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  • 1
    Electronic Resource
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    Springer
    Pure and applied geophysics 109 (1973), S. 1738-1742 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Free radial vibration of a non-homogeneous circular plate of variable thickness has been studied. The thickness at a distancer from the axis through the centre of the plate perpendicular to the middle surface is chosen to be a function ofr. The problem has been solved for a disc with a central hole and also for one having no central hole.
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  • 2
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    Pure and applied geophysics 109 (1973), S. 1718-1727 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Earthquake parameters for the forty aftershocks of the main Koyna earthquake of 10 December, 1967, have been determined. Depths of the foci of the earthquakes have been found to vary between 2 to 17 km. The velocities for the phasesP g ,P *,P n have been observed to be 5.78±0.00, 6.58±0.04, 8.19±0.02 km/sec, and forS g ,S *,S n to be 3.42±0.00, 3.92±0.01 and 4.62±0.01 km/sec respectively. A two-layered crustal model has been interpreted for the Peninsular shield with the average thickness of the granitic layer as 20 km and that for the basaltic layer as 18.7 km. A plot of the epicenters suggests a NNE to SSW orientation of the fault.
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  • 3
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    Pure and applied geophysics 109 (1973), S. 1752-1761 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The spectral amplitude fields of seismic waves produced by directed (non-spherical) and undirected (spherical) explosive sources are described. The following four cases were investigated: a spherical source located at the bottom of a borehole, a spherical, a hemi-spherical, and a conical source placed at the wall of a trench. The geophones measuring theX, Y andZ components of the seismic waves produced were situated on the Earth's surface within a circle round the epicentre of each source. The records were Fourier analyzed and amplitude spectra were used to establish spectral amplitude fields of these components. Amplitude and frequency variations of the seismic wave patterns are discussed in the paper.
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  • 4
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    Pure and applied geophysics 109 (1973), S. 1796-1809 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The electric and magnetic field variations over an arbitrarily sloping ocean floor are represented in series of Bessel functions forH-polarized uniform plane wave excitation. Calculation of the spatial variations of electric eurrents and apparent resistivity near a coastline will determine the usefulness of the magnetotelluric method in this application.
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  • 5
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    Pure and applied geophysics 109 (1973), S. 1781-1788 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Forced hydromagnetic oscillations in the outer core due to stress at its top are studied by means of a simple linear theoretical model originally proposed byHide [1] for the free oscillation studies. Both the magnetic and the inertial modes are excited. The expressions for the velocity, magnetic and vorticity fields are presented for a variety of stresses. They depend upon the wave number and frequency. In a numerical example wherein the stress varies periodically both in the space and the time, the amplitude of the induced magnetic field is found to be significant for reasonable values of various parameters.
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  • 6
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    Pure and applied geophysics 109 (1973), S. 1862-1869 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Résumé Dans le présent travail on a procédé à une expérience pour déterminer les variations temporelles des principaux paramètres aéronomiques en utilisant des données expérimentales par la méthode A3 de mesure de l'absorption ionosphérique, la méthode ‘phase-altitude’ et des données satellites aux rayons X durs. On a examiné les variations diurnes et les variations temporelles lors de SID effet durant le 21 Août 1969, de la densité électroniqueN(t) et du coefficient de récombinaison α′(t). On a montré que lors de SID effet α′(t) s'accroît.
    Notes: Summary In this paper an attempt is made to define the time variations of theD-region main aeronomical parameters under non-equilibrium conditions by using experimental data by the A3 method, phase-height method and satellite data for the short-wave X-radiation. The SID effect of day-time and time variations of 21 August 1969 electron concentrationN(t) and recombination coefficient α′(t) are investigated. It is shown that during SID effect α′(t) increases.
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  • 7
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    Pure and applied geophysics 11 (1948), S. 8-18 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Description / Table of Contents: Summary The vertical temperature gradient for selectet stations shows an annual variation which cannot be explained by the diurnal variation of temperature. The annual variation of temperature at fixed levels in the lower layers of atmosphere shows a trend opposite to these variations at fixed elevations in the middle layers. This fact indicates that the troposphere cannot be regarded as a layer of uniform structure. The interdiurnal variations of pressure and temperature for the individual levels and their opposite trend compel us to postulate within the troposphere a lower layer as has been observed before in various occasions and then called the layer of disturbation. It is possible to generalize these observations and to conceive of the lower layer as a planetary phenomenon and as the ground layer of the atmosphere.
    Abstract: Riassunto Il gradiente termico verticale presenta una variazione annuale che non può venir spiegata con la variazione diurna della temperatura. La variazione annuale della temperatura a livelli determinati nei bassi strati dell'atmosfera rivela un andamento opposto a quello che si riscontra negli strati centrali della troposfera. I due fatti dimostrano che la tropofera non può venir considerata come uno strato avente struttura uniforme. Le variazioni interdiurne della pressione e della temperatura nei singoli strati verticali ed il loro comportamento inverso conducono all'esistenza di uno strato inferiore in seno alla troposfera, già prima occasionalmente osservato e definito strato di perturbazione. Simili osservazioni sono atte a venir generalizzate in quanto questo strato inferiore è concepibile come fenomeno planetärio e come strato base dell'atmosfera.
    Notes: Zusammenfassung Der vertkkale Temperaturgradient hat bei ausgewahlten Stationen einen jährlichen Gang, der nicht durch den täglichen Temperaturgang erklärbar ist. Die jährliche Temperaturschwankung in Abhängigkeit von der Höhe zeigt ein gegenläufiges Verhalten zwischen den unteren und den mittleren Schichten der Troposphäre. Beide Erscheinungen weisen darauthin, dass man die Troposphäre nicht als eine Schicht von einheitlichem Aufbau ansehen kann. Die interdiurnen Anderungen von Druck und Temperatur in den einzelnen Höhenschichten und ihr gegenläufiges Verhalten zwingen dazu eine untere Schicht in der Troposphäre auszusondern, die scho gelegentlich früher beobachtet und dann als Störungsschicht bezeichnet wurde. Diese Beobachtungen sind aber einer Verallgemeinerung fähig, indem diese untere Schicht als planetarische Erscheinung aufzufassen und als Grundschicht der Atmosphäre zu kennzeichnen ist.
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  • 8
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    Pure and applied geophysics 112 (1974), S. 301-319 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Satellite pictures have been utilised to detect mountain waves on the lee of the Andes range. The wavelengths as observed in the pictures from the distribution of clouds in parallel bands lie between 20 and 30 km for the five cases examined. The wavelengths have also been computed theoretically for these cases by an analytical method and a quasi-numerical method, using linearised perturbation equations. Wavelengths so computed are in fairly good agreement with the observed wavelengths, Vertical velocities associated with the waves along the different sectors of the Andes have also been computed. Their maximum values are of the order of 1–5 m sec−1. Also, the quasi-stationary character of the waves, as noticed in some of the pictures, is discussed.
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  • 9
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    Pure and applied geophysics 112 (1974), S. 274-280 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Diabatic heating of the atmosphere at 800, 600 and 400 mbar surfaces over India has been calculated, making use of thermodynamic and quasi-geostrophic omega equations. The numerically obtained distribution of the diabatic heating field is seen to be in agreement with the observed weather patterns in magnitude. The maximum value of diabatic heating is of the order of 4.0 to 4.5 cal gm−1 12 hr−1. Normally it ranges between 1.0 to 4.0 cal gm−1 12 hr−1. The vertical distribution of the absolute mean value of diabatic heating is seen to be at its maximum at about the 500 mbar surface.
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  • 10
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    Pure and applied geophysics 112 (1974), S. 320-330 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary An attempt is made to construct a scheme of numerical integration for the wave operator that can detect which kind of non-homogeneous term has acted over the data and later use this knowledge to integrate the operator in time. Data is generated with a wave initially at rest, and a scheme is presented to detect these functions and study how these values can be extrapolated in time to be used. The use of known functions to generate data is required only to check the effectiveness of the numerical device.
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  • 11
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    Pure and applied geophysics 112 (1974), S. 331-338 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary The effect of couple-stresses on the propagation of waves in an elastic layer has been investigated in this paper. It is found that the velocity of the propagation of waves in an elastic layer increases due to the presence of couple-stresses.
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  • 12
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    Pure and applied geophysics 112 (1974), S. 403-412 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary In order to investigate the ground conditions at the Osaka-Tsuruyama Plateau, measurements of microtremors at different depths have been carried out. The purpose of this investigation was to obtain clear information of the underground structure at this site. The period distribution curves obtained by surface stations are characterized by a sharp peak around 0.20 sec which indicates rather good ground conditions. Upon examining period distribution curves obtained at underground conditions the predominant periods were almost the same but a secondary maximum appears at periods longer than 0.5 sec. These results were confirmed by applying Fourier transformation of the respective sample function of the microtremors.
