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1.
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
2.
Carlo Bernasconi 《Pure and Applied Geophysics》1958,39(1):26-34
Riassunto L'Autore dimostra che, nel sistema di coordinate polari , , , si possono determinare un numeros di funzioni della sola variabile :Q
1,Q
3, ....Q
2s–1 tali che la sommatoria delleQ
2i–1/2i–1 rappresenti il potenzialeV di un geoide di rotazione. La condizione di armonicità determina ciascunaQ (che si riduce a un polinomio nelle potenze di sen ) a meno di una costante arbitraria; si dispone pertanto dis costanti che servono per soddisfare la natura dellaV sulla superficie del geoide. Come esempio l'Autore ha determinato la gravità sul geoide sferico, confermando i risultati delSomigliana, e su uno sferoide generico dove ha ritrovato la relazione diClairaut.
Summary The Author proofs that, in the system of polar coordinates , , , it is possible to determine a numbers of functions only of the variable :Q 1,Q 3 ....Q 2s–1 in such a way as to make the summatory of theQ 2i–1/2i–1 represent the potential function of a rotational geoid. The condition of harmonicity determines, saving an arbitrary constant, each of theQ which is reduced to a polynom developed by the sin powers; therefore one disposes of a number of constants to make use for satisfing theV on the geoid. To illustrate his theory the Author determines the gravity on the spherical geoid, thus confirmingSomigliana's formulas and on a spheroidal on which he pointed outClairaut's relations.相似文献
3.
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
4.
Ivanka Jakubcová Miloš Pick Reviewer V. Kárník Reviewer J. Vondrák 《Studia Geophysica et Geodaetica》1986,30(2):148-152
Summary The seismic energy released by global earthquake activity with time was correlated with F=||, where || is the absolute value of the change of the Sun's acceleration with time. For deep earthquakes and probability P=0.95, the coefficient of correlation was found to be around 0.4. For shallow earthquakes, the dependence was not proved.
¶rt;a u uu (1900–1982.) ua ¶rt; F=||,¶rt; || am au uu u a. mu (h>60 ) u ¶rt; mmu =0.95 uum uu ¶rt;muam0.45. nm mu auum a n¶rt;m¶rt;a.相似文献
5.
Summary The geopotential scale factor R
0
=GM/W
0
has been determined on the basis of satellite altimetry as R
0=(6 363 672·5±0·3) m and/or the geopotential value on the geoid W
0
=(62 636 256·5±3) m
2
s
–2
. It has been stated that R
0
and/or W
0
is independent of the tidal distortion of surface W=W
0
due to the zero frequency tide.
¶rt;a nmu amumuu u ama amnmuaa R 0 =GM/W 0 =(6 363 672,5±0,3) m u/uu aunmuaa a nmuu¶rt;a W 0 =(62 636 256,5±3) m2 s–2. m, m R 0 u/uu W 0 auum m nm amu a a nuu ¶rt;au nmu W=W 0 .相似文献
6.
Summary The magnetic moments of Uranus and Neptune have been predicted using different scaling laws of planetary magnetism. The predictions for Uranus cover a broad band of values from very weak magnetic fields (tidal relations) to moderate fields (thermal convection hypothesis). Therefore, the direct measurements of this field by Voyager 2 (January 1986) will be very important for testing the individual hapotheses.
Presented at the Fifth Scientific Assembly of IAGA in Prague 1985. 相似文献
a m ama a ¶rt; amua nam ¶rt;a n aum m nam a a nm. aa n¶rt;nmu nuu mu, ¶rt;m u¶rt;am a aum n a nmu aa u u a nmu nma.
Presented at the Fifth Scientific Assembly of IAGA in Prague 1985. 相似文献
7.
