Long period variations of the geomagnetic field and their spatial distribution in Europe

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河套地震带分区地震空间相关长度变化特征

以河套地震带作为研究区域,选取2001年以来小震事件作为研究对象,采用单键群(SLC)方法,计算研究区地震空间相关长度,并分区域讨论其时序变化特征。计算结果表明,2001年以来,河套地震带5个子区域地震空间相关长度表现出不同变化特征,且无持续性变化,多在约3年时间尺度上表现出增长现象,表明地震空间相关长度的增长变化不太可能反映区域应力场的长期变化,而可能携带应力场的中期变化信息。通过设定不同计算窗长和滑动步长来考证计算结果,发现地震事件时空分布的非均匀性、空间窗形状和大小等因素,可能影响地震空间相关长度的数据变化幅度,但不影响整体变化趋势。     

基于ArcGIS的山东地震台站空间分布特征研究

本文以ArcGIS为平台,通过对山东省地震台站与行政区划图、活动断裂带图、地震峰值加速度区划图等进行叠加分析及缓冲区分析来研究山东省地震台站的空间分布特点。得出山东省地震台站在空间上分布具有不均匀性,近半数位于活动断裂旁6km范围内,绝大部分位于25km范围内,位于地震烈度Ⅶ度区区划内的数量超过了60%。     

太湖沉积物理化性质及营养盐的时空变化

在不同季节,采集太湖梅梁湾和贡湖湾沉积物柱状样,研究沉积物Eh、pH、总氮、总磷以及有机质四季垂向剖面分布变化特征.研究结果表明,在表层下(0-3 cm),Eh随沉积物深度的增加迅速下降,很快进入还原状态.沉积物剖面上pH变化幅度不大,在6.4-7.8之间,冬季沉积物pH均有所降低.太湖沉积物中含有丰富的营养盐,总氮和总磷最高浓度分别为2.68和0.864 mg/g,其剖面分布特征表明,沉积物表层总氮和总磷含量远高于底层,其含量随深度增加而降低,但四季变化趋势不明显.沉积物中有机质含量在10 cm以上变化幅度较大,随着沉积物深度的增加,有机质含量明显减少,季节变化幅度不大.比较不同采样点发现,位于梅梁湾生态系统试验区内的S1位点沉积物氮磷内源负荷最大.     

Dynamics of escape of high-energy electrons from a spherical plasma volume in the geomagnetic field

Using results of numerical modeling, the dynamics of escape of electrons, produced as a result beta-decay, to the external magnetic field from a spherical plasma volume with an expelled magnetic field is studied. The dependence of the fraction of escaped electrons on time and radius of the plasma volume has been obtained for two kinds of electron sources: a point isotropic source, located at the center of the sphere, and a volume isotropic source. It is shown that for a point source some part of electrons remains in the sphere, whereas for a volume source all electrons, at different values of the magnetic cavern radius, leave it at an identical relative escape rate.     

唐山地区尾波Q值时空分布特征

利用首都圈地震数字台网2009年1月至2016年3月记录的地震波形资料,采用Sato尾波单次散射模型,固定尾波窗长,计算唐山地区尾波Q值,时间和空间上分析Q值分布特征,结果显示,Q值在空间分布上呈现明显的横向不均匀性,在较长孕震时间上呈现降低—升高—降低—发震的过程,且中强震易发生在Q值高低值交界区偏高值一侧,震群易发生在Q值相对较低区域。     

