Early Estimation of Strong Aftershock Duration Time

In order to solve the problem of early estimation of moderately strong aftershock duration time in an earthquake sequence,this study has been conducted.First,the definition of the strong aftershock has been given.It is pointed out that there is a difference in the strong aftershock duration time between the main shock type sequence and the strong earthquake swarm sequence.After dividing the three cases,i.e.,a strong aftershock duration time larger than 1 day,smaller than 1 day,and no strong aftershock occurred in a main shock type sequence by using the pattern recognition method,we gave the rough correlation relation between strong aftershock duration time and first large shock magnitude for two types of sequences.Finally,the judgment index and method of estimating strong aftershock duration times for different sequence types have been given.     

正确使用X—CT球管的技术探讨

本文报道了我院连续六只Ｘ－ＣＴ球管的使用情况。寿命最长的曝光达３５８３００秒，而最短的只有１３５０００秒，其主要原因是缺乏正确地使用和维护知识，要想延长球管使用寿命，首先需加强对使用人员的专业素质训练，其次，在保证图像质量的前提下，降低ｍＡｓ；第三，保持扫描室恒业的温湿度；第四，定期检查球管的冷却散热系统。     

华北地区煤的显微组分结焦性热台试验

为探讨煤的显微组分的结焦性，对不同变质程度煤的镜质组、壳质组和惰性组分别进行了显微镜热台加热试验．在加热过程中，活性组分经历了３个明显不同的变化阶段，即变形阶段、胶质体形成阶段以及固化阶段．随煤变质程度的增加，镜质组的初变温度和胶质体形成时的温度逐渐增大，而固结温度变化规律不明显；壳质组在低变质阶段因受热而挥发掉，但随煤级增高其变形程度减弱；半镜质组在受热过程中也有变形和少量胶质体形成，而惰性组只发生微弱变化．在低变质阶段，活性显微组分形成的焦炭显微结构以各向同性为主；随变质程度的增高，焦炭显微结构中各向异性成分比例增大     

遥感技术在我国水电建设前期工作中的应用

本文回顾了我国水电遥感工作自８０年代以来的发展状况，详细介绍了我国水电遥感调查工作的内容，方法及其所到得的效益，指出我国水电遥感工作具规模宏大，内容广泛，协同攻关的特点，也存在着遥感资料应用尚不够充分等三方面的不足。够     

预警地震在地震预测中的意义

对新疆1970-2002年地震资料以不同范围、不同震级进行全时空扫描。结果表明，新疆台网监测能力较好地区绝大多数6级以上地震前地震活动关联图较为清晰。提出了预警地震的概念，认为预警地震在短临预报方面有一定的作用。     

液压传感间接测量水位计的研制及其应用

压力式水位计在水文自动测报系统中很难推广的主要原因是泥沙对传感器的影响,泥沙不但会使传感器测量精度达不到测验要求,而且由于泥沙淤积还会给水位计的日常维护带来很大不便。目前进口传感器测量精度高、稳定性能好,但仍避免不了泥沙的影响。针对这一问题,提出了一种新型压力式水位计———液压传感间接测量水位计,该水位计解决了泥沙对压力式水位计的影响,是一种具有很大发展前景的水位测量仪器。     

鄱阳湖区平垸行洪、退田还湖后的防洪减灾形势分析

根据鄱阳湖区“退田还湖”的实际资料，采用洪水模拟的方法分析计算出“退田还湖”降低湖口站洪水位和减少1954年洪水超额分洪量，分析了“退田还湖”后鄱阳湖区的防洪减灾形势，提出应继续加强对鄱阳湖区防洪工程的建设，探讨了“退田还湖”后江湖洪水关系的变化趋势。     