Summary Based on the relation between the relative sunspot number R, the number of sunspot groups f
0
generated per unit time on the Sun as a whole and their average lifetime T
0
, and on the extrapolation of time behaviour of f
0
and T
0
, it is proved that abnormally high solar activity may be expected in the first half of the 21st century. At this time, the maximum annual relative sunspot numbers RM of the 11-year cycles should reach values of about 300 units. This abnormally high solar activity in the next century can be understood as the antipole of the Maunderean minimum. This forecast is used to discuss some of the possible consequences of this abnormally high solar activity for the processes on the Earth: changes of climate (heat waves and draughts in Central Europe), in the higher layers of the Earth's atmosphere (anomalous propagation of radio waves, increased effect of the density of the upper atmosphere on the orbits of man-made satellites), in seismicity (increased seismic activity in Europe and Southeast Asia), for technical devices (induced electric currents), in the biosphere. etc.
a mu ¶rt; uau a R nm, unn nm f 0 uu ¶rt;uu u a ë u u ¶rt; n¶rt;ummu uu 0 , u a manuu ¶rt;a f 0 u 0 , naa, m n nu ¶rt; 21 a u¶rt;am uum amum. aua¶rt;u ua a R m¶rt; 11-mu ua m u ¶rt;muam au 300 ¶rt;uu. m uum amum ¶rt; nuam a amun¶rt; a¶rt; uua. a m na ¶rt;am m n¶rt;mu m uum amumu a n nmau a : a uu uama (aa u a n¶rt;a ¶rt; n), a u u am u (aa anmau a¶rt;u, uu n nmmu u am a ¶rt;uu um m), a um (na ua amum n u -m uu), a muu mma (u¶rt;ua muu mu), a u u ma ¶rt;a.相似文献
8.
a au au a ¶rt;am m ¶rt;uauu n¶rt;nu mau nua am u nu uu, m n amu n nua n uau mua mu. 相似文献
9.
Baidyanath Chattopadhya 《Pure and Applied Geophysics》1972,98(1):65-71
Summary Rotatory vibrations of a thick spherical shell of isotropic non-homogeneous material with rigidity and density given by (i) =
0
r
-2 withQ =Q
0
r
-2
e
2mr
and (ii) =
0
r
m with =Q
0
r
n have been discussed and the frequency equation is derived with numerical enumeration of frequency in each case. 相似文献
10.
— Starting with fundamental-mode Rayleigh-wave attenuation coefficient values (R) predicted by previously determined frequency-independent models of shear-wave Q (Q), we have obtained frequency-dependent Q models that explain measured values of R as well as of Lg coda Q and its frequency dependence at 1 Hz (Qo and , respectively) for China and some adjacent regions. The process combines trial-and-error selection of a model for the depth distribution of the frequency dependence parameter () for Q with a formal inversion for the depth distribution of Q at 1 Hz. Fifteen of the derived models have depth distributions of that are constant, or nearly constant, between the surface and a depth of 30 km. distributions that vary with depth in the upper 30 km are necessary to explain the remaining seven models. values for the depth-independent models vary between 0.4 and 0.7 everywhere except in the western portion of the Tibetan Plateau where they range between about 0.1 and 0.3 for three paths. These low values lie in a region where QLg and crustal Q are very low and suggest that they should also be low for high-frequency propagation. The models in which varies with depth all show a decrease in that value ranging between 0.55 and 0.8 in the upper 15 km of the crust and (with two exceptions where =0.0) between 0.3 and 0.55 in the depth range 15–30 km. The distribution of values between 0.6 and 0.8 (the higher part of the range) in the upper crust indicates that high-frequency waves will propagate most efficiently, relative to low-frequency waves, in a band that includes, and strikes north-northeastward from the path between event 212/97 and KMI to the path between event 180/95 and station HIA in the north.Acknowledgement. We thank Lianli Cong for providing his code for plotting crustal Q models and Robert Herrmann for writing the mode summation code for computing Lg synthetics used in this study. Our work benefited from helpful discussions with Jack Xie at Lamont-Doherty Earth Observatory of Columbia University. This research was sponsored by the Defense Threat Reduction Agency Contract No. DTRA-01-00-C-0213. 相似文献
11.
¶rt;m ¶rt; uuauu uum auu uu, a¶rt;a a nmunmuaa, ¶rt; n uu u. aa, m u u ¶rt;um nmu, uu n¶rt; m nm, u aaaa u aa m nmua. 相似文献
12.
