福建仙游ML5.0级地震波形分析     

蔡杏辉  段刚  张丽娜 《高原地震》2014,26(4):14-18

2013年9月4日,福建仙游发生ML5.0级地震,这是福建数字地震台网建成以来记录到的该区域最大地震.本文就此次地震的记录波形进行分析,结果表明：仙游ML5.0级地震的震相出现规律符合一般近震记录特征;在波形中分析出sPn震相,并据此测定地震的震源深度为11.1 km,与Hyposat方法测定结果一致;用初至首波估算出震区的地壳厚度约为25.2 km.  相似文献   

X射线相位衬度显微成像的原理与进展   总被引：1，自引：0，他引：1  

陈志华  潘琳  李红艳  黎刚  徐波  王自强  朱佩平  赵天德  姜晓明  吴自玉  唐劲天  陈惟昌 《CT理论与应用研究》2005,14(1):52-56

当前医学影像学的发展趋势是提高人体软组织成像的衬度分辨率及空问分辨率,由宏观影像学向微观影像学的方向发展。微观影像学能看见微米级的组织和细胞结构,能在活体上无损和动态地观察人体内部器官的微细病理变化,从而能早期做出准确的细胞病理学的定性和定位诊断,以及早期进行精确的定点清除治疗。在提高软组织成像的衬度分辨率方面,相位衬度成像技术是国内外关注的热点。据报道,软组织的X射线相位衬度的分辨率约为常规X射线CT吸收衬度分辨率的1000倍。本文以北京同步辐射装置产生的同步X射线束为光源,应用衍射增强成像（DEI）技术,对人和动物脏器的软组织进行相位衬度成像。结果表明：相位衬度显微成像可清晰显示肺泡、。肾小管、肝小叶等微细的组织结构,其空间分辨率可达20微米,这些在常规X射线CT吸收衬度成像是看不见的。医学相位衬度（简称“相衬”）显微CT成像将是医学显微影像学的未来发展方向。  相似文献   

Natural convection of compressible and incompressible gases in undeformable porous media under cold climate conditions     

Marc Lebeau  Jean-Marie Konrad 《Computers and Geotechnics》2009

A numerical model for convective heat and mass transport of compressible or incompressible gas flows with soil-water phase change is presented. In general, the gaseous phase is considered as compressible and the model accounts for adiabatic processes of compression heating and expansion cooling. The inherently compressible gaseous phase may nevertheless be considered as incompressible by adopting the Oberbeck–Boussinesq approximations. The numerical method used to solve the equations that describe natural convection is based on a Galerkin finite element formulation with adaptive mesh refinement and dynamic time step control. As most existing numerical studies have focused on the behavior of incompressible fluids, model substantiation examines the influence of fluid compressibility on two-widely used benchmarks of steady-state convective heat and mass transport. The relative importance of the effect of pressure-compressibility cooling is shown to increase as the thermal gradient approaches the magnitude of the adiabatic gradient. From these results, it may be concluded that pore-air compressibility cannot be neglected in medium to large-sized enclosures at small temperature differentials. After demonstrating its ability to solve fairly complex transient problems, the model is used to further our understanding of the thermal behavior of the toe drain at the LA2-BSU dam in the province of Quebec, Canada.  相似文献   

东喜马拉雅构造结石榴角闪岩变质作用P-T-t轨迹:相平衡模拟与锆石年代学   总被引：1，自引：1，他引：0  

田作林  康东艳  穆虹辰 《岩石学报》2017,33(8):2467-2478

东喜马拉雅构造结南迦巴瓦杂岩由多种类型的高级变质岩组成,包括片岩、片麻岩、大理岩、石榴角闪岩和基性麻粒岩。石榴角闪岩呈透镜状产出在片麻岩中,可见不连续分布的规模不等的浅色体。石榴角闪岩由石榴石、角闪石、黑云母、斜长石、石英、金红石、钛铁矿和榍石组成,石榴石变斑晶可见由浅色矿物组成的"白眼圈"。岩相学、矿物化学和相平衡模拟表明石榴角闪岩经历了一条顺时针型的P-T演化轨迹,可划分为两个阶段:(Ⅰ)升温升压的进变质阶段,由石榴石和斜长石斑晶记录,峰期矿物组合为石榴石+角闪石+黑云母+斜长石+石英+金红石+钛铁矿。运用石榴石变斑晶边部和斜长石变斑晶边部成分在视剖面图上的投点确定出峰期温压条件为~11.5kbar、790℃,达到了高压麻粒岩相条件,并经历了部分熔融,产生至少9%的熔体;(Ⅱ)降温降压的退变质阶段,由石榴石边部"白眼圈"冠状体记录。运用平均温压法计算冠状体中黑云母+斜长石+角闪石+石榴石组合的形成温压条件为~7kbar、~750℃。该阶段金红石消失,熔体结晶,并与早期矿物发生回反应。在石榴石角闪岩的锆石中获得了从29.2Ma到10.2Ma的连续变质年龄。由于锆石通常在熔体结晶过程中生长,因此确定该组年龄代表石榴石角闪岩退变质年龄。本文和以前的研究结果表明,南迦巴瓦杂岩中的高温和中温麻粒岩相亚单元具有相似的降温降压P-T轨迹,但高温单元具有较高的变质压力条件,表明其俯冲到了更大的深度。  相似文献   