四川雅安地质灾害时空预警试验区初步研究

借鉴美国旧金山湾和香港地区的经验,提出了地质灾害监测预警试验区建设和研究思路。经过近两年的工作,初步建成了四川雅安地质灾害监测预警试验区。取得的阶段性成果主要有:(1)根据现场考察和试验区地质灾害数据库,统计研究了降雨型滑坡的几何特征;(2)建成了由20台遥测雨量计构成的降雨观测网,取得了2002年4月～2003年8月的降雨观测数据;(3)结合历史降雨资料分析,初步研究了雅安试验区的年、日、小时和十分钟最大降雨特征;(4)研制了斜坡岩土体含水量野外监测仪,取得了桑树坡试验点2003年4月～8月的实时监测数据;(5)自上而下分4层研究了斜坡岩土层含水量变化,发现了岩土层含水量变化对降雨过程的滞后性;(6)基于区域地质灾害评价预警的递进分析理论与方法(AMFP),利用地质灾害因子分析结果,分别计算了雅安试验区地质灾害"发育度"和"潜势度";(7)利用2003年8月23～25日的过程降雨观测资料,对雅安试验区在该降雨过程中发生的地质灾害事件进行了时空预警反演模拟研究,计算出的地质灾害"危险度"分布比较符合实际,"危险度"可以作为预警指数使用。     

Holocene calcrete crust deposits on the moraine of Batura Glacier, northern Pakistan

Abstract   Calcretes can be observed on the surface of old moraines around Batura Glacier in the upper Hunza Valley, Karakoram Mountains, Pakistan. They develop as a calcareous crust cementing small gravels under boulders. In order to understand the genesis of the calcrete crust, a variety of methods were employed: (i) study of mineralogy and geochemistry of a calcrete crust precipitated on the lateral moraine using X-ray diffractometer and electron probe microanalysis; (ii) analysis of solute chemistry of surface water and ice bodies around the Batura Glacier; and (iii) accelerator mass spectrometry ¹⁴C dating of the crust itself. The results indicate that the calcrete crust has definite laminated layers composed of a fine-grain and compact calcite layer, and a mineral fragment layer. The chemical composition of the calcite layer is approximately 60% CaO and 1% MgO. The mineral fragment layer consists of rounded grain materials up to 0.2 mm in diameter. It shows a graded bedding structure with fine grains of quartz, albite and muscovite. Meanwhile, as the Paleozoic Pasu limestone is distributed around the terminal of Batura Glacier, Ca cations dissolve in the melt water of the glacier. Accordingly, the calcrete crust is precipitated by decreases in CO₂ partial pressure from glacier ice and evaporation of the melt water, including high concentration of Ca²⁺ at ephemeral streams and small ponds stagnating between the moraine and glacial ice. On the basis of the AMS ¹⁴C age, the calcrete is considered to have formed approximately 8200 calibrated years bp under the Batura glacial stage.     

Volcanic resurfacing and the early terrestrial crust: Zircon U-Pb and REE constraints from the Isua Greenstone Belt, southern West Greenland

The oldest known bona fide succession of clastic metasediments occurs in the Isua Greenstone Belt, SW Greenland and consists of a variety of mica schists and rare metaconglomerates. The metasediments are in direct contact with a felsic metavolcanic lithology that has previously been dated to 3.71 Ga. Based on trace element geochemical data for > 30 metasediments, we selected the six samples with highest Zr concentrations for zircon extraction. These samples all yielded very few or no zircon. Those extracted from mica schists yielded ion probe U/Pb ages between 3.70 and 3.71 Ga. One metaconglomerate sample yielded just a single zircon of 3.74 Ga age.The mica schist hosted zircons have U/Pb ages, Th / U ratios, REE patterns and Eu anomalies indistinguishable from zircon in the adjacent 3.71 Ga felsic metavolcanic unit. Trace element modelling requires the bulk of material in the metasediments to be derived from variably weathered mafic lithologies but some metasediments contain substantial contribution from more evolved source lithologies. The paucity of zircon in the mica schists is thus explained by incorporation of material from largely zircon-free volcanic lithologies. The absence of older zircon in the mica schists and the preponderance of mafic source material imply intense, mainly basaltic resurfacing of the early Earth. The implications of this process are discussed.Thermal considerations suggest that horizontal growth of Hadean crust by addition of mafic-ultramafic lavas must have triggered self-reorganisation of the protocrust by remelting. Reworking of Hadean crust may have been aided by burial of hydrated (weathered) metabasalt due to semi-continuous addition of new voluminous basalt outpourings. This process causes a bias towards eruption of Zr-saturated partial melts at the surface with O-isotope compositions potentially different from the mantle. The oldest zircons hosted in sediments would have been buried to substantial depth or formed in plutons that crystallised at some depth, from which it took hundreds of millions of years for them to be exhumed and incorporated into much younger sediments.