秦岭龙之脉

我幻想有一天登上秦岭的最高峰太白山山顶,伸开双臂宣布,我的左手在中国的南方,我的左手在中国的北方。我也幻想有一天可以到秦岭的终南山,寻找那传说中终南山后的活死人墓,看看是否还有神雕大侠和小龙女的后人在练着玉女素心剑法。我更幻想如果可以"穿越",我要回到200万年前的秦岭,游走在那寒冷的第四冰川期,和我们的祖先一起在秦岭的南北间穿行。     

城市抗震防灾规划的研究与展望

抗震防灾规划是提高城镇综合抗震能力的有效措施之一,与城市总体规划一并实施.重点回顾了我国抗震防灾规划工作的发展历程,同时对美国、日本在建立防灾规划方面的情况也进行了介绍.通过编制城市的抗震防灾规划,加强城市的综合抗震防灾能力,在丽江地震中被证明是一个有效的手段.综述了在这个方面的发展与变化,并就未来的可能的发展方向作了总结与展望,以期国内外同仁进一步研究.     

采用Ernst公式计算斜拉桥拉索振动特性的精度分析

斜拉桥拉索的动力特性是建立在斜拉桥的静力分析的基础上的.在静力分析中,几何非线性明显的索经常通过Ernst公式线性化成二力杆,但是,在动力分析中,很少有人研究过Ernst公式的精度.编制了基于弹性悬链线单元的斜拉索的非线性有限元分析程序,该程序可以一根索的任何一个参数值为已知条件来确定索的状态,研究了斜拉索不同张拉阶段索的频率和振型特性,并比较了Ernst公式计算拉索动力特性的精度和适用范围.     

介质的磁化率与包裹体浓度的关系

在第五卷第一期的地球物理学报上,我们曾讨论介质的磁化率与包裹体形状的关系,但是对于介质磁化率与包裹体浓度的关系没有详细讨论。在本文中,将根据巳知的材料,对这个问题加以讨论,作为“介质的磁化率与包裹体形状的关系”一文的补充。     

浅海海洋盐度、温度和深度调查的精确度与海水密度计算的关系

一、本文目的海水密度系海水的盐度、温度和压力的连续函数,而在海水的压力每增加1分巴值深度几增加1米的极近似情况下,海水密度即系海水的盐度、温度和深度的连续函数。在必须精确获知海水密度值的要求下,海水的密度是藉它与盐度、温度和压力三者的函数关系计算而得的。为了要使计算所得的海水密度值有一定的精确度,所以海洋盐度、温度和深度调查的精确度就必须有一定的要求。由於中国海皆系浅海,所以本文仅就浅海海洋盐度、温度和深度调查的精确度与海水密度计算的关系加以论述。     

青海湖表层底泥中放射性同位素137Cs的来源

青海湖是我国环境研究中的一个热点地区,近年来137Cs计年技术已在这一地区得到广泛的应用.已报道的青海湖沉积物中137Cs垂直分布曲线显示,剖面最表层0-1 cm泥沙的137Cs浓度约60 Bq/kg,大致为峰值浓度的2/3,远超过近年来大气沉降137Cs所应带来的沉积水平为查明青海湖表层底泥中放射性同位素137Cs的来源,深入理解湖泊沉积过程,本文对青海湖沉积剖面的137Cs面积活度与137Cs本底值、湖泊表层底泥的137Cs浓度与入湖河流洪水沉积泥沙开展了比对研究.结果表明核爆期间的大气直接沉降是青海湖东南湖湾表层沉积物中的137Cs主要来源,约占4/5,风沙和入湖径流河沙的间接输入的137Cs仅占1/5而最表层0-1 cm的沉积物中137Cs很可能主要来源于底泥扰动,在这样的情况下,利用沉积岩芯开展青海湖环境研究时,分辨率的选取需要慎重考虑这一因素.     

