Holocene relative sea level history and Storegga tsunami run‐up in Lyngen,northern Norway          下载免费PDF全文

Henrik Rasmussen  Stein Bondevik  Geoffrey D. Corner 《第四纪科学杂志》2018,33(4):393-408

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STUDY FOR ABNORMAL VARIATIONS OF UNDERGROUND FLUID IN LIJIANG AREA,YUNNAN PROVINCE BEFORE LUDIAN M_S6.5 EARTHQUAKE IN 2014     

YANG Zhu-zhuan  DENG Zhi-hui  YANG Yue-wen  DENG Sheng-chang  LI Qing 《地震地质》2018,40(2):480-498

The study is based on the underground fluid observation data in Lijiang area, northwest Yunnan Province. The data include the water level and temperature in Dangxiao well and Jinjia well, and the ion measurements in Ganze spring. Combining with the data of regional hydrogeology, rainfall, well structures, and the geothermal gradient, we analyzed the variations of each measurement item before the Ludian M_S6.5 earthquake on August 3, 2014 and discussed the possible mechanism for the abnormal variations. The water levels of both Dangxiao well and Jinjia well are influenced by local rainfall, but the former shows hysteresis according to rainy seasons and is the long trend influence; while the latter shows synchronization between high water level and rainy season, indicating good connection between well water and shallow aquifer. The recharge water for Dangxiao well is in relatively low temperature, and the temperature sensor is located at the major connecting section between the well water and the aquifer; the water temperature variation is mainly affected by the discharge status and variation of water level. The Jinjia well is always in static level, and the temperature sensor is below the major connecting section between the well water and aquifer, so the water temperature is affected little by water level variations and in smooth fluctuation. The recharge source for Ganze spring can generally increase the contents of calcium and magnesium ions, so does the conductivity. The water level data of Dangxiao well since 2012 are decomposed with wavelet technique. The results, excluding such high-frequency components as the noise and the semidiurnal and daily wave components influenced by earth tide, are further processed with difference method in order to eliminate the trend effect. The results show that the relative change of water level is enhanced and in relatively rapid increase before the Ludian M_S6.5 earthquake; the corresponding water temperature values are high. The tendency of water level in Jinjia well displays descending, while the corresponding water temperature shows ascending. The content of calcium ion, magnesium ion, bicarbonate ion, and conductivity of Ganze spring are descending, while the content of fluoride ion is ascending. The abnormal variations of underground fluid in Lijiang area appeared in turns and were accompanied with minor earthquakes before Ludian M_S6.5 earthquake, which indicates enhancing of regional stress and increasing of fluid activity.  相似文献   

西部省会城市新型城镇化水平综合测度研究          下载免费PDF全文

邹亚锋  李亚静  袁志鸿 《干旱区地理》2020,43(6):1612-1621

新型城镇化是中国经济社会健康、稳定、可持续发展的根本途径，也是消除中国城乡社会经 济“二元结构”的根本出路。根据新型城镇化的内涵，从人口、经济发展、生活质量、基础设施、资源 环境、城乡统筹 6 个方面，构建了包含 24 项指标的新型城镇化水平综合测度指标体系，运用熵值 法，对西部 11 个省会城市 2005—2015 年的城镇化发展水平进行综合测度。研究表明：西部省会城 市的新型城镇化发展水平存在显著差异，总体上可分为“高等水平”、“中等水平”、“低等水平”3 个 级别，基础设施建设是造成差异的主要驱动力。各城市不同年间的城镇化单项水平影响因素呈现 多元化，在今后的发展中应有所侧重，同时兼顾城镇化质量，推动城乡协调发展。  相似文献   

2013年夏季南极南设得兰群岛周边海域透光层水团结构          下载免费PDF全文

周梦潇  朱国平 《极地研究》2020,32(1):90-101

南设得兰群岛位于德雷克海峡南侧, 南经布兰斯菲尔德海峡与南极半岛相望。该区域一直是南大洋海洋学研究的热点区域, 近些年已成为南极磷虾渔业的重要作业区。透光层作为海洋生物活动最为集中的区域, 也是海洋中生产力最为丰富的区域。了解透光层水团的特性及变化, 一方面可为南极半岛海洋学研究提供基础信息, 同时也可为南极磷虾等中上层海洋生物的分布及其致因提供科学支撑。通过分析2013年1月至3月南设得兰群岛周边海域5个断面的透光层温、盐数据, 本研究梳理了该区域的水团属性和分布。结果显示, 南设得兰群岛北侧较深水区水团垂向结构明显, 由上至下依次为南极夏季表层水、冬季水和绕极深层水。位于南设得兰群岛南侧的布兰斯菲尔德海峡内, 威德尔海过渡水特征几乎占据了整个布兰斯菲尔德海峡。但布兰斯菲尔德海峡西南侧水团结构较为复杂, 包括了威德尔海过渡水、别林斯高晋海过渡水和德雷克海峡水等。阐明南设得兰群岛周边复杂的水团结构对于进一步开展南大洋生物-物理相互作用研究具有重要的科学意义。  相似文献   

