内蒙古河套断陷带及其邻区地壳磁性构造特征   总被引：1，自引：0，他引：1       下载免费PDF全文

张先  贺为民  沈京秀  赵丽  李长法 《地震工程学报》1995,17(1):31-35

本文依据航磁资料和频率域磁性单界反演方法，计算了河套断陷带及其邻区的基底磁性界埋深；依据三维磁性层反演方法求取了该区磁性层下界面，即居里界面的埋深；分析了磁性层上下界面的定量特征，并结合重力、地热、地形变诸方面的研究成果，讨论讨论了该区的地壳结构特征及地震成因。  相似文献   

Thermal effects of marine sedimentation in hydrothermally active areas   总被引：1，自引：0，他引：1  

Kelin Wang  Earl E. Davis 《Geophysical Journal International》1992,110(1):70-78

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广西特殊地震研究   总被引：3，自引：0，他引：3  

龙安明 《华南地震》1992,12(4):22-31

本文把发生在广西岩溶区的小震级(Ms≤3.0)高烈度(Ⅰ≥Ⅳ)的地震称之为特殊地震。列举了大量特殊地震的震害。根据岩溶区介质的特性,对地震波的传播作了分析;对岩溶区和非岩溶区台站记录到同等震级的地方震的波形做了最大熵谱分析。结果认为:广西岩溶区之所以产生特殊地震,其一、岩溶区饱含水的介质层对地震波具有放大作用。其二、岩溶区的地震波的卓越周期大于外岩溶区的卓越周期,这一卓越周期更接近地面3层以下的楼房的固有周期。由于这些原因,造成烈度偏高。  相似文献   

High-pressure metamorphism in the Western Cordillera of North America   总被引：1，自引：0，他引：1  

D. L. WHITNEY 《Journal of Metamorphic Geology》1992,10(1):71-85

The Skagit Gneiss, a major component of the crystalline core of the North Cascades, was metamorphosed during a mid-Cretaceous(?) to early Tertiary high-P event driven by the collision of the Insular and Intermontane superterranes. Maximum pressures recorded by metapelitic rocks are 8–10 kbar at 650–725° C. High pressures are also indicated by coexisting staurolite and hornblende in amphibolites in the Skagit Gneiss and adjacent Cascade River Schist. Mineral reactions continued during nearly isothermal decompression from 8–10 kbar to c. 3–5 kbar. Early high-P minerals (e.g. kyanite) are present as armoured relics in garnet in gneisses that contain sillimanite and cordierite in the groundmass. Skeletal relics of kyanite are also present in the groundmass of lower-grade, staurolite-bearing schists that contain texturally later cordierite. This matrix kyanite may have been preserved as a result of rapid uplift following initial decompression at high temperature. These results represent a revision of the metamorphic history of the Skagit Gneiss, which was formerly thought to have experienced only relatively low-P Barrovian metamorphism. Qualitative estimates of metamorphic conditions based on stable matrix mineral assemblages result in an underestimation of maximum pressures because mineral reactions continued during decompression. Geobarometric results for the Skagit Gneiss are interpreted as evidence for major crustal thickening in the North Cascades. Recognition that pressures of c. 9 kbar were attained supports a contractional model for North Cascades orogenesis and requires that tectonic syntheses account for the burial of the Skagit Gneiss protoliths to a depth of c. 25–30 km.  相似文献   