坦噶尼喀湖东北部入湖河流表层沉积物中磷的形态和分布特征

磷是坦噶尼喀湖生态系统中必不可少的营养元素,直接决定湖体初级生产力的高低,进而影响到周边居民对于动物蛋白的获取来源.为了解坦噶尼喀湖磷的外源输入,选择湖泊东北部的入湖河流,对表层沉积物(16个样点)中总磷(TP)和各形态磷含量及其分布特征进行分析,并探讨磷的形态分布特征与土地利用方式之间的相关关系.结果表明,入湖河流沉积物TP含量为73.05~239.94 mg/kg,平均含量为152.64±55.37 mg/kg,其中最高值出现在马拉加拉西河口.采用Psenner法对磷进行连续浸提并比较不同形态磷含量,由高及低依次为铁铝结合态磷(Fe/Al-P)钙结合态磷(CaP)有机磷(Org-P)残渣态磷(Res-P)弱吸附态磷(Labile-P).土地利用类型对TP及各形态磷含量影响较大,其中TP含量表现为河口湿地城镇附近林草地区,表明地表径流和人类活动会对TP含量产生影响,而对于不同形态磷含量,Laible-P、Fe/Al-P、Org-P含量均表现为河口湿地林草地城镇附近,Ca-P、Res-P含量均表现为城镇附近河口湿地林草地.分析沉积物理化性质与各磷形态之间的相关性,发现沉积物总氮(TN)、有机质和总有机碳与Fe/Al-P、LabileP和TP相关性较好,与Org-P、Ca-P和Res-P相关性较差,表明TN和有机质的输入,会伴随沉积物中磷含量的升高,其增量的赋存形态主要为氧化还原敏感态磷和Labile-P.沉积物粒径组成与各磷形态含量存在相关性,细粒径沉积物与各形态磷含量呈显著正相关,粗粒径沉积物与各形态磷呈显著负相关,表明细小颗粒更易吸附磷.     

鄱阳湖越冬雁类时空分布特征及热点区域识别

鄱阳湖是东亚—澳大利西亚迁徙路线上重要的水鸟越冬栖息地,雁类是迁徙路线上的优势种群。然而,近年来迁徙路线上的雁类种群数量有所下降,识别越冬地雁类时空分布特征,确定分布热点区域是科学、精准保护的前提。本研究利用2018—2021年越冬期在鄱阳湖区域开展的共58次水鸟调查数据,提取了基于时间序列的白额雁(Anser albifrons)、豆雁(Anserfabalis)、鸿雁(Anser cygnoid)的分布数据,分析了3种雁类在越冬地的种群动态、时间和空间分布动态,评估了鄱阳湖各子湖的重要性,确定了雁类分布热点区域。研究结果表明,3种雁类在越冬地的种群数量表现出一定的年际波动,雁类种群总数量维持在27.9万～44.8万只;不同雁类迁徙的时间节律存在差异,本次地面调查数据显示白额雁、豆雁、鸿雁分别是在10月初至11月初、11月中旬、12月中旬到达鄱阳湖,其中鸿雁到达最晚;高峰期集中在11月底至次年2月初,持续时间约为100天;3种雁类分别在2月中旬、2月底和3月中旬开始迁离鄱阳湖。3种雁类空间分布范围有所差异,豆雁分布范围最广,白额雁分布相对集中,高峰期雁类的分布范围最大,对子湖的利用强...     

Numerical modeling calculation for the spatial distribution characteristics of horizontal field transfer functions

Introduction There are two kinds of methods for the mathematic study on electro-magnetic induction in geo-field: one is analytic method, such as integral equation method; the other is numerical model-ing method, such as finite difference method and finite element method. The analytic method can only be applied to the conductor with very simple shape, such as sphere, circular cylinder, etc. With the increasing of computing speed and popularity of computer, the numerical modeling methods are use…     

利用浅层地震反射法探测夏垫断裂浅部特征及空间展布

为进一步深入研究夏垫断裂的发震构造及活动性,在夏垫断裂震中区开展浅层地震勘探,布设小道距、高密度地震勘探测线,对地震反射剖面进行综合解释。以潘各庄段为中心,向两侧展开布设,共布设浅层地震勘探测线12条,测线总长约18 km。野外数据采集采用中间激发、双边不对称接收、满覆盖次数不少于12次的观测系统。原始资料经过常规处理和精细处理,获得了高质量的反射波叠加时间剖面。地震反射时间剖面揭示的波组变化特征明显,断裂特征清晰,解释夏垫断裂为倾向SE、视倾角约为72°的正断层;同时展现了自小石各庄至南张岱延伸约20 km范围内夏垫断裂的空间展布及浅部构造特征,解释测线范围内夏垫断裂走向约为N40°E。在此基础上,结合微地貌测量和以往研究成果,推测夏垫断裂为全新世活动断裂,其中夏垫断裂中心段伴随次断裂发育和断层绕射波,该特征向两侧减弱,与断裂陡坎的分布和连续的高差变化相对应,同时验证了夏垫镇潘各庄附近为震中的结果。探测结果所揭示的夏垫断裂的空间展布及地层结构特征与地质资料吻合。      

