Spatial Distribution of Return Period in China Based on b-value Obtained by Using a New Method

ConsldeMle research has been po山med on the卜quency－删哪tude relation since仇tenbe恰Rlchterproposed the relationLog N＝a＋bM ()WhereM Is the nunlmumm昭nltude In the data sam卫ie for a celtaln region,N Is the cumulativeMquency ofevents In a celtaln time Interval ithm用刃ltude h锣rthan or equal to M,and a and bfilE COllstsfitS．Experimental researches on the G－R relation coMmed that the b decreases ith the de耶e ofbeteing6nelty and density Of the c。ohs In the。dlum(Mogi,1967)．The …     

Precursors Revealed by the Multifractal Dimension Around Ordos Block,North China

Seismicity around the Ordos Block in the northern part of China has been studied by the multifractal dimensions with the help of complete data set of earthquakes with M≥2.5 since 1977.Seven regions around this block have been examined whiere the eight large earthquakes with M≥6.0 for the complete data occurred.In oirder to display the temporal distribution of the correlation dimension D2,a moving window of fixed number of events is used in every of the seven regions.Except for two regions with less seismic activity,all other five regions have obviously been found to display sudden changes of the correlation dimension for the events with M≥4.5.     

Variation of fluxes of water vapor, sensible heat and carbon dioxide above winter wheat and maize canopies

Surface energy fluxes were measured using Bowen-Ratio Energy Balance technique (BREB) and eddy correlation system at Luancheng of Hebei Province, on the North China Plain from 1999 to 2001. Average diurnal variation of surface energy fluxes and CO₂ flux for maize showed the inverse “U” type. The average peak fluxes did not appear at noon, but after noon. The average peak CO₂ flux was about 1.65 mg m^-2 s^-1. Crop water use efficiency (WUE) increased quickly in the morning, stabilized after 10:00 and decreased quickly after 15:00 with no evident peak value. The ratio of latent heat flux (λE) to net solar radiation (R_n) was always higher than 70% during winter wheat and maize seasons. The seasonal average ratio of sensible heat flux (H) divided byR _n stayed at about 15% above the field surface; the seasonal average ratio of conductive heat flux (G) divided by R_n varied between 5% and 13%, and the averageG/R> _n from the wheat canopy was evidently higher than that from the maize canopy. The evaporative fraction (EF) is correlated to the Bowen ratio in a reverse function.EF for winter wheat increased quickly during that revival stage, after the stage, it gradually stabilized to 1.0, and fluctuated around 1.0. EF for maize also fluctuated around 1.0 before the later grain filling stage, and decreased after that stage.     

The Geoscience Transect from Xiangshui,Jiangsu Province to Mandal,Inner Mongolia

The Xiangshui to Mandal geoscience transect, which has a total length of 1,200 km, extends diagonally,from SE to NW, across the Sino-Korean plate and its ancient continental margin, passing through nine tectonicunits: the Subei-Jiaonan terrane, West Shandong block, North China rift basin, Taihang-Wutai block, Ordosblock, Hu-Bao (Hohhot-Baotou) Basin, Yinshan block and Inner Mongolian fold system. The graphic display of the transect is compiled according to the Guidelines for the Global GeoscienceTransect (GGT) Project on the basis of an integrated study of all available geological, geochemical andgeophysical data, thus bringing light to the process of cratonization of the Sino-Korean plate and its relation-ship with the transitional zone of the ancient continental margin, and the features of intraplate structures pro-duced by subsequent tectonic modifications and intraplate dynamics.     

华北山区坡地产流规律试验研究

人工模拟降雨是研究坡地产流规律的一种有效手段。在华北石质山区东台沟流域的5m×10m的坡面径流小区中,进行了13场不同雨强和历时的人工模拟降雨试验,并同步监测了降雨、地表径流、壤中流、风化带出流和土壤含水量。结果表明,各层出流过程均呈现起涨与回落迅速的特点;相比较而言,地表径流和壤中流的退水很快,而风化带出流的退水则相对缓慢。地表径流量是研究小区内总径流的主要组成部分,其占了总径流量的60%以上,在大雨强下甚至能超过90%。径流系数主要受雨强、降雨量、土壤前期含水量的影响,它们的多元线性回归关系式为琢=0.002P 0.182i 4.88Wa-0.821。地表径流、壤中流、风化带的出流滞时与降雨强度均符合幂函数关系。可将退水常数分为2层,计算得到地表径流退水常数为0.75,壤中流和基岩风化带出流的退水常数为0.94;研究区主要以超渗产流方式为主,可以用Horton模型来描述,在不同雨强下均监测到了约0.10mm/min的深层渗漏,该值可以认为是该区的稳定入渗率。     

极移与重力异常变化的关系

通过对重力的分析,就极移的自由项(常称为Chandle项)影响做了理论分析,并在此基础上做了进一步计算.表明,Chandle摆动对太原地区的重力影响幅度约为6×10~(-8)m/s~2,且这一影响呈周期变化.     

变形模型辨识与参数估计

本文从变形分析的目的出发,分多输入单输出(MISO)和多输入多输出(MIMO)两种类型,详细地讨论了变形模型的自动辨识与参数估计。通过分析和计算,得到了一种可联合各种观测值、精度高以及随着变形规律的改变而不断修正模型的分析方法,并编制了相应的通用程序。     

数字土地利用现状图的制图概括

数字土地利用现状图是当前进行土地利用研究的基础数据之一 ,在土地利用现状图绘制过程中将始终涉及制图概括的问题 ,本文在结合苏州工业园区农村地域土地利用现状调查的基础上 ,探讨了土地利用专题图的制图概括理论和技术方法。