基于剩磁各向异性方法对华北下三叠统红层磁倾角浅化效应的研究     

薛艺  黄宝春  赵千  韩露  李能韬 《地球物理学报》2021,64(3):916-924

本文报道利用岩石剩磁组构对华北下三叠统红层进行磁倾角浅化效应的进一步识别与校正研究结果.首先,采用45°等温剩磁各向异性方法,即通过沿与样品原始水平面(即层面)呈45°夹角方向施加磁化场获得等温剩磁,并进行逐步热退磁,获得平行于层面和垂直于层面的等温剩磁分量随外加磁场和热退磁温度的变化趋势,计算获得浅化因子f=0.70.其次,应用高场等温剩磁各向异性方法,结合峰值为100 mT的交变退磁和120℃热退磁处理,分离获得碎屑赤铁矿对剩磁各向异性的贡献;由直接测量获得的单颗粒碎屑赤铁矿的各向异性度(a=1.35),计算获得f=0.59.该结果与前人对刘家沟组红层进行E/I法磁倾角浅化校正的结果(f=0.60)具有很好的一致性;表明华北下三叠统刘家沟组红层磁倾角浅化效应显著,其浅化因子为f=0.59;高场等温剩磁各向异性方法是红层磁倾角浅化校正的最有效方法.同时,如果有足够的独立样品数,且特征剩磁来自于单一剖面或有证据表明多条采样剖面之间未发生显著的相对运动,E/I法对红层磁倾角浅化因子的估计也是可信的.  相似文献   

黄鳍棘鲷微卫星标记开发及其在鲷科鱼类中的跨物种扩增          下载免费PDF全文

吴仁协  翟云  肖瑶  牛素芳  张浩冉  黎晓  陈伟勇 《应用海洋学学报》2019,38(3):356-364

采用基于高通量测序平台的SLAF-seq技术,开发出47个高多态性的黄鳍棘鲷(Acanthopagrus latus)微卫星标记,其中二碱基重复位点17个,三至六碱基重复位点30个。各位点的等位基因数为2～27(均值为10),观测杂合度(Ho)和期望杂合度(He)分别为0. 156～0. 938(均值为0. 682)和0. 177～0. 963(均值为0. 741),多态信息含量(PIC)为0. 166～0. 946(均值为0. 705)。经Bonferroni校正后,有43个位点符合哈迪-温伯格平衡(HWE),其余4个位点偏离HWE。这些多态性微卫星标记为黄鳍棘鲷遗传资源研究提供新的有效分子标记。跨物种扩增结果显示,共有31个黄鳍棘鲷微卫星标记可在9种鲷科鱼类中成功扩增。其中17个标记在太平洋棘鲷(Acanthopagrus pacificus)、黑棘鲷(Acanthopagrus schlegelii)和澳洲棘鲷(Acanthopagrus australis)中具有较好的通用性,这些标记可为棘鲷属(Acanthopagrus)的系统进化和种群遗传学分析提供新的标记来源;另有3个标记在二长棘梨齿鲷(Evynnis cardinalis)、真赤鲷(Pagrus major)、蓝点赤鲷(Pagrus caeruleostictus)及黄牙鲷(Dentex hypselosomus)中具有通用性。  相似文献   

Stratigraphic architecture of a tide‐influenced shelf‐edge delta,Upper Cretaceous Dorotea Formation,Magallanes‐Austral Basin,Patagonia          下载免费PDF全文

Theresa M. Schwartz  Stephan A. Graham 《Sedimentology》2015,62(4):1039-1077

The Magallanes‐Austral Basin of Patagonian Chile and Argentina is a retroforeland basin associated with Late Cretaceous–Neogene uplift of the southern Andes. The Upper Cretaceous Dorotea Formation records the final phase of deposition in the Late Cretaceous foredeep, marked by southward progradation of a shelf‐edge delta and slope. In the Ultima Esperanza district of Chile, laterally extensive, depositional dip‐oriented exposures of the Dorotea Formation contain upper slope, delta‐front and delta plain facies. Marginal and shallow marine deposits include abundant indicators of tidal activity including inclined heterolithic stratification, heterolithic to sandy tidal bundles, bidirectional palaeocurrent indicators, flaser/wavy/lenticular bedding, heterolithic tidal flat deposits and a relatively low‐diversity Skolithos ichnofacies assemblage in delta plain facies. This work documents the stratigraphic architecture and evolution of the shelf‐edge delta that was significantly influenced by strong tidal activity. Sediment was delivered to a large slump scar on the shelf‐edge by a basin‐axial fluvial system, where it was significantly reworked and redistributed by tides. A network of tidally modified mouth bars and tidal channels comprised the outermost reaches of the delta complex, which constituted the staging area and initiation point for gravity flows that dominated the slope and deeper basin. The extent of tidal influence on the Dorotea delta also has important implications for Magallanes‐Austral Basin palaeogeography. Prior studies establish axial foreland palaeodrainage, long‐term southward palaeotransport directions and large‐scale topographic confinement within the foredeep throughout Late Cretaceous time. Abundant tidal features in Dorotea Formation strata further suggest that the Magallanes‐Austral Basin was significantly embayed. This ‘Magallanes embayment’ was formed by an impinging fold–thrust belt to the west and a broad forebulge region to the east.  相似文献   

