长江三峡大宁河流域3000年来的环境演变与人类活动

长江三峡大宁河流域张家湾东周-汉代古遗址的孢粉学和沉积学等分析结果表明3000年来该区环境演变与人类活动的互动影响，连续的孢粉和粒度记录证实，该区古人类活动初期处于暖湿的气候，东周-汉代时期转变为温凉略干的温带气候，东周-汉代后，该区经历了一次规模较大的大宁河洪水泛滥期，导致汉代文化层中断。此后不久，由于人类活动剧烈，自然植被严重破坏，水土流失比较严重，山洪灾害频繁，导致汉代之后该区没有连续的文化层堆积，而由于人类活动剧烈，自然植被严重破坏，水土流失比较严重，山洪灾害频繁，导致汉代之后该区没有连续的文化层堆积，而由于短暂洪水暴发引起大面积坡面片流，导致坡积物的大量堆积，汉代之后该区频繁的兴涝灾害和山洪灾害体现了人地关系的复杂性。     

Investigation of a landslide in the new site of Badong County by integrated geophysical survey

An integrated geophysical survey which combines vertical seismic profile method, shallow reflection seismic method, electric sounding, soil temperature measurement and radioactive gas measurement was used to investigate Zhaoshuling landslide in the new site of Badong County and to assess the stability of the landslide. By rational use of these methods together with borehole geological profile and other geological information, the spatial distribution of the landslide body, the formations and structures within and without the landslide body were determined and the stability of the landslide was also assessed, thus making great contribution to the successful and rational investigation and assessment of the landslide.     

GRASS数据结构分析

详细分析了ＧＲＡＳＳ的三种数据结构，为设计ＧＲＡＳＳ与其它系统数据格式转换接口提供了基础。     

Seeing Conditions at Sutherland. Results of the 1992/93 seeing campaign

In order to decide whether the seeing conditions at SAAO/Sutherland justify the erection of a 3.5 m telescope and also to compare Sutherland with the Gamsberg/Namibia site, a seeing campaign covering 15 months has been carried out. For direct comparison with the results of the seeing campaign at Gamsberg twenty years before the same QUESTAR telescope was employed. The seeing is determined by the scattering of the star-trail exposed on a film in the focal plane of the telescope. The campaign commenced in February 1992. Up to May 1993, data for 204 nights, that is 47.3% of the total number of nights, were collected. Due to wind speeds above 30 km h^-1, 25 out of the 204 nights were not considered in the final reduction. The useful 179 nights are evenly distributed over the campaign period. The median seeing value for the whole period is = 0.52. There are differences during the year: the best season gives = 0.42, the worst = 0.67. Each night was divided into three intervals, although data for each of the three intervals were not always available. Generally, there is an improvement in the seeing during the course of a night. The results are compared to the seeing values of Gamsberg/Namibia and ESO/La Silla.     

地裂缝场地施工降水对地表沉降和地层应力的影响研究

地裂缝是西安市典型的城市地质灾害，地下水位的变化是诱发地裂缝活动的重要因素。以西安地铁六号线暗挖段施工降水为研究背景，基于有限元数值模拟计算，分析了地裂缝场地施工降水引起的地表沉降规律和地层应力变化特征。计算结果表明:当地下水位下降时，地表沉降量上盘大于下盘，地裂缝带两侧地表存在差异沉降的现象，最大差异沉降量与地下水位下降深度近似呈直线关系；不同位置处地表的横向沉降呈现出"Z"形的变化特征，差异沉降区随地裂缝位置的变动而变化，且差异沉降量与横向地表位置近似呈二次函数曲线关系；地层竖向应力随着地下水位下降而增大，地裂缝位置处地层应力存在突变现象，上下盘应力影响区与地层深度近似呈三次函数曲线关系；基于分层总和法计算了地下水位下降时地表沉降量的解析解，并与数值模拟结果进行对比，发现两种方法计算结果基本一致，得到了计算地表最大沉降量的经验公式。研究结果可为地裂缝场地地铁隧道及其他地下工程安全施工提供科学指导。      

