Groundwater Exploration and Assessment in Rural Communities of Yobe State, Northern Nigeria

The provision of adequate water supply and sanitation to the rapidly growing urban populations is increasingly becoming a problem for governments throughout the world. The continuing expansion of the numbers of people in cities who need water and sanitation services form a continuous pressure to either invest in additional production capacity or to stretch the available supplies to serve more people. Due to rapid increase in population growth in the Yobe State north of Nigeria, there is a shortage in the water supply to Damaturu city the capital of the state and surrounding villages. At the present the total water supply is about 10,000 m³/day abstracted form the shallow alluvial groundwater aquifer using 29 production wells. Due to the expected increase in water demand and the limited potentiality of shallow aquifer system, other deep aquifers were explored and investigated to evaluate their potentiality for future water demand. Vertical Electrical Sounding Method was used for the geophysical survey of the study area. Groundwater flow model was developed and calibrated against the historical information. Three wellfields were designed to provide Damaturu city and surrounding villages with the required water. The calibrated model has been used to evaluate the aquifer potentiality and the effect of future withdrawals on the deep aquifer system. It was found that the aquifer system within the study area consists of two main layers. The upper layer is the Chad formation comprises an alluvial sand and gravel with intercalation of thin sility clay layers. The second layer is Keri-Keri formation consists of sandstone formation which is not explored before. During this study the Kerri-Kerri aquifer system was investigated as an alternative source for groundwater for future demand. The study presents an integrated groundwater resources management strategy for present and future water supply for rural communities.     

Engineering geological and geophysical investigation of the reclaimed Lekki Peninsula, Lagos, South West Nigeria

 It was hoped to develop an area of reclaimed land on the Lekki Peninsula of Lagos State. An investigation was therefore carried out in order to establish the subsurface geological/geo-electrical sequence; to identify the sand columns and determine their thickness and prepare a map of the geomorphological features of the original, pre-fill terrain. Vertical electrical resistivity soundings (VES) and penetrometer tests were carried out in a sand filled segment of the Lekki Peninsula. The information obtained showed a good correlation between the geomorphological features as interpreted from the aerial photographs and those identified from maps derived from the VES/penetrometer results. Received: 28 August 1998 · Accepted: 18 January 1999     

JaTS: a fully portable seismic tomography software based on Fresnel wavepaths and a probabilistic reconstruction approach

JaTS, a Java 2D seismic tomography software, is presented. It implements original algorithms achieving optimal accuracy with reasonable computing costs. A second-order Fast Marching Method (FMM) is used for solving the eikonal equation, therefore enabling a fast and robust computation of seismic traveltimes between sources and receivers. The wavepaths are materialized by Fresnel volumes rather than by conventional rays. This approach accounts for complex velocity models and has the advantage of considering the effects of the wave frequency in the velocity model resolution. The model is computed by a Simultaneous Iterative Reconstruction Technique (SIRT) which has been reformulated to integrate Fresnel wavepaths by using a probabilistic approach. In addition, various utilities are implemented, such as a tapering filter, used to decrease artifact effects occurring in the vicinity of the sources and receivers. The software also offers the possibility of reconstructing the velocity field on a grid larger than the one used for the wave propagation computation. This contributes to stabilize the estimated values. All of the seismic processing tools have been integrated with a user-friendly graphical interface. JaTS represents a tightly integrated tool suite that supports the entire process of importing the SG2 field records, first-break picking, forward modeling and velocity-field computing across multiple platforms.     

A review of the New Geophysics：a new understanding of pre-fracturing deformation in the crack-critical crust with implications for hydrocarbon production

The multi-factor recombination and processes superimposition model for hydrocarbon accumulation is put forward in view of the hydrocarbon geological characteristics of multiple episodes of structural evolution, multiple sets of source-reservoir-seal assemblage, multiple cycles of hydrocarbon accumulation and multiple episodes of readjustment and reconstruction in the complex superimposed basins in China. It is a system including theories and methods that can help to predict favorable exploration regions. According to this model, the basic discipline for hydrocarbon generation, evolution and distribution in the superimposed basins can be summarized in multi-factor recombination, processes superimposition, multiple stages of oil filling and latest stage preservation. With the Silurian of the Tarim basin as an example, based on the reconstruction of the evolution history of the four factors （paleo-anticline, source rock, regional cap rock and kinematic equilibrium belt） controlling hydrocarbon accumulation, this model was adopted to predict favorable hydrocarbon accumulation areas and favorable exploration regions following structural destruction in three stages of oil filling, to provide guidance for further exploration ofoil and gas in the Silurian of the Tarim basin.     

地球物理与中国的可持续发展

在20世纪中国的发展历程中,地球物理在资源探查、环境保护和减轻自然灾害服务等诸多方面发挥了举足轻重的作用。21世纪,中国走可持续发展之路已成为必然选择。随着可持续发展思想及内涵的逐渐丰富,地球物理必将为中国的可持续发展起到更大作用。     

瑞利波超前探技术在瓦斯突出预测中的应用

介绍了瑞利波探测法在阳泉煤矿进行瓦斯突出预测预报中的应用,通过对现场采集数据的处理、总结分析,以及开采验证,认为瑞利波超前探测技术可以有效发现瓦斯聚集区,对煤矿安全生产具有指导作用.     

新疆那拉提成矿带铜金矿找矿前景分析

通过对那拉提成矿带野外实地资料综合对比研究,阐述了该区区域地质特征、区域地球物理特征、区域地球化学特征和与邻区的关系,得出那拉提成矿带与该构造带上已知铜、金矿床具有非常相似的大地构造环境、构造演化和掘铜（金）建造条件,认为那拉提成矿带仍具有进一步发掘铜（金）矿床的较大潜力。     

Groundwater interaction in the coastal environment: hydrochemical,electrical and seismic approaches

The heterogeneous Plio-Quaternary coastal aquifer of the Mamora Basin is the most significant reservoir of Morocco. It is composed of sandstones, conglomerates, limestones and more or less argillaceous sands. The increase in the requirements for water in this area requires further information on the relations between the geometry of the aquifer and the salinity of the water. A hydrochemical analysis was undertaken and highlighted three zones of high mineralization. A geophysical approach allowed the determination of the principal aquifer levels, the localization of the various types of water (fresh, brackish and salt) and the geometry of the aquifer base. The results obtained by these two approaches provide a better image of the phenomena governing the groundwater flows and their interactions      

A FORTRAN IV program for interpolating irregularly spaced data using the difference equations for minimum curvature

The interpolation of potential field data is a common problem in geophysics. It is accomplished each time a contour map or profile is drawn. These operations can be difficult and subjective if the data points are irregularly spaced. The method described here produces a “numerical surface”, or grid of values, that approaches the smoothest surface passing through the control points. Such a grid can be contoured automatically by standard routines, producing acceptable results. Alternatively, sections can be drawn through the surface on any azimuth—a more satisfactory procedure for constructing profiles than projecting the data points onto straight lines.