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101.
102.
One of the puzzling features of the southern end of the Rhine graben is the Dinkelberg-Tabular Jura block on the eastern shoulder of the graben. It is dissected by a large number of faults, the most notable ones forming a field of narrow little grabens and half-grabens whose bordering faults converge at the level of the Middle Triassic evaporites, which points to décollement at that horizon. The little grabens were traditionally considered to be of Oligocene age, coeval with the main taphrogenesis of the Rhine graben. Two hypotheses were offered for their formation, one ascribing them to extension on the extrados of large basement folds, the other to gravity sliding on paleoslopes. Recent field work uncovered overwhelming evidence for an Eocene age of the little grabens, the time of the initial phase of Rhine graben formation. At that time there were neither large basement folds nor paleoslopes of any significance, and therefore the two hypotheses offered until now do not work. However, the map-view pattern of the field of faults offers a somewhat unusual way out of the dilemma. This pattern is most prominently displayed in the Dinkelberg area north of the Rhine. There a lane of narrow décollement grabens with a mean NNE strike is confined within the NW- striking Dinkelberg graben, which is much wider and rooted in the basement. It is also very shallow, with a subsidence on the order of 100 m. The lane of décollement grabens forms a dextral en-échelon pattern with respect to the Dinkelberg graben, suggesting stretching of the post-evaporite sequence above a basement essentially extended by strike slip. This model, though not as clearly expressed, is also compatible with the data in the rest of the Dinkelberg-Tabular Jura block. It also fits surprisingly well a theoretical model by Withjack and Scheiner (1982) that predicts a dominance of strike-slip in the marginal area of a system consisting of extension superimposed on doming. 相似文献
103.
台湾集集和华北大同地震序列的定量模型分析 总被引:4,自引:0,他引:4
介绍了传染型余震序列(ETAS)模型的基本原理和发展概况,并利用该模型分析了1999年开始的台湾集集地震序列(主震Ms7.6)和1989年开始的大同地震序列(主震为Ms5.7)。通过分析计算,得到了二个序列的ETAS参数向量,并结合各自的孕震环境和机制分析了二个地震序列的异同和序列衰减规律。 相似文献
104.
Hans-Dieter Vosteen Volker Rath Andreas Schmidt-Mumm Christoph Clauser 《Tectonophysics》2004,386(1-2):81-95
The thermal regime and the distribution of heat flow at the base of sedimentary basins is fundamental to the understanding of the process of basin evolution and the associated mobilization and migration of hydrocarbon and other fluids. For the Northeastern-German sedimentary basin, available information on structure, temperature, and thermal properties along a seismic DEKORP reflection profile allow high resolution 2-D forward and inverse simulations. This approach is attractive in situations where much information is available, if only with considerable uncertainty. In particular, this allows to introduce “soft” information into the analysis. In our case, forward simulations yield initial a priori estimates of the parameters while inversion calculations yield a posteriori estimates of the parameters and their uncertainty. The a priori parameters as well as their assumed uncertainty are input for a Bayesian parameter estimation scheme. In respect to the Northeastern-German sedimentary basin, the inverse analysis postulates a significant and characteristic a posteriori variation of thermal conductivity of the Zechstein unit along the entire profile as well as a generally large a posteriori thermal conductivity of the (pre-Permian) basement in the northern part of the basin. For inverse calculations, we used two alternative scenarios: One assumes the thermal conductivity of the Zechstein unit to be homogeneous along the profile while the other allows a lateral variation. A posteriori heat flow across the base of the model varies from 40 to 60 and 50 to 65 mW m−2 for models in which values for thermal conductivity and radiogenic heat generation rate were either based on literature values or direct measurements, respectively. 相似文献
105.
