有槽沙坝海岸交叉波浪作用下裂流特征

研究叠加波浪场作用下的裂流特征,有助于全面深入开展海岸裂流的致灾机理及风险评估。为分析水动力和水底地形共同作用下形成的裂流特征,开展了交叉叠加波浪作用下有槽沙坝海岸的裂流流动特征试验,即同时考虑沿岸地形变化（存在沟槽）和交叉波浪共同作用所形成裂流。通过对裂流槽附近ADV（Acoustic Doppler Velocimetry）流速测量结果,分析叠加波浪场和裂流沟槽同时存在时所产生的裂流分布特征。裂流中心位置和宽度受裂流槽和波浪节点共同控制,裂流长度依赖于波高和海岸坡度。无槽情况裂流的驱动力主要是由波浪沿岸不均匀所产生的平均水面沿岸压力梯度,有槽情况裂流的驱动力由平均水面沿岸压力梯度和辐射应力沿岸梯度共同决定,二者量值相对大小依赖于波浪周期。     

Autoassociation, a new geological tool

Autoassociation is a computer method of comparing a sequence of nonnumeric elements, e.g., of rock types. The sequence is slid past a replicate of itself. At each position of overlap the number of matching elements is noted and statistics of goodness-of-match are computed. The method allows several properties to be coded at each position in the sequence. It also allows unknown, missing, or not applicable elements. Reverse matches also are performed, i.e., with the duplicate sequences reversed in direction. Autoassociation is used to detect partial repetitions in stratigraphic sequences and to compare regressive and transgressive phases of cyclothems.     

Rip current-related fatalities in India: a new predictive risk scale for forecasting rip currents

This study analyzes fatalities caused by rip currents in important locations along east and west coasts of India for the period 2000–2010. Results include the frequency of fatalities from rip currents, their cause, and their spatial distributions. Rip current fatalities are most common in the southeastern India, with a non-uniform spatial distribution. August and October are identified as most favorable for rip current generation. In India, rip current-related drowning is estimated as 39 per year during the last decade. East coast of India averaged 30–40 drownings, and west coast of India averaged 5–10 drownings per year. In coastal Andhra Pradesh, more than 350 people had been drowned due to rip currents and only 10 people were rescued. Visakhapatnam recorded highest drowning (293); R. K. beach is the most vulnerable potential rip current zones. From 2007 onward, rip current deaths increased at an alarming rate. The frequency of rip current drownings increased markedly during shore-normal wave incidence and mid-low tidal stages. A new empirical forecasting technique has been developed for prediction of rip current risk in India for the first time. FORTRAN-based software was developed to generate automatic rip current forecast report for any given location. The scale’s performance was tested with field data and by using different statistical methods. The new predictive scale is predicting rip current occurrences reasonably well.     

GEOCITY: a drill-hole database as a tool to assess geological hazard in Napoli urban area

The geological investigations of Napoli city, which represent the basic data source for geological hazard assessment, are characterized by the absence of well exposed and continuous outcrops, mainly due to the development of the urbanized area occurred in the last 50 years. In order to increase the set of available geological information, a database named GEOCITY has been realized on the base of 900 drill holes with stratigraphies reflecting the main drill-hole surveys performed during the last century. The true key moments in its construction were the homogenisation of different data and the identification of the geological formations. A detailed analysis of the drill-hole raw data allowed us to define the database entities, while the features of the deposits, the distribution of products and the reference drill holes were used to identify the geological formation. The analysis performed using the GEOCITY database made it possible to better assess volcanic hazard from Campi Flegrei and Somma-Vesuvio and the hazard related to alluvial phenomena that Napoli city is exposed to.     

Radon soil–gas as a geological mapping tool: case study from basement complex of Nigeria

In an effort to quantify the geogenic radon soil–gas potential and appraise the use of radon technique as a geological mapping tool in a crystalline basement rock terrain of Ile–Ife Nigeria, radon measurement concentration were made using a radon detector instrument (EDA RD-200) that measures radon isotopes by a scintillator cell coupled to a photomultiplier tube. The data were collected from soils derived from three different lithologic rock units. The observed values were then correlated with the geology of the area. Significant differences in the radon soil–gas concentrations among the three geologic units were observed. Granite gneiss has the highest concentration, followed by grey gneiss and mica schist in that order. The geometric mean (GM) concentration of radon-222 measured in soils directly overlying the three different rock types were 301.4 pCi/l for granite gneiss, 202.8 pCi/l for the grey gneiss, and 199.4 pCi/l for mica schist. Conversely, the average values for radon-220 averaged 1510.0, 815.4, and 733.0 pCi/l for granite gneiss, grey gneiss, and mica schist rocks, respectively. Statistical t test (α=0.05) results indicated that there was no significant difference in the geometric mean of radon soil–gas measured between low and medium potential zones. However, significant differences were found between the low and high radon potential zones, and between the medium and high zones. The low concentrations of radon soil–gas emission observed in this study is explained in terms of the seasonal variation due to thermal convection fluid movement, while the radon concentrations were found to be controlled by the lithology and geochemistry of the underlying bedrock.     

