The low seismic activity of the Korean Peninsula surrounded by high earthquake countries   总被引：1，自引：0，他引：1  

S.G. Kim  E. Lkhasuren  P.-H. Park 《Journal of Seismology》2004,8(1):91-103

Although the Korean Peninsula is locatednear several great earthquake regions suchas NE China and SW Japan, it has neversuffered from catastrophic earthquakes forthe last 2000 years according to historicaland instrumental records. We investigatedthe low seismicity of Korea based on thehypothesis of the Baikal-Korea Plate (BKP)or Amurian Plate movement which isinitiated by the Baikal Rift Zone spreadingin a southeastward motion with acounter-clockwise rotation due to thecollision of the Indian Plate against theEurasian Plate. Many disastrous earthquakesof NE China, SW Japan and Sakhalin releaselarge amounts of seismic energy along theboundary of the Baikal-Korea Plate. It isnecessary to compute the released seismicenergy along the presumed boundary of theBaikal-Korea Plate compared to the KoreanPeninsula in order to estimate themicro-plate boundary. The total energyreleases (1900–1999) from the majordisastrous earthquakes (M6.0) alongthe Baikal-Korea plate are about10³–10⁴ times as much as theKorean Peninsula (M3.0). The focalmechanisms for the intra-continentalearthquakes near and/or along theBaikal-Korea Plate boundary of NE China, SW Japan, Sakhalin and Mongolia mostlyrepresent the horizontal motions of theright-lateral strike slip type, indicatingthat the Baikal-Korea Plate is acounter-clockwise and transcurrent motion. The relative displacement vectors of GPS(global positioning system) also indicatedthat the Baikal-Korea Plate movescounter-clockwise around the KoreanPeninsula. These factors may indicate thatthe Korean Peninsula is not located at thePlate boundary, but just within a margin ofthe Baikal-Korea Plate which movessoutheastward with a counter-clockwiserotation from the Baikal Rift Zone in NEAsia. Therefore there is no enoughaccumulated strain to generate largeearthquakes in the Korean Peninsula and itmakes the Korean Peninsula free fromseismic hazard of large catastrophicearthquakes.  相似文献   

Archean greenstone-tonalite duality: Thermochemical mantle convection models or plate tectonics in the early Earth global dynamics?   总被引：2，自引：0，他引：2  

Robert Kerrich  Ali Polat   《Tectonophysics》2006,415(1-4):141-165

Mantle convection and plate tectonics are one system, because oceanic plates are cold upper thermal boundary layers of the convection cells. As a corollary, Phanerozoic-style of plate tectonics or more likely a different version of it (i.e. a larger number of slowly moving plates, or similar number of faster plates) is expected to have operated in the hotter, vigorously convecting early Earth. Despite the recent advances in understanding the origin of Archean greenstone–granitoid terranes, the question regarding the operation of plate tectonics in the early Earth remains still controversial. Numerical model outputs for the Archean Earth range from predominantly shallow to flat subduction between 4.0 and 2.5 Ga and well-established steep subduction since 2.5 Ga [Abbott, D., Drury, R., Smith, W.H.F., 1994. Flat to steep transition in subduction style. Geology 22, 937–940], to no plate tectonics but rather foundering of 1000 km sectors of basaltic crust, then “resurfaced” by upper asthenospheric mantle basaltic melts that generate the observed duality of basalts and tonalities [van Thienen, P., van den Berg, A.P., Vlaar, N.J., 2004a. Production and recycling of oceanic crust in the early earth. Tectonophysics 386, 41–65; van Thienen, P., Van den Berg, A.P., Vlaar, N.J., 2004b. On the formation of continental silicic melts in thermochemical mantle convection models: implications for early Earth. Tectonophysics 394, 111–124]. These model outputs can be tested against the geological record. Greenstone belt volcanics are composites of komatiite–basalt plateau sequences erupted from deep mantle plumes and bimodal basalt–dacite sequences having the geochemical signatures of convergent margins; i.e. horizontally imbricated plateau and island arc crust. Greenstone belts from 3.8 to 2.5 Ga include volcanic types reported from Cenozoic convergent margins including: boninites; arc picrites; and the association of adakites–Mg andesites- and Nb-enriched basalts.Archean cratons were intruded by voluminous norites from the Neoarchean through Proterozoic; norites are accounted for by melting of subduction metasomatized Archean continental lithospheric mantle (CLM). Deep CLM defines Archean cratons; it extends to  350 km, includes the diamond facies, and xenoliths signify a composition of the buoyant, refractory, residue of plume melting, a natural consequence of imbricated plateau-arc crust. Voluminous tonalites of Archean greenstone–granitoid terranes show a secular trend of increasing Mg#, Cr, Ni consistent with slab melts hybridizing with thicker mantle wedge as subduction angle steepens. Strike-slip faults of 1000 km scale; diachronous accretion of distinct tectonostratigraphic terranes; and broad Cordilleran-type orogens featuring multiple sutures, and oceanward migration of arcs, in the Archean Superior and Yilgarn cratons, are in common with the Altaid and Phanerozoic Cordilleran orogens. There is increasing geological evidence of the supercontinent cycle operating back to  2.7 Ga: Kenorland or Ur  2.7–2.4 Ga; Columbia  1.6–1.4 Ga; Rodinia  1100–750 Ma; and Pangea  230 Ma. High-resolution seismic reflection profiling of Archean terranes reveals a prevalence of low angle structures, and evidence for paleo-subduction zones. Collectively, the geological–geochemical–seismic records endorse the operation of plate tectonics since the early Archean.  相似文献   

