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1.
Summary To clarify the ionization equilibrium near the ground, simultaneous measurements of the rate of ion pair production (q), the concentrations of small ions (n) and condensation nuclei (Z), and the diffusion coefficient of condensation nuclei (D) were carried out at several stations in the central area of Japan. The total rate of ion pair production (q) was estimated fromq=q(Rn)+q(Tn)+q()+q(+CR). The value ofq was estimated as 10J to 20J. The mean life () and the effective attachment coefficient () of small ions were also estimated at each station. Correlations amongn, Z, q, andD were also studied. If we take the variation ofD into consideration, the correlation was expressed by the simple formula;q=n Z. The dependence of upon size of nuclei (2r) were also measured, and was found to correlate well withD orr.  相似文献   

2.
Summary Records of underwater explosions in Iceland in 1959 and 1960, mainly performed for crustal studies, have been investigated with regard to amplitudes. The amplitudes ofP2 in the 1959 explosions and of the first arrivingP waves in the 1960 explosions were found to be proportional to the first power of the charge weight, whereas amplitudes ofP1 andS1 in the 1959 explosions were proportional to the 3/4-power of the charge up to 200 kg, but increased much slower for larger charges. The influence of water depth of shot point on the charge weights, required to obtain a certain amplitude, has been determined and it was found that the logarithm of the charge weight has a linear relation to water depth down to about 8 meters. The amplitudes of first arrivingP waves decrease as the inverse 2.2-power of the distance up to about 30 km. For greater distances an exponential decrease of the form (const./) exp (–) is valid. ForP2 waves with a frequency of 10 cps we found =0.027±0.003 km–1 for a profile across central Iceland and =0.009±0.004 km–1 for a profile in the western part of Iceland.
Zusammenfassung In den Jahren 1959 und 1960 wurden auf Island Unterwasser-Explosionen ausgelöst, deren Hauptziel Untersuchung der Erdkruste waren. Die Aufzeichnungen der Explosionen werden hier in Hinsicht auf die Amplituden der Wellen untersucht. DieP2-Amplituden in den Explosionen von 1959 und die Amplituden der zuerst ankommendenP-Wellen in den Explosionen von 1960 waren proportional der ersten Potenz des Ladungsgewichtes, während diePl-undSl-Amplituden in den Explosionen von 1959 proportional der 3/4-Potenz des Ladungsgewichtes bis 200 kg waren. Für höhere Ladungsgewichte wuchsen die Amplituden langsamer an. Es wurde der Einfluss der Tiefe des Schusspunktes unterhalb des Wasserspiegels auf das für eine gewisse Amplitude benötigte Ladungsgewicht bestimmt. Es ergab sich dabei, dass der Logarithmus des Ladungsgewichtes in einer linearen Beziehung zur Tiefe, bis etwa 8 m, steht. Die Amplituden der zuerst ankommendenP-Wellen sind umgekehrt proportional der 2.2-Potenz der Entfernung, bis etwa 30 km. Für grössere Entfernungen ist die Abnahme der Amplituden exponential und kann durch (Konst./) exp (–) dargestellt werden. FürP2 mit einer Frequenz von 10 cps haben wir =0.027±0.003 km–1 für ein Profil in Zentral-Island und =0.009 ± 0.004 km–1 für ein Profil in West-Island gefunden.
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3.
Zusammenfassung Es wird unter der Voraussetzung, dass die Laufzeitfunktion (r) oder 2 (r) durch eine abgebrochene Potenzreihe dargertellt werden kann, das Problem der Reflexionsseismik in einem einachsig inhomogenen Körper allgemein und exakt gelöst. Weiter wird für geneigte Sprungflächen eine Näherungslösung angegeben und ein Beispiel behandelt.
Summary Under the assumption, that the travel-time function (r) or 2 (r) can be represented by a restricted power serie, the problem of the reflection seismic in a uniaxial inhomogeneous medium is generally and exactly treated. Furthermore an approximate solution for inclined surfaces of discontinuity and an example are given.
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4.