山西代县震群尾波Q值研究

2006年4月至5月间山西代县及邻区发生了一系列小震(本文简称代县震群),依据Sato单次散射模型原理和朱新运等开发的Q值软件,对雁门关数字地震台记录的代县震群波形资料等进行了分析,探讨了其尾波衰减特征.结果表明,代县震群的QC值变化较为稳定,总体上拟合的误差较小,表明该地区当时的构造运动并不活跃,原震区短期内发生破坏性地震的可能性较小.     

海啸初期诱发形成阶段的研究

对近年来有关海啸初期阶段几种激发模式的理论与实验研究的成果做了总体的回顾与阐述,同时对一些存在的问题和前人未给予说明的地方做了些扩充.     

虎跳峡印象

去年暑假,妈妈带我去了向往已久的美丽云南。太多优美的景色让我大饱眼福,太多奇异的风土人情让我大开眼界,但一直让我记忆深刻的还要数虎跳峡了。我们从丽江赶往香格里拉的路上,一直是盘山路,急弯不断,而且海拔不断升高。虽然窗外美景处处,我却开始有晕车的感觉,昏昏欲睡。随着藏族导游的讲解指点,我抬头向窗外望去,一眼就看到了宽阔的金沙江横卧在眼前。别看金沙江有"金"字,江水却是奇妙的红色,缓缓、蜿蜒地向前流动着。不管怎样,这顿时让无精打采的我兴奋起来,猜测着将会有什么到来。     

东湖天蓝喇叭虫(Stentor coeruleus)种群的离散分化

利用筛选的12条10 bp的随机引物对采自武汉市东湖(3个样点)、南湖(3个样点)、月湖(1个样点)和关桥(1个样点)四个水体的天蓝喇叭虫(Stentor coeruleus)种群进行了随机扩增多态DNA(RAPD)研究,所得清晰条带显示不同样点样本之间存在着一定的变异,其遗传距离在0.076-0.416之间.用Rapdistance 1.04构建聚类图并探讨不同样点之间的遗传距离远近.结果显示南湖的3样点的遗传距离较近,在聚类图上聚成一枝,应该为同一个种群;而东湖的3个样点可能是由于地理隔离原因,在聚类图上有2个样点聚成一枝,而另1个样点被其他样点所分隔,不属于同一个种群.这种现象的发现从实例上支持了生物地理学关于物种形成的离散假说.更有意义的是本研究可启动水体微生物种群分化和物种形成及过渡的研究,并期望促进种群生态学方面的研究和谱系生物地理学及离散分化生物地理学的发展.     

三峡水库运行前后长江中下游干流及两湖的径流过程变化

为探索三峡水库运行前后长江中下游干流及两湖径流过程的变化及其驱动因素,利用宜昌、监利、大通、七里山、湖口共5个水文站的流量资料,分析了各站径流过程的变化特征及其成因。结论:(1)各站年径流量均减少,但除七里山站之外,其它各站减少比例均小于10%且变化不显著;(2)干流各站月径流量最大减幅发生在10月,而七里山站、湖口站分别发生在7月、4月;(3)干流各站月径流量最大增幅发生在3月,而七里山站、湖口站分别发生在1月、6月;(4)宜昌站,1—4月径流量增加是三峡水库入库径流增加和水库调度的共同作用结果,6—8月径流量减少的主因是三峡水库入库径流量减少,5、9、10月径流量变化的主因是三峡水库调度;(5)监利站,径流量的变化与宜昌站表现出高度的一致性,但冬季各月径流量的增幅均大于宜昌站;(6)大通站,4—6月径流量变化方向与湖口站一致,其它月份变化方向均与宜昌站一致。(7)七里山站,7月径流量减少的主因是洞庭湖流域来水减少,9、10月径流量减少的主要原因是荆江分流减少,但洞庭湖流域来水减少也是重要原因。(8)湖口站,4、5月径流量减少的主因是流域降水减少,9、10月径流量减少的主要原因是鄱阳...     

