Subsidence in the Kathmandu Basin,before and after the 2015 Mw 7.8 Gorkha Earthquake,Nepal Revealed from Small Baseline Subset-DInSAR Analysis     

Suresh Krishnan P.V.  Jungkyo Jung 《地理信息系统科学与遥感》2018,55(4):604-621

Land subsidence in densely urbanized areas is a global problem that is primarily caused by excessive groundwater withdrawal. The Kathmandu Basin is one such area where subsidence due to groundwater depletion has been a major problem in recent years. Moreover, on 25 April 2015, this basin experienced large crustal movements caused by the Gorkha earthquake (Mw 7.8). Consequently, the effects of earthquake-induced deformation could affect the temporal and spatial nature of anthropogenic subsidence in the basin. However, this effect has not yet been fully studied. In this paper, we applied the SBAS-DInSAR technique to estimate the spatiotemporal displacement of land subsidence in the Kathmandu Basin before and after the Gorkha earthquake, using 16 ALOS-1 Phased Array L-band Synthetic Aperture Radar (PALSAR) images during the pre-seismic period and 26 Sentinel-1 A/B SAR images during the pre- and post-seismic periods. The results showed that the mean subsidence rate in the central part of the basin was about ?8.2 cm/year before the earthquake. The spatial extents of the subsiding areas were well-correlated with the spatial distributions of the compressible clay layers in the basin. We infer from time-series InSAR analysis that subsidence in the Kathmandu basin could be associated with fluvio-lacustrine (clay) deposits and local hydrogeological conditions. However, after the mainshock, the subsidence rate significantly increased to ?15 and ?12 cm/year during early post-seismic (108 days) and post-seismic (2015–2016) period, respectively. Based on a spatial analysis of the subsidence rate map, the entire basin uplifted during the co-seismic period has started to subside and become stable during the early-post-seismic period. This is because of the elastic rebound of co-seismic deformation. However, interestingly, the localized areas show increased subsidence rates during both the early-post- and post-seismic periods. Therefore, we believe that the large co-seismic deformation experienced in this basin might induce the local subsidence to increase in rate, caused by oscillations of the water table level in the clay layer.  相似文献   

1980—2000年北极平流层冬季十年际变化形势的逐月演变          下载免费PDF全文

吴国华  刘仁强  黎颖 《大气科学学报》2021,44(4):585-591

采用1980—2000年的ERA-Interim再分析资料,计算北半球冬季各月(12月、1月、2月)行星波的Eliassen-Palm(EP)通量及其散度,并按冬季不同月份分析平流层整层温度和纬向风场的十年际变化特征与行星波活动变化的关系。结果表明,温度的十年际变化在高纬度中下平流层12月呈明显增温趋势,1月转为较弱的冷却趋势,2月为明显的冷却趋势。纬向风在中高纬平流层12月呈明显的减速变化,1月减速区与加速区相间分布但强度均较弱,而2月为明显的加速趋势。12月行星波沿低纬度波导向热带对流层顶的传播减弱,沿极地波导向平流层整层的传播明显加强;1月沿两支波导的传播趋势未变但均较弱;而2月行星波沿低纬度波导的传播转为加强趋势,沿极地波导的传播转为减弱趋势。相应地,EP通量散度场的十年际变化形势沿两支波导在12月与2月相反,1月为过渡阶段。因此,北极平流层温度、纬向风、EP通量及其散度场的十年际变化在冬季内呈现一个从北半球环状模(Northern Hemisphere Annular Mode, NAM)的负极趋势向正极趋势逐月演变的过程。  相似文献   

祁连山大通河河流阶地形成时代及地质意义          下载免费PDF全文

于航  步凡  胡道功  张绪教  杨金中 《中国地质调查》2018,5(3):43-48

祁连山是研究青藏高原隆升与构造变形的关键部位,其中大通河河流阶地是祁连山地区早更新世以来构造隆升和气候变化的载体,厘定大通河河流阶地的形成时代及地质意义对于分析祁连山地区的区域构造和气候环境改变具有重要意义。通过ESR测年技术,并对大通河流域江仓区域的剖面样品实测,获取岩层形成时代数据,分别为(42±4) ka B.P.、(71±5) ka B.P.、(121±12) ka B.P.、(210±20) ka B.P.和(602±60) ka B.P.。根据测年结果,确认剖面为河流相沉积环境,形成时代对应中晚更新世酒泉砾岩和戈壁砾岩时期,表明大通河河流阶地在542~662 ka B.P.之前就已经形成,推测其可能是受到中新世白杨河组之后的盆山运动或早更新世祁连山的褶皱变形影响而形成的。利用测年数据计算抬升速率,从中更新世晚期到晚更新世中期,抬升速率加快,反映了大通河流域的构造运动和气候变化加强,祁连山江仓地区在此期间快速隆升,为青藏高原东北缘以面积和体积扩张的观点提供了新的依据。  相似文献   