Zusammenfassung Es wird die Gleichung für die Elektronenproduktionq(z) abgeleitet, die die meteorologischen Elemente der Mesosphäre berücksichtigt. Nach Angaben über die mit Satelliten und Raketen gemessene Röntgenstrahlung mit 8 Å wird das Differentialspektrum des ionisierenden Energieflusses für eine mittlere Sonnenaktivität konstruiert. Auf dieser Grundlage und nach der bekannten Intensität der Strahlung Ly- sowie nach Angaben über dieElektronenproduktion der kosmischen Strahlung werden die Profileq Rö(z),q Ly-(z) undq CR(z) für mittlere geographische Breiten und Standardatmosphäre entwickelt. Nach eingehender Analyse der vollständigen Gleichung für den effektiven Rekombinationskoeffizienten wird für die Verhältnisse in der tiefen Ionosphäre der Beitrag jeder einzelnen Komponente der Gleichung bestimmt. ist eine recht veränderliche Grösse, die von den aeronomischen und meteorologischen Verhältnissen und der Sonnenzenitdistanz abhängt. Aus den fürq(z) und (z) erhaltenen Angaben werden zwei ElektronendichteprofileN(z) für =30° und 75° erhalten. Das ProfilN(z) bei =30° wird mit dem gemittelten Profil einer umfangreichen Gruppe experimentell gefundener VerteilungenN(z) verglichen; das Profil bei =75° wird durch Messung der deviativen und nondeviativen Absorption für eine längere Zeitperiode überprüft. In beiden Fällen hat sich die Richtigkeit der theoretisch erhaltenen Profile bestätigt. Die jahreszeitlichen Variationen der nondeviativen Absorption in derD-Region sind ausschliesslich durch die Variationen der meteorologischen Parameter im Bereich der Mesopause bei konstantem Energiefluss der ionisierenden Strahlung bedingt.
Summary An equation about the electron production is deduced in which the meteorological elements of the mesosphere are taken into account. The differential spectrum of the ionizing energy flux with 3 Å for average solar activity is constructed on evidence from rocket and satelitc measurements. The profilesq Rö(z),q Ly-(z) andq CR(z) for mean geographical latitudes and standard atmosphere are plotted on that basis as well as on data fot the known intensity of the Ly- emission and the electron production of the cosmic rays. An exhaustive analysis is made of the full equation for the effective recombination coefficient and the contribution of all its components at lower ionosphere conditions is determined. is a rather variable quantity, dependent on the aeronomical and meteorological condition of the area under consideration, as well as on the solar zenith angle. Two profiles for the electron concentrationN(z) at =30° and 75° are drawn on the basis of data forq(z) and (z). The profileN(z) at =30° is compared with the averaged profile of a large group experimentally obtained distributionsN(z); the profile at =75° is checked by measurements of the deviative and nondeviative absorption taken for a lengthy period. Both checks are in good agreement with the theoretically obtained profiles. The seasonal variations of the nondeviative absorption in theD region could be completely explained with the variations of the meteorological parameters in the mesopause area at constant energy flux of the ionizing radiation.
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5.
Zusammenfassung Mit Durchsichtigkeitsmessungen wird die durch Absorption und Streuung verursachte Gesamtextinktion eines Lichtstrahls im Meerwasser erfat. Als Mazahl der Extinktion eignet sich der physikalische Extinktionskoeffizient. Dem Ziel, geräteunabhängige absolute Mewerte zu erhalten, kann man im sichtbaren Teil des Spektrums durch Eichung der. Durchsichtigkeitsmegeräte mit einem Pulfrich-Photometer näher kommen. Doch bleibt die Genauigkeit der Mewerte besonders durch die Schwerpunktsverschiebungen, die für verschiedene mittlere Durchlässigkeiten des Meerwassers berechnet und tabellarisch zusammengestellt werden, und durch die technischen Eigenschaften der Megeräte und Photoelemente beschränkt. Es wird ein Meprinzip angegeben, das diese Nachteile weitgehend vermeidet und gestattet, auch im UV absolute Extinktionswerte in exakt definierten Punkten des Spektrums zu messen.
Quantitative measurements of transparency in the sea
Summary The total extinction of a ray of light in sea water caused by absorption and scattering is ascertained by measuring the transparency. The physical extinction coefficient is suitable to act as an indicator of extinction. In the visible part of the spectrum, it is possible to obtain approximately absolute measurements not influenced by the instruments used, by standardizing the transparency-meters with the aid of a Pulfrich-Photometer. The accuracy of the measurements continues, however, to be limited in particular by the shifting of the centres which are calculated and tabulated for various mean values of transparency of sea water, as well as by the technical properties of the instruments and the rectifier photocell. A principle for measuring transparency free of these deficiencies to a large extent and allowing the measurement of absolute extinction values at exactly defined points of the spectrum, including the ultra-violet, is described.

