隐伏断层在强震砂土液化中的作用——以2008年汶川Mw 7.9地震为例     

王鹏  刘静  张智慧  李志刚  张金玉  王伟  邢秀臣 《地质通报》2018,37(5):747-758

2008年汶川Mw7.9地震的强地面震动在龙门山前地区造成大量的砂土液化、喷砂冒水等地震灾害现象。震后野外调查发现,砂土液化点主要分布于地下水位只有几米深的山前河流的低阶地处,以大面积砾性土液化为特征,约58%的液化点位于距北川断层20~35km的范围内。对喷水高度及喷水过程进行了详细记录,喷水高度与峰值加速度并没有明显的相关性,喷水高度异常点(2m)集中于山前断裂系统近地表投影处。汶川地震中喷水高度异常、砾性土液化的位置与山前断裂系统的吻合性说明,沉积盆地内的地质构造可能在砂土液化强度和与震动相关的地震灾害方面起到促进作用,所以在类似的地质和水文环境中,除主震的断层错动外,应考虑地质构造在地震危险性评估和建筑物抗震设计中的重要作用。  相似文献   

Effects of sand burial on growth and antioxidant enzyme activities of wheat (Triticum aestivum L.) in northern China     

Hao Qu  HaLin Zhao  RuiLian Zhou  Jin Li  ChengChen Pan 《寒旱区科学》2015,7(1):0067-0073

Growth and physiological responses of wheat to sand burial were studied in Horqin Sandy Land, to determine the impact on productivity and survival as well as antioxidant enzymes responses. This study c...  相似文献   

Effects of sand burial on survival and growth of Artemisia halodendron and its physiological response     

HaLin Zhao  Hao Qu  RuiLian Zhou  JianYing Yun  Jin Li 《寒旱区科学》2015,7(1):0059-0066

There is a great deal of literature on the effects of sand burial upon the survival and growth of desert plants, but the physiological adaption mechanisms of desert plants to sand burial have as yet ra...  相似文献   

Influence of structural position on fracture networks in the Torridon Group,Achnashellach fold and thrust belt,NW Scotland     

《Journal of Structural Geology》2015

In fold-and-thrust belts rocks undergo deformation as fold geometries evolve. Deformation may be accommodated by brittle fracturing, which can vary depending on structural position. We use 2D forward modelling and 3D restorations to determine strain distributions throughout folds of the Achnashellach Culmination, Moine Thrust Belt, NW Scotland. Fracture data is taken from the Torridon Group; a thick, coarse grained fluviatile sandstone deposited during the Proterozoic. Modelling infers a correlation between strain and simple curvature; we use simple curvature to infer how structural position and strain control fracture attribute variations in a fold and thrust belt.In high curvature regions, such as forelimbs, fracture intensities are high and fractures are short and oriented parallel to fold hinges. In low curvature regions fractures have variable intensities and are longer. Fracture orientations in these regions are scattered and vary over short distances. These variations do not relate to strain; data suggests lithology may influence fracturing. The strain history of fold structures also influences fracturing; structures with longer deformation histories exhibit consistent fracture attributes due to moderate-high strain during folding, despite present day low curvature. This is in contrast to younger folds with similar curvatures but shorter deformation histories. We suggest in high strain regions fracturing is influenced by structural controls, whereas in low strain regions lithology becomes more important in influencing fracturing.  相似文献   

Intrinsic versus extrinsic variability of analogue sand-box experiments – Insights from statistical analysis of repeated accretionary sand wedge experiments     