G23FM: a tool for meshing complex geological media

We present G23FM, a mesh generation tool for discretizing two- and three-dimensional complex fractured geological media. G23FM includes different techniques to generate finite element grids that maintain the geometric integrity of input surfaces, and geologic data and produce optimal triangular/tetrahedral grids for flow and transport simulations. G23FM generates grid for two-dimensional cross-sections, represents faults and fractures, for three-dimensional fractured media, and has the capability of including finer grids. Different examples are presented to illustrate some of the main features of G23FM.     

Geochemical soil surveys over cambrian and lower devonian formations in the belgian ardennes as a tool for geological mapping

A geochemical soil survey was made over outcropping Cambrian and Lower Devonian formations in the Belgian Ardennes. About 300 soil samples were collected in an area of 2.5 × 1.1 km².Analysis of rock samples from scarce, but stratigraphically well-known outcrops show that the Cambrian rocks are richer in copper than those of the Lower and Upper Gedinnian (Lower Devonian). The Upper Gedinnian rocks are more nickeliferous than the other horizons.In the well-drained soils, copper and lead distributions permit precise location of the boundary between Cambrian and Lower Gedinnian formations. The nickel distribution seems to be a good stratigraphic indicator for distinguishing Upper from Lower Gedinnian. Zinc distribution seems unrelated to underlying bedrock geology.Regression analysis confirms that the content of Cu, Pb and Ni is essentially a function of lithostratigraphy. However, the distribution of these elements is more influenced by pedological factors in the poorly drained soils.     

Radon as a geochemical exploration tool

Radon (Rn-222) is a unique element in the radioactive decay chain of U that has properties quite different from the other isotopes. Because Rn is radioactive, it can be detected at extremely low concentrations and this provides the basis for a very sensitive geochemical method. Radon has proven useful in exploring for not only U but for other associated elements. It has also been used successfully in exploring for geothermal sources, in earthquake prediction and in many other applications. With wider use of Rn as a geochemical tool in recent times has come a better understanding of the factors influencing its release, movement and detection. Studies of Rn emanation from a wide variety of U- and Ra-containing minerals have shown the effects of water content and other chemical and physical factors on the emanation rates. Published results from field research on Rn movement and experience with Rn as an exploration tool for uranium exploration have resulted in new data about the movement of Rn and its precursors in typical field situations. A number of new techniques for making integrated Rn measurements have been developed, and some appear to have some distinct advantages over the older grab sampling methods. This paper will discuss some of the more recent developments of Rn as a geochemical exploration tool and present new data on the numerous applications now utilizing Rn.     

Thermoluminescence as a tool in uranium exploration

Fundamental principles of thermoluminescence (TL) and the special role of TL in uranium exploration techniques are given in this paper with examples from Australia illustrating its application.TL can be used in two ways in uranium exploration. The first usage stems from the property of minerals capable of TL, to act as dosimeters accounting for charging of available traps by ionizing radiation. The second usage relates to ionizing radiation interfering with the crystal structure of the host mineral and thereby changing the capability for TL. Studies at the Beverley and Westmoreland uranium deposits utilize this second property.At Beverley a continuous drop in TL intensity is observed upon approaching the orebody with TL intensity at a minimum within the orebody. Recognition of ore type TL glow curves and sensitized (or marginal) TL glow curves within the area surrounding the orebody have enlarged the exploration target beyond that of the orebody and its associated radiometric halo.Traverses examining the variations in glow peak intensities, ratios and temperatures across the Junnagunna orebody at Westmoreland show that the glow peak intensity of the high-temperature glow peak increases, that of the low-temperature peak fluctuates though generally decreases, the high temperature/low-temperature glow peak ratio increases upon approaching the orebody. The high-temperature glow peak temperature is at a minimum within the orebody. Similar variations detected nearby may indicate further potential exploration sites.An example from an unmineralized area at Bremer River has indicated a lack of widespread radiation sensitization indicating the unsuitability of the area for economic uranium accumulation.     

Tsunamis as geological agents

When a tsunami wave series approaches and interacts with a coast, the consequent passage shorewards of great volumes of water and their invasion of the land, especially within bays and up river valleys, results in the disturbance of existing sediment and the removal seawards of land debris and coastal and shallow‐water marine sediments. Tsunami action builds up sequences of peculiar sediments in shallow water; it at least assists in the formation and maintenance of submarine canyons and, through them, produces turbidity currents of a particularly powerful kind. Tsunami action may explain many puzzling sedimentary phenomena, for example, sudden and drastic changes in near‐shore bathymetry; the formation of chaotic sediments such as some paraconglomerates and edgewise conglomerates. It offers solutions to problems arising from the study of turbiditic sequences, both modern and ancient.     

