ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01398.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTThe well known quantities, delay and intercept times, can be made fully useful in the interpretation of multilayer refraction problems dealing with small undulating dips.The identification of the individual refractors is made by the use of reciprocal and intercept times and by applying an additional and useful relationship, namely that the delay time profile between two shot‐points should match the half‐intercept time profile when calculated using the true velocity of the refractor.With a suitable arrangement of shot‐points this relation permits us to obtain the true horizontal velocity of a refractor from one direction of shooting only.Presentation of the refraction results in the form of time sections, similar to those used in reflection surveys, is often desirable. These sections can be converted easily into depth sections, once the overburden velocities are defined.The use of the method is limited not only by the dip, but also by the depth of the refractor. Deep refractors can be, however, worked out by this method, by reducing a multilayer problem to that of two layers, using again the delay

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01399.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTA set of refraction line arrival times can be readily converted into a set of delay‐times providing the refractor velocity is known. If we then subtract the delay‐time at the shot‐point end, we arrive at a set of delay‐times representing the refractor depths at the receiving end. This paper is concerned with the conversion of such a set of delay‐times into a profile of the refractor.The method is semi‐graphical and very easy to apply. For each geophone station an arc of a circle is constructed, such that the envelope of the series of arcs represents the surface of the refractor. While the method is not quite exact, especially when the dips are large, it is of particular value in allowing for the effects of varying dips upon the offset distance. The method treats the overburden above the refractor as if it were of unifo

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01400.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTThe term shallow refraction, as used in this paper, refers to investigations confined to the superficial layer of rocks, composed primarily of unconsolidated material. To define the scope of the discussion it will be assumed that the term shallow refraction applies to work of which the lower limit is approximately 300 feet and the upper of the order of a few feet. The consideration of the small magnitude of quantities measured (distances and times) determines the perspective of the problems involved, since difficulties encountered in the interpretation, although equally disturbing whether in deep or shallow work, will cause a greater percentage of error in the latter case. The purpose of this paper is to discuss and illustrate these problems. The factors considered include the location of the geophone spread in relation to the topography of the site, influence of the ground conditions in the vicinity of geophones on recorded times, consideration of the shallow uphole shots and problems arising from the repeated use of the same shothole. The rapid variation in the vertical velocity of the overburden and errors due to it are discussed together with the effects of a non homogeneous unconsolidated material and velocity reversal. The effects of the ill‐defined solid rock surface are also considered. It appears that as the depth of investigations becomes shallower, the limits of the practical capabilities of the method are approached, because the differences between the theoretical assumptions and the actual conditions become more pronounce

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01401.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTThe parameters which characterize an explosive are derived from laboratory tests and none is directly usable for seismic purposes. Another one, derived from field experiments is proposed in this paper. It allows the comparison of two different explosives. The test must be conducted with care. Precautions concerning the equipment and the shot point detailed. The first available results suggest that the new parameter does not depend on the size of the charge nor on the shooting conditions, though the experimental data are not numerous enough to allow a general statement. It is shown how a coefficient of seismic efficiency can be used for selecting an explosive; and considerable amounts of money can be saved by the best choice. More studies on the generation of artificial seismic waves would be highly profitable.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01402.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

AbstractExperiments carried out using charges of up to 200 lbs. at a distance of about 20,000 ft. from the geophones suggest that the amplitude of the refracted wave ground motion is roughly proportional to the weight of charge. Simple energy considerations lead one to expect a relation of a form in which velocity amplitude is proportional to W.An explanation of the observed relation may be based on a theory according to which the efficiency of the explosion increases with the source size, that is the distance from the source at which the pressure wave of the explosion ceases to cause permanent deformation of the surrounding medium.The above theory was further confirmed by measurements of the radius of the cavity produced by explosions of charges of different size in clay. Also, explosion of charges in artificial water‐filled cavities were found to give seismic wave amplitudes three or four times greater than those produced by the same charge in a narrow hole. It is possible that these observations explain in part why the charges required in marine refraction experiments are very much smaller than those needed in refraction work on land, but additional reasons for this difference are also discusse

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01403.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

ABSTRACTSThe equation for the deformation of the homogeneous electrical field caused by a long inclined thin plate, is given. By means of this equation a diagram is designed for the direct depth determination of the upper and the lower edge and for the inclination of the plate. The equation and the diagram are proved by small scale model measurements and applied in field exploration.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01404.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY

摘要:

Book review in this article“Regional Gravity Investigations on the Eastern and Central Commonwealth of Australia”, by C. E. Marshall and H. Narain; University of Sidney, Department of Geology and Geophysics, Memoir 1954/2, October 1st, 1954, 101

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1956.tb01405.x

出版商:Blackwell Publishing Ltd    

年代:1956

数据来源: WILEY