新疆天山地区壳幔S波速度结构特征及变形分析   总被引：1，自引：0，他引：1       下载免费PDF全文

蔡妍  吴建平  明跃红  房立华  王未来  孔祥艳  杨婷  范莉苹 《地球物理学报》2019,62(11):4214-4226

天山地区地质构造复杂，地震活动频繁，其壳幔变形和深部结构一直受到学者们的高度关注.然而，由于天山地区地震台站资料较少，致使壳幔变形研究结果与解释存在诸多争议.本研究利用在天山地区（40°N-46°N，78°E-92°E）新布设的11个流动宽频带地震台站和该地区39个固定台站的观测资料，采用接收函数与面波联合反演方法，获得了研究区地壳厚度及壳幔S波速度结构.反演结果显示天山地区（41.5°N-44°N，78°E-88°E）平均地壳厚度为56 km，塔里木盆地（40°N-41.5°N，79°E-90°E）、准噶尔盆地（44°N-46°N，82°E-90°E）和吐鲁番盆地（42°N-43°N，88°E-90°E）具有较厚的沉积层，地壳平均厚度为43 km、53 km和46 km，整体表现为天山厚、盆地相对较薄的特征；在研究区南天山的最高峰（42°N，80.5°E）及北天山的最高峰（43.5°N，86°E）附近，中下地壳存在较厚的低速层，我们认为在强烈挤压作用下低速、低强度的中下地壳强烈变形可能是导致该区域快速隆升的主要原因.在研究区中部，位于塔里木盆地与准噶尔盆地之间的天山地区，中下地壳及上地幔均存在低速层，且盆地莫霍面向天山倾斜明显.结合前人的研究成果推测，在南北向构造挤压应力作用下，塔里木盆地与准噶尔盆地发生了向天山造山带方向的双向壳幔层间插入俯冲.在研究区东部，塔里木盆地东北缘与天山东部接触带的地壳内没有明显的低速层，推测应处在早期挤压变形状态，该区域的壳幔边界为缓变的速度梯度带，可能与上地幔热物质侵入或渗透有关.  相似文献   

苔藓生物结皮层腐殖质组成变化特征研究          下载免费PDF全文

闫德仁  张胜男  吴振廷 《干旱区地理》2019,42(6):1354-1358

腐殖质组成是表征土壤化学性质的主要指标之一，在某种程度对评价风沙土的发育过程具有意义。采集了不同气候区沙地沙漠苔藓生物结皮层样品，采用重铬酸钾容量法和光密度法测定了苔藓结皮层腐殖质组成含量和胡敏酸吸光特性。结果表明：随着干燥指数的增加，苔藓结皮层有机质含量由14.93 g·kg^-1降低到9.89 g·kg^-1，腐殖酸总量由5.1 g·kg^-1降低到2.0 g·kg^-1，胡敏酸含量由2.9 g·kg^-1降低到 0.7 g·kg^-1，富里酸含量由2.2 g·kg^-1降低到1.3 g·kg^-1，胡敏酸与富里酸比值（HA/FA）由1.32降低到0.54，E₄/E₆比值则由4.28增加到5.83。苔藓结皮层腐殖质组成含量及胡敏酸吸光特性具有地带性变化趋势，并影响着生物结皮层及流动风沙土的发育演变过程。  相似文献   

Reverse-Time Migration of Converted S-Waves of Varying Densities     

TONG Siyou  CHEN Ming  ZHOU Huawei  LI Linwei  XU Xiugang  WU Zhiqiang 《中国海洋大学学报(英文版)》2019,(5)

Ocean-Bottom Node(OBN) acquisitions provide both non-converted and converted reflection energy. There is a clear advantage to independently imaging both P-and S-waves, as they provide more information collectively than either does alone. In many conventional converted-wave pre-stack migration algorithms, density is treated as a constant, which is not the real-life case on earth. S-wave velocity and density information is crucial for hydrocarbon detection because it helps in the identification of porefilling fluids. In this paper, we focused on the effect of density on imaging, and developed a method of reverse-time migration(RTM) on converted s-waves of varying densities(VD-RTMCS). Phase correction was required prior to pre-stack migration to avoid constructive interference between data from adjacent sources. Synthetic data examples showed that when density variations were included, image profiles showed advantages in signal-to-noise ratio, vertical resolution and imaging of complex structures.  相似文献   

Dynamic changes in lakes in the Hoh Xil region before and after the 2011 outburst of Zonag Lake     

LIU Wen-hui  XIE Chang-wei  ZHAO Lin  WU Tong-hua  WANG Wu  ZHANG Yu-xin  YANG Gui-qian  ZHU Xiao-fan  YUE Guang-yang 《山地科学学报》2019,(5)

