二维横向各向同性介质中的差分法地震波正演   总被引：1，自引：0，他引：1  

闫贫  何樵登 《吉林大学学报(地球科学版)》1994,(1)

通过ｚ－τ变换，把（ｘ，ｚ，ｔ）域的波动方程变换为（ｘ，τ，ｔ）域的波动方程，以分离出波动方程中速度（或弹性系数）的变化项，并利用有限差分法来计算横向各向同性介质中的合成记录。差分格式采用二阶中心差商及一阶向前差商，边界条件为吸能边界。计算结果显示了横向各向同性介质中的ｑＰ、ｑＳＶ及ｑＳＨ波；在有界面的情形下，还较清楚地反映了反射波的存在。  相似文献   

3S技术在数据库数据更新中的应用     

付治河  王品  房玉华 《测绘与空间地理信息》2005,28(3):88-89

主要介绍了“3S”技术及其在数据库数据更新方面发展的状况，并以1：250000数据库更新为例，简述了利用“3S”技术进行数据库数据更新的基本过程及步骤。  相似文献   

基于多目标遗传算法的土地利用空间结构优化配置   总被引：12，自引：0，他引：12  

董品杰  赖红松 《地理与地理信息科学》2003,19(6):52-55

针对如何将土地利用数量结构落实到具体的地域空间，以实现土地资源的优化配置的土地利用总体规划编制难点，以及常规的叠加法等土地利用配置方法难以根据土地适宜性评价结果，有效地将土地利用数量结构匹配到具体的土地单元问题，该文利用遗传算法的内在并行机制及其全局优化的特性，提出了基于多目标遗传算法的土地利用空间结构优化配置方法。实例分析表明，该方法具有客观性强、灵活性高、操作简便等优点。  相似文献   

Late Neoproterozoic crustal growth in the European Variscides: Nd isotope and geochemical evidence from the Sierra de Córdoba Andesites (Ossa-Morena Zone, Southern Spain)     

Christian Pin  Eladio Lin  Emilio Pascual  Teodosio Donaire  Alfonso Valenzuela 《Tectonophysics》2002,352(1-2)

Because the Hercynian overprint was extremely weak, the Sierra de Córdoba (southeastern Ossa-Morena Zone, OMZ) provides an excellent opportunity to study the tectonic evolution of sequences deposited close to the Late Neoproterozoic–Early Palaeozoic boundary. In order to put constraints on the sources and geodynamic significance of the Late Proterozoic magmatism, a representative set of 18 igneous rocks, and 3 interbedded sedimentary rocks from the San Jerónimo Formation have been studied for major and trace element geochemistry and for the Sm–Nd isotopic systematics. The igneous rocks are generally porphyritic to microporphyritic andesites, with abundant plagioclase (±amphibole) phenocrysts. With the exception of two intrusive rocks, possibly not related to the Late Proterozoic episode, all the samples display positive _{Nd550 Ma} values, ranging from +2.9 to +7.6. Most of them, with +4<_{Nd550 Ma}<+6, exhibit LREE enrichment, high La/Nb ratios, and elevated Zr/Nb ratios ranging from 21 to 32. There is no obvious correlation between the shape of REE patterns, La/Nb ratios and _{Nd550 Ma} values, precluding simple models of late-stage interaction with typical crustal components having low _Nd and high LREE/HREE and La/Nb ratios. Based on their major element composition and enriched, continental crust-like trace element characteristics, combined with distinctly positive _Nd initial values, the Córdoba andesites document an episode of crustal growth through the addition of calc-alkaline magmas, extracted from a mantle reservoir which was strongly depleted in LREE on a time-integrated basis. The occurrence of interlayered sediments of continental provenance (negative _Nd values) does not favour a purely ensimatic arc setting, remote from continental land masses, for this subduction-related magmatism, but the geochemical data suggest an active margin environment located on relatively juvenile crust. In any case, the Córdoba andesites document the addition of materials chemically similar to the bulk continental crust which were extracted from mantle sources with strong time-integrated LREE depletion. Therefore, they provide evidence for crustal growth related to Cadomian orogenic events during Late Proterozoic times.  相似文献   

Substrate damage and recovery after giant clam shell mining at remote coral reefs in the southern South China Sea     

ZHOU Shengnan  SHI Qi  YANG Hongqiang  ZHANG Xiyang  LIU Xiaoju  TAN Fei  YAN Pin 《地理学报(英文版)》2021,31(11):1655-1674

