Numerical Simulation of Wave Field near Submerged Bars by PLIC-VOF Model

Investigating the wave field near structures in coastal and offshore engineering is of increasing significance. In the present study, simulation is done of the wave profile and flow field for waves propagating over submerged bars, using PLIC-VOF （Pieeewise Linear Interface Construction） to trace the free surface of wave and finite difference method to solve vertical 2D Navier-Stokes （N-S） equations. A comparison of the numerical results for two kinds of submerged bars with the experimental ones shows that the PLIC-VOF model used in this study is effective and can compute the wave field precisely.     

中祁连东段晋宁期碰撞型花岗岩及其地质意义

对中祁连地块东段西宁西部近S-N向展布的元古宙花岗岩带地质地球化学和年代学研究表明:它侵位于元古宙基底中浅变质岩系湟源群中,具有同碰撞S型花岗岩的性质;(917±12)Ma的单颗粒锆石U-Pb年龄记录了其侵位的时代为新元古宙晋宁期,这一新元古宙晋宁期碰撞型花岗岩带具有重要的地质意义.     

地闪回击的微秒级辐射场特征及近地面连接过程分析

利用１μｓ时间分辨率的慢天线电场变化仪在甘肃中川地区雷暴过程中测量得到的大量地闪辐射波形地地闪回击辐射场特征及回击的慢前沿过程进行分析,发现１８次正地闪和８５次负地闪产在周前沿过程上升时间为１９．２μｓ和９．４μｓ,８４次负地闪继后回击的前沿过程为４．３ μｓ。ＹＹ ＵＤＡ Ｏ ３．１μ;     

Earthquake swarms in continental rifts — A comparison of selected cases in America, Africa and Europe

The occurrence of earthquake swarms is typically related to magmatic activity in volcanoes, yet swarms are also common in other intracontinental regions such as continental rifts. We present here a summary of geophysical observations that have been made in earthquake swarm areas of the Rio Grande, Kenya, and Eger rifts, focusing on characteristic parameters for the origin and generation of the swarm earthquakes.Our compilation of seismological parameters such as spatial distribution and focal parameters of hypocenters, magnitude statistics, and the location of the swarm centres in the rift environments reveals major similarities. The earthquake swarms take place at shallow depth between 0 and 10 km. The maximum magnitudes are mostly less than 4.5. The b-values, indicating the magnitude frequency relation of the seismicity, are about 0.8. They are hence not deviating from a normal non-volcanic intraplate environment, but are considerably lower than those of volcanic earthquake swarms. Focal mechanism studies give uniform pictures of stress field orientation and faulting style for the swarm areas. In all three rifts, the centres of swarm activity seem to be restricted to rift valley sections that may be influenced by large-scale fracture or shear zones that intersect the rifts. We conclude that these deep-reaching zones of weakness allow intrusions of upper mantle material into crustal layers, where magma-related fluids or fluctuations of the magma bodies themselves cause the generation of earthquake swarms.     

华北地块北缘中元古界几个重要不整合面的地质特征及构造意义

华北地块北缘中元古代沉积层序中出现多个沉积间断和不整合面。此次研究对其中5个不整合面进行了野外考察,分析了它们的地质特征和空间分布,认为它们与不同的地质过程有关。大红峪组底部不整合面是早期裂谷盆地演化为被动大陆边缘的记录,属于裂解不整合面性质;高于庄组底部和杨庄组底部的不整合面是海平面变化造成被动大陆边缘内部高地沉积间断和海岸超覆沉积的结果;铁岭组顶部不整合面可能与弧后环境发生挤压抬升有关;下马岭组沉积后的抬升可能是相邻大陆地块碰撞作用的产物。华北地块北缘中元古代层序中不整合面的形成与Columbia和Rodinia超大陆的形成和裂解过程密切相关。     

Research Progress in Cenozoic N-S Striking Rifts in Tibetan Plateau

The formation of the Cenozoic N-S striking rifts in the Tibetan Plateau is the consequence of continuous contraction after the India-Asia collision. Its formation and evolution are of great significance for understanding the growth of the Tibetan Plateau. In recent years, geochronology, structural geology, geochemistry and geophysical exploration have been used to study the onset timing, mechanism and evolution process of the N-S striking rifts, and the N-S striking rifts are related to the deep dynamics in Tibet. However, it is still difficult to reach a consensus on the understanding of the N-S striking rifts in the Tibetan Plateau. This paper summarized the research status and existing problems on the onset timing, mechanism and their relationship with the deep layer of the plateau: the main extension period of the N-S striking rifts is Miocene; mechanisms controlling its formation are complex and may be various in different periods; the N-S striking rifts have a close genetic relationship with potassium and ultrapotassic rocks in the plateau, and their distribution may be affected by high-conductivity and low-velocity bodies. Based on existing knowledge, more precise geochronological constraints, deep process detection, and numerical modeling will be the future development trends in the study of N-S striking rifts.     