长江中游湖泊CDOM光学特性及其空间分布对比

根据2007年秋季洪湖、东湖和梁子湖的调查结果,分析了长江中游3个典型湖泊CDOM光学特性及其空间分布差异.结果表明:(1)CDOM吸收系数在洪湖最高,梁子湖最低;(2)在洪湖,CDOM吸收系数受陆源影响较大,与悬浮泥沙浓度呈现较好正相关关系,而在梁子湖,CDOM吸收系数主要受到浮游植物降解贡献,与叶绿素浓度具有显著的正相关关系;(3)洪湖与东湖指数函数斜率S值变化不大;梁子湖CDOM吸收系数空间分布差异较大,指数函数斜率S值与400nm波段CDOM吸收系数ag(400)显著负相关.在建立梁子湖CDOM遥感反演模型时,应引入上述指数甬数斜率S值与400nm波段CDOM吸收系数之间的线性函数,对CDOM吸收系数的指数模型进行优化.     

Origin of ULVZs near the African LLSVP: Implications from their distribution and characteristics

Ultra-low velocity zones (ULVZs) provide important information on the composition and dynamics of the core-mantle boundary (CMB). However, their global distribution and characteristics are not well constrained, especially near African large low-shear velocity provinces (LLSVPs). Here, we used ScS precursor (SdS) and postcursor (ScscS) phases recorded by various seismic networks in Africa and South America to investigate the ULVZ characteristics underlying the South Atlantic Ocean. We found no evidence of ULVZs near the SE boundary of South America, but an ULVZ was found within the SW boundary of the African LLSVP, with thicknesses ranging from 11–18 km and reductions in S-wave velocities of 18%–34%. Our results, combined with the global distribution of ULVZs, suggest that thermal activity may be essential to ULVZ formation. Moreover, subducted slab and mantle flow may also play a key role, depending on the location of the ULVZs.     

Effects of a kappa distribution function of electrons on incoherent scatter spectra

In usual incoherent scatter data analysis, the plasma distribution function is assumed to be Maxwellian. In space plasmas, however, distribution functions with a high energy tail which can be well modeled by a generalized Lorentzian distribution function with spectral index kappa (kappa distribution) have been observed. We have theoretically calculated incoherent scatter spectra for a plasma that consists of electrons with kappa distribution function and ions with Maxwellian neglecting the effects of the magnetic field and collisions. The ion line spectra have a double-humped shape similar to those from a Maxwellian plasma. The electron temperatures are underestimated, however, by up to 40% when interpreted assuming Maxwellian distribution. Ion temperatures and electron densities are affected little. Accordingly, actual electron temperatures might be underestimated when an energy input maintaining a high energy tail exists. We have also calculated plasma lines with the kappa distribution function. They are enhanced in total strength, and the peak frequencies appear to be slightly shifted to the transmitter frequency compared to the peak frequencies for a Maxwellian distribution. The damping rate depends on the electron temperature. For lower electron temperatures, plasma lines for electrons with a distribution function are more strongly damped than for a Maxwellian distribution. For higher electron temperatures, however, they have a relatively sharp peak.     

淮河流域周村水库夏季CDOM吸收光谱特征、空间分布及其来源分析

基于2015年8月采集的24个淮河流域以周村水源水库为代表的表层水样的有色溶解性有机物(CDOM)吸收系数数据,研究了CDOM吸收光谱的空间分布特征,考察了CDOM的吸收系数与水质参数的相关关系,同时探讨了周村水库夏季CDOM的潜在来源.结果显示:依据CDOM的吸收光谱空间分布特性及采样点分布特征,周村水库分为入库口、过渡区和主库区3个特征水域;CDOM的吸收系数沿入库口到主库区依次递减,S值呈现相反的趋势;分析发现S240~500与a(355)和a*(355)呈极显著负相关(R~2=0.98、0.88);CDOM吸收系数a(355)与溶解性有机碳(DOC)浓度具有良好的线性相关,有利于建立DOC遥感反演模型;同时,CDOM吸收系数a(355)与a_(ph)(440)存在极显著正线性相关,表明浮游植物的新陈代谢及其降解产物是夏季周村水库CDOM的潜在来源.综上,通过对夏季周村水库水体CDOM的研究,丰富了关于水源水体CDOM的调查资料,可为日后水库的管理提供技术支撑.     