青藏高原新生代岩浆活动与地热关系探讨          下载免费PDF全文

张朝锋  史强林  张玲娟 《中国地质调查》2018,5(2):18-24

青藏高原地热资源丰富,具有分布广、温度高、潜力大等特点。为了更好地评价该区地热资源潜力,探索符合青藏高原地热资源特点的勘查、开发方案,需要对地热资源分布规律及成因进行研究。在总结前人对青藏高原新生代岩浆活动和地热资源特征的基础上,从青藏高原地质演化的角度分析地热资源分布的控制因素,探讨新生代岩浆活动与地热资源的空间展布关系,重点讨论藏南地区地热区划和雅鲁藏布缝合带岩浆活动之间的关系。结果表明: 青藏高原地热活动受控于地质构造演化,具有南强北弱的分布特点; EW向区域性构造缝合带和SN向深大断裂的交汇部位是地热的主要活跃区域,不同的岩浆活动为地热提供热源。  相似文献   

铺前—清澜断裂西支晚更新世活动特征     

刘风香  苗雨雁  荆振杰  杜海娥 《世界地质》2018,37(1):148-153

海域浅层地震探测调查表明,铺前—清澜断裂向北西海域方向延伸,断裂走向NW-SE,倾向SW,为高倾角的正断层;在地震剖面上,断裂断错了第四系地层;进一步应用钻探技术对铺前—清澜断裂进行探测研究,结合层序地层学、岩性岩相分析与年代测定等方法建立了钻孔联合剖面,揭示断层性质为正断层,倾向SW,断距4.0 m,断层的最新活动时代为晚更新世,第四纪表现为张性活动,断裂的平均垂直速率为0.15 mm/a。  相似文献   

岸滩侧蚀崩塌速率的试验量测方法          下载免费PDF全文

假冬冬  陈诚  牛晨曦  张幸农 《水科学进展》2018,29(4):537-542

岸滩侧蚀崩塌现象普遍存在于冲积河流演变过程中,是河道治理需重点关注的问题之一,岸滩侧蚀崩塌速率的准确量测则是崩岸机理及其治理措施研究的关键基础。基于图像处理技术,建立了河岸侧蚀崩塌速率试验量测系统,通过图像追踪河岸模型上边缘示踪网格位置变迁,提出了一种河岸侧蚀崩塌速率测量方法。以试验水槽为例,对河岸侧蚀崩塌速率进行了量测,并与经验公式计算值进行了比对,两者基本吻合,可较好地反映流速、土体级配等岸滩侧蚀崩塌速率的影响因素及其变化规律。研究成果可为江河崩岸机理的深入研究提供技术支撑。  相似文献   

Late Quaternary Slip Rate of the Xiugou Segment,Eastern Kunlun Fault Zone   总被引：1，自引：0，他引：1  

Feipeng Huang  Junjie Ren  Yanwu Lü  Junxiang Zhao 《地球科学进展》2018,33(3):321-332

The Eastern Kunlun fault zone (EKLF) is a large left-lateral strike-slip fault, whose slip rate is meaningful to seismic hazard assessment and geodynamics of the Tibetan Plateau. Previous studies suggested that the late Quaternary average slip rate was stable and uniform (10~13 mm/a) in the central and western segment of the EKLF. But there were a few researches of accurate slip rate in the central segment on the EKLF. Therefore, we focused on an offset and well preserved alluvial fan from Xiugou basin, located in the east of Xidatan-Dongdatan, to make it clear. Moreover, we used high-resolution satellite images and digital elevation model extracted from SPOT7 stereo image pairs to restore the offset alluvial fan, and combined terrestrial cosmogenic nuclides method, including 13 quartz-rich samples from this fan surface, 1 quartz-rich sample from the main active channel bed and 1 ¹⁰Be depth profile from this fan edge to eliminate the ¹⁰Be concentration of inheritance accurately, with 1 optically stimulated luminescence sample to obtain the reliable age of this alluvial fan together. Referring to field observations, this alluvial fan was offset left-laterally by (1 862±103) m, and its age is (76.55±3.20)~(106.37±3.38) ka which can be determined through the actual geologic setting and improving chi-square test. Thus, we used the Monte Carlo method to obtain a left-lateral slip rate of (20.3+3.5/-2.3) mm/a with 68% confidence envelopes since the late Pleistocene in the Xiugou basin. As a result, combining with the results of previous studies, the left-lateral slip rate indicated that the obviously decreasing activity transferred from late Pleistocene to Holocene on the central segment of the EKLF.  相似文献   