集成波能转换功能的方箱—挡浪板式浮式防波堤水动力特性研究

浮式防波堤与振荡浮子式波浪能转换装置集成是一种较为合理的波浪能开发利用方式,基于方箱式浮式防波堤—波浪能转换集成系统和幕帘式防波堤的研究成果,提出了一种新型方箱—垂直挡浪板式浮式防波堤—波浪能转换集成系统,建立数学模型对该集成系统的水动力特性和能量输出特性进行研究。模型基于N-S方程,采用紧致插值曲线(CIP)方法结合浸没边界法(IBM)求解。运用数值模型探究在一定波浪条件下,动力输出系统(PTO)阻尼力的大小以及挡浪板对集成系统的水动力特性和能量转换特性的影响,得到如下结论:集成系统的俘获宽度比随PTO阻尼力的增大呈现先增大后减小的趋势,在阻尼力F_(PTO)=150 N时达到最大;相对于方箱型集成系统,增设0.1 m挡浪板后可使其最大俘获宽度比η_e提高33%左右;此外,集成系统的俘获宽度比随挡浪板长度增加而增大,增长趋势逐渐变缓,在挡浪板长度S_p=0.5 m时达到最大,此时俘获宽度比η_e=0.563 1。     

青藏高原西南部查孜地区中新世钾质火山岩地球化学及其成因

通常认为青藏高原的钾质-超钾质火山岩的形成多与地幔有着紧密的联系,然而最近对青藏高原的一些钾质-超钾质火山岩的研究显示一些钾质火山岩也可以起源于下地壳.青藏高原西南部查孜地区中新世火山岩是形成于13～11 Ma左右的一套钾质-超钾质岩石,根据岩石化学组成将其分为中基性火山岩组、中性火山岩组和流纹质火山岩.其中中基性火山岩组可能源于一个富含金云母的富集地幔源区;中性火山岩组可能是富钾的镁铁质下地壳部分熔融的产物;流纹质火山岩可能是拉萨地块在中新世时期的伸展构造运动而导致中上地壳因减压而发生部分熔融的产物.结合查孜地区及其邻近火山岩的年龄、化学组成以及岩浆组合,初步认为查孜地区火山岩可能与高原在中新世发生伸展活动而产生的南北向地堑系统有关.     

http://www.sciencedirect.com/science/article/pii/S1674987110000137

<正>This study attempts to acquire information on tectonic activity in western China from land surface temperature(LST) field data.On the basis of the established relationship between heat and strain,we analyzed the LST distribution in western China using the satellite data product MODIS/Terra.Our results show that:1. There are departures from annual changes of LST in some areas,and that these changes are associated with the activity of some active tectonic zones.2.When annual-change background values caused by climate factors are removed,the long-period component(LST_(LOW)) of temperature residual(△T) of the LST is able to serve as an indicator for tectonic activity.We have found that a major earthquake can produce different effects on the LST fields of surrounding areas.These effects are characterized by both rises and drops in temperature.For example, there was a noteworthy temperature decline associated with the Sumatran M9 earthquake of 2004 in the Bayan Har-Songpan block of central Tibetan Plateau.3.On the other hand,the LST field of a single area may respond differently to major shocks occurring in different areas in the regions surrounding China.For instance,the Kunlun M 8.1 event made the LST on the Longmen Mountains fault zone increase,whereas the Zaisan Lake M 7.9 quake of 2003,and the Sumatran M9 event of 2004.caused decreases in the same area's LST.4.The variations of land surface temperature(LST) over time are different in different tectonic areas.These phenomena may provide clues for the study of tectonic deformation processes.On the basis of these phenomena,we use a combination of temperature data obtained at varied depths,regional seismicity and strain results obtained with GPS measurements,to test the information related to tectonic activity derived from variations of the LST field,and discuss its implications to the creation of models of regional tectonic deformation.     

西藏沙拉岗锑矿控矿构造及成矿时代约束

西藏沙拉岗锑矿床位于中国北喜马拉雅地区然巴杂岩穹窿的东南部40km。该地区至少有4种矿床类型被发现:(1)金矿;(2)金锑矿;(3)锑矿;(4)铅锌(银,锑)矿。沙拉岗是该地区代表性的一个以辉锑矿为主要矿石矿物的脉状锑矿床。赋矿围岩为下白垩统甲不拉组板岩、粉砂岩、硅质岩以及辉长岩和闪长岩等侵入体。主要的矿体受控于近东西向和近南北向断裂构造。近东西向的断裂构造多为低角度浅层次的层间断裂,在成矿前和成矿后均有活动。近南北向的构造多为高角度的断裂,切割了矿区的近东西向断裂,闪长岩和辉长岩,是主要的导矿构造和成矿要素,连通了深部含矿热液和浅表近东西向断裂构造。当近东西向和近南北向的构造发生交汇,沿断裂构造分布的蚀变和矿化的规模随之扩大,往往存在较大规模的工业矿体。锆石SHRIMP U-Pb分析说明辉长岩形成于23.6Ma左右,近南北向断裂构造及其伴随的锑矿化的时间,至少要晚于23.6Ma。