Summary The problem of determining the gravitational potential inside the Earth is discussed under assumptions that the 3-D density distribution is known, that the external gravity field is described by known Stokes parameters and, finally, that the smoothed Earth surface is defined by a set of topography coefficients. The spectral method was used to separate the angular and radial parts. The solution of Poisson's equation for the internal gravitational potential was reduced to a system of ordinary differential equations with homogeneous boundary conditions and to a system of linear algebraic equations.
¶rt;am na uuaumau nmuaa mu u n¶rt;naa, m um nmam an¶rt;u nmm, m aumau n nua umu mu naamau u, a, m au mnaua nm u a¶rt;am ¶rt; mnauu uum. a¶rt;u u a¶rt;ua am num nma m¶rt;. u au aa ¶rt; maumau nmuaa ¶rt;um u um ¶rt;uua au ¶rt;¶rt;u au uu u um u aauu au.相似文献
13.
Summary On the basis of the 1966–73 data, the effect of the difference between pro- and anti-sectors of the IMF is found to be negligible in the winter midlatitude (Central Europe) ionosphere contrary to the dominant effect of this difference in the high-latitude ionosphere found earlier.
a ¶rt;a a 1966–73. u¶rt;m u m amu ¶rt; pro- u anti- mau . na a u ¶rt;um (¶rt; na) u, , a naa a, naum um u.相似文献
14.
Summary The propagator matrix is expressed in terms of cross-products of spherical Bessel functions and their derivatives. A fast computational algorithm is suggested. The matrix form of the variational principle with the boundary term is derived.
u nu u u u, n¶rt; u¶rt; nu¶rt;u uu u u u nuo¶rt;. ¶rt; au u . ¶rt; u uau nuuna u .相似文献
15.
Summary The convection in a rapidly rotating, electrically conducting, horizontal fluid layer, non-constantly stratified and penetrated by an inhomogeneous magnetic field, is studied. The convection is investigated for various ratios of the thickness of the stable and unstable stratified part of the layer. The thermal model of the layer, as well as the analysis of the results have been treated with regard to the physical conditions in the liquid core of the Earth.
am u¶rt;m u m aa mn¶rt; u¶rt;uma nm mamuuau, nua ¶rt;¶rt; aum n. u u¶rt;m ¶rt; a mu m u mu u mu mamuuuao amu . ua ¶rt; , a u aau mam, n¶rt;a anm uuu u u¶rt; ¶rt; u.相似文献
16.
Vladimír Kropáček Věra Vaňková Reviewer J. Fiala 《Studia Geophysica et Geodaetica》1985,29(3):290-299
Summary The distribution of radioactive(Th, U, K) and selected trace(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) elements in volcanic rocks from the Opole and Jawor regions of the Lower Silesia has been studied. The behaviour of these elements in the studied rocks indicates that the Lower Silesian volcanic rocks are characterized by less differentiated type than other volcanic rocks of the Bohemian Massif, the Opole rock types probably having a less differentiated character than the Jawor rock types.
¶rt;a an¶rt;u a¶rt;uamu(Th, U, K) u m ¶rt;u(Rb, Sr, Ba, Y, Zr, V, Cr, Ni) m auu n¶rt;a am n u u uuu. a n mam n¶rt;num, m aum u uuu n¶rt;mam ¶rt; aamuu n¶rt; u ¶rt;uuau, aum u ana¶rt; uu. au a n¶rt;num, m auu n¶rt; amu n ¶rt;uuau ma ua n¶rt; u amu .相似文献
17.
