首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 31 毫秒
1.
Permeability exerts significant control over the development of pore pressure excess in the crust, and it is a physical quantity sensitively dependent on the pore structure and stress state. In many applications, the relation between permeability and effective mean stress is assumed to be exponential and that between permeability and porosity is assumed to be a power law, so that the pressure sensitivity of permeability is characterized by the coefficient and the porosity sensitivity by the exponent . In this study, we investigate experimentally the dependence of permeability on pressure and porosity in five sandstones with porosities ranging from 14% to 35% and we review published experimental data on intact rocks, unconsolidated materials and rock fractures. The laboratory data show that the pressure and porosity sensitivities differ significantly for different compaction mechanisms, but for a given compaction mechanism, the data can often be approximated by the empirical relations. The permeabilities of tight rocks and rock joints show relatively high pressure sensitivity and low porosity sensitivity. A wide range of values for and have been observed in relation to the mechanical compaction of porous rocks, sand and fault gouge, whereas the porosity sensitivity for chemical compaction processes is often observed to be given by 3. We show that since the ratio / corresponds to the pore compressibility, the different dependences of permeability on porosity and pressure are related to the pore structure and its compressibility. Guided by the laboratory data, we conduct numerical simulations on the development of pore pressure in crustal tectonic settings according to the models ofWalder andNur (1984) andRice (1992). Laboratory data suggest that the pressure sensitivity of fault gouge is relatively low, and to maintain pore pressure at close to the lithostatic value in the Rice model, a relatively high influx of fluid from below the seismogenic layer is necessary. The fluid may be injected as vertically propagating pressure pulses into the seismogenic system, andRice's (1992) critical condition for the existence of solitary wave is shown to be equivalent to >1, which is satisfied by most geologic materials in the laboratory. Laboratory data suggest that the porosity sensitivity is relatively high when the permeability is reduced by a coupled mechanical and chemical compaction process. This implies that in a crustal layer, pore pressure may be generated more efficiently than cases studied byWalder andNur (1984) who assumed a relatively low porosity sensitivity of =2.  相似文献   

2.
Summary By comparing the equalities expressing the solar flux within a wide spectral region on the assumption of an extintion within the atmospheric aerosol given by – and that of an extintion represented by 1–1, a relationship is established by means of which: 1) The error is discussed which is done when the air opacity is expressed by 1, in the case when 1; 2) A simple and quick method is worked out for determining the parameters and from actinometric observations, carried out within the spectral regions <525 m and 525 m<<625 m.  相似文献   

3.
Summary A study of the wavelength exponent of aerosol scattering in the Ångström relation for extinction by aerosol has been made from the ground-based measurments of direct solar radiation using Ångström pyrheliometer with and without Schott filters. It has been observed that in India, mainly for the middle part of the year this exponent is zero or even negative which means that the aerosol scattering is nearly neutral which is in marked contrast with the condition prevailing in middle latitudes. It is evident from the -values that the aerosol size distribution in India is far different from that prevailing in middle latitudes. At four representative stations in India, the values of the wavelength exponent and the atmospheric turbidity coefficient have been determined using the method introduced byÅngström [1,2]) and are discussed here.  相似文献   

4.
Riassunto Il lavoro riguarda una serie di misure su campioni di 5 tipi diversi di rocce italiane aventi lo scopo di determinare la rispettiva conducibilità termica. Dopo la descrizione dell'apparecchiatura usata, vengono esposti i risultati ottenuti, analizzando in dettaglio l'influenza della scistosità. In base alle misure fatte su campioni di ardesia questa influenza può esprimersi con la formola:k =k 90+m cos , dove è l'angolo fra la direzione del flusso termico ed il piano di stratificazione, mentrem è una costante caratteristica della scistosità.
Summary Experiments made for obtain the thermal conductivity of different kinds of italian rocks are described and discussed. The effect of schistosity was derived for slate rocks and it can be represented with the formula:k =k 90+m cos , where is the angle between the direction of thermal flux and the plain of stratification, whereasm is a constant characterizing the schistosity.