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  • 13
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    Pure and applied geophysics 112 (1974), S. 413-445 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary The results of a time series analysis of earthquakes in the New Guinea region are presented. Two basic sets of data are used, the second being a subset of the first such that all estimated related earthquakes have been removed from the first set, leaving a residue of supposedly unrelated events. The primary results are as follows. Positive trends exist in the number of earthquakes as a function of time and there are slight indications of periodicity in the activity. The distribution of earthquakes does not approximate the Poisson distribution at all well for the raw data although this distribution is a much better model with all aftershocks and foreshocks removed from the series. The different seismic natures of the regions studied are reflected in the results of the analyses.
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  • 14
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    Pure and applied geophysics 112 (1974), S. 464-471 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Using geomagnetic horizontal intensity hourly mean values of Alibag for international quiet days for the years 1934 to 1953, split into two 10-year segments, the dependence of diurnal range on the maximum and minimum values is examined after elimination of secular trend in the data. Identical results are obtained for the two 10-year periods. The maximum value occures on 85% of days near local noon while the minimum value has two preferences, one for 05 LT and the other for 19 to 24 LT. Though the correlation coefficient (CC) of+0.7 is much higher for range and maximum hourly value, the scatter observed is very large, which is attributed mosly to fluctuations is base-level from one quiet-day to another. On correcting for these the scatter is much reduced and the CC registers an improvement to+0.95. Some remanent scatter, however, persits. This as well as the very small but statistically significant negative CC observed for range and minimum hourly value stress the influence of the minimum value on range even on quiet days.
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  • 15
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    Pure and applied geophysics 112 (1974), S. 131-139 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Fission track ages need to be corrected for the loss of fossil tracks due to geological and thermal annealing. The range distribution of full-length tracks can yield such corrections if calibration curves translating length reductions into density reductions are available. The study of the annealing characteristics of the three terrestrial minerals, i.e. biotite, apatite and sphene, as functions of temperature and time, has been completed from this point of view. A linear relation has been observed between etchable track length and track density, but slopes and intercepts of the curves tend to vary from mineral to mineral. Over-etching shows significant effect in retrieving partially faded tracks in the case of biotite only, and track density reduction always lags behind track length reduction. In apatite and sphene track density is reduced in the same proportion as track length when length reduction is ∼30 to 50%. For length reductions 〈10%, track density remains nearly unaffected and for length decrease 〉50% the density reduction progressively outweighs the former. The possible reasons for such variations and the usefulness of the calibration curves are briefly discussed.
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  • 16
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    Pure and applied geophysics 112 (1974), S. 281-288 
    ISSN: 1420-9136
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    Topics: Geosciences , Physics
    Notes: Summary Vertical velocities at the 800, 600 and 400 mbar surfaces over India have been calculated, making use of a 3-level geostrophic baroclinic model. Further, the effects of non-adiabatic heating is included into the model and vertical velocity due to diabatic heating is obtained for the same period. A numerically obtained vertical velocity field due to baroclinicity and diabatic heating is seen to be in agreement with the observed weather patterns.
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  • 17
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    Pure and applied geophysics 112 (1974), S. 352-364 
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    Notes: Summary A theoretical investigation is made into the propagation of small-amplitude waves across the free surface of an elastic medium, whose strain-energy function is of Mooney form. The medium is taken to be semi-infinite in extent, and to be subjected to a large primary extension (or compression) in a direction lying in the free surface. The dispersion equation is derived and the general nature of its solutions is explored. Detailed numerical results are given for certain special cases.
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  • 18
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    Pure and applied geophysics 112 (1974), S. 365-379 
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    Notes: Summary The problems of Cagniard and Abramovici-Alterman, regarding propagation of seismic pulses in horizontally layered media, are solved by a direct method without involving integral transforms.
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  • 19
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    Notes: Summary P- andS-wave travel times of 56 shallow earthquakes with their epicentres in and around the Andaman Sea, as recorded by the Indian Seismological Observatories situated at Madras, Visakhapatnam, Calcutta and Port Blair, have been analysed statistically. The travel times from Δ=1 ° to 17 ° can be represented by one straight-line segment. When epicentres of all the earthquakes are considered, scatter in the travel-time data is greater and the corresponding apparentP- andS-wave velocities have been found to be 8.56±0.20 km/sec and 4.84±0.36 km/sec respectively. On the other hand, if epicentres of the narrow seismic zone situated along the western border of the Andaman Sea alone are considered, the apparentP- andS-wave velocities have been found to be 8.24±0.09 km/sec and 4.74±0.10 km/sec respectively. The O-JB residuals are found to be consistently negative for the second set of epicentres which is indicative of an inclined Mohorovicic discontinuity in the Bay of Bengal region.
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  • 20
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    Notes: Summary The effect is studies of the inaccuracies due to the measurements of the input gravity data and of the inaccuracies due to an inaccurately derived fundamental boundary condition, as well as of the error, incurred in expressing the gravity field discretely for computing the quantities, describing the gravity field outside the perturbing masses.
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  • 21
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    Pure and applied geophysics 112 (1974), S. 456-463 
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    Notes: Summary The magnitude of the universal time (UT) component in the daily variation of geomagnetic disturbance which depends on the position of the earth's magnetic axis relative to the sunearth system is evaluated at two low-latitude stations, Alibag in the northern hemisphere and Hermanus in the southern hemisphere. To provide better resolution on time scale, mean hourly values of horizontal intensity are used rather than indexK of magnetic activity. During solstices the UT component has a mean amplitude of 6.8 γ at Alibag and 3.0 γ at Hermanus with maximum contribution near the predicted time of 0430 UT in June and 1630 UT in December. It is found that the UT component makes a significant contribution to the daily variation of disturbance field during equinoxes but the part dependent on the angle between the earth's magnetic axis and the sun-earth line is found to be larger during September than in March, suggesting an asymmetry in the incident solar wind. This is possibly due to the varying heliographic latitude of the earth and the asymmetry in activity in the two hemispheres of the sun.
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  • 22
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    Pure and applied geophysics 112 (1974), S. 498-505 
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    Notes: Summary Exact solution of the hydromagnetic flow between two parallel, non-conducting, infinite planes, one oscillating and the other fixed, has been obtained. The effect of an applied transverse magnetic field on various flow characteristics is studied in detail for a small magnetic Prandtl number (Pr m≪1). The viscous drag acting on the two planes has been determined.
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  • 23
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    Pure and applied geophysics 112 (1974), S. 506-511 
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    Notes: Summary Small-strain theory has been applied to find out the deformation and stresses in the interior of the earth considered as a self-gravitating, non-homogeneous, isotropic sphere of heterogeneous density distribution. Stresses have been compared at different layers due to different density distributions.
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  • 24
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    Pure and applied geophysics 112 (1974), S. 519-522 
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    Notes: Summary It is shown that for azimuthal wave numbers and period 0.5 (s+1) days, Hough's functions for tidal oscillations are the same as the associated Legendre polynomialsP s+1 s and Hough's functions are shown to form a complete set of orthogonal functions. The implication of this on the vertical variation of tides is discussed.
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  • 25
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    Pure and applied geophysics 112 (1974), S. 1059-1065 
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    Notes: Summary Values of the parameterb in the frequency-magnitude relation for seismic sequences, determined by several methods, show a systematic variation of this parameter with the magnitude range. When the difference in magnitude between the largest and smallest earthquake of a complete sequence is larger than about 1.4 this variation is not, as a rule, significant and a value of this parameter can be determined from the cumulative distribution with considerable confidence.
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    Pure and applied geophysics 113 (1975), S. 87-95 
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    Notes: Summary In the northern and central sections of the San Andreas Fault Zone, and along Calaveras and Hayward faults, clay gouges have been found to occur on the surface and at shallow depths. It is consistent with the available geochemical data that such gouges can exist at depths down to 10 km. If extensive gouge materials exist in a fault zone then their properties will determine, to a large extent, the behavior of the fault. From known properties of clays in the presence of water we can infer that, in such cases, the tectonic stress and the stress drops for earthquakes will be low and substantial creep will take place before earthquakes.