斥水性土壤水分入渗试验和模型          下载免费PDF全文

任长江  赵勇  王建华  龚家国  田济扬 《水科学进展》2018,29(6):839-847

为研究斥水性土壤水分入渗规律,并探寻适用于斥水性土壤水分入渗的数学模型,以妫水河流域亲水性和斥水性土壤为研究对象,开展室内一维垂直土柱入渗试验;分别采用Kostiakov分段函数、Fourier级数、一阶Gaussian函数以及Gaussian分段函数对斥水性土壤入渗率进行拟合。试验结果表明:亲水性土壤入渗率随时间呈单调减小变化趋势,斥水性土壤入渗一段时间后累积入渗量会出现翘尾现象,入渗率为先增大后减小的单峰曲线。模型图形分析表明: Kostiakov分段函数入渗率在拐点处同时存在一个极大值和极小值,Fourier级数存在多个波峰,一阶Gaussian函数不能反映入渗率在拐点后大于拐点前的试验现象,因而均难以真实反映斥水性水分入渗过程。忽略水分开始快速入渗过程,Gaussian分段函数模型不仅能够反映入渗率在拐点前的单调增以及拐点后的单调减过程,同时也能够体现入渗率在拐点后大于拐点前的试验现象。  相似文献   

基于MODIS数据的青藏高原冰川反照率时空分布及变化研究   总被引：1，自引：1，他引：0  

徐田利  邬光剑  张学磊  燕妮  杨松 《冰川冻土》2018,40(5):875-883

冰川反照率对冰川融化具有重要影响,以2000-2013年MODIS的MOD10A1逐日积雪反照率数据资料为基础,分析了青藏高原冰川反照率的时空分布及变化。结果表明：冰川年平均反照率变化范围是0.42（枪勇冰川）~0.75（PT5冰川）,其中夏季平均反照率变化范围是0.45（来古冰川）~0.69（东绒布冰川和古里雅冰川）。冰川反照率空间分布并没有明显的规律性,而冰川反照率的变化速率空间分布规律明显——南部较大往北减小,北部反照率出现增大现象。研究区内大部分冰川反照率呈波动降低的趋势,年平均反照率和夏季平均反照率变化速率最大值都出现在枪勇冰川,分别是-0.015 a^-1和-0.019 a^-1。木吉和木孜塔格冰川年平均和夏季平均冰川反照率都增大,木吉冰川是由于2012年的高反照率引起的,而木孜塔格冰川主要与该地区气温降低、降水增多有关。  相似文献   

碘化氨除锡后封闭酸溶-电感耦合等离子体质谱测定锡矿石中的共生和伴生元素   总被引：1，自引：1，他引：0  

马生凤  赵文博  朱云  孙红宾  王蕾  温宏利 《岩矿测试》2018,37(6):650-656

锡矿石是难分解的矿物,主要存在形式是锡石(SnO_2),且共生和伴生元素多,常用的酸溶方法几乎不能溶解SnO_2,从而给锡矿石中的共生与伴生元素的准确测定带来困难。本文基于碘化氨在较低温度下熔融可产生无水状态的碘化氢,利用碘化氢的酸性和氨的还原性分解SnO_2,使Sn呈SnI_4升华分离的原理处理锡矿石。实验中以高纯铂丝作催化剂,加入碘化铵在450℃的马弗炉中分解锡矿石30 min,使得Sn以SnI_4形式挥发,除锡率达到98%以上,再用2 mL氢氟酸和1 mL硝酸封闭溶解残渣,电感耦合等离子体质谱测定钴镍铜铌钽钍铀等24个共生和伴生元素。元素检出限在0. 001～2. 9μg/g之间,90%以上元素的相对标准偏差(RSD)小于5%,相对误差小于10%。本方法解决了锡矿石难分解的问题,可测定共存金属元素,也适合测定Sn含量在1. 27%～62. 49%之间的锡矿石中的微量和痕量元素及锡精矿中的微量元素。  相似文献