Zonag, Kusai, Hedin Noel and Yanhu Lakes are independent inland lakes in the Hoh Xil region on the Qinghai-Tibet Plateau. In September2011, Zonag Lake burst after the water level had increased for many years. Floods flowed through Kusai and Hedin Noel Lakes into Yanhu Lake; since then, the four small endorheic catchments merged into one larger catchment. This hydrological process caused the rapid shrinkage of Zonag Lake and continuous expansion of Yanhu Lake. In this study,based on satellite images, meteorological data and field investigations, we examined the dynamic changes in the four lakes and analyzed the influencing factors. The results showed that before 2011, the trends in the four lake areas were similar and displayed several stages. The change in the area of Zonag Lake corresponded well to the change in annual precipitation(AP), but the magnitude of the change was less than that of a non-glacier-fed lake. Although increased precipitation was the dominant factor that caused Zonag Lake to expand, increased glacier melting and permafrost thawing due to climate warming also had significant effects. After the 2011 outburst of Zonag Lake, due to the increasing AP and accelerating glacier melting, the increases in water volume of the three lakes were absorbed by Yanhu Lake, and Yanhu Lake expanded considerably. According to the rapid growth rates in water level and lake area, Yanhu Lake is likely to burst in 1-2 years.  相似文献   

Impacts of SIS and CICE as Sea Ice Components in BCC_CSM on the Simulation of the Arctic Climate     

CHU Min  SHI Xueli  FANG Yongjie  ZHANG Lujun  WU Tongwen  ZHOU Bing 《中国海洋大学学报(英文版)》2019,(3)

Sea ice is a sensitive indicator of climate change and an important component of climate system models. The Los Alamos Sea Ice Model 5.0(CICE5.0) was introduced to the Beijing Climate Center Climate System Model(BCC_CSM) as a new alternative to the Sea Ice Simulator(SIS). The principal purpose of this paper is to analyze the impacts of these two sea ice components on simulations of basic Arctic sea ice, atmosphere, and ocean states. Two sets of experiments were conducted with the same configurations except for the sea ice component used, i.e., SIS and CICE. The distributions of sea ice concentration and thickness reproduced by the CICE simulations in both March and September were closer to actual observations than those reproduced by SIS simulations, which presented a very thin sea ice cover in September. Changes in sea ice conditions also brought about corresponding modifications to the atmosphere and ocean circulation. CICE simulations showed higher agreement with the reference datasets than did SIS simulations for surface air temperature, sea level pressure, and sea surface temperature in most parts of the Arctic Ocean. More importantly, compared with simulations with SIS, BCC_CSM with CICE revealed stronger Atlantic meridional overturning circulation(AMOC), which is more consistent with actual observations. Thus, CICE shows better performance than SIS in BCC_ CSM. However, both components demonstrate a number of common weaknesses, such as overestimation of the sea ice cover in winter, especially in the Nordic Sea and the Sea of Okhotsk. Additional studies and improvements are necessary to develop these components further.  相似文献   

全球气候变化下南海诸岛保护优先区识别分析   总被引：3，自引：1，他引：2  

左秀玲  苏奋振  张宇  吴文周  吴迪 《地理学报》2020,75(3):647-661

全球变化下,珊瑚礁保护区是保护生物多样性、增强珊瑚礁对气候变暖抵抗力的有效方式,而维持珊瑚礁弹性是其核心内容。针对珊瑚礁最具有威胁性的热压力因子,基于南海1982—2009年卫星观测海表面温度（SST）数据和CMIP5加拿大地球系统模式CanESM2模型预估的2006—2100年南海SST数据构建热压力强度模型,从维持珊瑚礁弹性的角度识别IPCC RCP 4.5和RCP 8.5情景下南海诸岛保护优先区。结果表明：RCP 4.5和RCP 8.5情景下13%左右的南海诸岛珊瑚礁识别为保护优先区。根据热压力强度与珊瑚抵抗力及避难所关系,西沙群岛七连屿和晋卿岛近年观测与未来预估的热压力强度均比较低,在保障其服务功能的基础上建议实施完全保护;东沙群岛东沙环礁和中沙环礁排洪滩近年观测急性热压力强度较高但未来预估热压力强度较低,建议实施50%禁止利用保护;中沙群岛黄岩岛近年观测和未来预估的急性热压力强度均比较低,建议实施50%多用途保护。南沙群岛有14%左右的珊瑚礁识别为保护优先区,根据其热压力强度可实施30%~100%禁止利用保护或30%~50%多用途保护。RCP 4.5和RCP 8.5情景下的南海诸岛保护优先区及保护对策,可为维持珊瑚礁生态弹性及应对全球气候变化提供重要的参考价值。  相似文献   

川藏铁路交通廊道地质调查工程主要进展与成果     

郭长宝  王保弟  刘建康  涂杰楠  张永双  马剑飞  铁永波  韩冰  马鑫  刘峰  李雪  孟文  钟宁  杨志华  吴瑞安 《中国地质调查》2020,7(6):1-12

