Triggered seismicity in the Andean arc region via static stress variation by the MW = 8.8, February 27, 2010, Maule earthquake     

《Journal of South American Earth Sciences》2015

We localized crustal earthquakes in the Andean arc, between 35°S and 36°S, from December 2009 to May 2010. This research shows a seismicity increase, in a narrow longitudinal area, of more than nine times after the great M_w 8.8 Maule earthquake.The localized seismicity defines an area of ∼80 km long and ∼18 km wide and NNW to NNE trend. The M_d magnitudes varied from 0.7 to 3.1 except for two earthquakes with M_w of 3.9 and 4.5, located in the northern end of the area. The focal mechanisms for these two last events were normal/strike-slip and strike-slip respectively.During 2011, a network of 13 temporary stations was installed in the trasarc region in Malargüe, Argentina. Sixty earthquakes were localized in the study region during an 8 month period.We explored how changes in Coulomb conditions associated with the mega-thrust earthquake triggered subsequent upper-plate events in the arc region. We assumed the major proposed structures as receiver faults and used previously published earthquake source parameters and slip distribution for the Maule quake. The largest contribution to static stress change, up to 5 bars, derives from unclamping resulting consistent with co-seismic dilatational deformation inferred from GPS observations in the region and subsidence in nearby volcanoes caused by magma migration.Three different Quaternary tectonic settings–extensional, strike-slip and compressional-have been proposed for the arc region at these latitudes. We found that the unclamping produced by the Maule quake could temporarily change the local regime to normal/strike-slip, or at least it would favor the activation of Quaternary NNE to N-trending dextral strike-slip faults with dextral transtensional movement.  相似文献   

作物胁迫无人机遥感监测研究评述   总被引：1，自引：0，他引：1  

黄耀欢  李中华  朱海涛 《地球信息科学学报》2019,21(4):512-523

作物胁迫是全球农业发展的一个重要制约因素,实现快速、大范围、实时的作物胁迫监测对于农业生产具有重要意义。传统的作物胁迫监测方式,如田间调查、理化检测和卫星遥感监测总是受到各种田间条件或大气条件的制约。随着无人机和各种轻量化传感器的快速发展,其凭借高频、迅捷等优势为各种作物胁迫监测提供了一套全新的解决方案。本文在介绍了目前主流的多种无人机和传感器的基础上,首先对目前无人机遥感用于作物监测的主要胁迫类型进行了梳理,然后重点阐述了基于光谱成像和热红外传感器进行作物胁迫无人机遥感监测的应用和技术方法,最后提出了作物胁迫无人机遥感监测尚需解决的关键问题,并展望了未来无人机遥感用于作物胁迫监测的前景。  相似文献   

季冻土区临水内、外拱护墙结构冻胀特征分析及治理     

孙洪伟  翟利杰  任望忠  傅汝进 《吉林大学学报(地球科学版)》2020,50(6):1833-1843

为厘清季冻土区临水内、外拱护墙结构冻胀平位移冻害机理，测试隔离层防冻害装置的有效性，在20101110-20110531、20131110-20140531、20171110-20180531三个观测年内，以长春某湖泊临水内、外拱护墙结构为研究对象，选择内、外拱护墙结构和设隔离层防冻害装置的试验内拱护墙结构三者相对比，用钢尺量距法观测三者寒期的平位移状态。结果表明：内拱护墙结构出现倾斜、裂缝导致的内向冻胀平位移冻害，其内向平位移曲线随气温均呈"半驼峰型"，对应观测年持续降温-持续低温-持续升温-正温时段，内向冻胀平位移呈减小-增大-减小-稳定残余的位移运动，诱因是平冻胀应力的生成-增长-减弱-消失作用；外拱护墙结构出现较小的外向冻胀平位移，外向冻胀平位移曲线均呈"波浪型"，无冻害发生，冰凸拱平冻胀应力推动外拱护墙结构压缩冻土凹拱形成外向冻胀平位移，冻土凹拱限制了外向冻胀平位移发展；设隔离层防冻害装置的试验内拱护墙结构未发生平位移冻害，其内向冻胀平位移较自然冻胀的内拱护墙结构减小83.92%，较外拱护墙结构减小51.74%，表明隔离层防冻害装置防治冻胀平位移冻害有效。  相似文献   