Giant clam shell mining(GCSM),a unique phenomenon occurring at remote coral reefs in the southern South China Sea(SCS),forms striking scars on the reef flats and damages the reef flat substrate.Through image analyses at three times(2004.02.02,2014.02.26,and 2019.04.10)and in situ surveys at Ximen Reef,a representative site that has experienced GCSM,we quantified the GCSM-generated substrate damage and the corre-sponding recovery.GCSM was estimated to have occurred sometime between 2012 and 2014,causing reduction in live coral subarea and formation of micro-relief as trenches and mounds.GCSM-generated damage was restricted to the reef flat.After GCSM,coral and algae subarea increased,and the trenches and mounds tended to be filled and eroded,rep-resenting a natural recovery of the substrate.The legal prohibition on human disturbances at the coral reefs contributed to substrate recovery at Ximen Reef.This case also implied that recovery of the other coral reefs that suffered from GCSM is possible.  相似文献   

基于大比例尺矢量数据库建设的ArcInfo软件应用及二次开发     

王品 《测绘与空间地理信息》2008,31(2):143-145

结合"数字平顶山"基础地理空间数据库建设项目,用ArcInfo的AML语言开发实现数据转换、数据编辑、数据检查的矢量数据处理实用工具。  相似文献   

南海北部边缘盆地油气勘探现状与深水油气资源前景   总被引：18，自引：0，他引：18  

何家雄  施小斌  夏斌  刘海龄  阎贫  姚永坚  张树林 《地球科学进展》2007,22(3):261-270

自20世纪60年代初开展浅海油气苗调查及浅井钻探以来，南海北部边缘盆地迄今在陆架浅水区已勘探发现多个油气田，建成了一定储量规模的油气产能，基本构成了南海北部油气富集区的格[JP2]局。然而，如何保持油气可持续发展，尽快寻找油气储量接替的新领域，这是该区油气勘探所面临的关键问题。南海北部陆坡深水区与世界深水盆地一样，颇具油气资源潜力和勘探前景，近期LW311深水探井钻探的新发现表明，其应是该区油气资源接替非常现实的战略选区和勘探靶区。  相似文献   

西藏日土县拉热拉新花岗岩体特征及构造环境     

冯晔廖六根  黄俊平徐平 《华东地质学院学报》2005,28(4):317-324

拉热拉新花岗岩体属于唐古拉-东达山花岗岩带西段羌塘花岗岩区的组成部分,岩石类型主要为黑云角闪闪长岩、黑云角闪石英闪长岩、黑云角闪石英二长岩、黑云花岗闪长岩、黑云二长花岗岩、黑云花岗岩。其地球化学特征表现为：富Si,K,贫Ti,Mg,Fe,Ca,铝饱和指数ACNK〈1．1,稀土元素球粒陨石标准化图式呈右倾斜的“V”字型,LREE富集,HREE相对亏损,铕亏损。其形成时代为早白垩世,为多期次同碰撞的同熔型花岗岩。  相似文献   

Relics of an early-Panafrican metabasite–metarhyolite formation in the Brno Massif, Moravia, Czech Republic     

F. Finger  M. Tichomirowa  C. Pin  P. Hanžl 《International Journal of Earth Sciences》2000,89(2):328-335

The Brno Massif in Moravia, Czech Republic, is an important exposure of Precambrian basement in central Europe. It includes large volumes of Cadomian granitoids and a narrow fault-bounded zone with metagabbros, metadiorites, and metabasalts. This so-called Central Basic Belt also contains some metarhyolites; one of these was dated by means of the zircon evaporation method at 725 ±15 Ma. Chemical and isotope data show that the dated rock represents a mantle-derived magma which is cosanguinous with surrounding MORB-type metabasites. The data suggest that the Brno Massif hosts the oldest metabasite complex currently known in central Europe. Its formation apparently coincides with the main period of ocean-floor spreading and island-arc formation in the Panafrican orogens. This lends further support to the theory that the Brno Massif is a Gondwana-derived element. Received: 9 December 1999 / Accepted: 9 February 2000  相似文献   

南海北缘新生代盆地沉积与构造演化及地球动力学背景   总被引：32，自引：0，他引：32  

闫义  夏斌  林舸  刘宝明  阎贫  李忠诚 《海洋地质与第四纪地质》2005,25(2):53-61

南海北缘新生代沉积盆地是全面揭示南海北缘形成演化及与邻区大地构造单元相互作用的重要窗口。通过对盆地沉积-构造特征分析,南海北缘新生代裂陷过程显示出明显的多幕性和旋转性的特点。在从北向南逐渐迁移的趋势下,东、西段裂陷过程也具有一定的差异,西部裂陷活动及海侵时间明显早于东部,裂陷中心由西向东呈雁列式扩展。晚白垩世-早始新世裂陷活动应是东亚陆缘中生代构造-岩浆演化的延续,始新世中、晚期太平洋板块俯冲方向改变导致裂陷中心南移,印度欧亚板块碰撞效应是南海中央海盆扩张方向顺时针旋转的主要原因。  相似文献