基于ITRF2005框架的南美板块运动及形变分析     

敖敏思  胡友健  赵斌  叶险峰 《测绘科学》2012,(1):12-14,11

本文通过利用ITRF2005框架速度场以及IGS参考站近两年观测数据解算所得速度场对南美板块的运动及形变特征进行分析。结果表明,南美板块整体以约12.4mm/a的速率向北西方向运动,其欧拉矢量参数与NNR-NULVEL1A模型基本一致。形变特征表现为中南部区域西缘因纳兹卡板块俯冲向东凹陷,东侧受大西洋中脊海底扩张推力向西运动,东西向的挤压使其约以22mm/a的速度收缩并阻碍其北向运动。板块南端则受南极洲板块挤压向北西运动。  相似文献   

REASONS FOR THE LATE ONSET AND ANOMALOUS SOUTHWARD PERSISTENCE OF THE SOUTH CHINA SEA SUMMER MONSOON IN 2005     

鲍媛媛  琚建华  金荣花  康志明 《热带气象学报(英文版)》2010,16(1):27-34

Features of atmospheric circulation and thermal structures are discussed using the NCAR/NCEP data to reveal the reasons for the late onset and anomalous southward persistence of the South China Sea Summer Monsoon (SCSSM) in 2005. The results show that three factors are crucial. First, a strong Arabian High overlaps with a high-latitude blocking high and channels strong cold air to southern Asia. Second, the Tibetan Plateau has a bigger snow cover than usual in spring and the melting of snow cools down the surface. Third, the Somali Jet breaks out at a much later date, being not conducive to convection over Indochina. The former two factors restrict atmospheric sensible heating over the Tibetan Plateau and nearby regions while the third one limits latent heating over Indochina. All of the factors slow down atmospheric warming and postpone the onset of SCSSM. Long after the onset of SCSSM, strong cold air over India advances the Southwest Monsoon northward slowly, resulting in weaker convection and latent heating over the Tibetan Plateau and nearby areas. The negative feedback conversely inhibits further northward movement of Southwest Monsoon.  相似文献   

Evolution of east coast of India — A plate tectonic reconstruction     

N. K. Lal  A. Siawal  Anil K. Kaul 《Journal of the Geological Society of India》2009,73(2):249-260

The evolution of east coast of India sis discussed within the ambit of clearly identifiable four major tectonic stages which had a profound effect in shaping the tectonic grain of the east coast basins. The evolutionary process began with rift related crustal extension between India and Sri Lanka as a consequence of Africa-Antarctica rifting and development of Natal Basin. An arm of this rift led to initial extension in the Cauvery Basin and failed. Later, the India-West Australia rift propagated further in southwesterly direction initiating Mahanadi and Krishna-Godavari Basins. This extension was an oblique one with Nayudupeta high acting as pivot. The oblique extension followed by asymmetric seafloor spreading developed transpression along India-Sri Lanka and Antarctica junction, resulting in a NNW-SSE trending transcurrent fault along which Antarctica moved southward. Subsequently, entire east coast evolved through a more or less uniform post rift stage.  相似文献   

Principal faults in the Shatsky Rise and their influence upon the evolution of the geological structure in the East Black Sea Region     

A. L. Meysner 《Moscow University Geology Bulletin》2009,64(4):214-219

A fault was traced along the southwestern margin of the Shatsky Rise. It extends to land where it crosses the Mountainous Crimea. Interpretation and analysis of marine seismic and magnetic survey data, as well as geological data on land, allow stating that the fault originated during the rift evolution stage of the East Black Sea Basin. Currently, the fault is in the sea and is a channel for migrating hydrocarbon fluids. Another fault was traced from the West Caucasus into the sea, where it separates the Shatsky Rise into two structural units.  相似文献   

