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41.
Results of a single group participating in an international experiment are analyzed. The experiment served to verify computational predictions of the ground-motion variations due to near-surface geological effects at a site established for that purpose by the California Department of Conservation. Based on an acceleration record at a rock location, and geotechnical model of medium, records at the other locations of a nearby sedimentary deposit were predicted. A 2-D finite-difference sensitivity analysis suggested that the lateral wave-propagation effects are negligibly small, and locally 1-D computations are sufficient for the present site. Those computations are compared with observations not available to the authors during the blind prediction. Peak accelerations, peak velocities and RMS accelerations were predicted with errors less than 159%, 114% and 62%, respectively. Maxima of the response spectra were fitted within a factor of 2. The predicted and observed Husid's plots (i.e., the normalized cumulative plots of the acceleration squared) have the correlation coefficients 0.98. The detected misfits do not show any simple relation to the instrument location, component, frequency, or time. 相似文献
42.
On the practice of estimating fractal dimension 总被引:11,自引:0,他引:11
Coastlines epitomize deterministic fractals and fractal (Hausdorff-Besicovitch) dimensions; a divider [compass] method can be used to calculate fractal dimensions for these features. Noise models are used to develop another notion of fractals, a stochastic one. Spectral and variogram methods are used to estimate fractal dimensions for stochastic fractals. When estimating fractal dimension, the objective of the analysis must be consistent with the method chosen for fractal dimension calculation. Spectal and variogram methods yield fractal dimensions which indicate the similarity of the feature under study to noise (e.g., Brownian noise). A divider measurement method yields a fractal dimension which is a measure of complexity of shape. 相似文献
43.
44.
The true potential energy curves for the electronic ground states of astrophysically important AlH and CaH molecules are constructed by the Rydberg-Klein-Rees method. Empirical potential functions, of three-parameters by Lippincott, of five-parameters by Hulburt and Hirsch-felder and, of electronegativity by Szöke and Baitz, are examined for the adequacy to represent the true curve. From the best-fitting function, the dissociation energiesD 0 0 of AlH and CaH molecules are estimated to be 2.99 ± 0.08 and 2.72 ± 0.06 eV respectively. The force constants indicate that these values are of correct magnitude. 相似文献
45.
Dynamic recrystallization near the brittle-plastic transition in naturally and experimentally deformed quartz aggregates 总被引:1,自引:0,他引:1
The electron backscattering diffraction technique (EBSD) was used to analyze bulging recrystallization microstructures from naturally and experimentally deformed quartz aggregates, both of which are characterized by porphyroclasts with finely serrated grain boundaries and grain boundary bulges set in a matrix of very fine recrystallized grains. For the Tonale mylonites we investigated, a temperature range of 300–380 °C, 0.25 GPa confining pressure, a flow stress range of ~ 0.1–0.2 GPa, and a strain rate of ~ 10− 13 s− 1 were estimated. Experimental samples of Black Hills quartzite were analyzed, which had been deformed in axial compression at 700 °C, 1.2–1.5 GPa confining pressure, a flow stress of ~ 0.3–0.4 GPa, a strain rate of ~ 10− 6 s− 1, and to 44% to 73% axial shortening. Using orientation imaging we investigated the dynamic recrystallization microstructures and discuss which processes may contribute to their development. Our results suggest that several deformation processes are important for the dismantling of the porphyroclasts and the formation of recrystallized grains. Grain boundary bulges are not only formed by local grain boundary migration, but they also display a lattice misorientation indicative of subgrain rotation. Dynamic recrystallization affects especially the rims of host porphyroclasts with a hard orientation, i.e. with an orientation unsuitable for easy basal slip. In addition, Dauphiné twins within porphyroclasts are preferred sites for recrystallization. We interpret large misorientation angles in the experimental samples, which increase with increasing strain, as formed by the activity of fluid-assisted grain boundary sliding. 相似文献
46.
Borehole data reveals that during Late Quaternary, the Ganga river was non-existent in its present location near Varanasi.
Instead, it was flowing further south towards peripheral craton. Himalayan derived grey micaceous sands were being carried
by southward flowing rivers beyond the present day water divide of Ganga and mixed with pink arkosic sand brought by northward
flowing peninsular rivers. Subsequently, the Ganga shifted to its present position and got incised. Near Varanasi, the Ganga
river is flowing along a NW-SE tectonic lineament. The migration of Ganga river is believed to have been in response to basin
expansion caused due to Himalayan tectonics during Middle Pleistocene times.
Multi-storied sand bodies generated as a result of channel migration provide excellent aquifers confined by a thick zone of
muddy sediments near the surface. Good quality potable water is available at various levels below about 70 m depth in sandy
aquifers. Craton derived gravelly coarse-to-medium grained sand forms the main aquifer zones of tens of meter thickness with
enormous yield. In contrast, the shallow aquifers made up of recycled interfluve silt and sandy silt occur under unconfined
conditions and show water-level fluctuation of a few meters during pre-and post-monsoon periods. 相似文献
47.
48.
49.
海相碳酸盐岩层系不整合量化研究及其意义——以四川盆地北部二叠系为例 总被引:2,自引:1,他引:1
本文以四川盆地北部二叠系为例,将层序地层分析和沉积盆地波动过程分析相结合,提出了运用沉积波动过程分析研究沉积记录不完整性的量化方法,该方法可以相对准确地定量描述盆地形成演化过程中的升降运动,恢复无地层"记录"中的沉积-剥蚀过程,进而定量分析盆地的沉积-剥蚀过程、计算沉积间断(不整合)内的地层剥蚀量、认识其时空分布规律.同时,通过实际钻井及"人工井"的波动过程分析,结合地震剖面解释成果,可以作出主要不整合的空间分布图、各层位的剥蚀厚度图和原始厚度图、各期构造的剥蚀量分布图等重要基础图件,为盆地进一步系统分析及盆地模拟打好基础,结合沉积相研究及构造样式分析还可分析盆地沉积中心、生油层、盖层、储层等在时空中的变化规律.由于沉积盆地的升降波动过程直接影响着盆地的埋藏史、热史和生、排烃史,因此通过沉积波动过程的系统分析不仅能正确建立盆地演化的地质模型,还可以正确认识油气形成与分布规律,有效指导油气勘探. 相似文献
50.
不整合运移通道类型及输导油气特征 总被引:12,自引:1,他引:11
在对不整合空间结构特征研究的基础上,提出了油气沿不整合运移的通道类型:宏观上,存在由不整合面之上底砾岩和不整合面之下半风化岩石两种高效运载层组合成的双运移通道型和单运移通道型两种通道类型;微观上,底砾岩连通孔隙、半风化岩石构造卸荷风化裂缝系统及溶蚀孔洞系统可作为油气运移的主要通道。通过对不整合面上、下岩石物性分析,认为半风化岩石“孔洞缝”系统较底砾岩连通孔隙有更高的输导油气的能力。研究结果表明,不同的运移通道类型具有不同的输导油气特征。在地史时期,构造裂缝系统和溶蚀孔洞系统一直是不整合输导油气的主要通道;对于软地层构成的不整合来说,开始应是卸荷、风化裂缝系统和底砾岩连通孔隙共同构成不整合输导油气的主要通道,当上覆沉积载荷达到一定程度后,主要是底砾岩连通孔隙起输导油气通道作用;对于脆硬地层构成的不整合来说,卸荷、风化裂缝系统和底砾岩连通孔隙一直是不整合输导油气的主要通道。 相似文献