ABSENCE OF PREFERENTIAL FLOW IN THE PERCOLATING WATERS OF A CONIFEROUS FOREST SOIL

Evidence for the functioning of macropores and the presence of preferential flow in forest soils is equivocal. This is partly because many workers use only one diagnostic technique to indicate whether or not macropore flow occurs. In this paper three lines of evidence are used to suggest that preferential flow does not occur in the percolating waters of a coniferous forest soil under the range of hydrological conditions that prevail in the field. To simulate field conditions, realistic rainfall intensities were used in conservative solute transport experiments on four undisturbed soil columns. A method is described in which breakthrough data can be used to calculate the percentage of antecedent water displaced from a soil column during frontal-type breakthrough experiments. Calculations based on this method using the experimental data show that as little as five percent of the antecedent water was immobile. The simple form of the functional advection–dispersion equation, based on a single value for linear velocity and the dispersion coefficient was fitted to two of the breakthrough curves with reasonable accuracy, further suggesting that preferential flow did not occur in the experiments. Finally, soil moisture characteristic curves were determined for replicate soil samples from the forest soil. The operational water contents of the columns during the breakthrough experiments were compared with the soil moisture characteristics and it was found that pores exerting pressure heads greater than −0·5 kPa did not appear to contribute to flow through the columns, again suggesting an absence of preferential flow. © 1997 by John Wiley & Sons, Ltd.     

长江口海域断裂第四纪活动性特征

通过浅层人工地震勘察获知,长江口海域断裂构造发育,以北东、北西向断裂为主. 断裂以上新世－早更新世活动为主,最新活动可至中更新世. 断裂的最大断距一般为几十米,往上断距变小,中更新统底界的断距在12~13 m. 断裂平均垂直位移速率为10-3mm/a量级.     

1800年以来长江中下游地震区中强地震集丛分布和迁移特征

本文对长江中下游地震区1800年以来中强地震活动进行了分区讨论,总结其活动规律,类比外推对该区M≥5.5级地震活动趋势作了估计。     

长江三峡及其邻区断裂活动时间序列

本文将断裂活动的年龄值做为断裂活动的事件，通过长江三峡春邻区断层活动年龄的统计，建立了该区断裂活动的时间序列，将其同中国大陆地壳活动节变化相对化，讨论了两者之间的对应关系，获得若干新认识。