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    Pure and applied geophysics 113 (1975), S. 107-118 
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    Notes: Summary The relation between remanent magnetization and volumetric strain for gabbro samples stressed in uniaxial compression inside a near zero-field μ-metal shield has been examined. For samples with an induced IRM parallel to the axis of compression, remanent magnetization decreased linearly up to the onset of dilatancy. As increased stress produced additional dilatancy, the variation of remanent magnetization became nonlinear, and the stress dependence continually decreased until the rock failed. Stress cycling with the peak stress augmented for each cycle produced a continuous decrease in the zero stress value of the IRM although an appreciable amount of recovery was observed during unloading. When the sample was loaded in constant stress increments after the onset of dilatancy and held for several minutes at each level, time-dependent variations in remanent magnetization coincided with time-dependent increases in inelastic volumetric strain. In general as the inelastic creep rate increases, the rate of change in remanent magnetization increases. These results suggest that dilatancy related effects of the intensity of rock magnetization should be observed in magnetic rocks in epicentral regions prior to earthquakes and may serve as both long- and short-term precursors.
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    Pure and applied geophysics 112 (1974), S. 545-552 
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    Notes: Summary It is well known that the activity of the summer monsoon, as measured by rainfall, undergoes variations from one month to another. In this study, the monsoon activity has been examined in detail to find if any major climatological discontinuities in the activity exist in the field of the Asian summer monsoon. From amongst the possible criteria for major discontinuity, the criterion based on the lower and the upper quartiles has been selected. The study brings out that major climatological discontinuities do exist over some parts of Asia. These are (i) a marked decrease in activity from July to August, right in the middle of the monsoon season, over the west coast of India, between Bombay and Trivandrum; (ii) a marked decrease from August to September over a small portion of the Indian west coast in the neighbourhood of Mangalore; (iii) a marked decrease from August to September over the Arakan coast; and (iv) a marked increase from August to September over the Viet Nam coast. Possible causes of these discontinuities have been discussed.
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    Pure and applied geophysics 112 (1974), S. 563-570 
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    Notes: Summary A 68-cm long probe of 2.5 cm diameter, containing a NaI (Tl) crystal, photomultiplier, HV stabilization and preamplifier, is described. Special attention is paid to the probe-cable coupling: it is designed to withstand hydrostatic pressures up to 10 atm. For logging of inclined, up to 20 m long holes, aluminium extension pipes assembled by push-button closures are used. The probe, operated together with a portable ratemeter, has a sensitivity of 1200 c.p.s. per mR/h (Ra226). For quantitative log interpretation the conversion factor was determined to be 0.4 p.p.m. U/c.p.s. Radiometrically determined uranium contents agree remarkably well with results of chemical analysis of cores.
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  • 30
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    Notes: Summary A comparison is made between the multimode Rayleigh wave response to dip-slip motion along a vertical fault plane in structures with and without a low-velocity channel. The use of the higher mode amplitude spectra is proposed as a discriminant between the two types of structure.
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  • 31
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    Pure and applied geophysics 112 (1974), S. 633-633 
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    Pure and applied geophysics 112 (1974), S. 727-736 
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    Notes: Summary The values of parameters of the relation logN=a−bM characterize the earthquake activity of individual regions. Their magnitude depends substantially on the method of computation used, on the preparation of data for computing and on the use of simple or cumulative frequency distribution. In this paper the particular procedures of computation were tested and their efficiency was judged.
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    Pure and applied geophysics 112 (1974), S. 739-752 
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    Notes: Summary The present study deals with the approximate scattering characteristics of optically thin cirrus clouds which are known to exist in the vicinity of the tropopause. The assumed homogeneous ice model cloud is composed of randomly oriented circular cylinders of uniform size. The spectral region investigated extends from 0.6–0.7 μ, where absorption by ice and atmospheric gases is negligible Radiative upward and downward intensities are calculated for a uniform ground albedo of 0 and 0.25 using the assumption that multiple-scattering can be disregarded. A rough comparison with the Rayleigh scattering characteristics in this spectral region indicates that remote sensing of the atmosphere is affected very little by the presence of optically thin cirrus assuming the validity of the above assumptions.
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    Pure and applied geophysics 112 (1974), S. 777-785 
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    Notes: Summary The question this paper is examining is the following: to what extent are the Love numbers dependent on certain characteristics of the inner structure of the Earth? It has been proven — on the basis of calculations carried out by the author-that these quantities are only in a small degree dependent on the density values measured on the surface of the Earth and on the selection of the density function in the mantle of the Earth. On the other hand the value of Love numbersh, k andl is considerably influenced by the assumptions made about the core of the Earth, namely by the position of the boundary between the core and the mantle and by the magnitude of the rigidity coefficient presumed in the core in the vicinity of the core-mantle boundary. The results of the calculations are compared with those mean values of Love numbers obtained from the data of stations operating at different places of the Earth. By reason of this it can be assumed that the core of the Earth has, in the vicinity of the core-mantle boundary, a coefficient of effective rigidity of the order of 1010 dyn/cm2, if the core-mantle boundary is placed at the relative Earth radius of 0.545 from the centre of the Earth.
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    Pure and applied geophysics 112 (1974), S. 855-862 
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    Notes: Summary The parameters and seismotectonics of an earthquake in the Baltic Shield, northern Finland, were studied. The instrumentally determined epicentre, 65.94°N, 27.21°E, falls in the intensity area ofI〈5. The results of the macroseismic study were: the area of perceptibility=6700 km2, maximum intensityI 0=5.25±0.05, focal depthh=10.0±0.5 km, absorption coefficient α=0.0035±0.0015 km−1 and magnitudeM m=4.0±0.1. The location of the focus was exact enough for seismotectonic study. The epicentre is located in the 0°-striking fractures and a parallel contact zone between granites and basement gneisses. On the other hand, it lies at the northern boundary (270–285°) of a tectonic block separated by fracture zones striking 270°, 285°, 330° and 30–40°. There have been seven known earthquakes in the area of the present study since 1891. Six of them occurred at the northern boundary of the block, of which five (including the Simojärvi earthquake of 1969) occurred within a period of three years. This block, with its deep (h=10 km) fractured boundaries, has been seen as a minor seismogenic unit and its northern boundary as the seismoactive part of this unit.
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    Pure and applied geophysics 112 (1974), S. 887-899 
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    Notes: Summary Eight vertical profiles compiled from simultaneous measurements of Aitken nuclei and ozone concentrations over Germany in different weather conditions are discussed. The position and shape of the profiles is shown to depend on the prevailing weather conditions and the type of air masses. High aerosol concentrations in smoke plumes correlate in some cases with lower ozone concentrations, indicating that ozone in such cases is destroyed in the presence of high concentrations of pollutants such as aerosols and gases. A layered structure in the profiles was found only in association with temperature inversions and where the air above 2 km was subsiding, and was not found in convective parts of the troposphere.
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    Notes: Summary The levels of Pb-214 (Ra-B) and Pb-212 (Th-B) in surface air at two coastal stations (Bombay and Thumba) and at a third high-altitude station (Gulmarg) in India are presented. A seasonal variation in activity at the coastal stations with winter maximum and summer minimum and the absence of a similar variation at the high-altitude station at Gulmarg is discussed. From a study of the relevant meteorological data, it is concluded that at the coastal stations, the major factor influencing the activity levels is likely to be the stability of the lower atmosphere, advective effects possibly playing a secondary role. At Gulmarg, however, factors affecting emanation from the soil, like rainfall, snowfall, etc., could be significant.
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    Pure and applied geophysics 112 (1974), S. 977-985 
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    Notes: Summary In this work we study the effects on the surface impedance of a one-dimensional structure, caused by a perturbation due to the introduction of a deep perfect reflector. An algorithm for presenting the impedance in a rational polynomial form is outlined and the properties concerning the location of poles and zeros, corresponding to this function, are investigated. It is shown that perturbing the structure by the introduction of a perfect reflector at any finite depth will affect the analytic behaviour of the surface impedance for any frequency range.
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    Pure and applied geophysics 112 (1974), S. 1011-1029 
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    Notes: Summary The classical ray-series method for electromagnetic wave propagation in inhomogeneous media is applied to the problem of wave propagation in isotropic, homogeneous, linear viscoelastic media characterized by virtually arbitrary time-dependent relaxation or creep functions. The full three-dimensional treatment is presented, followed by the specialization to the one-dimensional propagating pulse problem. In this last case, the ray-series is evaluated numerically for the creep function $$\psi (t) = \frac{1}{\mu }\left\{ {1 + \frac{q}{\alpha }\left. {\left[ {\left. {\left( {1 + \frac{1}{\tau }} \right)^\alpha - 1} \right]} \right.} \right\}} \right.H(t)$$ for various model parameter ranges and for various initial source functions.
