正下方目标体异常与旁侧不均匀体异常的区别问题,指出旁侧不均匀体的影响是产生电阻率法假异常的主要原因之一.  相似文献