南北地震带上倾斜潮汐因子的空间分布特征研究

从理论上讲,纬度对潮汐因子造成影响的改正值极小,一般不予考虑.通过对位于中国南北地震带上18个地倾斜观测台站的地倾斜潮汐观测资料进行调和分析,研究倾斜固体潮潮汐振幅较大的两个潮波O1波和M2波NS、EW分量的空间分布特征,结果发现γO1、γM2的空间分布与该带特殊的地质构造背景之间有一定的相互关系.并对可能存在的其他原因如海潮负荷效应、仪器本身的频率响应差异以及局部负荷效应影响等,进行了初步探讨.     

洱海沉积物有色可溶性有机物(CDOM)三维荧光空间分布特性及指示意义

采用荧光光谱区域体积积分法定量研究洱海沉积物有色可溶性有机物（CDOM）三维荧光空间分布特性,结果表明,洱海沉积物CDOM中类腐殖酸组分占比最高（44.5%~74.2%）,其次为溶解性微生物代谢产物（10.7%~20.4%）和类富里酸物质（8.19%~19.7%）,而类蛋白组分占比最低,类腐殖酸占比与H/C和N/C均呈显著负相关;南部湖心平台区域沉积物类富里酸和类蛋白组分占比较高,其CDOM自生源占比较高;北部水生植物分布区溶解性微生物代谢产物占比较高,CDOM陆源性较强;中部深水区及南北湖湾区域类腐殖酸占比较高,随水深增加沉积物CDOM自生源特征增强.随沉积物深度增加类腐殖酸和溶解性微生物代谢产物占比呈下降趋势,类富里酸占比呈上升趋势,CDOM自生源特征增强,脂肪化程度增高.随湖泊富营养化程度增加沉积物CDOM受微生物代谢产物影响增强,陆源性增加,而自生源性降低,湖泊沉积物CDOM具有富营养化指示意义.     

云南地区中强地震长期平静被打破后首发强震空间分布特征

1 研究背景 2021年5月21日漾濞MS 6.4地震的发生,打破了云南地区5级地震368天的平静和6级地震6.6年的平静.此次地震平静被打破后,相继于6月10日、6月12日发生双柏5.1级和盈江5.0级地震,云南地区中强地震呈连发态势.云南地区中强地震连发研究结果(钱晓东等,2007)表明,在1/3连发震例中均有6级...     

Evaluating the spatial distribution of water balance in a small watershed,Pennsylvania

A conceptual water‐balance model was modified from a point application to be distributed for evaluating the spatial distribution of watershed water balance based on daily precipitation, temperature and other hydrological parameters. The model was calibrated by comparing simulated daily variation in soil moisture with field observed data and results of another model that simulates the vertical soil moisture flow by numerically solving Richards' equation. The impacts of soil and land use on the hydrological components of the water balance, such as evapotranspiration, soil moisture deficit, runoff and subsurface drainage, were evaluated with the calibrated model in this study. Given the same meteorological conditions and land use, the soil moisture deficit, evapotranspiration and surface runoff increase, and subsurface drainage decreases, as the available water capacity of soil increases. Among various land uses, alfalfa produced high soil moisture deficit and evapotranspiration and lower surface runoff and subsurface drainage, whereas soybeans produced an opposite trend. The simulated distribution of various hydrological components shows the combined effect of soil and land use. Simulated hydrological components compare well with observed data. The study demonstrated that the distributed water balance approach is efficient and has advantages over the use of single average value of hydrological variables and the application at a single point in the traditional practice. Copyright © 2000 John Wiley & Sons, Ltd.     

Sediment delivery processes and the spatial distribution of caesium-137 in a small Sicilian basin

The sediment delivery processes occurring in a small Sicilian basin are modelled using the spatially distributed SEDD model recently proposed by Ferro and Minacapilli. The model is applied by using soil data (grain-size distribution, organic matter content, etc.) of 129 samples uniformly distributed over the study area and compiling the available information (topographic map, soil data, etc.) into a Geographical Information System. Finally, the predictive capability of the distributed sediment delivery approach is tested experimentally using the caesium-137 measurement technique. The comparison between calculated sediment yield and the corresponding measured caesium-137 loss is used to validate the SEDD model at the scale of both the single morphological unit and the entire basin. © 1998 John Wiley & Sons, Ltd.