藏南吉隆地区大喜马拉雅结晶杂岩的新生代变质作用和构造意义     

董昕  刘国威  苟正彬 《岩石学报》2017,33(8):2342-2356

大喜马拉雅结晶杂岩位于喜马拉雅造山带的核部,其变质作用的研究是揭示碰撞造山作用和动力学的关键。本文对喜马拉雅造山带中部吉隆地区的大喜马拉雅结晶杂岩中的片麻岩和片岩进行了岩石学和锆石U-Pb年代学的研究,表明这些高级变质岩经历了高角闪岩相的变质作用和部分熔融,以及近等温降压的退变质过程。片麻岩和片岩的峰期变质矿物组合为斜长石+钾长石+黑云母+白云母+石英±石榴子石±钛铁矿和石榴子石+蓝晶石+斜长石+黑云母+白云母+钛铁矿+石英,晚期退变质矿物组合为斜长石+钾长石+黑云母+白云母+夕线石+石英±石榴子石和石榴子石+夕线石+斜长石+黑云母+白云母+钛铁矿+石英。相平衡模拟研究表明,岩石的峰期变质条件为685~755℃和9.5~12kbar,退变质作用条件为675~685℃和6~7.4kbar。锆石U-Pb年代学表明,高级变质岩的部分熔融时间为38~16Ma,熔体结晶时间为17~15Ma。本次研究表明,大喜马拉雅结晶杂岩中、上部并没有普遍经历高压麻粒岩相变质作用,部分地区包括吉隆地区经历的是高角闪岩相变质作用。此外,本文在吉隆地区高级变质的大喜马拉雅结晶杂岩中识别出较低级变质的特提斯喜马拉雅岩系单元。结合已发表的藏南拆离断裂的主要活动时间,本文认为构造楔模型更适用于研究区喜马拉雅造山过程的解释。  相似文献   

25 ℃时NaClNH4ClH2O三元水盐体系相平衡的研究          下载免费PDF全文

王卫东  汪春华 《盐湖研究》2007,15(2):42-44

利用湿渣法,研究了25℃时NaCl-NH4Cl-H2O三元水盐体系的固液相平衡关系,测出了NaCl和NH4Cl在水中的溶解度数据,并绘制了相图。结果表明该体系在25℃时的相图存在6个区域,即:纯NH4Cl结晶区;纯NaCl结晶区;以NH4Cl为主的固溶体结晶区;以NaCl为主的固溶体结晶区;以NH4Cl为主的固溶体和以NaCl为主的固溶体共同结晶区以及不饱和溶液区。  相似文献   

蒙古中南部地区面波相速度层析成像   总被引：2，自引：2，他引：0       下载免费PDF全文

余大新  吴庆举  李永华  潘佳铁  张风雪  何静  高孟潭  M. Ulziibat  S. Demberel 《地球物理学报》2015,58(1):134-142

本文采用小波变换频时分析技术提取了1893条蒙古中南部地区双台间基阶Rayleigh波相速度频散曲线,通过对提取到的相速度频散进行二维反演,首次重构了蒙古高原中南部10~80s周期内分辨率为0.5°×0.5°的相速度分布图.结果表明,短周期相速度频散(10~20s)明显受地表地形控制,表现为杭爱—肯特山盆地为相对高速异常,而南部的戈壁带表现为相对低速异常;在30s到60s周期内,南部的戈壁带和北部的杭爱—肯特山盆地都显示出稳定的高速异常,而中部戈壁带则表现为低速异常.该低速异常区与新生代火山岩出露位置的一致性,暗示该低速异常可能与新生代火山活动有关.穿过蒙古高原中部的两条主要断裂带与研究区内的地震波速度分布具有很好的一致性,可能暗示两条断裂带一直延伸到整个岩石圈.此外,蒙古中南部地区的壳幔速度低于全球平均大陆值,且其相速度频散曲线与遭受破坏的克拉通,尤其大陆裂谷很相似,可能暗示着研究区具有薄的、活跃的岩石圈构造.  相似文献   

