ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02011.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractA method is described in which various gravity maps (regional, residual, first and second derivatives, upward and downward continuation, etc….) may be quickly constructed, without manual plotting and visual interpolation, which are often a source of error. The coordinates and theg‐values (x, yandg) of the field stations are introduced into the electronic computer on perforated cards. The computations are carried out by means of a hexagonal network. The computed values and their respective positions on the network are plotted directly on a sheet of paper by the electronic computer. The map is obtained by assembling these sheets and contour

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02012.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractDuring a regional gravity survey in Central Ireland a series of intense Bougueranomalies of very limited extent was encountered. They are all negative, the largest being ‐6.4 mgal and each covers an area of the order of one square km. Gradients up to 9 mgal/km have been measured. The country rock is Carboniferous Limestone, density 2.7 g/cm3, but outcrops are scarce particularly in the region of the anomalies and the surface is in general covered by glacial gravels, drift and bog. Most of the anomalies lie on an approximate straight line running northeast‐southwest for a distance of 115 km.An analysis indicates that the cause of each anomaly is a mass with a negative density contrast of at least 0.3 g/cm3, probably 0.5 g/cm3, and so positioned that its top is not deeper than 0.5 km from the surface.As no rock with a density less than 2.5 g/cm3is known to exist in the neighbourhood, it is postulated that the cause of the anomalies lies in a sequence of solution cavities in the limestone now filled with water or lightly packed rock debris and gravel aligned along a large fault. No such system has been known or suspected in Ireland.The presence of such large faults would have serious consequences on the possibility of oil accumulation while the infillings of the cavities might have economic importa

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02013.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractIn gravimetry the observer cannot exert any influence on the quantity he wants to measure, as he can in seismic exploration. This might easily tempt him to ascribe failures of the gravimetric method to natural causes outside his control.However, he keeps control of a sufficient number of factors to allow him to play a major part in a lot of cases. In this paper the conditions that govern the use of gravimetry are analyzed and subdivided into three classes, viz. natural, technical and economic conditions.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02014.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractIn many situations, because of the great influence of a surface layer on apparent resistivity values, the interpretation of electrical soundings may be very indeterminate, according to the “equivalence principle”.For these situations, an arrangement which includes an underground electrode has been proposed. With this method, the interpretative indeterminatecy may be often eliminated, as may be seen from the diagrams calculated for some typical situati

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02015.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractTables are presented giving the two reflection coefficients and the two transmission coefficients resulting from the incidence of a plane longitudinal wave upon a plane boundary between two elastic media, for hundred different combinations of the elastic parameters and the density of the two media. The effect of these parameters upon the change of the reflection or transmission coefficient with the angle of incidence is discussed. For incidence beyond the critical angle the phase shift between the incident wave and the reflected or transmitted wave is also given.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02016.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

AbstractThere are various methods of measuring the porosity of rocks. The direct methods are based on the definition of the porosity ratio. The indirect procedures, which have often been adopted purely for economic reasons require interpretation methods that relate certain measured quantities to the porosity ratio.In the present article, the relationship between acoustic velocity and porosity will be examined. The interpretation method most commonly in use today is based on an approximative equation developed by Wyllie, Gregory and Gardner. This equation obtains the travel time of acoustic waves in a porous medium saturated with liquid by linear interpolation with respect to the porositynbetween the travel timeT0in the compact medium (n= o) and the travel timeT1in the pure liquid (n= 1).As observed values of the travel timeTdiffer from those that follow from this linear equation, it seems obvious to attempt a higher degree of approximation, e.g. by means of a polynomial of the third degree.BesidesT0andT1other quantities are needed in order to obtain the coefficients of such a polynomial. These quantities must bear some relation to the physical constants of the rock. Only in the neighbourhood ofn= o andn= 1 is it possible to make general statements concerning the behaviour of rocks and, in particular of the skeleton. Therefore, in the pointsn= o andn= i not only the values of the approximative functionT=f(n) itself are given, but also those of its derivative with respect ton.The values of these derivatives ∂T/∂/Tn=0and ∂T/∂/n‐1depend on the properties of the material filling the pores and on data concerning the structure of the skeleton and the stresses in it. The considerations leading to a mathematical formulation of this dependence are dealt with in this article.The elastic constants of the skeleton were developed in Taylor series inn,that, for skeletons with low porosity were truncated after the linear term. The coefficients ofnare functions of the constants of the material of the skeleton, the shape of the pores and the stresses in the skeleton. These functions were approximately computed for two limiting cases. For a more general application, it is useful to assume that these coefficients are the same for both Young's modulus and Poisson's ratio and then obtain the functional relation between the coefficient and the residual pressure from measurements performed in the laboratory with various kinds of rock. When this relation is established from such laboratory experiments, the cubic interpolation method can be applied.Whereas the linear interpolation method, as it has been in use up to now, presents a relation between porosity and acoustic velocity only, the cubic interpolation method makes it possible to determine the influence of pressure and the state of cementation of the rocks. Comparison with data obtained from direct measurements shows good

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02017.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY

摘要:

Books reviewed in this article:AlfredWegener, Die Entstehung der Kontinente und Ozeane (Origin of Continents and Oceans)

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1962.tb02018.x

出版商:Blackwell Publishing Ltd    

年代:1962

数据来源: WILEY