Changes in polar amplification in response to increasing warming in CMIP6          下载免费PDF全文

Shenlin Cai  Pang-Chi Hsu  Fei Liu 《大气和海洋科学快报》2021,14(3):54-59

由于全球变暖,极地地区的气候经历了明显的变暖放大.在本项研究中,我们根据CMIP6模式的三种变暖情景(SSP1-2,6,SSP2-4.5和SSP5-8.5)下,极地放大变化对各个反馈机制(包括普朗克,温度递减率,云,水蒸气,反照率反馈,CO2强迫,海洋热吸收和大气热传输)的响应进行了分析.结果表明,通过用“辐射核”方法量化不同反馈机制对地表温度的增温贡献,北极放大(AA)强于南极放大(ANA),由温度递减率反馈主导,其次是反照率和普朗克反馈.此外,海洋的热吸收导致冬季比夏季有更强的极地变暖.在冬季,温度递减率反馈主导了AA大于ANA.AA和ANA的模式间差异随着全球变暖的增强而减小.  相似文献   

Study of the soil–atmosphere moisture exchanges through convective drying tests in non‐isothermal conditions     

Pierre Gerard  Angélique Léonard  Jean‐Pierre Masekanya  Robert Charlier  Frédéric Collin 《国际地质力学数值与分析法杂志》2010,34(12):1297-1320

This paper deals with the moisture exchanges occurring between soils and the surrounding atmosphere. Convective drying tests are performed on Awans silts at different drying temperatures and air relative humidities in order to reproduce the natural drying conditions. The experiments improve the understanding of the vapour transfers kinetics between the soil samples and the atmosphere. The experimental results are analysed assuming that the transfers take place in a boundary layer existing at the surface of the porous medium. The influence of the thermal conditions on the evaporation is also taken into account. In our model, coupled vapour and energy exchanges are controlled by mass and heat transfer coefficients characterizing the boundary layer. These coefficients are determined from the drying experiments. The modelling of the drying tests in non‐isothermal conditions is performed in order to validate the formulation of the vapour and heat exchanges. The numerical results present a good agreement with the kinetic of the materials desaturation determined during the tests. The analysis of the moisture transport mechanisms into the sample and at the boundary shows that at the beginning of the test, the drying is first achieved by the transport of moisture in its liquid form and its evaporation at the sample outer boundary in contact with the atmosphere. In a second step, vapour diffusion becomes predominant into the sample and it corresponds to the most important decrease of relative humidity. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

交叉偏振滤波技术提高飞秒超强激光信噪比的研究     

刘成  王兆华  李伟昌  刘峰  魏志义 《海洋学报》2010,32(10):7036-7040

对交叉偏振波滤波技术理论分析的基础上,在"极光-III"装置中采用该技术进行了钛宝石飞秒放大激光脉冲对比度提高的实验研究,不仅显著的抑制了纳秒范围内再生放大器产生的预脉冲,而且也将皮秒范围内的信噪比由10^-5提高到了10^-7,实验测得基波到交叉偏振波的转化效率大于10%.研究表明,该技术可以有效地提高飞秒超强激光的信噪比.  相似文献