We propose the pseudo-periodicity method and its quantitative prediction indexes for the occurrence time of earlier strong aftershock. We conducted tests of regressive prediction, and the R-value of the tests is 0.45, indicating that this method is effective for prediction. 相似文献
The paper presents a simple constitutive model for normally consolidated clay. A mathematical formulation, using a single tensor-valued function to define the incrementally nonlinear stress–strain relation, is proposed based on the basic concept of hypoplasticity. The structure of the tensor-valued function is determined in the light of the response envelope. Particular attention is paid towards incorporating the critical state and to the capability for capturing undrained behaviour of clayey soils. With five material parameters that can be determined easily from isotropic consolidation and triaxial compression tests, the model is shown to provide good predictions for the response of normally consolidated clay along various stress paths, including drained true triaxial tests and undrained shear tests. 相似文献
By combining the carbon cycle model with the records of carbonate and organic (kerogen) carbon isotope, this paper presents
the calculation of the fraction of organic carbon burial (forg) of beds 23–40 at the global boundary stratotype section and point (GSSP) of the Permian-Triassic boundary at Meishan, Zhejiang
Province. The resulting calculation produces two episodes of forg maxima observed to occur at beds 23–24 and 27–29, which respectively corresponds to the two episodic anoxic events indicated
by the flourish of green sulfur bacteria. Two episodic forg minima occurred at beds 25–26 and 32–34, generally coincident with the flourish of cyanobacteria (bed 26 and upper part of
beds 29 to 34) as shown by the high value of 2-melthyhopnoanes. It appears that the forg is related to the redox conditions, with greater forg values observed under the reductive condition. The relationship between forg and the total organic carbon (TOC) content was complex. The forg value was low at some beds with a high TOC content (such as bed 26), while high observed at some beds with a low TOC content
(e.g. bed 27). This association infers the important contribution of primary productivity to the TOC content. The original
organic burial could be thus calculated through the configuration of the function of the primary productivity and forg, which can be used to correct the residual TOC measured today. This investigation indicates that compiling the organic-inorganic
carbon isotopes with the carbon cycle model favors to understand the fraction of organic carbon burial, providing information
for the reconstruction of the coupling among biota, environments and organic burial.
Journal of China University of Geosciences, 2007, 32(6): 767–773 [译自: 地球科学—中国地质大学学报] 相似文献
Using more than three million Landsat satellite images, this research developed the first global impervious surface area (GISA) dataset from 1972 to 2019. Based on 120,777 independent and random reference sites from 270 cities all over the world, the omission error, commission error, and F-score of GISA are 5.16%, 0.82%, and 0.954, respectively. Compared to the existing global datasets, the merits of GISA include: (1) It provided the global ISA maps before the year of 1985, and showed the longest time span (1972–2019) and the highest accuracy (in terms of a large number of randomly selected and third-party validation sample sets); (2) it presented a new global ISA mapping method including a semi-automatic global sample collection, a locally adaptive classification strategy, and a spatio-temporal post-processing procedure; and (3) it extracted ISA from the whole global land area (not from an urban mask) and hence reduced the underestimation. Moreover, on the basis of GISA, the long time series global urban expansion pattern (GUEP) has been calculated for the first time, and the pattern of continents and representative countries were analyzed. The two new datasets (GISA and GUEP) produced in this study can contribute to further understanding on the human’s utilization and reformation to nature during the past half century, and can be freely download from http://irsip.whu.edu.cn/resources/dataweb.php.