Herrn Prof. Dr. G. Wüst gewidmet zum 60. Geburtstag.  相似文献   

6.
Fundamental-mode Rayleigh wave attenuation data for stable and tectonically active regions of North America, South America, and India are inverted to obtain several frequency-independent and frequency-dependentQ models. Because of trade-offs between the effect of depth distribution and frequency-dependence ofQ on surface wave attenuation there are many diverse models which will satisfy the fundamental-mode data. Higher-mode data, such as 1-Hz Lg can, however, constrain the range of possible models, at least in the upper crust. By using synthetic Lg seismograms to compute expected Lg attenuation coefficients for various models we obtained frequency-dependentQ models for three stable and three tectonically active regions, after making assumptions concerning the nature of the variation ofQ with frequency.In stable regions, ifQ varies as , where is a constant, models in which =0.5, 0.5, and 0.75 satisfy fundamental-mode Rayleigh and 1-Hz Lg data for eastern North America, eastern South America, and the Indian Shield, respectively. IfQ is assumed to be independent of frequency (=0.0) for periods of 3 s and greater, and is allowed to increase from 0.0 at 3 s to a maximum value at 1 s, then that maximum value for is about 0.7, 0.6, and 0.9, respectively, for eastern North America, eastern South America, and the Indian Shield. TheQ models obtained under each of the above-mentioned two assumptions differ substantially from one another for each region, a result which indicates the importance of obtaining high-quality higher-mode attenuation data over a broad range of periods.Tectonically active regions require a much lower degree of frequency dependence to explain both observed fundamental-mode and observed Lg data. Optimum values of for western North America and western South America are 0.0 if is constant (Q is independent of frequency), but uncertainty in the Lg attenuation data allows to be as high as about 0.3 for western North America and 0.2 for western South America. In the Himalaya, the optimum value of is about 0.2, but it could range between 0.0 and 0.5. Frequency-independent models (=0.0) for these regions yield minimumQ values in the upper mantle of about 40, 70, and 40 for western North America, western South America, and the Himalaya, respectively.In order to be compatible with the frequency dependence ofQ observed in body-wave studies,Q in stable regions must be frequency-dependent to much greater depths than those which can be studied using the surface wave data available for this study, andQ in tectonically active regions must become frequency-dependent at upper mantle or lower crustal depths.On leave from the Department of Geophysics, Yunnan University, Kunming Yunnan, People's Republic of China  相似文献   

7.
We consider the second-order differential equations ofP-SV motion in an isotropic elastic medium with spherical coordinates. We assume that in the medium Lamé's parameters , r p and compressional and shear-wave velocities , r, wherer is radial distance. With this regular heterogeneity both the radial functions appearing in displacement components satisfy a fourth-order differential equation which provides solutions in terms of exponential functions. We then consider a layered spherical earth in which each layer has heterogeneity as specified above. The dispersion equation of the Rayleigh wave is obtained using the Thomson-Haskel method. Due to exponential function solutions in each layer, the dispersion equation has similar simplicity, as in a flat-layered earth. The dispersion equation is further simplified, whenp=–2. We obtain numerical results which agree with results obtained by other methods.  相似文献   

8.
This work is part of an attempt to quantify the relationship between the permeability tensor (K) and the micro-structure of natural porous media. A brief account is first provided of popular theories used to relate the micro-structure toK. Reasons for the lack of predictive power and restricted generality of current models are discussed. An alternative is an empirically based implicit model whereinK is expressed as a consequence of a few pore-types arising from the dynamics of depositional processes. The analytical form of that implicit model arises from evidence of universal association between pore-type and throat size in sandstones and carbonates. An explicit model, relying on the local change of scale technique is then addressed. That explicit model allows, from knowledge of the three-dimensional micro-geometry to calculateK explicitly without having recourse to any constitutive assumptions. The predictive and general character of the explicit model is underlined. The relevance of the change of scale technique is recalled to be contingent on the availability of rock-like three-dimensional synthetic media. A random stationary ergodic process is developed, that allows us to generate three-dimensional synthetic media from a two-dimensional autocorrelation functionr( x , y ) and associated probability density function measured on a single binary image. The focus of this work is to ensure the rock-like character of those synthetic media. This is done first through a direct approach:n two-dimensional synthetic media, derived from single set ( ,r( x , y )) yieldn permeability tensorsK i-1,n i (calculated by the local change of scale) of the same order. This is a necessary condition to ensure thatr( x , y ) and carry all structural information relevant toK. The limits of this direct approach, in terms of required Central Process Unit time and Memory is underlined, raising the need for an alternative. This is done by comparing the pore-type content of a sandstone sample andn synthetic media derived fromr( x , y ) and measured on that sandstone-sample. Achievement of a good match ensures that the synthetic media comprise the fundamental structural level of all natural sandstones, that is a domainal structure of well-packed clusters of grains bounded by loose-packed pores.  相似文献   