《Journal of Structural Geology》2015

Analogue models are not perfectly reproducible even under controlled boundary conditions which make their interpretation and application not always straight forward. As any scientific experiment they include some random component which can be influenced both by intrinsic (inherent processes) and extrinsic (boundary conditions, material properties) sources. In order to help in the assessment of analogue model results, we discriminate and quantify the intrinsic versus extrinsic variability of results from “sandbox” models of accretionary wedges that were repeated in a controlled environment. The extrinsic source of variability, i.e. the parameter varied is the nature of the décollement (material, friction and thickness). Experiment observables include geometric properties of the faults (lifetime, spacing, dip) as well as wedge geometry (height, slope, length).For each variable we calculated the coefficient of variance (CV) and quantified the variability as a symmetric distribution (Normal, Laplacian) or asymmetric distribution (Gamma) using a Chi squared test (χ²). Observables like fault dip/back thrust dip (CV = 0.6–0.7/0.2–0.6) are less variable and decrease in magnitude with decreasing basal friction. Variables that are time dependent like fault lifetime (CV = 0.19–0.56) and fault spacing (CV = 0.12 – 0.36) have a higher CV consequently affecting the variability of wedge slope (CV = 0.12–0.33). These observables also increase in magnitude with increasing basal friction. As the mechanical complexity of the evolving wedge increases over time so does the CV and asymmetry of the distribution. In addition, we confirm the repeatability of experiments using an ANOVA test. Through the statistical analysis of results from repeated experiments we present a tool to quantify variability and an alternative method to gaining better insights into the dynamic mechanics of deformation in analogue sand wedges.  相似文献   

The Cosmolian program for simulating aeolian dynamics and its application to central Australia     

Shlomy Vainer  Yoav Ben Dor 《地球表面变化过程与地形》2021,46(9):1631-1639

The wide spatial coverage of sand dunes in continental interiors makes the understanding of their activity and accumulation history valuable for palaeoenvironmental reconstructions and the interpretation of landscape evolution. Nevertheless, the study of aeolian landscape development at the million-year timescale is hampered by the complex interaction of factors determining dune migration and the inherently self-destructive nature of their chronostratigraphy, thus limiting the applicability of traditional dating methods. This study presents a standalone program that simulates aeolian transport based on luminescence-derived chronologies coupled with numerical modelling of the accumulation of cosmogenic nuclides. This integrative approach to modelling the history of aeolian landforms reveals phases of emergence of aeolian sand into the landscape, and provides a data-based scheme that facilitates the morphodynamical study of aeolian processes over multiple timescales and up to several millions of years. The application of the program for reanalysing previously reported data from the Australian Simpson Desert reveals multiple pulses of sand dispersion into central Australia at 3.8–3.4, 2.9–2.5 and 1.5–1 Ma, corresponding to pronounced changes in climatic conditions and landscape deformation events. The synchronicity of the results with the established environmental framework that would promote the production and aeolian distribution of sand exemplifies the applicability of process-based modelling in constructing a timeframe of key landscape evolution events in arid environments by studying aeolian deposits. The dependence of the parameters used to determine environmental settings on sand transportation patterns additionally makes the program a powerful tool to further investigate the triggers and mechanisms of aeolian processes.  相似文献   

Luminescence chronology of the inland sand dunes from SE India     

Dontireddy Venkat Reddy  Vuddaraju Singaraju  Rakesh Mishra  Devender Kumar  Puthusserry Joseph Thomas  Karra Kameshwa Rao  Ashok Kumar Singhvi 《Quaternary Research》2013

Records of past climate changes have been preserved variously on the earth's surface. Sand dunes are one such prominent imprint, and it is suggested that their presence is an indicator of periods of transition from arid to less arid phases. We report inland sand dunes from Andhra Pradesh (SE India) spread over an area of ~ 500 km², ~ 75 km inland from the east coast. The dune sands are examined to understand their provenance, transportation, timing of sand aggradation and their relationship to past climates. The dune distribution, grain morphology and the grain-size studies on sands suggest an aeolian origin. Physiography of the study area, heavy mineral assemblage, and abundance of quartz in the parent rocks indicate that the dune sands are largely derived from first-order streams emanating from hills in the region and from weathering of the Nellore schist belt. It appears that the geomorphology and wind direction pattern both facilitated and restricted the dune aggradation and preservation to a limited area. OSL dating of 47 dune samples ranged from the present to ~ 50 ka, thereby suggesting a long duration of sand-dune aggradation and/or reworking history.  相似文献   

