Effects of fracture intersections on seismic dispersion: theoretical predictions versus numerical simulations          下载免费PDF全文

Junxin Guo  J. Germán Rubino  Stanislav Glubokovskikh  Boris Gurevich 《Geophysical Prospecting》2017,65(5):1264-1276

The detection and characterisation of domains of intersecting fractures are important goals in several disciplines of current interest, including exploration and production of unconventional reservoirs, nuclear waste storage, CO₂ sequestration, and groundwater hydrology, among others. The objective of this study is to propose a theoretical framework for quantifying the effects of fracture intersections on the frequency‐dependent elastic properties of fluid‐saturated porous and fractured rocks. Three characteristic frequency regimes for fluid pressure communication are identified. In the low‐frequency limit, fractures are in full pressure communication with the embedding porous matrix and with other fractures. Conversely, in the high‐frequency limit, fractures are hydraulically isolated from the matrix and from other fractures. At intermediate frequencies, fractures are hydraulically isolated from the matrix porosity but can be in hydraulic communication with each other, depending on whether fracture sets are intersecting. For each frequency regime, the effective stiffness coefficients are derived using the linear‐slip theory and anisotropic Gassmann equations. Explicit mathematical expressions for the two characteristic frequencies that separate the three frequency regimes are also determined. Theoretical predictions are then applied to two synthetic 2D samples, each containing two orthogonal fracture sets: one with and another without intersections. The resulting stiffness coefficients, Thomsen‐style anisotropy parameters, and the transition frequencies show good agreement with corresponding numerical simulations. The theoretical results are applicable not only to 2D but also to 3D fracture systems and are amenable to being employed in inversion schemes designed to characterise fracture systems.  相似文献   

A history of breaking laws—Social dynamics of non-compliance in Vietnamese marine fisheries     

Wiebren J. Boonstra  Nguyen Bach Dang 《Marine Policy》2010

Whether or not fishers comply with regulation depends on the economic and social context in which they operate their vessels. This is how conventional theory explains the phenomenon of non-compliance. It treats state–community interaction processes not as direct causes for non-compliance but rather as background conditions shaping individual fishers’ perception and decisions for action. This paper argues that conventional theory fails to include the dynamics of tempo-relational processes between state and communities, which explains collective patterns of non-compliance in fisheries. The paper addresses this hiatus in the literature, using a process-sociological approach to analyse non-compliance in Vietnamese marine fisheries. The analysis highlights that Vietnamese marine fisheries are mainly regulated through informal networks of trust and mistrust, which function through their interplay with the highly centralised and formalised Vietnamese state. Based on this assessment, the paper concludes that outcomes of processes of the dynamic social interplay between state and communities are semi-dependent on individual perception and action, and as such have a causal effect of their own on patterns of non-compliance in fisheries.  相似文献   

The art of adaptation: Living with climate change in the rural American Southwest     

Julie Brugger  Michael Crimmins 《Global Environmental Change》2013,23(6):1830-1840

As adaptation has come to the forefront in climate change discourse, research, and policy, it is crucial to consider the effects of how we interpret the concept. This paper draws attention to the need for interpretations that foster policies and institutions with the breadth and flexibility to recognize and support a wide range of locally relevant adaptation strategies. Social scientists have argued that, in practice, the standard definition of adaptation tends to prioritize economic over other values and technical over social responses, draw attention away from underlying causes of vulnerability and from the broader context in which adaptive responses take place, and exclude discussions of inequality, justice, and transformation. In this paper, we discuss an alternate understanding of adaptation, which we label “living with climate change,” that emerged from an ethnographic study of how rural residents of the U.S. Southwest understand, respond to, and plan for weather and climate in their daily lives, and we consider how it might inform efforts to develop a more comprehensive definition. The discussion brings into focus several underlying features of this lay conception of adaptation, which are crucial for understanding how adaptation actually unfolds on the ground: an ontology based on nature–society mutuality; an epistemology based on situated knowledge; practice based on performatively adjusting human activities to a dynamic biophysical and social environment; and a placed-based system of values. We suggest that these features help point the way toward a more comprehensive understanding of climate change adaptation, and one more fully informed by the understanding that we are living in the Anthropocene.  相似文献   

