弹性波入射时半圆弧凹陷地形对地表位移影响研究          下载免费PDF全文

马荣  李永强  景立平  单振东  刘廷峻  汪刚 《地震工程学报》2019,41(2):392-398

基于数值模拟方法系统研究脉冲与正弦SH波及P波垂直入射半圆弧凹陷场地时的地表位移响应,并与相应解析解进行了对比分析。P波入射时,半圆弧凹陷场地由于P波与反射SV波的干涉产生Rayleigh波,会对场地自由表面的稳态位移响应幅值产生较大影响。凹陷内部的归一化Z向位移幅值相比没有考虑Rayleigh波生成时有较大的不同,其在凹陷边缘处没有什么变化,而在凹陷向两侧延伸的方向,会有压缩作用;归一化X向位移幅值在凹陷内部无太大变化,在凹陷向两侧延伸的方向,会有波动状的归一化X向位移幅值。  相似文献   

冲绳海槽西南部新发现"通道-天然堤"系统的成因   总被引：3，自引：0，他引：3  

李军 《海洋地质前沿》2004,20(2):5-7

Sibuet等(1998)首次发现了冲绳海槽西南部发育有两条大型的海底“通道一天然堤”沉积系统。这一大型海底冲积扇典型组成单元的发现为冲绳海槽南部以海底峡谷为主要渠道的陆源物质输运作用和浊流沉积作用提供了直接证据。结合地球物理调查资料,同时对比其他典型区域的特征,对其成因和形成时代进行了初步探讨。  相似文献   

南极中山站附近海域水深地形特征   总被引：5，自引：1，他引：4       下载免费PDF全文

冯守珍 《极地研究》2004,16(1):75-80

南极普里兹湾是我国南极中山站建站的重要依托海域 ,是科考船前往中山站进出的必由之路。本文根据普里兹湾近岸的中山站附近海域概略水深 ,研究分析了地形基本概况 ,崎岖不平的中山站近海湾部水下地形 ,沿其湾顶部轴线SN向形成了一条绵延弯曲的水深达 80 0m以浅的海底峡谷 ,通往冰盖底部。峡谷两侧地形复杂 ,水下丘岭嶙峋。从冰盖沿峡谷崩裂下来的冰山 ,最终依其适宜的水深 ,绕过地形障碍 ,沿海底峡谷西侧随风和流往西离去。除中山锚地抛锚区域属于浅水低洼的平缓台地外 ,湾内其它水域可供科考船抛锚的优越水下地形极少  相似文献   

Migration of the lower North Palawan submarine canyon: characteristics and controls     

Shaoru Yin  Weiwei Ding  Weifeng Ding  Yuanyuan Wang 《International Geology Review》2020,62(7-8):988-1005

ABSTRACT

The North Palawan Canyon is a large, previously undescribed submarine canyon that incises the continental shelf and slope of the southern South China Sea. Using multibeam bathymetric data and two-dimensional seismic reflection data, we have characterized current canyon morphology and documented lower-canyon migration in cross-section since the middle Miocene. We have also explored possible causes for the ancient migrations. The 175 km modern canyon is flanked by sediment waves outside its northern bank, and depositional lobes fan out from the canyon mouth. Over the past 15 million years, at least 20 cycles of significant canyon incising and infilling have occurred, along with significant canyon migration. This migration, as recorded in the sedimentary (seismic) record near a leftward bend in the canyon’s lower reach, can be divided into three stages: southward migration during the middle Miocene (averaging 1.24 km/m.y.), northward migration during the late Miocene (1.34 km/m.y.), and stationarity since the Pliocene. The overall zigzagging pattern of the canyon thalweg (as seen in cross-section through time) results from lateral and downstream migration in an aggradational environment. The early (middle to late Miocene) rapid zigzagging migration of the lower main channel, first southward and then northward, was probably associated with the strong collision of the North Palawan Block with the Philippine Mobile Belt, which would have triggered submarine instabilities and deformed the seafloor. The more recent (Pliocene and later) slowing or cessation of canyon migration is likely the result of the now quieter tectonic setting and long-term climatic cooling and drying.  相似文献   