Seismic interferometry by tangent‐phase correction          下载免费PDF全文

Flavio Poletto  Biancamaria Farina  Gualtiero Böhm  Kees Wapenaar 《Geophysical Prospecting》2015,63(3):567-586

We present a modified interferometry method based on local tangent‐phase analysis, which corrects the cross‐correlated data before summation. The approach makes it possible to synthesize virtual signals usually vanishing in the conventional seismic interferometry summation. For a given pair of receivers and a set of different source positions, a plurality of virtual traces is obtained at new stationary projected points located along the signal wavefronts passing through the real reference receiver. The position of the projected points is estimated by minimizing travel times using wavefront constraint and correlation‐signal tangent information. The method uses mixed processing, which is partially based on velocity‐model knowledge and on data‐based blind interferometry. The approach can be used for selected events, including reflections with different stationary conditions and projected points with respect to those of the direct arrivals, to extend the interferometry representation in seismic exploration data where conventional illumination coverage is not sufficient to obtain the stationary‐phase condition. We discuss possible applications in crosswell geometry with a velocity anomaly and a time lapse.  相似文献   

扬子地块北缘晚二叠世长兴期岩相古地理   总被引：1，自引：0，他引：1       下载免费PDF全文

牟传龙  王瑞华  谭钦银  付建元  程锦翔  王正和 《地学前缘》2011,18(4):1-8

扬子地块北缘与秦岭接壤,晚二叠世长兴期岩石地层单元为长兴组和大隆组。长兴组为一套碳酸盐岩沉积,沉积单元包括台地相、台地边缘礁滩相以及台地边缘斜坡相等;而大隆组则主要为一套灰黑至黑色薄层硅质岩、炭质页岩夹薄层泥晶灰岩,为一套较深水盆地沉积的产物。研究结果表明,这一深水盆地环境大致从西边的广元开始,向东经旺苍、南江与鄂西地区相连成为一广阔海域,扬子地块与华北地块隔海相望。这一沉积格局不仅为油气勘探工作的部署奠定了坚实的基础,而且可能反映出扬子地块与华北地块在此之前已经成为统一陆块。  相似文献   

Spinel–quartz high temperature paragenesis in Al–Fe granulites from the Ihouhaouene area (NW Hoggar, Algeria)     

Saïda Aït-Djafer  Zouhir Adjerid  Assia Badani  Khadidja Ouzegane  Jean Robert Kienast   《Journal of African Earth Sciences》2009,55(1-2):79

The spinel–quartz-bearing Al–Fe granulites from Ihouhaouene (In Ouzzal, West Hoggar) have a migmatitic appearance with quartzo-feldspathic layers intercalated with restitic layers. These granulites are characterized by a hercynitic spinel–quartz assemblage typical of high grade terranes. The stability of the spinel–quartz assemblage is attributed to an elevation of temperature (from 800 to >1100 °C) at high pressures (10–11 kbar), followed by an isothermal decompression from 9 to 5 kbar, an evolution typical of the In Ouzzal clockwise P–T path. The Al–Fe granulites’ history can be subdivided into different successive crystallisation stages. During the first stage, the spinel–quartz assemblage formed, probably following a prograde event that also produced partial melting. During a second stage, the primary spinel–garnet–sillimanite–quartz paragenesis broke-down to give rise to the secondary assemblage. The metamorphic evolution and phase relations during this stage are shown in P–T–X pseudosections calculated for the simple FMASH system. These pseudosections show that the orthopyroxene–cordierite–spinel symplectite appeared during a high temperature decompression, as a product of destabilisation of garnet in sillimanite-free microdomains with high X_Mg values. At the same time, the spinel–quartz association broke-down into cordierite in Fe-rich microdomains. Average pressure and temperature estimates for the orthopyroxene–spinel–garnet–cordierite–quartz association are close to the thermal peak of metamorphism (1000 ± 116 °C at 6.3 ± 0.5 kbar). With decreasing temperatures garnet–sillimanite corona developed from the breakdown of the primary spinel–quartz assemblage in the Fe-rich microdomains, whereas cordierite–spinel formed at the expense of primary sillimanite and garnet in the Mg-rich microdomains.  相似文献