川藏铁路是我国正在规划建设的重点工程,由于其位于地形地貌和地质构造都极为复杂的青藏高原东部,在铁路规划建设中面临一系列迫切需要解决的关键地质问题: 区域性活动断裂与断错影响、地质灾害、高地应力及其引起的岩爆和大变形、高温热害、断裂带高压水与涌水突泥、高陡边坡稳定性等。为满足技术支撑川藏铁路规划建设、精准服务国家重大战略实施的需要,中国地质调查局部署了“川藏铁路交通廊道地质调查工程”,聚焦制约川藏铁路规划建设的关键问题,充分发挥地质调查工作对国家重大工程规划建设的支撑作用。2019年主要完成铁路沿线1:5万区域地质调查1 350 km²、1:5万地质灾害调查5 000 km²,建设6口大地热流地质参数井、8个地温监测站,完成地应力测量20孔,编制完成11份地质调查专报,提出的大渡河大桥段、理塘车站段、毛垭坝盆地段等线路优化建议/防灾建议被采纳; 首次将1:5 000大比例尺航空物探技术引入复杂山地铁路工程勘察,创新形成千米级超长水平钻孔定向取心钻进技术,实现500 m深的水平孔地应力测量突破等。该工程通过2019年调查研究,全力提升了铁路沿线地质调查程度与精度,并创新了复杂艰险山区重大工程地质问题与探测技术、地质灾害风险防控理论与减灾关键技术,有效支撑服务了川藏铁路规划建设。  相似文献   

基于条件平差的卫星双向时间传递链路性能优化方法          下载免费PDF全文

王翔  宋会杰  王威雄  高喆  张继海  武文俊  董绍武 《天文学报》2020,61(3):25

卫星双向时间传递(Two-Way Satellite Time and Frequency Transfer, TWSTFT)是目前精度最高的时间传递方法之一,同时也是参与国际原子时计算的守时实验室之间比较原子时尺度的一种主要方法.提高TWSTFT链路的短期稳定度,降低周日效应对链路时间传递结果的影响,对优化TAI (International Atomic Time)的性能具有现实意义.提出了一种基于条件平差的TWSTFT链路性能优化方法,先依据TWSTFT链路测量噪声水平与谱分析结果建立TWSTFT链路性能优化网络(简称优化网络),再根据优化网络中各链路测量噪声分析结果设置权系数阵,建立条件平差模型.选取亚太地区的中国计量科学研究院(National Institute of Metrology, NIM)-中国科学院国家授时中心(National Time Service Center, NTSC)卫星双向时间传递链路作为待优化链路,以NTSC、NIM以及德国联邦物理技术研究所(Physikalisch-Technische Bundesanstalt,PTB)之间的TWSTFT链路组成优化网络,对优化网络的组网方法和条件平差模型进行实验验证.结果表明,平差后待优化链路短期稳定度得到了改善,同时其受周日效应的影响降低了约24.6%.使用该方法,能够有效提高待优化链路的时间传递性能.  相似文献   

福建北部近岸东台山岛火山岩形成时代、地球化学与古太平洋板块俯冲的响应          下载免费PDF全文

王飞飞  张勇  韩宗珠  宋维宇  吴浩  宁泽 《中国地质》2020,47(5):1426-1437

福建北部沿岸岛屿岩石组合以晚中生代火成岩为主，研究认为是古太平洋俯冲消减的产物，对反演洋盆构造演化具有重要的指示意义。本次对其中的福建北部海域东台山岛上广泛发育的酸性火山岩进行了锆石U-Pb定年以及全岩主微量地球化学分析工作。2件年代学样品分别获得了92 Ma和86 Ma的锆石U-Pb年龄，确定东台山岛火山岩形成于晚白垩世。全岩地球化学特征指示火山岩样品以酸性钙碱性岩石为主，整体富集Rb、Ba等元素，亏损Nb、Ta、Sr、Eu等元素，显示弧型岩浆岩的地球化学组成。研究认为东台山岛火山岩起源于古老下地壳变沉积岩熔融，并在浅层岩浆房内经历了不同程度的结晶分异过程。结合区域上晚中生代岩浆作用由陆向海的时空迁移特征，福建北部沿岸岛屿火山岩形成的深部动力学机制应该与古太平洋俯冲过程中的板片回转过程相关。  相似文献   

Mantle Response to Slab Breakoff in the North Qaidam Tectonic Belt: Geochemical Constraints from Syn-subduction Mafic Igneous Rocks     

LI Xiucai  NIU Manlan  CAI Qianru  WU Qi  SUN Yi  YUAN Xiaoyu  LI Chen 《《地质学报》英文版》2020,94(Z1):26-27

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