A numerical study has been made of the heat transfer through a fluid layer with recirculating flow. The outer fluid surface was assumed to be spherical, while the inner surface consisted of a sphere concentrically or eccentrically located with respect to the outer spherical surface. The recirculating flow was assumed to be driven by a gas flow creating stress on the fluid's outer surface so that creeping (low Reynolds number) flow developed in its interior. The present study solves the Stokes equation of motion and the convective diffusion equation in bispherical coordinates and presents the streamline and isotherm patterns.Nomenclature
a
i
inner sphere radius
-
a
d
outer sphere radius
-
A
1
defined by equation (5)
-
A
2
defined by equation (6)
-
B
1
defined by equation (7)
-
B
2
defined by equation (8)
-
c
dimensional factor for bispherical coordinates
-
C
constant in equation (4)
-
d
narrowest distance between the two eccentric spheres
-
E
2
operator defined by equation (1) in spherical coordinates and by equation (21) in bispherical coordinates
-
G
modified vorticity, defined in equation (22)
-
G
*
non-dimensional modified vorticity, defined in equation (28)
-
h
metric coefficient of bispherical coordinate system, defined in equation (18)
-
k
w
thermal conductivity of water
-
K
1
defined by equation (9)
-
K
2
defined by equation (10)
-
N
Re
Reynolds number=2a
dU/gn
-
N
Pe,h
Peclet number=2a
dU/
-
n
integer counter
-
q
heat flux
-
r
radius
-
r
*
non-dimensional radius=r/a
d
-
S
surface area
-
t
time
-
t
*
non-dimensional time=t/a
d
2
-
T
temperature
-
T
o
temperature at inner sphere surface
-
T
a
temperature at outer sphere surface
-
T
*
non-dimensional temperature;=(T–T
o)/(Ta–To)
-
u
velocity
-
u
r
radial velocity in spherical coordinates
-
u
angular velocity in spherical coordinates
-
u
radial velocity in bispherical coordinates
-
u
angular velocity in bispherical coordinates
-
U
free stream velocity
-
u
r
*
=u
r/U
-
u
*
=u
/U
-
u
*
=u
/U
-
u
*
=u
/U
Greek symbols a
1
small displacement
-
vorticity, defined in equation (17)
- *
non-dimensional vorticity, defined in equation (27)
-
radial bispherical coordinates
- o
bispherical coordinate of inner sphere
- a
bispherical coordinate of outer sphere
-
angular coordinate in spherical coordinates
-
thermal diffusivity
- w
thermal diffusivity of water
-
kinematic viscosity
-
angular bispherical coordinate
-
spherical coordinate
-
streamfunction
-
non-dimensional streamfunction for spherical coordinates, = /(U
a
d
2
)
- *
non-dimensional streamfunction for bispherical coordinates, defined in equation (26) 相似文献
18.
¶rt;m uu nau mu m a nu a¶rt;u ¶rt; D-amu u. a¶rt; m nu u u. u¶rt;a a a mu nma u nma mu m (20 ¶rt; 150 ). 相似文献
19.
Vladimír Schenk Zdeňka Schenková Lubomil Pospíšil Antonín Zeman Reviewer J. Zahradník 《Studia Geophysica et Geodaetica》1986,30(4):321-330
Summary A correlation of the earthquake occurrence on the territory of Czechoslovakia and in its close neighbourhood with the data on the neotectonic and geomorphological development of the respective area, the recent movements of the Earth's crust, the courses of photolineations and on the geophysical fields enabled the fundamental structural blocks in the upper part of the Earth's crust to be singled out. The contact zones established between the above blocks exhibit increased long-term movement tendencies particularly in the Neoid period. A seismotectonic model of the upper part of the Earth's crust of Czechoslovakia, compiled with the use of the data mentioned above, is described.
u m uu mu a mumuu auu u mmu ¶rt;au n mmu,uu, ¶rt;uu , u nmu u uuuu n nua ¶rt;um mm u amu . a a ¶rt; muu au a¶rt;am amau ¶rt; ¶rt;uu, u¶rt; nu¶rt;. m n¶rt;aaa mmua ¶rt; amu aa a au¶rt;uauu n, nu¶rt;u a ua mumuu, u a u u n¶rt;uu au.相似文献
20.
au u uu mu a amu am a¶rt; mum ma¶rt;amuauau nmm m a, ¶rt;a m u ¶rt;u naam — aum¶rt; a, nu¶rt; a¶rt;u uu na¶rt;u am — nu muaua muam ¶rt; m ¶rt;a. ¶rt;aa n ma¶rt;amuauu nm naam ¶rt;u munaua nmmu ¶rt;. 相似文献