Multi‐variable relations for soil effects on seismic ground motion

Soil effects on peak ground acceleration, velocity and elastic response spectra (5% damping) are expressed by simple approximate relations in terms of five key parameters: (a) the fundamental vibration period of the non‐linear soil, T_S, (b) the period of a bedrock site of equal thickness, T_b, (c) the predominant excitation period, Te, (d) the peak seismic acceleration at outcropping bedrock, a, and (e) the number of significant excitation cycles, n. Furthermore, another relation is proposed for the estimation of T_S in terms of the soil thickness H, the average shear wave velocity of the soil V?_S,o and a. The aforementioned parameters were first identified through a simplified analytical simulation of the site excitation. The multivariable approximate relations were then formulated via a statistical analysis of relevant data from more than 700 one‐dimensional equivalent‐linear seismic ground response analyses, for actual seismic excitations and natural soil conditions. Use of these relations to back‐calculate the numerical results in the database gives an estimate of their error margin, which is found to be relatively small and unbiased. The proposed relations are also independently verified through a detailed comparison with strong motion recordings from seven well‐documented case studies: (a) two sites in the San Fernando valley during the Northridge earthquake, and (b) five different seismic events recorded at the SMART‐1 accelerometer array in Taiwan. It is deduced that the accuracy of the relations is comparable to that of the equivalent‐linear method. Hence, they can be readily used as a quick alternative for routine applications, as well as for spreadsheet computations (e.g. GIS‐aided seismic microzonation studies) where numerical methods are cumbersome to implement. Copyright © 2003 John Wiley & Sons, Ltd.     

整地对栗钙土物理性质和杨树人工林苗木生长的影响

采用定位观测的方法,系统研究了不同整地规格对栗钙土的物理性质和杨树人工林苗木生长的影响.试验结果表明经整地后土壤物理性质总体上得到改善.但不同规格的整地对栗钙土土壤物理性质的改善程度和对杨树人工林苗木生长的促进作用是不同的.在当前的经济发展水平下,综合考虑整地后土壤物理性质的变化和苗木生长的实际效果,在栗钙土上应采用B规格的整地.     

A Study of Seismicity and Earthquake Hazard at the Proposed Kalabsha Dam Site,Aswan, Egypt

High and Aswan Dams Authority (HADA) proposed a plan aiming at constructing a rockfill dam in the Kalabsha area, about 60 km south of Aswan High Dam. The aim of this dam is to restrain the overflow of water to the Kalabsha Valley for keeping one billion cubic meters from being lost due to seepage and evaporation. The safety of dams during earthquakes is extremely important because failure of such a structure may have disastrous consequences on life and property. Therefore, different factors were considered as part of a site assessment. Five seismic source zones, close enough to the site to give rise to potentially damaging earthquake ground motions, were identified. Seven active faults that have the potential for producing significant earthquakes and that pass through or near the dam site were also identified. The earthquake loading represented by ground motions at the site was evaluated. Probabilistic seismic hazard procedures were used for assessing the earthquake loading at six individual sites using Area-and Line-Source Models (ASM & LSM). The ASM is based on current observed seismicity, whereas the LSM is based on geological slip rates. The output represents the expected acceleration amplitude with 90 percent probability of not being exceeded in exposure times of 20, 50, and 100 years. The results from the two models appear to be different, the expected ground motions from ASM were twice as high as expected from LSM. This difference is due to the load of the Aswan reservoir (Nasser Lake) triggering earthquakes on those parts of the faults that lie under the lake at Kalabsha area. The hazard at the selected sites is given by the hazard curve that is represented by the relationship between the peak ground acceleration and its annual exceedance probability. By comparing the curves for the six individual sites for the same source model, it can be concluded that the potential ground acceleration level for all the sites is almost the same. Considering the mean results from the two models, the annual exceedance probability of the expected ground acceleration from ASM is approximately ten times higher than the annual exceedance probability from LSM.Since ASM is based on current seismicity, it is more appropriate forrepresenting the actual hazard for the dam site.     

四川三星堆遗址多源遥感研究

运用遥感考古技术，通过对卫星和航空遥感图像的处理、解译及相互映证，对三星堆的古河道、古城池进行了全面调查，发现了马牧河由南往北的多期古河道及一些未曾被发现的古城遗址，得出三星堆古城池分为内外二层的结论。