Lavoro eseguito con un contributo del Consiglio Nazionale delle Ricerche (Comitato per la Geologia).  相似文献   

5.
Z. Vörös 《Annales Geophysicae》2000,18(10):1273-1282
  相似文献   

6.
Summary Measuring, with the aid of two filters, the instantaneous intensity of the solar radiation in two wave lengths ( B = 0.44 , R = 0.64 ) by means of a sun photometer designed byVolz, we carried out determinations of the decadic turbidity coefficientB (=0.5 ) and the wave length exponent of the haze extinction for Mexico City. Observations were made for almost two and a half years (1960 to 1962 period). A seasonal size distribution in both parameters was found. Although the data thus obtained are provenient of a contaminated atmosphere, comparison of our data is made with those found for higher latitudes ofÅngström, Schüepp andVolz. The height of the homogeneous haze layerH D was calculated showing pronounced variations for a given wind direction. The maximum and minimum values ofB enable us to get, by the first approximation, the aerosol size distribution ofJunge for our latitudes. However, for exceptional very clear days having maximum actinometric intensity of the solar radiation the sensitivity of the microamperimeter in theVolz sun photometer fails.  相似文献   

7.
Summary Using a fit-extended balance equation for the electron-density-variations during a sun eclipse a possiblity has been found to confirm by observation theF-layer processes deduced hitherto theoretically. Moreover, the rate of electron-productionq=q(h), of the recombination-coefficient =(h) and a temperature profilT(h) can be given. These data are self-consistent. The smallness of is remarkable, whereby a slow decomposition of the nightly layer can be understand now. Also the computed temperatures coincide with rocket and satellite results.
Zusammenfassung Durch Verwendung einer passend erweiterten Bilanzgleichung für die Elektronendichte-Änderungen während einer Sonnenfinsternis gelinght es erstmalig, die bisher nur theoretisch abgeleiteten Prozesse in derF-Schicht durch die Beobachtungen zu bestätigen und Zahlenmaterial über die Größe der Elektronenproduktionq=q(h), des Wiedervereingungskoeffizienten =(h) und die TemperaturT=T(h) zu erhalten. Dieses Zahlenmaterial ist in sich widerspruchsfrei; bemerkenswert ist die Kleinheit von , wodurch nunmehr auch der nur langsame Abbau der Schicht in der Nacht verständlich wird. Die errechneten Temperaturwerte stimmen gut mit den Ergebnissen von Satellitenmessungen überein.

Report presented on 18th April 1963 at the Eleventh Annual Meeting of theSocietà Italiana di Geofisica e Meteorologia (Genova: 18–20 April 1963).  相似文献   

8.
Non-linear - dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of - solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo waves amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunders minimum.  相似文献   

9.
Multifractal measures,especially for the geophysicist   总被引：9，自引：0，他引：9  
This text is addressed to both the beginner and the seasoned professional, geology being used as the main but not the sole illustration. The goal is to present an alternative approach to multifractals, extending and streamlining the original approach inMandelbrot (1974). The generalization from fractalsets to multifractalmeasures involves the passage from geometric objects that are characterized primarily by one number, namely a fractal dimension, to geometric objects that are characterized primarily by a function. The best is to choose the function (), which is a limit probability distribution that has been plotted suitably, on double logarithmic scales. The quantity is called Hölder exponent. In terms of the alternative functionf() used in the approach of Frisch-Parisi and of Halseyet al., one has ()=f()–E for measures supported by the Euclidean space of dimensionE. Whenf()0,f() is a fractal dimension. However, one may havef()<0, in which case is called latent. One may even have <0, in which case is called virtual. These anomalies' implications are explored, and experiments are suggested. Of central concern in this paper is the study of low-dimensional cuts through high-dimensional multifractals. This introduces a quantityD q, which is shown forq>1 to be a critical dimension for the cuts. An enhanced multifractal diagram is drawn, includingf(), a function called (q) andD q.This text incorporatesand supersedes Mandelbrot (1988). A more detailed treatment, in preparation, will incorporateMandelbrot (1989).  相似文献   

10.
Summary A comparison has been made between the Townsend primary ionization coefficient, , for dry air and for air with humidities typical of those in the atmosphere. is defined as the number of new electrons produced by an electron per centimeter of drift in a field. A range of field/pressure ratios,E/p 0, of 40 to 100 V (cm torr)–1 was employed. The variation of with humidity is very small.Over the range ofE/p 0 from 50 to 100 V (cm torr)–1, the secondary ionization coefficient, , of a water surface has been found from sparking potential data to be typically 2×10–4. represents the fraction of primary ionizing collisions that ultimately result in the production of additional electrons at the surface.  相似文献   

11.
We consider the effect of including both dipole and quadrupole parities in the previous mean-field model of Hollerbach and Jones (1995), which considered dipole parity only. Allowing for both parities, we find that the onset of dynamo action occurs at 0 6, in the form of a purely quadrupolar dynamo wave. A symmetry-breaking bifurcation then occurs at 0 11, beyond which the solutions are of mixed parity. The quadrupolar component still oscillates about a zero time-average, but the dipolar component about a non-zero average. For even greater 0 we obtain an unconnected upper-branch solution. In sharp contrast to the HJ95 pure-parity upper branch, however, this mixed-parity upper branch is steady-state rather than periodic. Although it does not appear to be possible to connect these two upper branches by any simple sequence of bifurcations, we nevertheless suggest how aspects of the mixed-parity branch may help in understanding features of the previous pure-parity branch.  相似文献   