利用自组织特征映射神经网络和K-means聚类算法挖掘区域化探数据中的地质信息

区域化探数据包含丰富的地质信息,从区域化探数据中挖掘出这些信息,对于区域地质研究具有重要意义.笔者提出了一种利用自组织特征映射网络和K-means聚类算法挖掘区域化探数据中地质信息的方法,将标准化之后的元素含量数据作为模型输入值,通过自组织神经网络进行聚类,再通过K-means算法进行二次聚类,从聚类结果中分析其中包含的地质信息.以英格兰西南部某区水系沉积物区域化探数据为例,进行实例研究以检验该方法的实际效果.实例结果表明:①利用该方法得出的聚类结果图很好地响应了地质体的空间分布,可用于推断地质体的分布特征;②地质信息隐藏在每个聚类类型的地球化学特征之中,通过对这些特征进行分析和解释,可以挖掘出其中所包含的信息;③基于SOM网络和K-means聚类的区域化探数据挖掘方法是一种有效的地质信息获取方法,对于传统区域地质研究可以起到补充和增强的作用.     

Geomorphological models as a tool for environmental studies

Relief is understood as a fundamental component of the environmental system. The structure of geomorphodynamic processes and of the relief sphere as the main energy transformation surface is a determining factor for environmental conditions of both sites and areas. Modelling is the instrument of the applied and systems analytic approach to geomorphology. Geomorphological tools are appropriate means of determining, structuring, assessing and predicting the geoecological potential of the environment. This is demonstrated by quantitative and multivariate models to describe spatial patterns of the environment (fluvial network analysis) and to evaluate and present environmentally relevant geomorphological disposition (slope stability analysis).     

Gravity data as a tool for landfill study

This paper shows the potential of gravity data to map a buried landfill bottom topography. To this end, a gravity inversion method is presented for estimating the landfill’s bottom depths at discrete points assuming a decrease of the density contrast with depth according to a hyperbolic law. The method’s efficiency was tested using synthetic data from simulated waste landfills, producing estimated bottom topographies very close to the true ones. The method’s potentiality has been further evaluated in applying it to the gravity data from the abandoned Thomas Farm Landfill site, Indiana, USA, whose bottom topography is known. The estimated topography showed close agreement with the known Thomas Farm Landfill’s bottom topography.     

The geological occurrence of lithic material and stone tool production strategies

This study shows how the occurrence of lithic raw-materials articulate with hunter gatherer technological organization. Three archaeological data sets representing 109 different sites and one ethnographic data set from Australia are examined to show that lithic raw-material size, shape, quality, and availability play a major role in hunter gatherer decisions to make various kinds of stone tools. These characteristics of lithic material occurrence are used to help explain why expedient technologies such as bipolar tool production are sometimes used, and why formalized technologies such as bifacial production may be selected as a tool production strategy. Stone tool morphological variability and technological variability are shown to be directly related to the geological occurrence of stone tool raw materials. © 1994 John Wiley & Sons, Inc.     

Photogrammetry as a tool for detecting recent crustal movements

Progress in model building and in advanced exposure and evaluation methods is leading photogrammetry up into the field of precise point determination, up to now solved by classical geodetic triangulation and/or trilateration. In combination with the statistical test theory, photogrammetry can be used as a tool to detect recent crustal movements or deformations of man-made constructions, such as in coal mining or oil and gas exploitation.

For these reasons, this paper deals with model building for modern aerial triangulation with respect to hypothesis tests to detect point displacements greater than the measurement noise. An example from brown-coal mining demonstrates accuracies and the application of some statistical tests shows the efficiency of advanced aerial photogrammetry.     

Using the SyNaRMa system as a disaster management tool

Natural disasters have a considerable effect in human, infrastructure and economy. In the case of a, e.g., catastrophic earthquake that happens and affects the urban environment, immediate and efficient actions are required that ensure the minimization of the damage and loss of human lives. Local and national authorities should respond in order to meet the above objective. Nowadays, one of the most appropriate tools for this purpose is the web-based geographic information systems (GIS). Such a system, named SyNaRMa (Information System for Natural Risk Management in the Mediterranean), has been developed in the frame of an INTERREG IIIB ArchiMED project (2006?C2008). The present paper aims at addressing the role of the SyNaRMa system as a tool for facilitating disaster management. It is argued that the development of a web-based GIS can assist disaster management agencies to improve the quality of their decision making and increase efficiency and effectiveness in all levels of disaster management activities. This research is primarily based on the findings of the abovementioned project that resulted in the development of an information system for natural risk management in the Mediterranean that can facilitate sharing, access and usage of spatial data in disaster management, i.e., preparedness, response and recovery activities.     

Light rings in subarctic conifers as a dendrochronological tool

Light rings are characterized by one or a very few latewood-cell layers, an indication of shortened growing seasons, and are particularly frequent in black spruce (Picea mariana (Mill.) BSP) at the treeline in Québec. The construction of a light-ring chronology spanning the period AD 1398–1982 showed that the highest frequency (>25%) of light rings among 160 trees and krummholz occurred in 1593, 1620, 1634, 1784, 1816, 1817, 1853, 1969, and 1972. These diagnostic rings be a useful cross-dating tool for dendroecologists working with living and dead krummholz with a low-growth variability. About two-thirds of the 65 light-ring years coincide with years (or triads) of major volcanic eruptions. The climatic conditions (low temperature) occurring at the end of the growing season, in part induced by the climatic effect of volcanism, seem to initiate light rings.