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    Pure and applied geophysics 112 (1974), S. 1051-1057 
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    Notes: Summary The stress drop and average dislocation of some earthquakes in the Indian sub-continent have been determined after deducing the relationship between the aftershock areaA, and the magnitudeM L of the main shock which is given by $$\log A = 0.89M_L - 2.67 for 5 \leqslant M_L \leqslant 7.$$ It has been found that the stress drop is considerably larger for the great Assam earthquake of 15 August, 1950, occurring near the continent-continent boundary of the Indian-Eurasian plates, compared to that of a similar magnitude earthquake in a continent-island are type collision boundary in the Pacific (near Japan). The stress drop in smaller events of comparative magnitude in different regions are, however, of the same order and thus do not bring out the distinguishing features of the source regions in different kinds of plate boundaries.
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    Pure and applied geophysics 112 (1974), S. 1067-1069 
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    Notes: Summary In a recent paper,Verma andSrivastava [1] discussed the vibrations of an inhomogeneous, transradially isotropic, spherical shell. An assumption made by these authors at the very outset appears to be incorrect. Consequently, most of the equations and results obtained by them are either wrong or irrelevant. The purpose of this note is to point out these mistakes and give the corresponding correct results. The notation of Verma and Srivastava is used throughout.
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    Pure and applied geophysics 113 (1975), S. 97-106 
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    Notes: Summary Deformation causes changes in gravity even though the measuring station is fixed relative to the center of the earth and the total mass in the vicinity of the station does not change. Deformation has two effects: the density at a point changes in response to changes in local stresses and the point itself moves relative to the station. The general expression derived here shows that the gravity change depends on the uplift immediately beneath the station and the deformation of cavities at depth — cracks, pores, magma reservoirs, etc. The approximation is made that density is uniform except for cavities, but no assumptions about the constitutive behavior of the medium are necessary. The gravity change studied here shows interesting analogies with the gravity effect due to buried bodies with anomalous density. For example, I find that the net volume change due to deformation can be found by integrating the gravity anomaly over the earth's surface, in analogy with the calculations for excess mass. The theory is especially useful when both deformation and net fluid flow into or out of the system occurs. The results are applied to uplift and gravity changes observed during the great Alaskan earthquake, the Matsushiro earthquake swarm, and a draw-down operation at the Wairakei geothermal field. The data at Wairakei are used to estimate the net amount of water taken from the aquifer. The data at Matsushiro is not sufficiently precise to discriminate between the various mechanisms that have been proposed, but the Alaskan earthquake data suggest that no dilatancy or fluid flow occurred between the survey in 1962 and the resurvey in 1964 just after the event.
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    Pure and applied geophysics 113 (1975), S. 141-147 
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    Notes: Summary A physical interpretation of empirical formulas for earthquake magnitude (M) and spatial extents of land deformation and aftershock area is attempted on the basis of a dilatancy model. It is demonstrated that the precursor time interval (τ) vs.M relation approximately fits in that for the τ vs. typical length of earthquake zone provided the above formulas hold good. A diffusion process in a dilatant region seems also to account for these approximate formulas.
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    Pure and applied geophysics 113 (1975), S. 169-181 
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    Notes: Summary Similar precursory phenomena have been observed before earthquakes in the United States, the Soviet Union, Japan, and China. Two quite different physical models are used to explain these phenomena. According to a model developed by US seismologists, the so-called dilatancy diffusion model, the earthquake occurs near maximum stress, following a period of dilatant crack expansion. Diffusion of water in and out of the dilatant volume is required to explain the recovery of seismic velocity before the earthquake. According to a model developed by Soviet scientists growth of cracks is also involved but diffusion of water in and out of the focal region is not required. With this model, the earthquake is assumed to occur during a period of falling stress and recovery of velocity here is due to crack closure as stress relaxes. In general, the dilatancy diffusion model gives a peaked precursor form, whereas the dry model gives a bay form, in which recovery is well under way before the earthquake. A number of field observations should help to distinguish between the two models: study of post-earthquake recovery, time variation of stress and pore pressure in the focal region, the occurrence of pre-existing faults, and any changes in direction of precursory phenomena during the anomalous period.
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    Pure and applied geophysics 112 (1974), S. 1070-1070 
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    Pure and applied geophysics 113 (1975), S. 69-86 
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    Notes: Summary Three types of triaxial compression experiments are used to characterize the frictional processes during sliding on quartz gouge. They are: 1) pre-cut Tennessee Sandstone sliding on an artificial layer of quartz gouge; 2) fractured Coconino Sandstone sliding along experimentally produced shear fractures; and 3) a fine-grained quartz aggregate deformed in compression. The specimens were deformed to 2.0 kb confining pressure at room temperature and displacement rates from 10−2 to 10−5 cm/sec dry and with water. There is a transition in sliding mode from stick-slip at confining pressures〈0.7 kb to stable sliding at〉0.7 kb. This transition is accompanied by a change from sliding at the sandstone-gouge contact (stick-slip) to riding on a layer of cataclastically flowing gouge (stable sliding). Quartz gouge between the pre-cut surfaces of Tennessee Sandstone lowers both the kinetic coefficient of friction and the magnitude of the stick-slip stress drops compared to those for a pre-cut surface alone. Stick-slip stress drops are preceded by stable sliding at displacements of 10−5 cm/sec. For a decrease in displacement rate between 10−3 and 10−5 cm/sec, stress-drops magnitudes increase from 25 to 50 bars. Tests on saturated quartz gouge show sufficient permeability to permit fluidpressure equilibrium within compacted gouge in 10 to 30 seconds; thus the principle of effective stress should hold for the fault zone with quartz gouge. Our results suggest that at effective confining pressures of less than 2.0 kb, if a fault zone contains quartz gouge, laboratory-type stick-slip can be an earthquake-source mechanism only if a planar sliding-surface develops, and then only when the effective confining pressure is less than 0.7 kb.
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    Pure and applied geophysics 113 (1975), S. 119-125 
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    Notes: Summary Opening of cracks before an earthquake (dilatancy) causes inelastic crustal uplift. Raising the pore pressure in these cracks as pore fluid diffuses into the dilatant zone produces further elastic uplift. Since the time between resaturation of the dilatant zone and the earthquake is shorter than the life of thev p /v s anomaly, the elastic uplift is less than the inelastic. The magnitude of thev p /v s anomaly gives a lower bound on the compressibility of the dilatant zone. Velocity and uplift measurements lead to the conclusion that if dilatancy occurred before the 1971 San Fernando earthquake, the pore pressure in the hypocentral region at the time of the event must have been at least an order of magnitude below hydrostatic.
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    Notes: Summary A radiative-conductive model is constructed to study short-term effects of various carbon dioxide concentrations on the atmospheric boundary layer for different seasons. The distribution of the exchange coefficient is modeled with the aid of the KEYPS formula. Infrared radiation calculations are carried out by means of the emissivity method and by assuming that water vapor and carbon dioxide are the only radiatively active gases. Global radiation is computed by specification of Linke's turbidity factor. It is found that doubling the carbon dioxide concentration increases the temperature near the ground by approximately one-half of one degree if clouds are absent. A sevenfold increase of the present normal carbon dioxide concentration increases the temperature near the ground by approximately one degree. Temperature profiles resulting from presently observed carbon dioxide concentration and convective cloudiness of 50% or less are compared with those resulting from doubled carbon dioxide concentrations and the same amounts of cloud cover. Again, it is found that a doubling of carbon dioxide increases the temperature in the lower boundary layer by about one-half of one degree. The present results are obtained on the basis of fixed temperature boundary conditions as contrasted to the study ofManabe andWetherald (1967). Howeve, the conclusions are not addressed to global climate change, but to the distribution of the temperature of the air layer near the ground.
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    Pure and applied geophysics 113 (1975), S. 419-433 
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    Notes: Summary Geophysical survey data represent a class of information currently subjected to computer contouring techniques. The gridded network is a feature inherent to a large portion of these surveys. Taking advantage of this feature, a simple and highly efficient computer program has been developed, minimizing the contouring effort in terms of the money, time and programming involved in the interpretation process. The program includes interpolation between data points in two directions, determination of contour line coordinates, and subsequent plotting.
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    Pure and applied geophysics 113 (1975), S. 183-196 
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    Notes: Summary A dilatancy model is presented which seems capable of simulating the results of laboratory tests on rock samples. The fundamental assumption incorporated in the model is that dilatancy is caused by the opening of cracks, where the cracks open in the least compressive stress direction (Brace et al., 1966). Its simplicity and compatibility with numerical techniques, involving the simulation of both static and dynamic stress fields, permits prediction of dilatancy induced effects for stress states and loading conditions which are not experimentally attainable.
