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We present an explicit extended finite element framework for fault rupture dynamics accommodating bulk plasticity near the fault. The technique is more robust than the standard split‐node method because it can accommodate a fault propagating freely through the interior of finite elements. To fully exploit the explicit algorithmic framework, we perform mass lumping on the enriched finite elements that preserve the kinetic energy of the rigid body and enrichment modes. We show that with this technique, the extended FE solution reproduces the standard split‐node solution, but with the added advantage that it can also accommodate randomly propagating faults. We use different elastoplastic constitutive models appropriate for geomaterials, including the Mohr–Coulomb, Drucker–Prager, modified Cam‐Clay, and a conical plasticity model with a compression cap, to capture off‐fault bulk plasticity. More specifically, the cap model adds robustness to the framework because it can accommodate various modes of deformation, including compaction, dilatation, and shearing. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
944.
Natural ecosystems in the region of the lower Tarim River in northwestern China strongly deteriorated since the 1950s due to an expanding desertification. As a result, the downstream Tarim River reaches became permanently dry land. This historical evolution in land‐use change is typically the result of the anthropogenic impact on natural ecosystems. On the basis of a spatially distributed hydrological catchment model bidirectionally linked with a fully hydrodynamic MIKE11 river model, land‐use changes characterized by historical changes in leaf area index (LAI) of vegetation, as well as the evolution of irrigated surface areas, can be causally related to changes in water resources (groundwater storage and surface water resources). An increased surface area of irrigated (agricultural) land, together with a majority of inefficient irrigation methods, did lead to a strong increase of water resources consumption of the farmlands located in the upper Tarim River area. Evidently, this evolution influenced available water resources downstream in the Tarim basin. As a result, farmland has been gradually relocated to the upstream regions. This has led to reduced flows from the upper Tarim stream, which subsequently accelerated the dropping of the groundwater level downstream in the basin. This study moreover demonstrates that land surface biomass changes (cumulative LAI) along the lower Tarim River are strongly related to the changes in groundwater storage. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   
945.
The sequence architecture and depositional systems of the Paleogene lacustrine rift succession in the Huanghekou Sag, Bohai Bay Basin, NE China were investigated based on seismic profiles, combined with well log and core data. Four second‐order or composite sequences and seven third‐order sequences were identified. The depositional systems identified in the basin include: fan delta, braid delta, meander fluvial delta, lacustrine and sublacustrine fan. Identification of the slope break was conducted combining the interpretation of faults of each sequence and the identification of syndepositional faults, based on the subdivision of sequence stratigraphy and analysis of depositional systems. Multiple geomorphologic units were recognized in the Paleogene of the Huanghekou Sag including faults, flexures, depositional slope break belts, ditch‐valleys and sub‐uplifts in the central sag. Using genetic division principles and taking into consideration tectonic features of the Paleogene of the Huanghekou Sag, the study area was divided into the Northern Steep Slope/Fault Slope Break System, the Southern Gentle Slope Break System and T10 Tectonic Slope Break System/T10 Tectonic Belt. Responses of slope break systems to deposition–erosion are shown as: (1) basin marginal slope break is the boundary of the eroded area and provenance area; (2) ditch‐valley formed by different kinds of slope break belts is a good transport bypass for source materials; (3) shape of the slope break belt of the slope break system controls sediments types; (4) the ditch‐valley and sub‐sag of a slope break system is an unloading area for sediments; and (5) due to their different origins, association characteristics and developing patterns, the Paleogene slope break belt systems in the Huanghekou Sag show different controls on depositional systems. The Northern Fault Slope Break system controls the deposition of a fan delta‐lacustrine‐subaqueous fan, the Southern Gentle Slope Break system controls the deposition of a fluvial–deltaic–shallow lacustrine and sublacustrine fan, and the T10 Tectonic Slope Break System controls the deposition of shallow lacustrine beach bar sandbodies. The existence of a slope break system is a necessary but not a sufficient condition for studying sandbody development. The formation of effective sandbodies along the slope break depends on the reasonable coupling of effective provenance, necessary association patterns of slope break belt, adequate unloading space and creation of definite accommodation space. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   
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Variability in precipitation is critical for the management of water resources. In this study, the research entropy base concept was applied to investigate spatial and temporal variability of the precipitation during 1964–2013 in the Songhua River basin of Heilongjiang Province in China. Sample entropy was applied on precipitation data on a monthly, seasonally, annually, decade scale and the number of rainy days for each selected station. Intensity entropy and apportionment entropy were used to calculate the variability over individual year and decade, respectively. Subsequently, Spearman’s Rho and Mann–Kendall tests were applied to observe for trends in the precipitation time series. The statistics of sample disorder index showed that the precipitation during February (mean 1.09, max. 1.26 and min. 0.80), April (mean 1.12, max. 1.29 and min. 0.99) and July (mean 1.10, max. 1.20 and min. 0.98) contributed significantly higher than those of other months. Overall, the contribution of the winter season was considerably high with a standard deviation of 0.10. The precipitation variability on decade basis was observed to increase from decade 1964–1973 and 1994–2003 with a mean value of decadal apportionment disorder index 0.023 and 0.053, respectively. In addition, the Mann–Kendall test value (1.90) showed a significant positive trend only at the Shangzhi station.  相似文献   
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