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991.
The data analysis of the source parameters of five sets of earthquake sequences, aftershocks and earthquakes scattered in
a region shows that the scalar seismic moment is correlated with the linear size of the fault and the static stress drop.
We tentatively imply that a correlation also exists between the radius of the faults and the static stress drops and it is
suggested that the static stress drop may be decreasing with increasing radius of the source. It is shown that the density
distribution of the source radius, calculated through the source rupture duration obtained from the body wave pulse (Boatwright,
1980) using the time T between the P-wave onset and the first zero crossing on the seismogram, may be represented by a power law as the density
distribution of the stress drops and of the moment which are also computed. It is also suggested, and tentatively verified,
that the density distribution of the areas of the broken barriers on the faults is similar to that of the density distribution
of the static stress drops. It is finally suggested that the seismicity of a region may be studied two-dimensionally as a
function of the stress drop and the radius of the source instead of the classic b and b0 values. Concerning the discussion on the range of the values of the static stress drop, whether it is almost constant in
a seismic region and varies only from one region to another, it is seen that in the aftershocks of the 1994 Northridge earthquake
it covers a range of almost 5 orders of magnitudes. Finally it is ascertained that the density distribution of the source
parameters does not give equipartition of seismic moment release. 相似文献
992.
The TOPEX/POSEIDON (T/P) satellite altimeter data from January 1, 1993 to January 3, 2001 (cycles 11–305) was used for investigating the long-term variations of the geoidal geopotential W
0 and the geopotential scale factor R
0 = GM÷W
0 (GM is the adopted geocentric gravitational constant). The mean values over the whole period covered are W
0 = (62 636 856.161 ± 0.002) m2s-2, R
0 = (6 363 672.5448 ± 0.0002) m. The actual accuracy is limited by the altimeter calibration error (2–3 cm) and it is conservatively estimated to be about ± 0.5 m2s-2 (± 5 cm). The differences between the yearly mean sea surface (MSS) levels came out as follows: 1993–1994: –(1.2 ± 0.7) mm, 1994–1995: (0.5 ± 0.7) mm, 1995–1996: (0.5 ± 0.7) mm, 1996–1997: (0.1 ± 0.7) mm, 1997–1998: –(0.5 ± 0.7) mm, 1998–1999: (0.0 ± 0.7) mm and 1999–2000: (0.6 ± 0.7) mm. The corresponding rate of change in the MSS level (or R
0) during the whole period of 1993–2000 is (0.02 ± 0.07) mm÷y. The value W
0 was found to be quite stable, it depends only on the adopted GM, and the volume enclosed by surface W = W
0. W
0 can also uniquely define the reference (geoidal) surface that is required for a number of applications, including World Height System and General Relativity in precise time keeping and time definitions, that is why W
0 is considered to be suitable for adoption as a primary astrogeodetic parameter. Furthermore, W
0 provides a scale parameter for the Earth that is independent of the tidal reference system. After adopting a value for W
0, the semi-major axis a of the Earth's general ellipsoid can easily be derived. However, an a priori condition should be posed first. Two conditions have been examined, namely an ellipsoid with the corresponding geopotential which fits best W
0 in the least squares sense and an ellipsoid which has the global geopotential average equal to W
0. It is demonstrated that both a-values are practically equal to the value obtained by the Pizzetti's theory of the level ellipsoid: a = (6 378 136.7 ± 0.05) m. 相似文献
993.
994.
IntroductionHistorically, surface waves provided much of our understanding of the lateral heterogeneity in the crust and the upper mantle, especially in oceans or desert areas. Traditional method utilizes the great circle theorem for surface waves. It assumed that surface wave propagates along the great circle connecting epicenter with station. Firstly, traditional surface wave analysis was carried out by using multi-frequency-filter dispersion analysis to acquire the group or phase velocity d… 相似文献
995.
分析了吉林省中部地区中等地震前分维曲线Ds,Dt及地震活动演化指数YH值异常变化过程,所得结果对吉林省未来中强地震预报是有一定意义的。 相似文献
996.
997.
998.
Praween Chusilp Tsutomu Usami Hanbin Ge Hirofumi Maeno Tetsuhiko Aoki 《地震工程与结构动力学》2002,31(11):1993-2014
An experimental investigation of the cyclic shear behaviour of steel box girders was conducted on one‐quarter scale models, comprising of two specimens with longitudinally unstiffened webs and one specimen with longitudinally stiffened webs. All the specimens exhibited ductile behaviour. The tests evidenced significant increases in the shear strength and energy dissipation capacity regarding the use of thicker webs and the provision of longitudinal web stiffeners. The web stiffeners also enhanced the stable hysteresis behaviour without substantial degradation in the energy dissipation due to pinching. The test results are compared with the shear behaviour simulated by inelastic large deformation analysis incorporated with a sophisticated constitutive model. The hysteresis behaviour, peak cyclic shear stresses, energy dissipation, and deformation shapes of the three specimens are satisfactorily predicted by the analysis. It is verified that the presented analytical method can be used precisely for further investigations of box girders in shear. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
999.
应用分形理论研究煤孔隙结构 总被引:6,自引:0,他引:6
通过对淮南、淮北两个研究区内各煤矿不同煤级煤样进行的压汞法孔隙测量结果的分析,表明用分形维数可以表示煤的孔隙结构特征,而且煤孔隙体积分形维数随着变变质程度的增高而减小,渗透性随煤级的增加而减弱。 相似文献
1000.
Generalized equations using fractional-flow dimensions were derived to estimate the Darcy and groundwater-flow velocities
obtained from the point-dilution and the single-well injection-withdrawal field tests. Flow velocities can only be estimated
from single-well tests if the kinematic porosity or the hydraulic conductivity and hydraulic gradient are known a priori.
A pumping test performed on the boreholes will yield an estimate of the fractional-flow dimension and the extent of the flow
region by applying the generalized radial flow (GRF) model of Barker [Barker JA (1988) A generalized radial flow model for
hydraulic tests in fractured rock. Water Resour Res 24(10):1796–1804]. These parameters are used in the generalised equations
for the single-well tracer tests to estimate the flow-through area and, therewith, the Darcy or flow velocity.
The generalized procedure, described in detail in Part 1 of this paper, is applied to two boreholes on the Campus Test Site
located at the University of the Free State, Bloemfontein, South Africa, and it is shown that the two independent tests (i.e.
the point-dilution and the single-well injection-withdrawal tests) yield similar estimates of the natural-seepage velocity
in the aquifer. The estimated natural-flow velocity obtained by using fractional dimensions is about two times higher than
the velocity estimated by using the standard method (i.e. flow dimension n=2, flow thickness equal to length of the sealed-off section of the borehole).
Electronic Publication 相似文献