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    Pure and applied geophysics 113 (1975), S. 219-227 
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    Notes: Summary More than 20 coseismic resistivity steps were observed by a resistivity variometer at a station about 60 km south of Tokyo during a six-year period of observation. The logarithmic magnitude of steps normalized to an epicentral distance (δ) of 100 km is linearly correlated to earthquake magnitude (M). The larger the earthquake magnitude is, the longer is the time required for completing a resistivity step. Earthquakes, that produced a step, as plotted on anM-δ graph are clearly separated by a straight line $$M = - 12.5 + 2.5\log _{10} \Delta $$ from those that did not produce a step, δ being measured in units of km. The straight line is approximately equivalent to a resolution of strain steps of the order of 10−9. As the smallest rate of resistivity change that can be observed by the variometer is 10−5 or so, it is apparent that mechanical strain is amplified by a factor of 104 or thereabouts when it is measured in terms of resistivity change. Some of the steps are preceded by a premonitory effect. When long-period changes, mostly due to tidal loadings, are eliminated by a numerical filtration technique, precursors are brought out very clearly in a number of cases. The precursor time ranges from 1 to 7 hours and appears to be independent of magnitude.
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    Pure and applied geophysics 113 (1975), S. 735-746 
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    Notes: Abstract High resolution 3-cm weather radar was used to observe the three dimensional structure of a weak echo region of a severe convective storm in northern Minnesota, U.S.A. Observations show that a seemingly steady-state updraft in the lower portion of the storm broke into an unsteady structure in the upper levels. This is interpreted as indicating that precipitation loading gradually decelerated the upper reaches of the updraft, resulting in periodic breakout of a new updraft core on the inflow side. This periodic behavior of the updraft may be related to hailstreaks and what has been termed the multi-celled storm.
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    Pure and applied geophysics 113 (1975), S. 281-292 
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    Notes: Summary Teleseismic arrivals for large earthquakes occurring in the Circum-Pacific seismic source regions have been analysed forP-velocity variations prior to the February 24, 1972, Bear Valley earthquake at several stations in the vicinity of Bear Valley, California. The teleseismic arrivals have been analysed by the method of two-station residuals and corrected for observed azimuthal variations. The data covers the time period of July, 1971, through April, 1972, and suggests that during part of January, 1972, aP-velocity anomaly occurred beneath station BVL 2 km from the epicenter of the magnitude 5.1 Bear Valley event. A maximum vertical travel time delay of 0.15 seconds is observed. No other anomalous behavior associated with this event is suggested by the data for the other stations ranging from 7 to 19 km from the event's epicenter. These results support an anomalous zone of limited size with a maximum horizontal extent of less than 5 km perpendicular and about 10 km parallel to the San Andreas fault relative to the epicenter and confined within a 5 to 10 km portion of the uppermost crust. Also aP-velocity delay for waves travelling essentially along the intermediate stress axis would imply in this case that theP-velocity anomaly is caused by a bulk modulus mechanism such as that proposed by the dilatancy-fluid flow theory.
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    Pure and applied geophysics 113 (1975), S. 293-296 
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    Notes: Summary Quarry blasts provide an excellent source of waves with which to study temporal variations of seismic travel times. Using sources from several active quarries we found no time changes at Gold Hill (GHC), California from 7 months before the 1966 Parkfield mainshock to at least 13 months following the event. GHC is within 0.5 km of the zone of ground breakage associated with the earthquake. This event was one of the largest to occur in central California since 1906. The negative result of our experiment does not rule out the existence of an anomaly prior to the event, rather it emphasizes the difficulty of detecting such anomalies without a fortuitous combination of sources and stations. The routine monitoring of temporal changes in seismic velocity along the San Andreas fault may require not only dense networks of high quality seismic stations, but also sources whose spatial location and origin time can be controlled.
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    Pure and applied geophysics 113 (1975), S. 311-320 
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    Notes: Summary As a part of the Japanese earthquake prediction programme, deep borehole observation of the earth's crustal activities has been planned in and around Tokyo by the National Research Center for Disaster Prevention. The first place selected was in the city of Iwatsuki, about 30 km from the centre of Tokyo. Starting in 1970, the main construction was completed at the end of 1973. The tentative observation of micro-earthquakes and crustal movement by tiltmeters has been carried out since May, 1973. As expected, noise at the bottom of the hole (3500 m depth) is extremely small, about 1/1000–1/300 of that at the surface. We could, possibly, detect earthquakes with magnitudes greater than 2.0 within 50 km radius from the Iwatsuki observatory.
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    Pure and applied geophysics 113 (1975), S. 355-364 
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    Notes: Summary Lunar barometric tidal determinations (L 2) have been made by the Chapman-Miller method for Zürich (493 m) and Säntis (2000 m) based on 49 years' data. The seasonal variations ofL 2 are much larger at Zürich than on the Säntis summit. However, a comparison with the five other pairs of stations for which tidal determinations at different altitudes, but short horizontal distances, are available do not indicate that this result is as an altitude effect, nor do they show any other systematic differences betweenL 2 at the lower and the higher station. The solar tidal determinations agree well with those made byEggenberger (1944) and fit in with those obtained for other stations. From the difference between the pressure oscillations at Zürich and on Säntis the corresponding meantemperature oscillations of the air column between the two stations has been computed.
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    Pure and applied geophysics 113 (1975), S. 389-402 
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    Notes: Summary New measurements on the stratospheric distribution of H2, CH4, CO and N2O are presented and used to demonstrate the natural variability of the trace gas concentrations. The present CH4 and H2 measurements and data from older balloon flights are combined to give average vertical profiles. These profiles are compared with water vapor data from various authors to see if the vertical decrease in CH4 is matched by a corresponding increase in H2O. By comparing the average measured profiles to those predicted by a one-dimensional chemical model, profiles of the vertical eddy diffusion coefficientk z are deduced. Generally, a barrier in the low stratosphere and increasing transport in middle and upper stratosphere seem required to match theoretical and experimental profiles. The limitations of the calculatedk z are discussed.
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    Pure and applied geophysics 113 (1975), S. 461-466 
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    Notes: Summary A migration pattern is found for epicenters of the largest earthquakes which occurred between 1918 and 1964 inclusive. The pattern indicates that for three consecutive earthquakes which occurred at a predetermined distance of each other in a seismic belt, the third earthquake tends to be located close to the first one, and not away from it. The hypothesis that the reverse migration pattern is not true, can be accepted at statistical significance levels of only 5% or lower. A tectonophysical explanation of the pattern is proposed.
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    Pure and applied geophysics 114 (1976), S. 425-433 
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    Notes: Summary We propose a method that may be used to determine the spatial orientation of the fracture plane developed during hydraulic fracture. In the method, magnetic particles are injected into the crack with the fracturing fluid so as to generate a sheet of magnetized material. Since the magnetization of a body with extreme dimension ratios, such as a crack, exceeds that of an equidimensional body and since this magnetization is sensitive both to orientation and geometry, this could be used to obtain information about the crack. By measuring the vertical and horizontal components of the magnetic field and field gradients at the earth's surface surrounding the injection well with superconducting magnetometers having 10−4 gamma sensitivity and also by measuring field direction within the well itself, it should be possible to calculate the orientation and perhaps infer the approximate geometry of the fracture surface. Experiments on electric field potential operated in conjunction with this experiment could further constrain estimates of shape and orientation.
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    Pure and applied geophysics 114 (1976), S. 461-467 
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    Notes: Summary The relative detection capability of nine seismological stations situated north of 20°N in India has been studied. The best stations were the WWSSN stations NDI and SHL, followed by CHA, DDI, BOK and BHK. The remaining stations CAL, SEH and TOC are inferior in their detection capability.
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    Notes: Abstract Based on the average variability of the skewness with respect to the droplet mode radius, a wide set of mean size-distribution models is presented in terms of the modified gamma function for fog and stratified cloud droplets. These models appear appropriate for giving reliable size-distribution curves relative to the various formation stages of the droplet population both in fogs and in stratus and stratocumulus clouds. The corresponding volume extinction coefficient has been computed at various wavelengths from 0.4 to 17 μm using Van de Hulst's (1957) approximation multiplied by Deirmendjian's (1960) correction factors. This set of theoretical extinction data has been compared with experimental extinction measurements performed in atmospheres characterized by a marked thermal inversion for describing the evolutionary features of the water droplet size distribution within the whole ground layer.