A note on the lake level variations of Nam Co,south-central Tibetan Plateau from 2005 to 2019     

ShiQiao Zhou 《寒旱区科学》2020,12(6):430-435

Tibetan lake levels are sensitive to global change, and their variations have a large impact on the environment, local agriculture and animal husbandry practices. While many remote sensing data of Tibetan lake level changes have been reported, few are from in-situ measurements. This note presents the first in-situ lake level time series of the central Tibetan Plateau. Since 2005, daily lake level observations have been performed at Lake Nam Co, one of the largest on the Tibetan Plateau. The interannual lake level variations show an overall increasing trend from 2006 to 2014, a rapid decrease from 2014 to 2017, and a surge from 2017 to 2018. The annual average lake level of the hydrological year (May-April) rose 66 cm from 2006 to 2014, dropped 59 cm from 2014 to 2017, and increased 20 cm from 2017 to 2018, resulting in a net rise of 27 cm or an average rate of about 2 cm per year. Compared to the annual average lake level based on the calendar year, it is better to use the annual average lake level based on the hydrological year to determine the interannual lake level changes. As the lake level was stable in May, it is appropriate to compare May lake levels when examining interannual lake level changes with fewer data. Overall, remote sensing results agree well with the in-situ lake level observations; however, some significant deviations exist. In the comparable 2006-2009 period, the calendar-year average lake level observed in-situ rose by 10-11 cm per year, which is lower than the ICESat result of 18 cm per year.  相似文献   

Mantle plumes,triple junctions and transforms:A reinterpretation of Pacific Cretaceous-Tertiary LIPs and the Laramide connection     

《地学前缘(英文版)》2020,11(4):1133-1144

The Shatsky and Hess Rises,the Mid-Pacific Mountains and the Line Islands large igneous provinces(LIPs) present different challenges to conventional plume models.Resolving the genesis of these LIPs is important not only for a more complete understanding of mantle plumes and plume-generated magmatism,but also for establishing the role of subducted LIP conjugates in the evolution of the Laramide orogeny and other circum-Pacific orogenic events,which are related to the development of large porphyry systems.Given past difficulties in developing consistent geodynamic models for these LIPs,it is useful to consider whether viable alternative geodynamic scenarios may be provided by recent concepts such as melt channel networks and channel-associated lineaments,along with the "two mode"model of melt generation,where a deeply-sourced channel network is superimposed on the plume,evolving and adapting over millions of years.A plume may also interact with transform faults in close proximity to a mid ocean ridge,with the resultant bathymetric character strongly affected by the relative age difference of lithosphere across the fault.Our results suggest that the new two-mode melt models resolve key persistent issues associated with the Shatsky Rise and other LIPs and provide evidence for the existence of a conduit system within plumes that feed deeply-sourced material to the plume head,with flow maintained over considerable distances.The conduit system eventually breaks down during plume-ridge separation and may do so prior to the plume head being freed from the triple junction or spreading ridge.There is evidence for not only plume head capture by a triple junction but also for substantial deformation of the plume stem as the distance between the stem and anchored plume head increases.The evidence suggests that young transforms can serve as pathways for plume material migration,at least in certain plume head-transform configurations.A fortuitous similarity between the path of the Shatsky and Sio plumes,with respect to young spreading ridges and transforms,helps to clarify previously problematic bathymetric features that were not readily ascribed to fixed plumes alone.The Line Island Chain,which has been the subject of a vast number of models,is related mainly to several plumes that passed beneath the same region of oceanic crust,a relatively rare event that has resulted in LIP formation rather than a regular seamount track.Our findings have important implications for the timing and mechanism for the Laramide Orogeny in North America,demonstrating that the Hess Rise conjugate may be much smaller than traditionally thought.The Mid Pacific Mountains conjugate may not exist at all,given large parts of these LIPs were formed at an ‘off-ridge' site.This needs to be taken into account while considering the effects of conjugate collision on mineralization and orogenic events.  相似文献   

基于多变量LSTM神经网络的地下水水位预测     

闫佰忠  孙剑  王昕洲  韩娜  刘博 《吉林大学学报(地球科学版)》2020,50(1):208-216

为解决以往模型未考虑地下水位相关影响因素的问题，探讨长短期记忆（LSTM）神经网络在地下水位预测中的应用，利用长短期记忆神经网络，采用多变量输入的方式，构建了基于多变量LSTM神经网络的地下水水位预测模型。以泰安市岱岳区J1号监测井为例，采用2001-2014年地下水水位动态监测资料与相关影响因素数据，利用多变量LSTM神经网络对2015-2016年地下水位进行预测，并与单变量LSTM神经网络和反向传播（BP）神经网络进行对比。研究结果表明：以相关影响变量为输入的BP神经网络无法考虑时序变化规律，预测均方根误差最大，为2.399 3；以地下水位为变量输入的单变量LSTM神经网络仅能根据时序变化作出相应预测，无法考虑相关变量影响，预测均方根误差为2.102 2；基于多变量输入的LSTM神经网络的预测精度显著高于单变量LSTM神经网络和BP神经网络，预测均方根误差最小，仅为1.919 1。总体上，多变量LSTM神经网络地下水位预测模型仅在某些峰值处误差较大，但总体预测效果较为理想。  相似文献   