12.
The vertical velocity, , and the diabatic heating were computed at 800, 600, 400 and 200 mb surfaces using the Omega equation. The highest contribution to is from the diabatic heating produced by condensation associated with the precipitations appearing to be the main source of diabatic heating. The net radiative cooling and the thermal advection in the upper troposphere over the warm anticyclone result in diabatic cooling over the eastern part of the Bay of Bengal and adjoining northern and eastern regions.List of Symbols Used C p Heat capacity at constant pressure - f Coriolis parameter - g Acceleration due to gravity - P Atmospheric pressure - Q Diabatic heating rate per unit mass - R Gas constant of air - S Static stability parameter - t Time - U, V Zonal and meridional wind components - Specific volume - Relative vorticity - Absolute vorticity - Potential temperature - Geopotential - Vertical velocity (dP/dt) - 1 Adiabatic vertical velocity - 2 Vertical velocity due to certain forcing - 3 Diabatic vertical velocity - Isobaric gradient operator - 2 Laplacian operator - J(A, B) Jacobian operator  相似文献   

13.
Summary Six Younger Granite localities showing normal and reverse magnetizations in equal proportion have given a Jurassic palaeomagnetic pole position =62.5°N, =241.6°E; (Fisher's precision parameter (k)=27.8 and 95=13°). Individual palaeopole-positions have also been obtained for a Cretaceous pyroclastic rock and for two Pleistocene basalt flows.  相似文献   

14.
Résumé Il s'agit de la détermination de l'aplatissement de la Terre et de la pesanteur équatoriale en utilisant la définition de l'ellipsoïde de référence donnée par l'auteur dans une publication antérieure et les anomalies isostatiques moyennes calculées parL. Tanni. Les résultats obtenus, e =978.055, =1/296.3, sont sensiblement égaux à ceux qui proviennent de la méthode habituelle des moindres carrés; l'aplatissement calculé est compris entre les limites déduites parA. Véronnet de la précession terrestre.
Summary This article contains the numerical computation of the Earth's flattening and the equatorial gravity on the basis of the definition of the reference ellipsoid, given by the author in a former work, and the mean isostatic anomalies computed byL. Tanni. The results, e =978.055, =1/296.3, show that the method of least squares is accurate enough under the present conditions; the flattening computed is bounded by the values derived byA. Véronnet from the terrestrial precession.
  相似文献   

15.
Summary The source functions of the stress wave patterns at an elastic source of these waves are analysed. The comparison of the properties of the functions with the stress wave records obtained earlier showed that their parameters do not satisfy, to a greater or lesser extent, the stress wave patterns in the neighbourhood of explosive sources. For this reason a new source function (1) was defined, which fully approximates the observed stress wave patterns in gravel sandy soil. The coefficientsP 0, , , and were experimentally determined as functions of the distance from the source, its size and the radius of the elastic source in the medium considered. The properties of source function (1) are demonstrated on an example.Paper presented at the XIIIth General Assembly of the European Seismological Commission, Braov (Romania), 28 August to 6 September, 1972.  相似文献   

16.
A recurrence procedure is outlined for constructing asymptotic series for surface wave field in a half-space with weak lateral heterogeneity. Both horizontal variations of the elastic parameters and of the wave field are assumed small on the distances comparable with the wavelength. This is equivalent to the condition that the frequency is large. The Surface Wave Asymptotic Ray Theory (SWART) is an analog of the asymptotic ray theory (ART) for body waves. However the case of surface waves presents additional difficulty: the rate of amplitude variation is different in vertical and horizontal directions. In vertical direction it is proportional to the large parameter . To overcome this difficulty the transformation equalizing vertical and horizontal coordinated is suggested, Z = z. In the coordinates x,y,Z the wave field is represented as an asymptotic series in inverse powers of . The amplitudes of successive terms of the series are determined from a recurrent system of equations. Attention is paid to similarity and difference of the procedures for constructing the ray series in SWART and ART. Applications of SWART to interpretation of seismological observations are discussed.  相似文献   

17.
A method for the determination of resuspension parameters of radioactive fall-out from nuclear explosions, deposited on soil from the stratospheric reservoir, is presented. The seasonal variation ofk -137Cs resuspension parameter, the trend ofk with time in 1963–1978, the trend over this period of time of the wind component fraction of the concentration of global137Cs in the surface boundary layer over arable and natural soils are given. An estimate of radioactive contamination of vegetation by the effect considered is given as an example of practical use of this work.  相似文献   

