摘要:

AbstractPrecision calibration tests carried out with a Worden gravimeter in environment conditions as varied as possible have led to the following conclusions. The secular variation curve of the calibration shows that the secular relative variation has been very appreciable in the first year of life of the instrument, precisely of 1.3 × 10−3in 13 months, while it has been practically zero in the second year. This must be ascribed to the fact that at the beginning of the operations the gravity‐meter had just arrived from the factory with its measuring body renewed.On the other side the effect of 24°C of temperature difference between two series of determinations reveals itself in a variation of 0.0022 of the value of the calibration, so that it can be established that the variation of the calibration is I‰ for each 10°C of temperature v

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01458.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractA series of repeat observations during a period of 5 years reveal a variation with time of the Worden gravimeter No. 142 small dial spring system. A possible change in the gravity difference concerned is ruled out. It is shown that the small dial scale factor has diminished by about 0.25 % within the last two years against about 0.5 % four to five years ago. The ratio of L.D. to S.D. has been analysed and the results obtained show confirmation of the change in the small dial system and prove a consistency in the large dial system.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01459.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractThe elastic impulse‐from an explosion is propagated through the earth as an expanding shell bounded by the wavefront. This wavefront and its motion are a physical reality while rays or trajectories are much less sharply defined and cannot actually be observed because the wavelengths involved in seismic processes are too long. This means that the visualization and the interpretation of seismic processes can be carried out in a more satisfactory, simple and comprehensible way with wavefronts than with rays.H. R. Thornburgh (1930) introduced the very lucid and simple method of interpreting seismic refraction sections, using Huygen's principle to construct wavefronts from two symmetrical shotpoints by working back from their observed arrival times at the surface. The depths are found first with only a knowledge of the velocities down to the refractor and after that the velocities in the refractor can be determined.The pattern of the two wavefronts at equal time intervals, obtained when carrying out Thornburgh's construction, leads to the very simple, approximative “Plus‐Minus” method. The additions of the travel times from two symmetrical shotpoints to‐each geophone give the relative depths and their subtractions give the velocities of the refractor. The method extrapolates exact quantities from the refractor boundary up to the surface by the “Plus”‐ and “Minus” lines. This extrapolation introduces errors that can, more or less, be corrected for. A number of hypothetical cases are presented to give an insight into the applicability and reliability of the “Plus‐Minus” method. Its main applications are for fairly shallow refraction investigations and for determining weathering corrections for refra

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01460.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractA 3‐component flux gate magnetometer has been built for use in 1½ inch drill‐holes. It has an accuracy of 1 mgs. It requires 2–3 men to operate it and they can take measurements in up to 3 100 metre holes in one day. The instrument has definitely proved its worth in describing the‘general’ geology of an ore‐body, and it is now used on a r

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01461.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractDue weight must be given to three factors (1) its purpose, (2) the limitations imposed by nature, industry and environment, (3) the effect of errors in auxiliary measurements. Together the last two factors give an estimate of the accuracy which can be achieved. If this is sufficient for the instrument to fulfil its purpose design and construction can proceed. If it is not, a detailed survey of the last two factors is necessary in order to estimate the research effort that will be required when directed into the most effective channels. If the project is considered worth the effort it can proceed. These factors are discussed in relation to a borehole gravimeter. It is shown that the purpose will be served only if the accuracy is comparable with the best surface gravimeters. Borehole versions of some surface instruments are considered and it is concluded that none is suitable without considerable modifications. A successful borehole gravimeter is likely to be a completely new instrument.

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01462.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractAnisotropy measurements were carried out in two wells 300 km apart in the Northern Sahara, in order to improve the interpretation of seismic refraction surveys.These measurements were based on; the shortening of experimental oblique travel‐times with respect to theoretical, travel‐times computed by disregarding anisotropy. A perfect knowledge of the velocity distribution is required in order to eliminate all influence of refraction; therefore a continuous velocity log is indispensable.The results in the two wells are in agreement, and show that anisotropy is essentially a function of lithology. The following values were obtained:Consequences pertaining to seismic refraction are as follows:— Depths computed without anisotropy are too small by 8 % to 9 %, i.e. about 300 meters.— The error on offsets reaches 70 %.— Depth computations carried out by assigning anisotropy factors at the sight of lithology gave very satisfactory results.— High velocity, highly anisotropic formations such as anhydrite play a very important part in the propagation of refracted waves and in interpretation.Consequences pertaining to seismic reflection are as follows:— Velocity profiles yield velocities closer to horizontal velocities than to vertical velocities.— Depth and migration computations are significantly influenced by high velocity, highly anisotropic formations su

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01463.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractTo obtain inferences useful in predicting the overburden velocities, a statistical study of velocity data was undertaken on 46 well velocity surveys confined mainly to Eastern England. Five formations were particularly studied: Keuper, Bunter, Permian, Coal Measures and Millstone Grit. Their interval velocities plotted against the mean depth of the interval below the surface supplied five equations of the formV=k. H1/n, which cover the range of depth explored down to 7000 ft. Comparison of these results shows that the interval velocities increase with depth and in the Keuper and Permian attain a maximum value nearly twice that in the remaining three formations. The interval velocities of these formations are confined within a relatively narrow band of 9000–12000 ft/sec. and the formations cannot be distinguished satisfactorily by their interval velocities alone. More practical results were obtained considering the relation between the vertical time and depth to the top of the Permian, Coal Measures, Millstone Grit and Carboniferous Limestone. For each of these a linear relationT=k. H+ To, was obtained from which the vertical timeTcan be predicted from the known depth with a probable error of ± 4 millise

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01464.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

AbstractRecently, quite good determinations of interfaces have been made by means of seismic well surveys. These were carried out for various oil companies in Northwest Germany, especially on salt‐domes, and in Southern Germany, and in the area of the Upper Rhine Valley. It was the purpose to determine the configuration and position of salt‐flanks and important planes of stratification in the neighbourhood of deep wells, and thus to reduce the risk of expensive wells.For the delineation of the boundary surfaces the method described by Gardnerin “Geophysics 1949” was applied.The problems arising and the results obtained are discussed in connection with some interesting examples. From them we see, above all, that a knowledge as precise as possible of the seismic velocities of all media involved in the measurement is very important. A good idea of the general stratification in the area of deep wells seismically surveyed will make possible a rational and adequate planning of the survey program and will facilitate the interpr

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01465.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01466.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY

摘要:

Book Reviewed in this article:Handbuch der Physik. Herausgegeben von S. Flügge.Der geologische Bau des Untergrundes von Schleswig‐Holstein und seine Erdöllager‐st

ISSN:0016-8025    

DOI:10.1111/j.1365-2478.1959.tb01467.x

出版商:Blackwell Publishing Ltd    

年代:1959

数据来源: WILEY