渭河盆地深部构造活动的地裂缝孕育机理

渭河盆地是我国乃至世界上地裂缝最发育、灾害最严重的地区。基于渭河盆地深部构造模式,采用有限元数值分析方法,分析了上地幔上隆、中地壳流展和上地壳拉张3种深部构造作用下盆地浅表岩土介质的应力和变形响应特征,从而揭示了渭河盆地深部构造活动与该区域地裂缝群发之间的孕育关系。结果表明：上地幔的隆起和中地壳侧向流展形成了浅部拉张应力环境,这种效应与盆地周边块体运动形成的伸展引张构造应力场叠加,再附加断裂伸展倾滑形成的局部拉伸应力场构成了地裂缝形成的主要动力来源。     

Rural tourism development in China: Principles, models and the future

Rural tourism in China,has undergone a rapid development in the last three decades.It is an emerging and effective catalyst that promotes industrial restructuring,agricultural development and the upgrading of rural areas.However,there remains little understanding about the core issues of rural tourism in China:the exact connotation,the principles,the development models and the future directions.This review paper identifies the key issues based on literature analysis,national statistics and press reports to form a general picture of the past,the current and the future prospects of China’s rural tourism.The paper firstly addresses the definition,content and principles of rural tourism,and then provides an overview and brief evaluation of the progress and the current development models in China.Finally,based on the analysis of the experiences and problems,the authors sum up with five pathways of the future development of China’s rural tourism from the perspective of rural tourism resources,product,market and promotion.     

绿洲土地整合是增加耕地和保护生态的重要措施——以新疆玛纳斯河流域为例

保护耕地资源,“坚决守住1.2×10⁸ hm²(18亿亩)耕地红线”,是中国政府的一项基本国策。以新疆为代表的干旱区绿洲农业,近年来耕地面积增长很快,从1995-2008年均每年增加15.4×10⁸ hm²,这对抑制全国耕地面积下滑和促进新疆农业发展起了重要作用,但同时也对生态环境带来严重影响。如何在保护生态的前提下使耕地面积稳中有增,通过在玛纳斯河流域利用遥感图像解释和实际调查,提出通过绿洲内部土地综合整治,改变现土地利用中的“破碎化”程度,提高净耕地利用系数的思路;在不开荒不增加引水量情况下,耕地面积一般可增加8%~10%,而在一些土地利用规划差和管理粗放地区可增加到15%。通过土地整合使土地化零为整,还为节水灌溉、发展现代农业、实行农业规模化、集约化经营及农民致富创造了条件。     

Identifying the sensitive areas in targeted observation for pre-dicting the Kuroshio large meander path in a regional ocean model

With the Regional Ocean Modeling System(ROMS), this paper investigates the sensitive areas in targeted observation for predicting the Kuroshio large meander(LM) path using the conditional nonlinear optimal perturbation approach. To identify the sensitive areas, the optimal initial errors(OIEs) featuring the largest nonlinear evolution in the LM prediction are first calculated; the resulting OIEs are localized mainly in the upper2 500 m over the LM upstream region, and their spatial structure has...     

Holocene evolution of a rock‐bounded barrier‐lagoon system,Cíes Islands,northwest Iberia

Coastal geomorphology results from the combined effects of contemporary dynamics, sea‐level rise and the inherited geological framework, yet the relative importance of these driving mechanisms may change throughout the evolutionary history of coastal deposits. In this contribution, we analyse the depositional history of the Cíes Islands barrier‐lagoon system, based on lithofacies, radiocarbon ages, and pollen analysis. Our results reveal a sedimentary sequence that provides evidence for striking changes in the dynamical functioning of this complex since the mid‐Holocene. The sedimentary sequence commenced about 7700 cal years bp by fresh‐water ponding of an upland depression located about 4 m below present mean sea‐level. Fresh‐water ponds were infilled by aeolian sediments following a gradual lowering of the water‐table 4000 cal years bp . Post‐3600 cal years bp sea‐level rise allowed water oscillations to reach the elevation of the bedrock causing the inundation of fresh‐water ponds and subsequent lagoonal and marine sedimentation. Subsequently, landward and upward migration of a sand‐barrier led to overwash and deposition of sand in the newly formed lagoon. The resultant sedimentary sequence suggests that climatic conditions played an important role controlling the sedimentation regime during the entire history of the basin; changing water‐table levels during early stages of evolution and increasing storminess during more recent times. In addition, background sea‐level rise related to the Holocene transgression was a key factor in controlling the evolution of the system, yet its influence depended to an extent on the relative elevation of the bedrock topography. Copyright © 2009 John Wiley & Sons, Ltd.     

Exploring for Geothermal Resources with Electromagnetic Methods

Electrical conductivity of the subsurface is known to be a crucial parameter for the characterization of geothermal settings. Geothermal systems, composed by a system of faults and/or fractures filled with conducting geothermal fluids and altered rocks, are ideal targets for electromagnetic (EM) methods, which have become the industry standard for exploration of geothermal systems. This review paper presents an update of the state-of-the-art geothermal exploration using EM methods. Several examples of high-enthalpy geothermal systems as well as non-volcanic systems are presented showing the successful application of EM for geothermal exploration but at the same time highlighting the importance of the development of conceptual models in order to avoid falling into interpretation pitfalls. The integration of independent data is key in order to obtain a better understanding of the geothermal system as a whole, which is the ultimate goal of exploration.     

