Imaging the rupture process of the 10 January 2018 MW7.5 Swan island,Honduras earthquake*          下载免费PDF全文

Chuang Cheng  Dun Wang 《地震科学（英文版）》2020,33(4):194-200

The 10 January 2018 M_W7.5 Swan island, Honduras earthquake occurred on the Swan island fault, which is a transform plate boundary between the North American and Caribbean plates. Here we back-project the rupture process of the earthquake using dense seismic stations in Alaska, and find that the earthquake ruptured at least three faults (three stages) for a duration of ~40 s. The rupture speed for the longest fault (stage 3) is as fast as 5 km/s, which is much faster than the local shear wave velocity of ~4 km/s. Supershear rupture was incidentally observed on long and straight strike-slip faults. This study shows a supershear rupture that occured on a strike-slip fault with moderate length, implying that supershear rupture might commonly occur on large strike-slip earthquakes. The common occurrence of supershear rupture on strike-slip earthquakes will challenge present understanding of crack physics, as well as strong ground motion evaluation in earthquake engineering.  相似文献   

基于正交匹配追踪的声层析方法   总被引：2，自引：0，他引：2  

李倩倩  史娟  李整林  罗宇  阳凡林  张凯 《海洋学报(英文版)》2019,38(11):149-157

声速剖面的变化会对声传播产生较大的影响，经验正交函数模型经常用来实现对声速剖面数据的简化描述。然而在内波、湍流等海水不均匀性存在时，这种正则化操作会造成声速重构精度的大幅降低。本文利用字典学习生成声速剖面的非正交原子，在稀疏编码时采用正交匹配追踪（OMP，Orthogonal Matching Pursuit）算法，更新字典则使用KSVD （Kernel Singular Value Decomposition）的字典更新算法。由于字典学习不需要强制使用正交条件，对于训练数据更加灵活，从而可以使用少数的原子组合达到更高的重构精度。利用一次浅海声学实验多次测量的声速剖面研究了海水声速剖面的经验正交函数表示和字典学习，研究表明：相比于正交函数表示，学习字典可以利用少数原子（甚至一个原子）更好的解释声速剖面扰动。字典学习可以提高声速剖面的稀疏性，从而提高声速剖面的反演精度。  相似文献   

高速铁路无砟轨道地基泥岩膨胀性分类分级研究     

薛彦瑾  王起才  马丽娜  张戎令  代金鹏  王强 《岩土力学》2020,41(9):3109-3118

红层泥岩是一种典型侏罗系沉积岩，其含有微量黏土矿物，易遇水软化、失水崩解，具有一定膨胀性，是引起兰新高速铁路路基持续上拱变形的一个重要因素，故重新判定该种土体膨胀性对高速铁路无砟轨道设计和施工具有重要意义。为此，选取等效蒙脱石含量、阳离子交换量、自由膨胀率和液限为泥岩膨胀性判别指标，通过兰新高速铁路上拱地段大量钻孔实测资料，提出了泥岩膨胀等级分级标准，采用改进层次分析法、基尼系数法和直觉模糊理论确定了判别指标组合权重，基于逼近理想解排序法(TOPSIS法)建立了泥岩膨胀性直觉模糊综合评价模型。结果表明：直觉模糊综合评价模型将泥岩膨胀性进行了定量化，克服了同一试样不同指标属于不同等级判别缺陷；室内膨胀量试验验证了膨胀等级分级标准和直觉模糊综合评价模型对兰新高铁地基泥岩适用性和准确性。研究成果对地基红层泥岩高速铁路路基长期持续上拱变形风险评估和工程控制措施提供技术支撑。  相似文献   

筒型桩靴在饱和砂土中的贯入阻力研究          下载免费PDF全文

吴曲楠  刘润  张海洋  王宇飞 《地震工程学报》2018,40(6):1183-1190

桩靴贯入阻力的准确预测是自升式钻井平台安全作业的前提。通过小比尺模型试验,研究饱和砂土中桩靴贯入速度对筒型桩靴插桩性能的影响,并基于地基承载力理论提出筒型桩靴贯入阻力的计算方法,进而采用CEL有限元方法模拟筒型桩靴的贯入过程,并与试验结果进行比较。研究发现:当模型试验中桩靴贯入速度在0.1～0.3mm/s时,桩靴的贯入可看作是准静态过程,此时贯入阻力变化不大,采用基于地基承载力理论中的Hansen公式和Vesic公式可较为准确地计算出对应某一深度的贯入阻力;CEL有限元方法可有效模拟筒型桩靴的贯入过程,当桩靴的贯入速度为0.1～0.3mm/s时,数值模拟结果与试验结果吻合较好。  相似文献   