9.
Summary On the basis of investigating 10 storms (1965–1967) good correlation was found between the density of the solar wind energy (2=1/2mNv2) and the intensity of the main phase of the geomagnetic storms, expressed in terms of the maximum decrease of the horizontal intensity (B=H/cos). The relation between 2, or Nv2, and B could then be used to determine the quantities and 0 ( is the factor expressing the increase in energy density in the magnetosphere, 0 is the energy density of the particles in a quiet magnetosphere). A comparison with the directly observed distribution of the energy density of the particles in the magnetosphere indicates that the computed value of 0 seems to be realistic. The magnitude of the factor will have to be checked again.  相似文献   

10.
Data from 41 moderate and large earthquakes have been used to derive a scaling law for fault parameters. Fault lengthL, widthW and areaS are empirically related byLS andWS where 0.6<<0.7, 0.3<<0.4 and +=1. These relations indicate that the growth pattern of earthquake rupture zones is statistically self-affine. It is also found that these relations are similar to the relation derived from a diffusion-limited aggregation (DLA) model with anisotropic sticking probability. This suggests that a modified DLA model could describe the evolution of earthquake rupture zones.  相似文献   

11.
Summary The frequency equation of Rayleigh waves propagating over the free surface of an isotropic, perfectly elastic, heterogeneous semi-infinite medium with material properties varying as = 0 e az , = 0 e az , = 0 e az (a>0) has been obtained. Solution of the frequency equation in closed form is obtained in two cases (i) =0, (ii) =, and the Rayleigh wave dispersion curves for phase and group velocities drawn. In both the cases the medium yields single Rayleigh modes which cannot propagate below certain cut-off frequencies. It is found that in case (i), <c<c 0 and 0.87500 <c g <c 0, and in case (ii), 1.03082 <c<c 1 and 0.90850 <c g <c 1, wherec andc g denote phase nad group velocities respectively, is the constant shear wave velocity of the mediumc 0 andc 1 are the corresponding Rayleigh wave velocities of the homogeneous medium of the same Poisson's ratio. The motion of the surface particles is found to be retrograde elliptical as in the homogeneous case, but the ratic of the major and minor axes now becomes frequency dependent and is plotted against frequency. In both the cases (i) and (ii), the ratio starts at a lower value at the cut-off frequency and approaches the corresponding value of the homogeneous medium at high frequencies.  相似文献   

12.
Summary The magnetic susceptibility of a rock under a uniaxial compression () decreases along the axis of compression and increases along the direction perpendicular to the axis, with an increase of . Thus, the magnetic susceptibility of a compressed rock becomes anisotropic.The decrease of longitudinal susceptibility,K (), and the increase of transverse susceptibility,K (), are theoretically derived from a model of rock which assumes the uniaxial anisotropy and the isotropic magnetostriction of magnetic minerals in rocks and a random orientation of the minerals. Results show thatK () decreases toward zero whereasK () increases and approaches a finite asymptotic value with an increase of , and –(/)K () is twice as large as /K () for small values of . These results are in good agreement with experimental data.
Zusammenfassung Die magnetische Suszeptibilität eines Steines unter zunehmender uniachsigen Druckspannung () nimmt ab längs der Achse der Druckspannung und nimmt zu längs der Richtung senkrecht der Achse. Somit wird die magnetische Suszeptibilität des gedrückten Steines anisotrop.Die Abnahme der longitudinalen Suszeptibilität,K (), und die Zunahme der transversalen Suszeptibilität,K (), werden theoretisch von einem Modell eines Steines hergeleitet, das die uniachsige Anisotropie, die isotrope Magnetostriktion, und eine nichtbevorzugte Orientierung der magnetischen Minerals im Stein annimmt. Die Ergebnisse zeigen, dass mit einer Zunahme des ,K () gegen Null abnimmt, währendK () zunimmt und sich einem begrenzten asymtotitschen Wert nähert und, dass für kleine Werte des , –(/)K () zweimal so gross wie /K () ist. Diese Ergebnisse stimmen gut mit den Versuchangaben überein.
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13.
To obtain the temperatureT and volumeV (or pressureP) dependence of the Anderson-Grüneisen parameter T , measurements with high sensitivity are required. We show two examples:P, V, T measurements of NaCl done with the piston cylinder and elasticity measurements of MgO using a resonance method. In both cases, the sensitivity of the measurements leads to results that provide information about T (,T), where V/V 0 andV 0 is the volume at zero pressure. We demonstrate that determination of T leads to understanding of the volume and temperature dependence ofq=( ln / lnV) T over a broadV, T range, where is the Grüneisen ratio.  相似文献   