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    Pure and applied geophysics 114 (1976), S. 479-494 
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    Notes: Summary Recently determined gravity anomalies along the NW-SE oriented Swiss Geotraverse from Basel to Bellinzona are used in combination with seismic refraction data to deduce a crustal section across the Swiss Alps. Topographic, Bouguer, free air, isostatic and geological corrections were applied to the data. Geological features considered in the corrections are the Swiss Molasse basin filled with sediments and the Ivrea body of high-density material. The resultant Bouguer anomaly over the Gotthard massif is 130 mgal lower than the Bouguer anomaly at the northern end of the profile near Basel. The Alpine region is associated with negative isostatic anomalies down to −20 mgal. The crustal thickness is found to increase gradually from the northern end of the profile (thicknessH=30 km) towards the Helvetic nappes at the northern margin of the Alps (H=38 km) and more rapidly towards the Gotthard massif (H=50 km) and further south to Biasca down to a depth of 58 km. From Biasca southward the crustal thickness thins quite rapidly to reach a depth of 30 km at the southern end of the profile near Bellinzona. Thus the Alps have a distinct asymmetric crustal root whose maximum thickness is almost twice the average crustal thickness in Central Europe. With the Mohorovičić-discontinuity deduced from seismic observations an average constant density contrast of −0.33 gcm−3 is found between the lower crust and upper mantle underneath the Alps.
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    Pure and applied geophysics 114 (1976), S. 61-69 
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    Notes: Summary Six Younger Granite localities showing normal and reverse magnetizations in equal proportion have given a Jurassic palaeomagnetic pole position ϕ=62.5°N, Λ=241.6°E; (Fisher's precision parameter (k)=27.8 and α95=13°). Individual palaeopole-positions have also been obtained for a Cretaceous pyroclastic rock and for two Pleistocene basalt flows.
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    Pure and applied geophysics 114 (1976), S. 95-107 
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    Notes: Summary Body force equivalents can be computed for subsidence of the Po delta in the twentieth century. Their preferred location suggests that not all of the subsidence is caused by pumping of fluids or other processes occurring at shallow depths. Some of the deformation may be due to crustal response to a north-south compressive stress.
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    Pure and applied geophysics 114 (1976), S. 158-158 
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    Pure and applied geophysics 114 (1976), S. 163-164 
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    Pure and applied geophysics 114 (1976), S. 119-139 
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    Notes: Abstract A theory of deep earthquakes, termed the inclusion collapse theory, is proposed in this paper. In the inclusion theory of crustal (or shallow) earthquakes, faults were shown to terminate within an inclusion zone. This zone represents a region within the brittle portion of the lithospheric plate that contains open cracks (voids) of varying sizes that, to a first order approximation, are uniformly distributed throughout the inclusion zone. When the lithospheric plate containing these faults and their associated inclusions is subducted into the mantle, the stress normal to the fault planes must increase. A depth is eventually reached where slippage along the fault planes is no longer possible. Earthquakes are postulated to occur at a specified depth within the mantle as a result of processes leading to collapse of these voids. When the long-term modulus of the plate is much greater than the long-term modulus of the mantle, large pressures are shown to develop within the plate during periods of active subduction. These pressures are shown to be sufficient to initiate partial collapse of voids of similar geometry throughout the inclusion zone. The inclusion collapse theory and the concentration of pressure within the plate lead to four results. (1) Earthquakes that are produced by a void collapse mechanism will not occur below a subduction depth calculated to be between 350 and 1000 km (2) The physical process most likely responsible for producing void collapse is the formation of shear, melt zones whose thicknesses are on the order of 1 to 10 cm in the immediate vicinity of the voids. This mechanism, is shown to produce a ‘precursor’ time on the order of a few hundred seconds during which there is a release of shear strain prior to the earthquake. (3) The maximum energy released by void collapse is independent of the source depth. (4) The number of earthquakes produced by this process will decrease hyperbolically with source depth. Source depth, in the context used in this article, refers to the depth in the mantle to the inclusion zone where voids of similar geometry are undergoing partial collapse. The maximum source depth refers to the depth where all voids have closed.
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    Pure and applied geophysics 113 (1975), S. 577-581 
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    Notes: Summary The determination of the residual circulation is essential to the interpretation of the sedimentation pattern. The classical picture of the residual circulation in the Southern Bight could not explain the observation of mud deposition in front of the Belgian coast. Hence, a more refined model was built where, although the shear and the Reynolds stresses are approximated by dispersion terms, the tidal stress was explicitly calculated using a preliminary tidal model. It is shown that the new model predicts the existence of a residual gyre off the Belgian coast which, increasing the residence time of the water masses and in particular the entrained water from the Scheldt estuary, fully explains the observed sedimentation pattern.
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    Pure and applied geophysics 114 (1976), S. 195-206 
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    Notes: Summary Measurements of bulk magnetic properties, including the natural remanent magnetization (NRM), susceptibility and the Königsberger ratio, on over 250 samples of Tertiary basalts from Disko and Nûgssuaq, West Greenland are reported. The NRM intensities in basalts (geometric mean value 3.3 A/m in SI units) were on average three to four times as large as the induced magnetization intensities. The susceptibilities (geometric mean value 2.1×10−2 SI units) were much more uniform than the NRM intensities. In the majority of samples, the NRM was predominantly of reverse (R) polarity, but samples from a few sites showed a remanence of normal (N) polarity. The NRM of both polarity classes (N, R) was very stable against alternating field (AF) demagnetization with median destructive fields of the order of 20,000–30,000 A/m (250–350 Oe), comparable to those for many stable continental and oceanic basalts. The viscous remanence intensity, as studied by storage tests on some specimens, was found to be an insignificant fraction of the original NRM, except in few cases. The low field hysteresis loops (Rayleigh loops) were studied for some specimens. A qualitative association was noted between wide hysteresis loop and relatively low AF stability, but no correlation was apparent between the loop type and the Königsberger ratio (Q n) of a specimen.
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    Pure and applied geophysics 114 (1976), S. 251-262 
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    Notes: Summary Since 1945 in Poland density measurements have been completed on drilling samples to obtain data for reduction and interpretation of geophysical results. In this paper the developments in density measurements techniques and data processing in Poland are reviewed. Mean density maps have been constructed for the following Pre-Devonian divisions: Volhynian, Valdai and Subholmian Cambrian, Holmian and Protoolenus Cambrian, Middle Cambrian, Lower Ordovician, Middle Ordovician, Upper Ordovician, Lower Silurian, Middle Silurian, Upper Silurian. On the basis of the same data the dependence of mean densities on the present depth of all the above divisions has been examined. This dependence has been approximated by regression equations of the following type: σ(h)= ah + b , σ(h) = ah2 + bh + c, σ(h)= alnh + b(σ(h): mean density,h: present depth). In addition to the coefficients of these equations the correlation coefficient, regression standard error, and confidence intervals have been calculated. Analysis of the results obtained revealed a dominant effect of compaction on the mean density values. Hypotheses have been presented concerning other geological factors responsible for the variation of these values. Regression curves constructed for the individual stratigraphic horizons served to estimate the maximum earlier depth of the Palaeozoic rocks of the Holy Cross Mountains and their vertical displacement. Similar studies have been completed for two adjacent boreholes situated in the Bug River depression. Their results indicate that mean density values can readily serve to estimate the amount of vertical tectonic displacement.
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    Pure and applied geophysics 114 (1976), S. 285-286 
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    Notes: Summary It is argued that normally the stresses in the lithosphere are hydrostatic or pseudohydrostatic. Several mechanisms are discussed that account for this feature, the more important one being plastic deformation leading to a situation in which the crustal material can be considered as ‘pre-stressed’ inthe horizontal plane. The proposed stress distribution has consequences for crustal model studies, especially when ductile flow is involved.
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    Notes: Summary A comparison is made between the multimode Rayleigh wave response to strike-slip fault motion in earth models with and without a low-velocity channel in the upper mantle. On the basis of this and previous studies it is concluded that for any focal mechanism the higher-mode amplitude spectra are useful for discriminating between the two types of structures.
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    Pure and applied geophysics 113 (1975), S. 257-280 
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    Notes: Summary About twenty blasts are used to determine crustal structure and to monitor temporal seismic velocity changes in southern California. The shot time is determined up to 10 msec by using a disposable pick-up placed directly on the explosive. About 17 permanent stations and 20 temporary stations are used for the recordings. With a fast paper speed (typically 1 cm/sec) and the WWVB radio signals superposed on the seismic trace, absolute timing accuracy of up to 10 msec is achieved. A representative structure thus determined consists of a 4 km thick 5.5 km/sec layer underlain successively by 23.4 km thick 6.3 km/sec layer, 5.0 km thick 6.8 km/sec layer and 7.8 km/sec half space. The details of the lower crust are somewhat uncertain. This structure can explain the travel time data, corrected for the station and source elevations and for the station delays, to ±0.15 sec. Small but systematic temporal velocity changes up to 3% have been found for some of the profiles. If the effect of the migration of the shot point is small enough, these changes are larger than experimental errors and represent real temporal change in the material property between the shot point and the stations.