Aeolian sediment transport and morphologic change on a managed and an unmanaged foredune

Sediment transport and short‐term morphologic change were evaluated at a site where sand fences are deployed and the beach is raked (Managed Site) and a site where these human adjustments are not practiced (Unmanaged Site). Data were gathered across the seaward portion of a low foredune when winds blew nearly shore‐normal at mean speeds 8.9 to 9.3 m s^‐1. Data from traps revealed sediment transport rates at unvegetated portions of the foredune crest (40.2 to 43.5 kg m^‐1 h^‐1) were greater than on the backshore (4.9 to 11.2 kg m^‐1 h^‐1) due to onshore decreases in surface moisture and speed‐up of the wind passing over the foredune. Data from erosion pins indicate sediment input to the dune was 1.48 m³ m^‐1 alongshore at the Managed Site and 1.25 m³ m^‐1 at the Unmanaged Site. The Unmanaged Site had deposition at the dune toe, erosion at mid‐slope, and deposition at the crest. Deposition occurred at mid‐slope on the Managed Site near a partially buried (0.58 m high) fence with a porosity of about 65%. Deposition at partially buried wrack on the upper backshore and dune toe at the Unmanaged Site was about twice as great as deposition in this zone at the Managed Site. Results indicate that: (1) the seaward slope of the foredune can be a more important source of sand to the lee of the crest than the beach; (2) wrack near the toe can decrease transport into the foredune; (3) a scour zone can occur on the foredune slope above the wrack line; (4) a fence placed in this location can promote deposition and offset scour, but fences can restrict delivery of sediment farther inland. Evaluation of alternative configurations of fences and strategies for managing wrack is required to better determine the ways that humans modify foredunes. Copyright © 2012 John Wiley & Sons, Ltd.     

Occurrence and distribution of bacteria indicators,chemical tracers and pathogenic vibrios in Singapore coastal waters

Water quality in Singapore's coastal area was evaluated with microbial indicators, pathogenic vibrios, chemical tracers and physico-chemical parameters. Sampling sites were grouped into two clusters (coastal sites at (i) northern and (ii) southern part of Singapore). The coastal sites located at northern part of Singapore along the Johor Straits exhibited greater pollution. Principal component analysis revealed that sampling sites at Johor Straits have greater loading on carbamazepine, while turbidity poses greater influence on sampling sites at Singapore Straits. Detection of pathogenic vibrios was also more prominent at Johor Straits than the Singapore Straits. This study examined the spatial variations in Singapore's coastal water quality and provided the baseline information for health risk assessment and future pollution management.     

Temporal trends and spatial characteristics of drought and rainfall in arid and semiarid regions of Iran

Drought, a normal recurrent event in arid and semiarid lands such as Iran, is typically of a temporary nature usually leaving little permanent aftermath. In the current study, the rainfall and drought severity time series were analyzed at 10 stations in the eastern half of Iran for the period 1966–2005. The drought severity was computed using the Standardized Precipitation Index (SPI) for a 12‐month timescale. The trend analyses of the data were also performed using the Kendall and Spearman tests. The results of this study showed that the rainfall and drought severity data had high variations to average values in the study period, and these variations increased with increasing aridity towards the south of the study area. The negative serial correlations found in the seasonal and annual rainfall time series were mostly insignificant. The trend tests detected a significant decreasing trend in the spring rainfall series of Birjand station at the rate of 8.56 mm per season per decade and a significant increasing trend in the summer rainfall series of Torbateheydarieh station at the rate of 0.14 mm per season per decade, whereas the rest of the trends were insignificant. Furthermore, the 12‐month values of the standardized precipitation index decreased at all the stations except Zabol during the past four decades. During the study period, all of the stations experienced at least one extreme drought which mainly occurred in the winter season. Copyright © 2011 John Wiley & Sons, Ltd.     

An intense SFE and SSC event in geomagnetic H, Y and Z fields at the Indian chain of observatories