波致应力的近似求解及其太平洋特征分析     

王倩  宋金宝  曹海锦  乔文丽 《海洋与湖沼》2018,49(3):524-534

基于波致应力计算中对海浪谱和波浪增长率公式的敏感性分析,选择适当的波致应力近似求解方法,计算和探讨了太平洋波致应力的时空分布特征。敏感性分析中,选择了4种常用的波浪增长率公式和3种经验解析海浪谱。推导了计算波致应力的单波公式,并将其与JONSWAP谱积分公式和Elfouhaily谱积分公式进行比较,同时使用了由风速和有效波高资料构造的Elfouhaily谱积分公式计算太平洋波致应力。结果表明:Belcher等(1993)的波浪增长率计算公式估算的波致应力与实验数据吻合度较好,同时适用ERA-interim数据;当波龄小于1.2时运用Elfouhaily谱积分公式更合适,当波龄大于1.2时运用单波公式更快速有效;太平洋的波致应力分布与风场之间存在明显的相关性;2009年1月、4月、7月和10月太平洋波致应力的季节性特征分析表明四个季节的西风带波致应力较其他地区都更强盛,而在时间变化上1月和10月为波致应力整体较为强盛的时期。  相似文献   

呼图壁地区震源机制解及构造应力场特征分析   总被引：2，自引：0，他引：2  

李艳永  王成虎  杨佳佳 《大地测量与地球动力学》2018,38(12):1246-1250

基于新疆测震台网记录的数字地震波形，运用CAP方法测定呼图壁地区2010-01-15~2017-01-02共50次MS≥3.0地震的震源机制解，同时结合早期23次MS≥3.0地震的震源机制解数据，应用MSATSI软件反演研究区时空应力场。结果表明，研究区应力结构类型表现为逆断型，整个区域主压应力P轴近NNE向且倾角较小，说明整个呼图壁地区应力场以NNE向水平挤压作用为主要特征。从空间上看，东部的水平挤压作用更为显著；从时间上看，2010~2016年受到更为显著的NNE向应力场控制，反映了研究区在不同时段应力场的调整变化，但没有改变该区域最大主压应力轴呈NNE向的总体特征，说明整个呼图壁地区可能主要受一种较稳定的NNE向应力场控制。  相似文献   

多氯联苯(Aroclor 1242)胁迫下鲤鱼肝脏组织氧化应激   总被引：1，自引：0，他引：1  

王仁君  王建国  丁宁  孙萌  高配科 《海洋与湖沼》2018,49(6):1286-1293

本文在实验室条件下通过静态水质染毒方式在生理生化和转录水平上探究了我国重要经济鱼种鲤鱼(Cyprinus carpioio)对多氯联苯Aroclor 1242的氧化应激:鲤鱼肝脏组织抗氧化酶[超氧化物歧化酶(SuperoxideDismutase,SOD)和过氧化氢酶(Catalase,CAT)]活性、脂质过氧化产物丙二醛(Malonydialdehyde,MDA)含量、相关抗氧化酶编码基因(Cu/Zn-SOD、Mn-SOD、CAT)、应激蛋白HSP70、转录因子Nrf2和芳烃受体AhR2基因表达。结果表明:Aroclor 1242胁迫下,鲤鱼肝脏组织抗氧化酶活性表现出低浓度促进高浓度抑制的趋势;肝脏组织丙二醛含量显著升高,其中390μg/L暴露组鲤鱼肝脏组织MDA含量在第6d高于对照组92.1%(P0.01),表明肝脏组织发生脂质过氧化,膜系统受到损伤;鲤鱼肝脏组织中Cu/Zn-SOD、Mn-SOD、CAT、HSP70、Nrf2和AhR2编码基因表达出现不同程度下调。本文从酶学和基因转录水平上揭示了Aroclor1242胁迫下鲤鱼肝脏组织细胞的氧化应激。  相似文献   

黄土山区煤层群分层开采地表位移规律分析     

沈宇恒 《北京测绘》2020,(4):490-494

为了研究黄土山区地形对煤层群开采地表位移的影响,以榆林某矿为地质原型,利用数值软件模拟地表为近水平、正坡、负坡、凸面和凹面五种地形条件下煤层群开采。结果表明:黄土山区地形的变化,对煤层群开采顶板垂直应力影响不明显,对地表位移影响较大;单向坡开采,斜坡滑移引起的下沉量在坡顶与开采沉陷量形成“叠加”,在坡底形成“抵消”;在组合坡中,煤层群开采地表位移量相差很大,说明在变坡点附近地表位移较为复杂。  相似文献   