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    Pure and applied geophysics 113 (1975), S. 673-682 
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    Notes: Summary Records from Swedish seismograph stations of underwater explosions in northern Scandinavia on 1 and 3 August, 1972-the so-called ‘Blue Road’ experiment-are used to calculate the average structure of an assumed two-layered crust. This model can serve as a basis in the process of locating earthquakes and explosions in and near the Scandinavian area. The values of the wave velocities with their standard deviations are (km/s):Pn 7.87±0.02,P * 6.69,Pgl 6.27±0.03,Sn 4.55±0.03,S * 3.69±0.03,Sgl 3.54±0.02,Sg2 3.40±0.01 andRg 2.81±0.02. Except forRg, these values, like those of the thicknesses of the two horizontal layers-the granitic layer 10 km and the basaltic layer 26 km-are similar to the values found byBåth [1] in 1971 for the same area. A more extensive material from explosions at various places in and around Sweden would give still more reliable values and might also be helpful in the construction of more local travel-time tables.
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    Pure and applied geophysics 113 (1975), S. 683-693 
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    Notes: Summary The earthquake activity in Europe is investigated in the paper using return periods of earthquakes in fifteen European seismic regions. The variations of return periods are compared with the fundamental structure of Europe and with the observed migrations of epicentres. The probabilities of occurrence of earthquakes and their return periods are obtained by applying the theory of largest values to the data in Kárník'sCatalogue of European Earthquakes 1901–1967.
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    Pure and applied geophysics 113 (1975), S. 713-734 
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    Notes: Abstract The structure and dynamics of severe convective storms and their mesoscale environments is described on the basis of current literature. Numerical modeling of regional and cloud-scale meteorology is reviewed with respect to its contribution to the understanding of convective storm evolution. Observation techniques are surveyed briefly. Critical questions, principally on the triggering of convective storms, are listed and a U.S. national program (Project SESAME) aimed at answering them is briefly described.
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    Pure and applied geophysics 113 (1975), S. 747-764 
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    Notes: Abstract Migration velocities of convective storms are summarized for six situations, with different environmental wind fields. Small-and medium-sized storms generally moved to left of the direction of, and at speeds somewhat less than, the vector mean wind in the troposphere. Large-diameter (ca. 20–30 km) storms generally deviated to the right, in proportion to their sizes and to the veering of wind with height. This behavior, and the tendency for large storms to move appreciably slower than the mean wind, are even more pronounced when giant clusters of thunderstorms are considered. An example is analyzed in which a multicellular storm, 80 km wide, moved 55° to right of the mean wind and with half its speed. This behavior results from a characteristic pattern of propagation, in which new cells tend to form on the general upwind side of the cluster, with the larger and more intense cells developing on its right flank. The individual cells move through the cluster, dissipating on approach to its advancing and left flanks. Preferential formation of cells toward the rear side of the cluster is shown to be compatible with the probable origin and trajectories (relative to the moving storm) of air ascending from the lower part of the subcloud layer. The sometimes-observed rapid movement of large multicellular storms to left of the mean wind is partly accounted for by an opposite (left forward flank) pattern of propagation.
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    Pure and applied geophysics 113 (1975), S. 837-849 
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    Notes: Abstract The latent heat released by cumulus clouds is very important to the energies of many large-scale tropical disturbances. The number of cumulus clouds involved in these disturbances is usually very large. The collective effects of cumulus clouds must therefore be incorporated into a large-scale model in a parameterized fashion. Present parameterization schemes are briefly reviewed. Recent advances in our understanding of the control and feedback processes between cumulus clouds and the large-scale circulations are discussed. Emphasis is placed on the implications of the results of recent diagnostic studies on the future development of the theory of cumulus parameterization.
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    Pure and applied geophysics 113 (1975), S. 851-867 
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    Notes: Abstract Observations of air flow in and around convective clouds are summarized and discussed in light of the requirements for parameterization of midlatitude convection. Both theory and observation indicate that a substantial portion of the compensating subsidence occurs as dry downdrafts in the immediate vicinity of convective clouds, which suggests that an additional physical mechanism is necessary in linking convection to the large scale. A conceptual three-dimensional model of midlatitude organized convection along with its implications for parameterization, particularly in mesoscale modeling, is presented. The effects of moist downdrafts are also considered and some differences between midlatitude and tropical convection are discussed.
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    Pure and applied geophysics 113 (1975), S. 909-923 
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    Notes: Abstract Equations are developed to describe the energetics of atmospheric convection as simulated by a two-dimensional axisymmetric numerical cloud model with parameterized microphysics of the liquid phase. Expressions that are compatible with the Boussinesq cloud model are given for specific energy, energy density, and energy flux at each grid point, and variations in time and space are considered. Energy is subdivided into categories, including kinetic energy, potential energy, thermal enthalpy, and latent enthalpy, so that the relative importance of various cloud properties and processes to the transformation and redistribution of energy can be studied. One of the prime goals of the investigation is to gain better understanding of the ways in which cloud-scale convection in an ensemble of cells affects circulations of larger scale. A description of the use of the energy equations in an actual numerical experiment is given in a companion report.
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    Description / Table of Contents: Summary The Guil valley permian volcanic rocks have NRM whose direction is very near to the plane of alpine schistosity affecting these rocks. During the alpine orogeny, their permian magnetization was probably modified by tectonic stresses (mechanical modification, or new magnetization by piezo-magnetic effect). The NRM of the Guil valley rocks cannot be used as a reference for geotectonic study of the Alps.
    Notes: Résumé Les roches volcaniques permiennes de la vallée du Guil présentent une ARN de direction voisine du plan de la schistosité alpine qui les affecte. Leur aimantation permienne a probablement été modifiée, lors de l'orogénèse alpine, par les efforts tectoniques (modification d'origine purement mécanique, ou acquisition d'une nouvelle aimantation par effet de pression). L'ARN des roches du Guil ne peut donc pas être prise en référence pour une étude géotectonique de l'arc alpin.
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    Pure and applied geophysics 114 (1976), S. 701-710 
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    Notes: Abstract A spectral theory of seismic sources is developed which treats earthquake foci as band-pass filters. This concept is applied to focal mechanisms of the type double-couple with moment, and the obtained spectral function of the source is compared with those obtained by other authors. Finally some formulae for the determination of geometric and dynamic source parameters from the ‘bandpass’ parameters are presented.
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    Pure and applied geophysics 114 (1976), S. 743-743 
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    Pure and applied geophysics 114 (1976), S. 747-751 
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    Notes: Abstract Observations of surface waves depend both on the structure traversed and the nature of the source, and therefore inversion of surface wave data can yield information about both structure and sources. The available methods for structural inversion are compared and discussed and a suggestion made for improved source inversion.
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    Pure and applied geophysics 114 (1976), S. 727-739 
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    Notes: Abstract The scale invariant inclusion theory of failure is applied to the problem of aftershock sequences. In the inclusion theory, a macrocrack, or void of low aspect ratio, the length of which depends upon the magnitude of the impending mainshock, forms within the inclusion zone of the impending earthquake. The fault zone that precedes the inclusion zone represents that part of the macrocrack that has closed. It is shown that bifurcation (branching) of the macrocrack and its associated fault must occur within the focal region of the inclusion during the growth phase of the earthquake. The bifurcation process produces extensive faulting of the material that comprises the focal region. A prediction of the inclusion theory is that each fault within the focal region will terminate within a zone of concentrated dilatancy that may or may not be in an unstable state. When the zone is unstable, an aftershock will occur. It is shown that these inclusion zones will, on the average, occur near the boundaries of the focal region. Failure of these unstable zones leads to additional failures within the interior portions of the focal region. These failures represent ‘lock point’ failures along the fault(s) and will, in general, exhibit few or no additional aftershocks. The bifurcation model of aftershock sequences leads to five results: (1) The aftershock sequence will exhibit an inverse hyperbolic time decay law when the stresses that are applied at distances far removed from the hypocenter remain constant during the sequence and when there isno interaction between the brittle lithosphere (where aftershocks occur) and the underlying asthenosphere. (2) The mean magnitude of any group of aftershocks within the sequence will be approximately constant in time. (3) The aftershocks will, in general, have focal mechanisms identical to that of the mainshock. (4) Large seismic events that occur throughout the aftershock zone will be independent of one another when the aftershocks are sufficiently far apart (∼two-three ‘fault’ lengths) and when the applied tectonic stresses remain constant during the sequence. (5) The bifurcation model predicts that theb-value of the aftershock sequence will be 1.0 when both the Utsu relationship between aftershock area and mainshock magnitude and the Gutenburg Richter frequency-magnitude relationship are satisfied.