Aeolian sediment transport and morphologic change on a managed and an unmanaged foredune     

Nancy L. Jackson  Karl F. Nordstrom 《地球表面变化过程与地形》2013,38(4):413-420

Sediment transport and short‐term morphologic change were evaluated at a site where sand fences are deployed and the beach is raked (Managed Site) and a site where these human adjustments are not practiced (Unmanaged Site). Data were gathered across the seaward portion of a low foredune when winds blew nearly shore‐normal at mean speeds 8.9 to 9.3 m s^‐1. Data from traps revealed sediment transport rates at unvegetated portions of the foredune crest (40.2 to 43.5 kg m^‐1 h^‐1) were greater than on the backshore (4.9 to 11.2 kg m^‐1 h^‐1) due to onshore decreases in surface moisture and speed‐up of the wind passing over the foredune. Data from erosion pins indicate sediment input to the dune was 1.48 m³ m^‐1 alongshore at the Managed Site and 1.25 m³ m^‐1 at the Unmanaged Site. The Unmanaged Site had deposition at the dune toe, erosion at mid‐slope, and deposition at the crest. Deposition occurred at mid‐slope on the Managed Site near a partially buried (0.58 m high) fence with a porosity of about 65%. Deposition at partially buried wrack on the upper backshore and dune toe at the Unmanaged Site was about twice as great as deposition in this zone at the Managed Site. Results indicate that: (1) the seaward slope of the foredune can be a more important source of sand to the lee of the crest than the beach; (2) wrack near the toe can decrease transport into the foredune; (3) a scour zone can occur on the foredune slope above the wrack line; (4) a fence placed in this location can promote deposition and offset scour, but fences can restrict delivery of sediment farther inland. Evaluation of alternative configurations of fences and strategies for managing wrack is required to better determine the ways that humans modify foredunes. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

弹性参数直接反演技术在储层流体识别中的应用     

李红梅 《物探与化探》2014,(5):970-975

叠前地震反演是目前应用于流体识别的主要技术,但在具体研究区储层地质地震特点的应用过程中,存在岩石物理基础研究薄弱、多解性等问题。为提高流体地震识别精度,以KD地区为例,开展了陆相碎屑岩典型储层的岩石物理基础、叠前地震反演技术研究及应用。利用河道砂岩实验室岩石物理测试数据,分析了岩性、物性及孔隙流体对岩石物理参数的影响;基于弹性阻抗方程,通过弹性参数直接反演获取对储层流体敏感的参数,对KD地区河道砂岩储层进行了流体识别,提高了流体地震识别精度,取得了较好的地质效果。  相似文献   

枫丹白露砂土的环境箱蒸发试验          下载免费PDF全文

宋卫康  丁文其  崔玉军 《水科学进展》2014,25(1):69-76

为研究土壤水分的蒸发机理,自主开发了大型环境箱试验装置,并以枫丹白露砂土为研究对象,室内模拟土壤水分的蒸发过程。该试验在控制大气参数和保持土壤底部水位稳定的条件下,对蒸发过程中大气参数（空气温度、相对湿度和流量）和土壤参数（土壤温度、基质吸力和体积含水量）的变化,特别是土壤表面基质吸力的变化进行了研究。同时根据试验结果对蒸发速率及累积蒸发量进行了计算分析。研究结果表明:蒸发主要限制在土壤浅层区域,浅层土壤的体积含水量和温度的变化均较大;空气温度和土壤蒸发过程对土壤温度的变化具有较大的影响;土壤表面空气相对湿度与蒸发过程具有相关性;土壤基质吸力随着蒸发的进行逐渐增大; 实际蒸发速率呈现3个阶段。  相似文献