Energy saving performance analysis of contra-rotating azimuth propulsor     

《Applied Ocean Research》2018

The energy saving performance of contra-rotating azimuth propulsor (CRAP) is investigated based on low order potential-based panel method. The hydrodynamic interactions among the forward propeller (FP), rear propeller (RP) and the pod unit (PU) which includes the pod body and the strut are considered through induced velocities which are obtained by panel method. In order to have a better understanding about the energy saving performance of CRAP, the hydrodynamic performance of a conventional propeller (CP) supplying the same thrust with CRAP at design condition is also calculated. At design condition, CRAP has a decrease in delivered power by approximately 8% comparing with CP, and the tangential induced velocities in slipstream show that CRAP recovers the rotational energy of slipstream effectively. At off-design conditions, the rotational speed of CRAP is adjusted to supply the same thrust with CP. In general, the delivered power of CRAP is significantly smaller than that of CP, and the energy saving performance of CRAP increases with the decrease of inflow velocity.  相似文献   

基于MISR多角度光学遥感影像的海面风速估算实验          下载免费PDF全文

王艺霖  王晓林  张华国 《海洋学研究》2018,36(2):19-26

太阳耀光是来自粗糙海面的直接太阳反射光,其强度与海面粗糙度密切相关,而海面粗糙度主要受海面风场影响。因此,包含太阳耀光信息的光学遥感影像在海洋动力过程和海面风速探测中具有积极意义。本文利用2016年2月到2017年3月期间成像的25幅Terra卫星MISR(Multi-angle Imaging Spectro Radiometer)传感器的多角度遥感影像,分别提取了太阳的高度角和方位角、正视和后视影像的卫星观测角、方位角等信息,校正获得正视和后视影像的太阳耀光辐射强度,进一步反演海表面粗糙度信息,进而计算海面风速。最后利用ECMWF(European Centre for Medium-Range Weather Forecasts)的模式风速数据与反演获得的风速结果进行对比验证。结果表明,两者的相关系数较高(R=0.745),均方根误差和平均绝对偏差值分别为1.514 m·s^-1和1.319 m·s^-1。初步实验结果表明,利用MISR多角度光学遥感影像估算海表面风速是可行性的。  相似文献   

敦煌-格尔木铁路沿线风动力环境特征     

鱼燕萍  张克存  安志山  张余 《中国沙漠》2020,40(1):41-48

敦煌-格尔木铁路沿线地形复杂、起沙因素多变、沙源丰富，沙害问题日益严重。目前对其风沙活动规律还未有研究，不利于防沙工作的开展。为此，通过对自北向南的5个观测点（S1、S2、S3、S4、S5）风速和风向的观测、计算和分析，利用平均风速、起沙风况及输沙势对敦格铁路沿线的风动力环境特征进行研究。结果表明：S5、S4和S3的风况对铁路风沙灾害防治意义较大。S5年平均风速、起沙风频率和输沙势最大，春季风沙活动最为强烈，且风向单一、风力强劲，风沙运动方向基本与铁路垂直，沙粒易在铁路附近堆积。S4夏季风沙活动最为强烈；S3春季风沙活动最为强烈，且风向单一，S4和S3的风沙运动方向与铁路夹角小于90°，附近沙源广阔，铁路易受风沙侵蚀，阻碍交通运营。  相似文献   