资源三号影像质量及测图应用评价

从影像辐射质量和影像实际应用两个方面,对资源三号卫星影像数据的质量进行了评价与分析。影像辐射质量评价从辐射精度、信息度、清晰度、信噪比和纹理特征等方面进行,通过对比相近的ALOS卫星数据,结果显示资源三号卫星数据优于ALOS卫星数据;影像实际应用评价则通过秦岭地区1:25 000和1:50 000测图成果精度分析来进行,结果显示DEM高程精度、DEM平面精度和DLG采集精度均符合现行成果标准要求,可以满足国家基础比例尺测图要求。     

Grassland coverage inter-annual variation and its coupling relation with hydrothermal factors in China during 1982–2010

GIMMS (Global Inventory Modeling and Mapping Studies) NDVI (Normalised Difference Vegetation Index) from 1982 to 2006 and MODIS (Moderate Resolution Imaging Spectroradiometer) NDVI from 2001 to 2010 were blended to extract the grass coverage and analyze its spatial pattern. The response of grass coverage to climatic variations at annual and monthly time scales was analyzed. Grass coverage distribution had increased from northwest to southeast across China. During 1982–2010, the mean nationwide grass coverage was 34% but exhibited apparent spatial heterogeneity, being the highest (61.4%) in slope grasslands and the lowest (17.1%) in desert grasslands. There was a slight increase of the grass coverage with a rate of 0.17% per year. Increase in slope grasslands coverage was as high as 0.27% per year, while in the plain grasslands and meadows the grass coverage increase was the lowest (being 0.11% per year and 0.1% per year, respectively). Across China, the grass coverage with extremely significant increase (P<0.01) and significant increase (P<0.05) accounted for 46.03% and 11% of the total grassland area, respectively, while those with extremely significant and significant decrease accounted for only 4.1% and 3.24%, respectively. At the annual time scale, there are no significant correlations between grass coverage and annual mean temperature and precipitation. However, the grass coverage was somewhat affected by temperature in alpine and sub-alpine grassland, alpine and sub-alpine meadow, slope grassland and meadow, while grass coverage in desert grassland and plain grassland was more affected by precipitation. At the monthly time-scale, there are significant correlations between grass coverage with both temperature and precipitation, indicating that the grass coverage is more affected by seasonal fluctuations of hydrothermal conditions. Additionally, there is one-month time lag-effect between grass coverage and climate factors for each grassland types.     

Inducing Unstable Grassland Equilibrium States Due to Nonlinear Optimal Patterns of Initial and Parameter Perturbations: Theoretical Models

Due to uncertainties in initial conditions and parameters,the stability and uncertainty of grassland ecosystem simulations using ecosystem models are issues of concern.Our objective is to determine the types and patterns of initial and parameter perturbations that yield the greatest instability and uncertainty in simulated grassland ecosystems using theoretical models.We used a nonlinear optimization approach,i.e.,a conditional nonlinear optimal perturbation related to initial and parameter perturbations (CNOP) approach,in our work.Numerical results indicated that the CNOP showed a special and nonlinear optimal pattern when the initial state variables and multiple parameters were considered simultaneously.A visibly different complex optimal pattern characterizing the CNOPs was obtained by choosing different combinations of initial state variables and multiple parameters in different physical processes.We propose that the grassland modeled ecosystem caused by the CNOP-type perturbation is unstable and exhibits two aspects:abrupt change and the time needed for the abrupt change from a grassland equilibrium state to a desert equilibrium state when the initial state variables and multiple parameters are considered simultaneously.We compared these findings with results affected by the CNOPs obtained by considering only uncertainties in initial state variables and in a single parameter.The numerical results imply that the nonlinear optimal pattern of initial perturbations and parameter perturbations,especially for more parameters or when special parameters are involved,plays a key role in determining stabilities and uncertainties associated with a simulated or predicted grassland ecosystem.     

基于遥感影像的祁连山区俄博岭热融滑塌发育特征

热融滑塌是山地多年冻土退化最直接的表现形式之一,通过解译祁连山俄博岭地区遥感影像,结合实地考察,对俄博岭热融滑塌的空间分布和时间变化进行了研究,明确了热融滑塌的发育特征。结果表明,俄博岭热融滑塌发育活跃,1997~2015年热融滑塌数量增加(11~13个),面积增大(7765~20605m^2),其中1997~2009年面积增加速率为679.9m^2/a,2009~2015年面积增加速率为780.2m^2/a。通过分析热融滑塌景观分布与地形因子的关系,发现俄博岭热融滑塌在海拔3570~3700m,坡度3°~10°的富冰多年冻土区北向斜坡发育;通过对典型热融滑塌溯源后退速率分析发现,1997~2009年其平均后退速率为2m/a,2009~2015年平均后退速率为5m/a,呈明显增大趋势,且其后退速率主要与坡度、地下冰含量和地表径流相关。