亚洲大陆边缘海底峡谷的形态、分布及演化进程          下载免费PDF全文

王雁冰  韩喜彬  胡智龙  赵宁  阳凡林  葛倩  许冬  高金耀 《海洋学研究》2020,38(4):48-57

基于SRTM15_Plus水深数据,利用地形表面流水分析与等高线几何分析相结合的方法对亚洲大陆边缘海底峡谷进行识别,分析峡谷的形态、分布及演化进程。共识别出海底峡谷531条,按照平面形态分为直线型、蛇曲型和树枝型三种,数量分别为239条、75条和217条。直线型峡谷主要分布在白令海盆地、千岛盆地、南海等海域;蛇曲型峡谷主要分布在孟加拉湾东部俯冲带海域;树枝型峡谷主要分布在日本海沟、伊豆小笠原海沟和南海海槽交界处,南海以及苏门答腊俯冲带海域。根据峡谷的形态与分布,结合研究区内构造背景,讨论了峡谷“直线型-蛇曲型”的形态演化进程,并依据树枝型峡谷主干谷的形态信息,推测存在“蛇曲型-树枝型”、“直线性-树枝型”的形态演化进程。  相似文献   

泰宁寨下大峡谷地学旅游资源及科学价值     

梁诗经  文斐成  陈润生 《福建地质》2012,31(1):50-59

泰宁寨下大峡谷由悬天峡、通天峡和祈天峡3条峡谷构成,地貌景观优美、生态环境优良、地学旅游资源丰富,是泰宁山原-峡谷型青年期丹霞地貌的典型代表,峡谷中丹崖高耸,洞穴密布,线谷纵横,地质遗迹众多,科学内涵丰富,集中展示了丹霞线谷、巷谷及洞穴发育演化。经科学规划和精心建设,现已成为泰宁世界地质公园开展丹霞地貌科考、科普、地学与生态旅游的主要线路。  相似文献   

饱和层状场地中任意凹陷地形对入射SV波的散射          下载免费PDF全文

尤红兵  梁建文  赵凤新 《地震学报》2011,33(6):735-745,843

利用饱和土层的精确动力刚度矩阵和动力格林(Green)函数,采用间接边界元法,在频域内求解了层状饱和场地中任意凹陷地形对入射SV波的散射问题.通过自由场反应分析,求得凹陷地形表面各点的位移和各单元的应力响应;同样计算了虚拟分布荷载的格林影响函数,求得相应的位移和应力响应;根据边界条件确定虚拟分布荷载,将自由场位移响应和...  相似文献   

基于GIS的高山峡谷地区土地适宜性评价——以云南省澜沧县为例   总被引：1，自引：0，他引：1  

蒋翌帆  邓钢  卢冬爱 《测绘科学》2011,36(1):155-157

选择高山峡谷较为明显的澜沧县为研究区域,根据适宜性理论基础,科学地选择评价因子并建立评价体系,采用层次分析法确定各因素的权重,采用多因子加权叠加法对研究区域进行土地适宜性评价.在GIS技术支持下,建立土地信息的空间和属性数据库,对研究区域进行不同用地适宜性评价,将结果划分等级,衡量高山峡谷地区土地对农、林、牧及建设用地...  相似文献   

琼东南盆地中央峡谷深水天然堤—溢岸沉积   总被引：7，自引：0，他引：7  

李冬  王英民  王永凤  徐强  王杰平 《沉积学报》2011,29(4):689-694

中央峡谷位于琼东南盆地深水区,发育面积较广,内部天然堤—溢岸沉积发育。深水天然堤—溢岸可作为良好的油气储集体,深受油气工业界的关注。为了指导中央峡谷的油气勘探,利用三维地震资料,结合地震剖面以及均方根振幅属性对中央峡谷内部天然堤—溢岸沉积的形态和控制因素进行了分析,总结了天然堤—溢岸的沉积模式,并对其油气勘探前景进行了...  相似文献   

Discovery of Messinian canyons and new seismic stratigraphic model,offshore Provence (SE France): Implications for the hydrographic network reconstruction     

《Marine and Petroleum Geology》2014

The interpretation of high-resolution 2D marine seismic profiles together with the analysis of sea-bottom cores allowed a stratigraphic and structural framework of the Provence continental shelf to be proposed. The integration of onshore and offshore stratigraphy, structure and geomorphology provided new insights into Messinian paleotopography and paleohydrography. A geological map of the offshore Provence continental shelf, isobath map of the base Plio-Quaternary surface are presented for the first time in this area. The base Plio-Quaternary surface is a polyphased unconformity that is composed of deep canyons developed by fluvial erosion during the Messinian event, and wave-cut surfaces formed during post-Messinian transgressions. The study evidenced a deep, E–W-trending canyon (Bandol canyon) connected to the head of the Cassidaigne canyon, and filled with up to 600 m-thick Plio-Quaternary deposits. The development of canyons on the Provence margin during the Messinian event was dominantly controlled by the lithology and structure of pre-Messinian formations. A map of the Messinian paleo-drainage network is proposed to explain the presence of deep canyons in the Eastern area and the lack of incision in the Western area. An underground karst drainage scheme is proposed, linked with the current submarine Port-Miou spring.  相似文献