Changes in the three components of geomagnetic field are reported at the chain of ten geomagnetic observatories in India during an intense solar crochet that occurred at 1311 h 75° EMT on 15 June 1991 and the subsequent sudden commencement (SSC) of geomagnetic storm at 1518h on 17 June 1991. The solar flare effects (SFE) registered on the magnetograms appear to be an augmentation of the ionospheric current system existing at the start time of the flare. An equatorial enhancement in AH due to SFE is observed to be similar in nature to the latitudinal variation of SQ (H) at low latitude. AF registered the largest effect at 3.6° dip latitude at the fringe region of the electrojet. AZ had positive amplitudes at the equatorial stations and negative at stations north of Hyderabad. The SSC amplitude in the H component is fairly constant with latitude, whereas the Z component again showed larger positive excursions at stations within the electrojet belt. These results are discussed in terms of possible currents of internal and external origin. The changes in the Y field strongly support the idea that meridional current at an equatorial electrojet station flows in the ionospheric dynamo, E.Presently at: School of Physics, University of New South Wales, Sydney, Australia     

重复绝对重力测量观测的滇西地区和拉萨点的重力变化及其意义

根据近年来在滇西地区和西藏拉萨绝对重力点上的一些新的绝对重力重复观测结果 ,对1990年以来在这些点上绝对重力重复观测结果进行了分析. 滇西地区的5个绝对重力观测 点的近10年的重复观测结果表明,大部分观测时段没有出现与地球动力学事件有关的重力变 化,只有丽江和洱源2个绝对重力观测点的观测结果显示丽江地震前后有变化. 为了研究该 重力变化的原因,本文正演模拟了出现重力变化期间丽江地震同震位错引起的重力变化,模 拟结果与实际观测结果有较好的一致性. 西藏拉萨近10年以来的重复观测结果给出了拉萨点 的绝对重力值以-1.82±0.9×10-8m·s-2·a-1速率下降,这从重力学 的角度反映出青藏高原的隆升. 对拉萨点的重力变化机制进行了探讨,根据印度板块与欧亚 大陆俯冲模型计算的拉萨点重力变化速率与观测到的重力变化速率较一致,表明现今拉萨地 区重力变化是由于印度板块与欧亚大陆俯冲所引起. 根据印度板块向欧亚大陆俯冲的位错模 型计算的拉萨点的重力变化与地表垂直位移的关系,将重力变化转换为拉萨点的隆升速率为 8.7mm/a.      

新老测点之间的地磁对比观测研究

１９９３年８─１１月，在马起乏与新测点上进行了较长时间的地磁场对比观测，获得了大量准确可靠的地磁资料。应用通化处理法、同步差值法、日变特征量比较法、快速谱分析法（ＦＦＴ）、幅比与位相差值法，分析研究了地磁对比观测资料。结果表明，在相同时间段内，各测点地磁变化形态相当一致，两个测点之间的同步差值平稳。由各测点地磁场总强度日变化的定量分析比较得出，其日变化是相当一致的。快速谱分析显示，在相同时间段内，各测点的幅度随周期的变化形态十分相似，总体上看，ＦＦＴ幅度随周期的减小呈下降趋势；从ＦＦＴ幅度Ａ，位相以及快谱幅比Ａ＿ｉ／Ａ与位相差的定量比较结果上看，各测点的ＦＦＴ有着良好的一致性。此外，还得到了新老测点之间的地磁数据的接点差。     

地震前兆与短临预报探索

针对地震短临预报面临的科学问题,分析研究了地震前兆(近场前兆、远场前兆和大尺度动态前兆)预报地震的物理基础;总结了地震短临前兆时空演化特征和同步耦合现象。高空技术在地震前兆观测中的应用将有利于短临预报实践与探索。     

Lidar observations and formation mechanism of the structure of stratospheric and mesospheric aerosol layers over Kamchatka

Lidar observations during 2007–2008 in Kamchatka revealed aerosol layers in the upper stratosphere at heights of 35–50 km and in the mesosphere at heights of 60–75 km. It is well known that forces of gas-kinetic nature, i.e., photophoretic forces, act on aerosol particles that absorb solar radiation and terrestrial IR radiation; these forces can counteract the gravitational force and even lead to the levitation of these particles at particular heights. The accumulation of particles at these heights may lead to the formation of aerosol layers. We calculated these forces for the conditions of lidar observations in Kamchatka. Aerosol layers were observed at heights where particle levitation can occur. Thus, the stratospheric and mesospheric aerosol layers, detected at heights of 30–50 and 60–75 km, respectively, may be due to the effect of the photophoretic force on aerosol particles.