14.
The rotational form of the vertically averaged equations of motion is applied to derive a formula, linear friction included, which establishes a direct connection between sense of rotation of tidal currents and features of tidal amphidromic systems. Two factors in the formula, called and , influence the sense of rotation of tidal currents; the factor involves the frequency of the tidal signal , the Coriolis parameter f, and the linear friction coefficient r. The sign of the cross-product of the logarithm of sea-surface elevation (), and phase () gradients determines whether the factor favors clockwise or anticlockwise sense of rotation. is a unit vector and is the angle between ln and . The limits ||0, ||0 and 0 lead to a clockwise sense of rotation in the Northern Hemisphere. 0 favors anticlockwise rotation in the Northern Hemisphere. Friction and low frequencies favor an anticlockwise sense of rotation. The theory works well in semi-enclosed regions like the North Sea. Although only linear friction and sea-surface elevation gradients were considered, there are ocean regions where the agreement between theory and observations is also good.Responsible Editor: Hans Burchard  相似文献   

15.
Franz Nusser 《Ocean Dynamics》1950,3(3-4):220-227
Zusammenfassung Aus dem praktischen Eisdienst entstand die Frage, wieviele zusammenhängende Tage mit negativem Mittel der Lufttemperatur nötig sind, bis sich in den verschiedenen Gebieten der deutschen Küsten das erste Eis bildet. Diese Zeit, in vorliegender Arbeit Eisvorbereitungszeit genannt, wurde aus einer 28jährigen Beobachtungsreihe ermittelt. Es zeigte sich, da die Eisvorbereitungszeit, im einzelnen modifiziert durch hydrographische und klimatologische Einflüsse, vor allem von der Morphologie der Küstengebiete abhängt. Die Nordseeküste mit ihren vorgelagerten Watten und Flachwassergebieten braucht eine kürzere Eisvorbereitungszeit als die rascher abfallende Ostseeküste. Dieser Unterschied wird besonders deutlich, wenn man die Schles wig-Holsteinische Küste der Ostsee zum Vergleich heranzieht.
Regions of equal duration of ice-generation on the German coasts
Summary The following problem arose from the practical ice service: How many consecutive days with a negative mean temperature are required for the generation of the first ice in the different regions of the German coastal waters ? This span of time which in the present paper is called the Eisvorbereitungszeit (duration of ice generation) was calculated from a period of 28 years. Its length was found to depend chiefly on the morphology of the coastal regions, with modifications due to the special hydrographical and climatological features. In the German Bight of the North Sea the duration of ice generation is shorter than in the Baltic owing to the shallow water, especially the Watt, i. e. the banks which dry at low water, whereas the shores of the Baltic are in comparison steeper. This difference becomes particularly evident by comparing the west and east coasts of Schleswig-Holstein.
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16.
Summary An explicit solution is obtained for the system of equations describing the spheroidal motion in a homogeneous, isotropic, gravitating, elastic medium possessing spherical symmetry. This solution is used to derive the Green's dyad for a homogeneous gravitating sphere. The Green's dyad is then employed to obtain the displacement field induced by tangential and tensile dislocations of arbitrary orientation and depth within the sphere.Notation G Gravitational constant - a Radius of the earth - A o =4/3 G - Perturbation of the gravitational potential - Circular frequency - V p ,V s Compressional and shear wave velocities - k p =/V p - k s =/V s - k p [(2.8)] - , [(2.17)] - f l + Spherical Bessel function of the first kind - f l – Spherical Hankel function of the second kind - x =r - y =r - x o =r o - y o =ro - x =r k s - y =r k p - x o =r o k s - y o =r o k p - =a - =a - [(5.17)] - m, l   相似文献   