四川后高坪地区晚泥盆世植物和遗迹化石的新发现   总被引：2，自引：0，他引：2  

张立军  龚一鸣 《地层学杂志》2009,33(2)

在扬子板块西缘后高坪地区新发现植物化石Cyclostigma kiltorkense(平圆印木)和Lepidodendropsis hirmeri(希氏拟鳞木),以及遗迹化石Zoophycos(动藻迹)和Chondrties(丛藻迹),据此及相关地层和沉积相标志,确定该地层时代为晚泥盆世,沉积环境为由早期为滨岸较粗碎屑岩和浅海中上部细碎屑岩沉积,晚期为碳酸盐台地相。  相似文献   

西藏班公湖-怒江板块结合带岩金遥感找矿模式   总被引：1，自引：0，他引：1  

白朝军  陈瑞保  王跃峰  张玉明  左爱萍 《国土资源遥感》2003,14(2):15-18

西藏班公湖-怒江板块结合带地质构造复杂,成矿条件优越,具备形成金矿的地质背景条件,是西藏最具潜力和规模巨大的贵金属成矿带.但由于该区地质工作程度较低和对成矿规律认识不清,至今没有一个可供开发的岩金矿产地.通过班公湖-怒江板块结合带砂金、岩金矿(化)点,地球化学异常和重砂异常的分布并进行控矿因子分析,建立了该带两种岩金遥感找矿模式,通过验证发现该区具有大型远景规模的岩金矿产地,并认为蚀变岩型金矿和穆龙套型金矿是该带最重要的两种矿床类型,具有巨大的找矿潜力.  相似文献   

华南陆区板块活动与构造体系的形成演化——纪念李四光先生诞辰130周年     

杨明桂  王光辉 《地质学报》2019,93(3):528-544

本文通过华南陆区中新元古代以来板块活动与构造体系的"一体化"融合研究,从构造体系形变特征、形成演化历史、形成机制等方面分析了其与板块活动的成生联系。构建了区内以扬子反S型构造体系、新华夏构造体系、南岭纬向带为主体的多体系复合构造格局。其中,新厘定的扬子反S型构造体系为扬子板块的主体构造,原属于华夏系,奠基于晋宁期扬子、华夏板块的陆陆碰撞,定型于燕山陆内活化造山时期。新华夏构造体系为滨西太平洋的主体构造,包括具有成生联系的北东向华夏式和北北东向新华夏式两种型式,共同经历了燕山期挤压扭动成型、造山后伸展和第四纪以来的弱挤压的演变过程。著名的南岭纬向带主要成型于燕山期的板内经向挤压,以东西向叠加褶皱-花岗岩带为主要特征,活动至今。在此基础上,简要论述了主要构造体系复合控制区域成矿区带和分级控制矿集区、矿田、矿床特征以及燕山期岩浆成矿大爆发的核幔式扩展模式。论证了区内燕山期陆内活化造山具有以欧亚板块与太平洋板块近南北向相对左行扭动为主导的多向汇聚、多因复合的动力学特征。  相似文献   

Seafloor Geomorphology and Processes on the Western Continental Margin of India based on Multibeam Acoustic Backscatter Data Analysis     

Sumanta Dandapath  Andrew Menezes  Bishwajit Chakraborty  John Kurian  Koppella N. Prudhvi Raju 《Marine Geodesy》2018,41(2):177-200

An assessment of the multibeam sonar data of the central Western Continental Margins of India has been carried out to evaluate the seafloor geomorphology and processes by examining the geomorphological attributes e.g., slope, sediments, structures, etc. associated with geomorphic features. The variation in relief and the features located in the region have been mapped and interpreted collectively by utilizing several geospatial mapping tools. The backscatter strength across the area, apparently congruent with the local relief, has helped to examine the sediment movement on the seafloor. The prominent features found in the region include faults, pockmarks, mounds, submarine terraces, and submerged fossil reefs. Several areas with varying topography engender comparable fractal dimension at short scale breaks, and the probability density functions (PDFs) utilizing backscatter data depicting overlapping classes. The present study highlights how fractals and scale break parameters can be utilized to determine the seafloor processes and associated sedimentological dynamics in a complex geographical environment with strong bottom currents, seasonal upwelling, and faulted structure. The role and impact of the various geomorphic processes on the reworking of sediment movement and the overall progression of the seafloor morphology has been revealed for the first time in this part of the ocean bottom.  相似文献