Including prior information in the estimation of effective soil parameters in unsaturated zone modelling 总被引:2,自引:0,他引:2
In this paper we propose a methodology to include prior information in the estimation of effective soil parameters for modelling the soil moisture content in the unsaturated zone. Laboratory measurements on undisturbed soil cores were used to estimate the moisture retention curve and hydraulic conductivity curve parameters. The soil moisture content was measured at 25 locations along three transects and at three different depths (surface, 30 and 60 cm) on an 80×20 m hillslope for the year 2001. Soil cores were collected in 84 locations situated in three profile pits along the hillslope. For the estimation of the effective soil hydraulic parameters the joint probability distribution of measured parameter values was used as prior information. A two-horizon single column 1D MIKE SHE model based on Richards' equation was set-up for nine soil moisture measurement locations along the middle transect of the hillslope. The goal of the model is to simulate the soil moisture profile at each location. The shuffled complex evolution (SCE) algorithm has been applied to estimate effective model parameters using either wide parameter ranges, referred to as the ‘no-prior’ case, or the joint probability distribution of measured parameter values as prior information (‘prior’ case). When the prior information is incorporated in the SCE optimisation the goodness-of-fit of the model predictions is only slightly worse compared to when no-prior information is incorporated. However, the effective parameter estimates are more realistic when the prior information is incorporated. For both the no-prior and prior case the generalised likelihood uncertainty estimation procedure (GLUE) was subsequently used to estimate the uncertainty bounds (UB) on the model predictions. When incorporating the prior information more parameter sets were accepted for the estimation of the predictive uncertainty and the parameter values were more realistic. Moreover, UB better enclosed the observations. Thus, incorporating prior information in GLUE reduces the amount of model evaluations needed to obtain sufficient behavioural parameter sets. The results indicate the importance of prior information in the SCE and GLUE parameter estimation strategies. 相似文献
106.
G.R. Dargahi-Noubary 《Soil Dynamics and Earthquake Engineering》1998,17(5):297-309
A statistical method is proposed for estimation of the corner frequency. It is based on inference for a stochastic model whose short-term behavior resembles the established source time functions. Properties of the estimates are investigated and some numerical examples are presented. A discussion concerning earthquake–explosion discrimination and the way corner frequency can be related to the rate of zero-crossings is also included. The paper is concluded with some numerical examples. 相似文献
107.
证明了主成分估计实质上是附着条件的参数平差,并根据此性质结合算例分析了主成分估计的局限性,提出了改进方法。 相似文献
108.
Karl-Heinz Schmidt 《地球表面变化过程与地形》1985,10(5):497-508
The variation of mechanical and chemical denudation is investigated using discharge and sediment yield data from the Upper Colorado River System. Annual precipitation ranges from approximately 150 mm to 1500 mm. Mean specific yield ranges from 0-2 1/s km2 ( = 6 mm p a) to 151/s km2 ( = 475 mm p a). The hydrological-geomorphological system adjusts itself to these varying climatic conditions; in some areas, however, the effects of lithology or land use seem to override the climatic controls. It is demonstrated that the increase in the absolute and particularly the relative amount of suspended sediment is closely related to a decrease in annual runoff and to an increase in the importance of high magnitude/low frequency events. This indicates that in areas of low annual runoff and high runoff variability, soluble rocks are more resistant than in more humid areas. During high magnitude/low frequency events, suspended sediment concentrations and loads are very high in semiarid areas due to sparse vegetation cover and dominance of direct runoff. Events of moderate magnitude and frequency, which in more humid areas transport most of the dissolved load, seldom occur. The trend towards increasing mechanical denudation is even observed in areas of very low runoff (0-221/s km2 = 7 mm p a). The peak of sediment yield in dry areas seems to approximate the point of no runoff very closely. Mechanical and chemical denudation are of equal importance at a runoff of about 300 mm per year. 相似文献
109.
Mechanical properties of high porosity chalks are strongly dependent on the type of fluid in the pores. Dry chalk is considerably stronger than water-saturated chalk, and this phenomenon is often referred to as the water-weakening effect. To address the problem of chalk–fluid interactions, several series of tests have been performed with glycol and high concentration brines as saturating fluids. Glycol is a fluid that in many aspects resembles oil, except that glycol is miscible with water. Glycol-saturated chalk turns out to have properties very similar to oil-saturated chalk. Compared to dry chalk, both oil and glycol make the chalk somewhat weaker, but this weakening effect is much less than with water. Several series of tests with brines with high concentrations of calcium chloride or sodium chloride show that the water-weakening effect is considerably reduced in high ionic strength solutions. Most tests were performed as quasi-hydrostatic tests, with a constant stress ratio of 0.9. In such tests, the yield point marks the onset of accelerated pore collapse, and the yield value is close to the hydrostatic yield stress. In addition to these compressive tests, a series of Brazilian tests were performed, revealing the same trend. The variations in mechanical strength have been correlated with the activity of water in the brines. Within the experimental accuracy of the compressive tests, there is a linear trend between reduction of water activity and the corresponding increase in strength. This leads to the hypothesis that the water activity may be a key parameter in the water-weakening mechanism. But this conclusion also indicates that water weakening may be a special case of general chalk–fluid interactions where the degree of weakening depends on the strength of adsorption of the fluid molecules to the calcite surfaces. 相似文献
110.