18.
Zusammenfassung Aus der schon früher bewiesenen Eindeutigkeit des Dichtegesetzes der sphäroidischen Gleichgewichtsfiguren ergibt sich die Möglichkeit, aus einer gegebenen Gleichgewichtsfigur durch «Entblätterung» eine unendliche Reihe neuer Gleichgewichtsfiguren derselben Rotationsgeschwindigkeit mit ständig abnehmender Größe und Masse zu bilden. Auf diese Weise kann man jede beliebige innere Niveaufläche der ursprünglichen Figur bloßlegen und aus der von ihr umschlossenen TeilmasseE, der Rotationsgeschwindigkeit , der Äquatorachsea und der Äquatorachsea h des homogenen Ausgangsellipsoides der zugehörigen Figurenreihe (,C) die Abplattung berechnen und gewinnt so die Abplattungsfunktion im Innern einer Gleichgewichtsfigur gänzlich unabhängig von derClairautschen Differentialgleichung. Die Methode der Entblätterung ist auch auf höherparametrige Gleichgewichtsfiguren mit unstetigem Dichtegesetz anwendbar; sie liefert für dasWiechertsche Modell die Kernoberfläche in einer Tiefe von 3864.75 km und einen Dichtesprung von 17.84.
Summary In a previous paper I have shown, that the law of density of the spheroidal figures of equilibrium is strictly individual. This makes it possible from a given figure of equilibrium by the so called method of «stripping of leaves» to gain an infinite series of new figures of equilibrium with permanently decreasing size and mass. In this manner any inner level surface of the given figure can be laid bare and its flattening can be calculated from the enclosed part of massE, the rotation velocity , the equator axisa and from the equator axisa h of theMacLaurin ellipsoid in the beginning of the series (,C) belonging to the seeked figure. So the function of flattening in the interior of any equilibrium figure is gained totally independant fromClairaut's differential equation. The method of «stripping of leaves» also can be used for figures of equilibrium with more than one form-parameter and with discontinual density distribution. It yields forWiechert's model the surface of the core in a depth of 3864.75 km and a discontinuity of 17.84 in density.
  相似文献   

19.
We present some results of the analytical integration of the energy rate balance equation, assuming that the input energy rate is proportional to the azimuthal interplanetary electric field, Ey, and can be described by simple rectangular or triangular functions, as approximations to the frequently observed shapes of Ey, especially during the passage of magnetic clouds. The input function is also parametrized by a reconnection-transfer efficiency factor (which is assumed to vary between 0.1 and 1). Our aim is to solve the balance equation and derive values for the decay parameter compatible with the observed Dst peak values. To facilitate the analytical integration we assume a constant value for through the main phase of the storm. The model is tested for two isolated and well-monitored intense storms. For these storms the analytical results are compared to those obtained by the numerical integration of the balance equation, based on the interplanetary data collected by the ISEE-3 satellite, with the values parametrized close to those obtained by the analytical study. From the best fit between this numerical integration and the observed Dst the most appropriate values of are then determined. Although we specifically focus on the main phase of the storms, this numerical integration has been also extended to the recovery phase by an independent adjust. The results of the best fit for the recovery phase show that the values of may differ drastically from those corresponding to the main phase. The values of the decay parameter for the main phase of each event, m, are found to be very sensitive to the adopted efficiency factor, , decreasing as this factor increases. For the recovery phase, which is characterized by very low values of the power input, the response function becomes almost independent of the value of and the resulting values for the decay time parameter, r, do not vary greatly as varies. As a consequence, the relative values of between the main and the recovery phase, m/r, can be greater or smaller than one as varies from 0.1 to 1.  相似文献   

20.
A general formula for the Dieterich-Ruina friction constitutive law with rate and state (n-state variables,n=1, 2,...) dependences has been obtained and discussed under the assumption that the slip acceleration a varies ion a linearly with the slip displacement , namelya = a 0 + (-0). Wherea 0, 0 are initial constants, is the acceleration rate and constant.a 0 and may be arbitrary constants (positive, negative or zero).The extreme value of frictional resistance and the existence condition of the extreme value, which are very important and govern to some degree the motion process of a frictionally slipping mechanical system, have been analyzed. A critical value c which is the measure of the velocity weakening and velocity strengthening of the mechanical system, and its properties and the relationship to the extreme problem have been studied. Again, according to the critical value c, the concepts of light or strong velocity weakening (or strengthening) are introduced.A possibly new phenomenon that frictional resistance may vary in some kind of decayed oscillation is found. Finally, the condition for the smallest frictional resistance for a slipping mechanical system with nonuniform acceleration has been obtained.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号