强人类活动驱动下珠江磨刀门河口径潮动力的季节性异变特征     

张先毅  杨昊  黄竞争  傅林曦  王恒  刘俊勇  欧素英  刘锋  蔡华阳  杨清书 《海洋与湖沼》2020,51(5):1043-1054

人类活动对河口环境影响巨大,揭示在强人类活动驱动下河口径潮动力非线性相互作用的异变特征,有利于了解人类活动影响河口动力地貌的机制,对河口区水利工程建设及环境保护等具有重要指导意义。基于1960—2016年珠江磨刀门河口沿程潮位站(甘竹、竹银、灯笼山、三灶)的逐月高、低潮位数据及马口水文站的月均流量数据,统计分析了磨刀门河口在强人类活动驱动下月均水位、潮波振幅及其空间梯度(即月均水位坡度和潮波振幅衰减率)的季节性异变特征。结果表明,1990年和2000年为磨刀门河口径潮动力的异变年份, 1990年前为自然演变阶段, 2000年后为恢复调整阶段,1990—2000年为过渡阶段;高强度采砂导致的河床下切使磨刀门河口月均水位及月均水位坡度显著减小,夏季减小幅度最为明显,沿程平均分别减小0.53m和8.93×10~(-6);月均水位坡度减小导致潮波衰减效应减弱,进而使沿程潮波振幅增大,多年平均增大0.071m;磨刀门河口径潮动力相互作用具有明显的季节性差异,夏季月均水位坡度随流量增大在上游抬升明显,冬季月均水位坡度在上游显著减小,但在下游略有抬升;随着流量的增大潮波振幅的衰减作用增强,但当流量超过阈值20000m~3/s时,月均水位坡度引起的底床摩擦增大效应不足以抵消横截面积辐散效应,潮波衰减效应略有减弱。  相似文献   

气候变化对东北大西洋渔获物组成、多样性和营养级的影响     

陈爽  陈新军 《海洋学报》2020,42(10):100-109

东北大西洋是世界上重要的捕捞海域，气候变化对该海域捕捞产生了重要的影响。本文基于联合国粮农组织所提供的1982?2016年东北大西洋渔获产量数据，对该海域渔获物组成、多样性、平均营养级及主成分变化特征进行时间序列上的分析，并结合东北大西洋海域气候、环境因子，应用广义可加模型探究渔获物组成与气候变化之间的关系。结果显示:渔获物多样性的变化总体上呈下降趋势，2002?2010年间处于较低水平；平均营养级在2002年之前呈平缓下降的趋势，2002年之后开始波动上升，相关性分析表明这两个指标与海域环境因子的变化较为相关。对渔获物组成进行主成分分析显示，第一主成份变化的方差解释率达到35.3%，且与海域气候、环境因素有较高的相关性，第一主成分变化能够较好地表征气候影响下渔获物组成变化的情况。广义可加模型分析结果显示，渔获物组成变化的影响因素按解释率由高到低分别为:海表温度、海平面高度、盐度、海冰和北大西洋涛动指数。该研究有助于认识气候变化对海洋渔业资源及其结构组成的影响。  相似文献   

长江感潮河段潮波传播变化特征及影响因素分析     

黄竞争  张先毅  吴峥  刘锋  蔡华阳  杨清书 《海洋学报》2020,42(3):25-35

径潮相互作用是感潮河段水动力变化的典型特征，受其影响潮波传播具有明显的洪枯季及沿程变化。本文基于长江感潮河段天生港、江阴、镇江、南京、马鞍山及芜湖6个潮位站2002?2014年连续高低潮位资料及大通站月均流量数据，统计分析长江感潮河段潮波振幅衰减率、潮波传播速度及余水位坡度等传播特征值的洪枯季及沿程变化特征，并探讨这些潮波传播特征的变化规律及其主要影响因素。结果表明，潮波传播特征的洪枯季差异自上游至下游逐渐减小，其分界点位于天生港与江阴之间（其中，天生港和江阴站的多年平均洪枯季潮差差值约为0.01 m和?0.04 m）；径流动力对潮波衰减的影响主要位于江阴以上河段，江阴以下河段主要受潮汐动力控制；径流驱动下余水位坡度引起的余水位及水深增加，导致潮波传播的有效摩擦减小，当流量超过某个阈值时潮波振幅衰减反而减弱，特别是上游马鞍山-芜湖段最为明显，统计结果表明该河段流量阈值约为33 000 m3/s。本文分析结果作为前人研究的重要补充，可为长江河口感潮河段径潮相互作用机制研究及河口治理等提供基础参考。  相似文献