A smoothed cap model for variably saturated soils and its robust numerical implementation          下载免费PDF全文

P. Gamnitzer  G. Hofstetter 《国际地质力学数值与分析法杂志》2015,39(12):1276-1303

This paper deals with the numerical implementation of a cap model for unsaturated soils. It provides a brief review of existing cap model approaches, based on which an improved model formulated in terms of generalised effective stress and matric suction is derived and described in detail. Although the proposed model is a multisurface plasticity model, it can efficiently be implemented using only single‐surface projections because of the smoothness of the model, which is obtained by construction. Numerical algorithms are provided for these single‐surface stress projections, using a single‐equation approach whenever possible. The robustness of the utilised single‐equation approaches is enhanced by proposing problem‐fitted start‐up procedures based on investigations of the nonlinear projection equations. A comparison of the model response with extensive material test data is used to validate the model and to demonstrate the robust application of the approach to silty sands and low to medium plasticity clays. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Energy partitioning over a semi‐arid shrubland in northern China          下载免费PDF全文

X. Jia  T. S. Zha  J. N. Gong  B. Wu  Y. Q. Zhang  S. G. Qin  G. P. Chen  W. Feng  S. Kellomäki  H. Peltola 《水文研究》2016,30(6):972-985

During the last decade, the widely distributed shrublands in northern China have shown significant signs of recovery from desertification, the result of widespread conservation practices. However, to support the current efforts in conservation, more knowledge is needed on surface energy partitioning and its biophysical controls. Using eddy‐covariance measurements made over a semi‐arid shrubland in northwest China in 2012, we examined how surface energy‐balance components vary on diurnal and seasonal scales, and how biophysical factors control bulk surface parameters and energy exchange. Sensible heat flux (H) exceeded latent heat flux (λE) during most of the year, resulting in an annual Bowen ratio (β, i.e. H/λE) of 2.0. λE exceeded H only in mid‐summer when frequent rainfall co‐occurred with the seasonal peak in leaf area index (LAI). Evapotranspiration reached a daily maximum of 3.3 mm day^?1, and summed to 283 mm yr^?1. The evaporative fraction (EF, i.e. λE/R_n), Priestley–Taylor coefficient (α), surface conductance (g_s) and decoupling coefficient (Ω) were all positively correlated with soil water content (SWC) and LAI. The direct enhancement of λE by high vapour pressure deficit (VPD) was buffered by a concurrent suppression of g_s. The g_s played a direct role in controlling EF and α by mediating the effects of LAI, SWC and VPD. Our results highlight the importance of adaptive plant responses to water scarcity in regulating ecosystem energy partitioning, and suggest an important role for revegetation in the reversal of desertification in semi‐arid areas. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

基于简化力学模型的隧道锚极限承载力估值公式     

王东英  汤华  尹小涛  杨光华  姜燕 《岩土力学》2020,41(10):3405-3414

悬索桥隧道式锚碇的设计理念为锚碇夹持岩体协同承载，因而承载能力远超同体积的重力式锚碇。但因目前对围岩协同作用认识尚不充分，在当前隧道式锚碇设计中仍保守地忽略锚碇和岩体间的挤压效应。为弄清锚碇?岩体协同承载的机制，揭示隧道锚承载能力提高的本质，通过分析隧道式锚碇建设至成桥全过程受力，建立隧道锚的简化力学模型，并引用Mindlin应力解分析了荷载沿锚碇轴向的传递规律以及荷载产生的作用于锚碇?岩体间的挤压应力分布，最终给出了隧道式锚碇极限承载力的简化估算方法，并通过伍家岗大桥隧道锚工程实例分析了结果的合理性。所得结论主要有：锚碇?岩体界面力主要由锚碇自重和锚碇?岩体相互挤压产生；锚碇?岩体界面附加应力自后锚面向前锚面呈先增后减的变化趋势，在距后锚面约1/3L处达到应力峰值；以容许抗剪强度为破坏判据解得的伍家岗长江大桥隧道式锚碇的极限承载力为3 504 MN，约为16倍的设计荷载，与室内试验值基本吻合。  相似文献