Monte-Carlo模拟与经验路径模型预测台风极值风速的对比   总被引：2，自引：2，他引：0  

郭云霞  侯一筠  齐鹏 《海洋学报》2020,42(7):64-77

台风是我国东南沿海区域每年发生的严重自然灾害之一。本文分别采用传统的Monte-Carlo模拟方法以及较为先进的经验路径模拟方法预测中国东南沿海区域台风的极值风速(10 m高度处10 min平均值)，并对两种方法的预测结果进行了对比。本文将东南海岸线向内陆扩展约200 km的区域划分为0.25°×0.25°的网格，以每个网格点作为研究点。首先采用Monte-Carlo模拟方法产生每个研究点1 000年间的虚拟台风事件。然后采用经验路径模型方法构建了西北太平洋1 000年的热带气旋事件集，采用模拟圆方法从中提取对各个研究站点有影响的台风事件。接着采用Yan Meng风场模型计算每个研究点台风的最大风速，构成极值风速序列。最后采用极值分布模型预测每个研究点不同重现期的极值风速，并对两种不同方法预测的结果进行了对比。研究发现在研究区域的内陆侧经验路径方法预测的风速略高于Monte-Carlo模拟方法预测的结果，而在海岸沿线一带经验路径方法预测的结果略低，这主要是由两种方法构造的虚拟台风的中心压强存在差异以及模型本身的不确定性造成的。本文的研究结果可以为防灾减灾系统提供有益的参考。  相似文献   

近20年渤海叶绿素a浓度时空变化   总被引：3，自引：0，他引：3  

田洪阵  刘沁萍  Joaquim I. Goes  Helga do Rosario Gomes  杨萌萌 《海洋学报》2019,41(8):131-140

浮游植物作为食物链的基础，对海洋生态系统具有重要作用。渤海作为我国最大的内海和重要渔业生物的产卵场、育幼场和索饵场，该区浮游植物研究具有重要意义。叶绿素a浓度是反映浮游植物生物量的重要指标。利用Google Earth Engine平台，对1997–2010年的宽视场海洋观测传感器(SeaWiFS)叶绿素a浓度数据和2002–2018年的水色卫星中分辨率成像光谱仪传感器(MODIS Aqua)叶绿素a浓度数据进行合并，并研究其时空变化特征。研究表明，近20年来，渤海全年叶绿素a浓度增加了14.1%，且增加显著。叶绿素a浓度在所有季节都呈现增加趋势；除11月外，其他各月都呈现稳定或增加趋势。从滦河入河口沿岸至渤海海峡的渤海中部，叶绿素a浓度增加较明显。同时也分析了海洋表面温度、风速和降水量数据。夏季渤海周边区域降水量和风速增加以及秋季海表温度的降低都有助于同季叶绿素a浓度的升高。渤海浮游植物可能受陆源营养物质输入影响较大。  相似文献   

Relative quantification of wind erosion in argan woodlands in the Souss Basin,Morocco     

Miriam Marzen  Mario Kirchhoff  Irene Marzolff  Ali Aït Hssaine  Johannes B. Ries 《地球表面变化过程与地形》2020,45(15):3808-3823

The endemic argan woodlands cover large parts of South Morocco and create a characteristic landscape with areas of sparsely vegetated and bare soil surfaces between single trees. This unique ecosystem has been under extensive agrosilvopastoral management for centuries and is now at risk of degradation caused by overgrazing and increasing scarcity and variability of rainfall. To investigate susceptibility to wind erosion, we conducted an experimental–empirical study including wind tunnel tests and a drone-generated digital elevation model and quantified wind-erodible material on five different associated surface types by means of sediment catchers. The highest emission flux was measured on freshly ploughed surfaces (1875 g m^–2 h^–1), while older ploughed areas with a re-established crust produced a much lower emission flux (795 g m^–2 h^–1). Extensive tillage may have been a sustainable practice for generations, but increasing drought and uncertainty of rainfall now lead to an acute risk of severe soil erosion and dust production. The typical crusted surfaces characterized by residual rock fragment accumulation and wash processes produced the second highest emission flux (1,354 g m^–2 h^–1). Material collected from tree-shaded areas (933 g m^–2 h^–1) was revealed to be a considerable source of organic material, possibly affecting substrate conditions positively on a larger regional scale. The lowest flux was measured on rock fragment-covered surfaces (301 g m^–2 h^–1). The data show that open argan woodland may be a considerable source for wind erosion and dust production, depending on surface characteristics strongly related to management. An adapted management must include the conservation of argan trees to offer a promising approach to prevent severe wind erosion and dust production and mitigate possible impacts of land-use change and climate change related shifts in wind and rainfall patterns. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献