17.
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   

18.
Summary In this paper the quasi-static temperature and stress distributions set up in an elastic sphere by radiation from a point source at a finite distance from the centre of the sphere and out-side it, have been discussed. The temperature boundary condition has been taken in the general form involving an arbitrary function of time. The final solutions have been obtained in terms of series involving Legendre polynomials. Numerical calculations have been done on IBM 1620 Computer and a desk calculator. The results have been represented in graphs.Notation the del operator - u the displacement vector - T the excess of temperature over that at state of zero stress and strain - , Lamé's constants - /2(+) Poisson's ratio - coefficient of linear expansion - 2(1+) - a radius of the sphere - d distance of the point source from the centre of the sphere - d o a/d - K coefficient of thermal conductivity - h heat transfer coefficient of the surface  相似文献   

19.
Zusammenfassung An Hand von Beobachtungen über periodische und unperiodische Temperaturschwankungen im Nordatlantischen Ozean wird versucht, die Frage Anomalietransport oder lokale Anomaliebildung zu klären, bzw. festzustellen, welche von beiden Entstehungsursachen für die auftretenden Schwankungen die wichtigere ist. Die Frage wird zu Gunsten der lokalen Anomaliebildung entschieden. Die Temperaturschwankungen treten in groen Gebieten des Atlantischen Ozeans fast gleichzeitig auf und verschwinden ebenso. Sie zeigen eine auffallende Gegensätzlichkeit im nordwestlichen und südöstlichen bzw. östlichen Teil des Nordatlantik, so da von einer nordatlantischen Wärmeschaukel gesprochen werden kann. Das Erscheinen der Anomalien hat dynamische Gründe und steht im Zusammenhang mit Schwankungen der ozeanischen Zirkulation, die dem Meere durch Schwankungen der atmosphärischen Zirkulation aufgeprägt werden.
On temperature anomalies at the sea surface and their relation to atmospheric circulation
Summary Based on observations on periodic and aperiodic temperature oscillations in the North Atlantic an attempt is made to discover whether these oscillations are due to wandering or locally generated anomalies, or which of these two phenomena is predominant. The problem is settled in favour of local generation of anomalies. Oscillations of temperature appear and vanish almost simultaneously in wide regions of the Atlantic. In their occurrence there is a striking contrast between the north western and the south eastern or eastern parts of the North Atlantic — one may speak of a North Atlantic temperature see saw. The anomalies are of dynamic origin and are connected with oscillations of the oceanic circulation which are impressed on the sea surface by oscillations of the atmospheric circulation.

Herrn Prof. Dr. Georg Wüst zum 60. Geburtstag gewidmet.  相似文献   

20.
Scattering of seismic waves can be shown to have a frequency dependenceQ –1 3–v if scattering is produced by arrays of inhomogeneities with a 3D power spectrumW 3D(k) k –v. In the earth's crust and upper mantle the total attenuation is often dominated by scattering rather than intrinsic absorption, and is found to be frequency dependent according toQ –1 , where –1<–0.5. IfD 1 is the fractal dimension of the surface of the 3D inhomogeneities measured on a 2D section, then this corresponds respectively to 1.5<D 11.75, since it can be shown that =2(D 1–2). Laboratory results show that such a distribution of inhomogeneities, if due to microcracking, can be produced only at low stress intensities and slow crack velocities controlled by stress corrosion reactions. Thus it is likely that the earth's brittle crust is pervaded by tensile microcracks, at least partially filled by a chemically active fluid, and preferentially aligned parallel to the maximum principal compressive stress. The possibility of stress corrosion implies that microcracks may grow under conditions which are very sensitive to pre-existing heterogeneities in material constants, and hence it may be difficult in practice to separate the relative contribution of crack-induced heterogeneity from more permanent geological heterogeneities.By constrast, shear faults formed by dynamic rupture at critical stress intensities produceD 1=1, consistent with a dynamic rupture criterion for a power law distribution of fault lengths with negative exponentD. The results presented here suggest empirically thatD 1-1/2(D+1), thereby providing the basis for a possible framework to unify the interpretation of temporal variations in seismicb-value (b-D/2) and the frequency dependence of scattering attenuation ().This is PRIS contribution 046.  相似文献   

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