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    Pure and applied geophysics 114 (1976), S. 753-763 
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    Notes: Summary A detailed description is given of a data analysis procedure for phase velocity determination from long period seismograms.
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    Pure and applied geophysics 114 (1976), S. 765-774 
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    Notes: Summary Three methods of computing the partial derivatives of dispersion curves are briefly described and compared: numerical differentiation, variational methods and an implicit function method.
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    Pure and applied geophysics 114 (1976), S. 775-790 
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    Notes: Summary The dispersion of higher modes of surface waves over a region covered by an array of stations can be measured by applying a frequency-wavenumber transform to segments of the signals in these stations, centered at a number of group-velocities. Thus, at a fixed period, modes appear as separate maxima in a display of the power spectrum on a phase-velocity vs. group velocity plane. For regions of mild lateral heterogeneity, the main source of error is shown to be due to the inadequacy of the array-response. Numerical experiments with synthetic signals indicate that a precision of the order of 1% can be obtained with a realistic number of stations. Improvements should be obtained by averaging data obtained from different events. The danger of misidentification of modes can be reduced by iteratively removing the sidelobes from the mode-separation diagram.
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    Pure and applied geophysics 114 (1976), S. 821-832 
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    Notes: Summary Two different viewpoints of the phase velocities of the elastic surface waves in isotropic, laterally inhomogeneous media have led to inconsistent results. Arguments in terms of surface wave modes give the conclusion that the phase velocity is independent of the propagation direction, while the outcome of calculations based on a constructive interference of body waves in a surface layer is that the phase velocity is dependent on the propagation direction. Both arguments are summarized and an error in the calculations giving dependence is pointed out. The calculations and observations of surface wave amplitude changes in laterally inhomogeneous media are also summarized.
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    Pure and applied geophysics 114 (1976), S. 877-878 
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    Pure and applied geophysics 115 (1977), S. 301-316 
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    Keywords: Stress drop ; Earthquake source theory ; Earthquake source dimension
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    Notes: Abstract We discuss the inversion of stress drops from seismic observations on the basis of crack or stress-drop models of earthquake mechanism. Since a formal inverse problem cannot be posed at present we discuss implications of solutions to direct problems. We first discuss the static approximations used to obtain stress drop from seismic moment and source dimensions. We show that the geometrical effects are quite significant if only one source dimension has been retrieved from seismic observations. The effect of variable stress drop is discussed and we show that the inverted stress drop is not a simple average of the actual stress drops on the fault. We discuss the energy release during faulting and show that the apparent stress has a complicated relation to the stress drop on the fault. We also show that the static stress drops obtained by seismologists are a lower bound to the actual dynamic stress drops on the fault. This may in part explain disagreements with laboratory results. Finally, we discuss the inversion of source dimensions from the far-field radiation. We analyse two extreme, simple dynamical source models, a circular fault and a rectangular fault and show that geometry has a much more pronounced effect on radiation than is usually acknowledged.
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    Pure and applied geophysics 115 (1977), S. 317-331 
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    Keywords: Stress drop ; Intraplate stress ; Apparent stress
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    Notes: Abstract The magnitude of shear stress in the lithosphere is bounded from below by the apparent stress and stress drop during intraplate earthquakes. Apparent stresses and stress drops for a number of mid-plate earthquakes are calculated from the earthquake magnitude, SH wave amplitude spectra, and estimates of the length of the fault zone. Apparent stresses vary between 0.1 and 2 bars, ifm b is used as a measure of seismic energy, and stress drops lie between 2 and 70 bars. There is no systematic difference in either apparent stress or stress drop between these intraplate events and typical plate boundary earthquakes. These bounds on intraplate shear stresses are consistent with the inference from current models of plate tectonic driving forces that regional stress differences in the plates are typically on the order of 100 bars. The highest stress drops measured for midplate earthquakes under this model represent nearly total release of local tectonic stress.
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    Pure and applied geophysics 114 (1976), S. 919-923 
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    Pure and applied geophysics 114 (1976), S. 965-974 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Linear trend analysis of geophysical time series is considered in connection with the problem of determining long-period variations (possibly of man-made origin) in the presence of short period noise of larger amplitude. Criteria for testing hypotheses about linear trends are presented for the cases of independent observations and of the observations whose correlation function is known. The possibility of increasing the precision of the results using area-averaged values is investigated. Examples are given of the long time series analysis of air temperature, carbon dioxide and water vapor content. Time series of total atmospheric ozone content at some stations are also considered, and conditions for correct statistical analysis of such data are given.
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    Pure and applied geophysics 114 (1976), S. 1009-1020 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The presence of lateral contrasts of electrical conductivity modifies the original pattern of electromagnetic fields radiated from remote sources. A magnetic transverse plane wave field, interacting with a vertical conductive and outcropping dike placed between two quarter-spaces of unequal electrical conductivities, creates an anomalous vertical component of the magnetic field. This anomalous field has been analysed by computation, and drafting of master curves. Two case histories are presented to illustrate the application and the effectiveness of the solution. It is concluded that: (i) the response is higher for intermediate values of the conducting body induction number; (ii) the curves can be used for the inter-pretation of magnetotelluric, AFMAG, and VLF exploration data; (iii) it is necessary to develop solutions taking into account the vertical as well as the lateral variation of conductivity.
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  • 96
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    Pure and applied geophysics 114 (1976), S. 287-299 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The microwave emissivity of relatively low-loss media such as snow, ice, frozen ground, and lunar soil is strongly influenced by fine-scale layering and by internal scattering. Radiometric data, however, are commonly interpreted using a model of emission from a homogeneous, dielectric halfspace whose emissivity derives exclusively from dielectric properties. Conclusions based upon these simple interpretations can be erroneous. Examples are presented showing that the emission from fresh or hardpacked snow over either frozen or moist soil is governed dominantly by the size distribution of ice grains in the snowpack. Similarly, the thickness of seasonally frozen soil and the concentration of rock clasts in lunar soil noticeably affect, respectively, the emissivities of northern latitude soils in winter and of the lunar regolith. Petrophysical data accumulated in support of the geophysical interpretation of microwave data must include measurements of not only dielectric properties, but also of geometric factors such as finescale layering and size distributions of grains, inclusions, and voids.
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  • 97
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    Pure and applied geophysics 114 (1976), S. 321-331 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The results of comparisons of experimental data on the A3 2775 kHz absorption, X-ray (1–8 Å) flux and Lyman-α radiation are compared with model data on ionization-rate and radio-wave absorption height profiles. The Lyman-α radiation is found to dominate even in the upper D-region ionization (except flare conditions). A significant increase of usually used nitric oxide concentrations from rocket airglow measurements is required for achieving the best agreement between experimental and model data.
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  • 98
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    Pure and applied geophysics 114 (1976), S. 357-363 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary An analysis of the characteristics of the eddy diffusivity is made, and the equation for turbulent diffusion in a linear flow is derived. This diffusion equation is solved analytically.
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  • 99
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    Pure and applied geophysics 114 (1976), S. 403-414 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary Internal waves are considered on the hypotheses of small disturbances and the Boussinesq approximation. Consideration is given to the lowest internal mode propagating along athin thermocline, and an approximate calculation is made of the dispersion relation, including an explicit representation of the dominant correction for thermocline thickness. Then, the Stokes drift velocity is calculated (a) approximately for this mode in the thin-thermocline model, and (b) numerically for the first two internal modes associated with a single thick thermocline. Finally, a calculation is made of the mass transport velocity field induced by the interaction between pairs of waves (surface or internal), having thesame frequency but arbitrary directions of propagation.
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  • 100
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    Pure and applied geophysics 114 (1976), S. 415-423 
    ISSN: 1420-9136
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Summary The decrease in elastic constants due to dilatancy in the earth's crust may bring about changes of its loading response to ocean tides. The amount of change is estimated by two-dimensional finite element analysis. The results show that if a dilatant zone of thicknessd underneath a coastline extends seaward and under the land, then amplitude changes will be detectable at distances 3d andd inland for strain and tilt tides, respectively. An anisotropic decrease of elastic constants in the vertical direction only will reduce the range by one half at most for strain tides especially.
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