Rainfall,runoff and shallow groundwater response in a mixed-use,agro-forested watershed of the northeast,USA     

Kaylyn S. Gootman  Jason A. Hubbart 《水文研究》2021,35(8):e14312

Stream and shallow groundwater responses to rainfall are characterized by high spatial variability, but hydrologic response variability across small, agro-forested sub-catchments remains poorly understood. Conceivably, improved understanding in this regard will result in agricultural practices that more effectively limit nutrient runoff, erosion, and pollutant transport. Terrestrial hydrologic response approaches can provide valuable information on stream-aquifer connectivity in these mixed-use watersheds. A study was implemented, including eight stream and co-located shallow groundwater monitoring sites, in a small sub-catchment of the Chesapeake Bay watershed in the Northeast, USA to advance this ongoing need. During the study period, 100 precipitation-receiving days (i.e., 24-hour periods, midnight to midnight) were observed. On average, the groundwater table responded more to precipitation than stream stage (level change of 0.03 vs. 0.01 m and rainfall-normalized level change estimate of 3.81 vs. 3.37). Median stream stage responses, groundwater table responses, and response ratios were significantly different between sub-catchments (n = 8; p < 0.001). Study area average precipitation thresholds for runoff and shallow groundwater flow were 2.8 and 0.6 cm, respectively. Individual sub-catchment thresholds ranged from 0.5 to 2.8 cm for runoff and 0.2 to 1.3 cm for shallow groundwater flow. Normalized response lag times between the stream and shallow groundwater ranged from −0.50 to 3.90 s·cm⁻¹, indicating that stormflow in one stream section was regulated by groundwater flow during the period of study. The observed differences in hydrologic responses to precipitation advance future modelling efforts by providing examples of how terrestrial groundwater response methods can be used to investigate sub-catchment spatial variability in stream-aquifer gradients with co-located shallow groundwater and stream stage data. Additionally, results demonstrate asynchronous stream and shallow groundwater responses on precipitation-receiving days, which may hold important implications for modelling hydrologic and biogeochemical fate and transport processes in small, agro-forested catchments.  相似文献   

Numerical study of the influence of Kuroshio Current on the thermocline in the sea area around Taiwan Island     

张文静  沙文钰 《海洋预报》2001,18(Z1):17-24

1 INTsoDUcrIONTemperature is one of the most impoFtant essential factors of ocean, and its verticalstructure, especially the phenomenon ofthermocline, is concerned by military and manufacturepractices at all times. There are two classes of research methods for thermocIine, statisticmethod and numerical method. In recent years, more attention has been paid to the latterwhich becomes the primary development direction. Since Munk et al (1948) pot forward1-D model of thermocline at steady sta…  相似文献   

青岛市作为2008年奥运会海上赛场可行性分析   总被引：5，自引：0，他引：5  

陈静  冯秀丽  沈渭铨  冯小莉 《海洋湖沼通报》2002,(2):80-86

为支持北京申办2008年奥运会，青岛已在前年四月份、六月份和去年四月份先后三次向国家体育总局和北京市政府递交了要求承办2008年奥运会海上项目的申办报告。前年十月国际帆船联合会主席保尔－亨德森先生在视察青岛时认为，就青岛的城市环境、水域状况而完全有条件承办奥运会的帆船、帆板比赛，同意把奥运帆船比赛放在青岛举行。本文从青岛市优越的自然环境有社会环境来分析将其作为奥运海上赛场的可行性。  相似文献   

海洋木栖真菌抗菌活性的初步研究   总被引：6，自引：0，他引：6  

林昕  黄耀坚  胡志钰  郑忠辉  苏文金 《台湾海峡》2004,23(3):308-313

从福建厦门海沧、集美及漳州浮宫等地采集到的红树林等海洋潮间带的各种腐木样品中分离得到176株海洋木栖真菌,对其进行抗菌活性检测.其结果表明共有96株海洋木栖真菌对大肠杆菌、枯草杆菌及白色假丝酵母中的一种或多种拮抗指示菌具有抑制作用,占供测菌株总数的54.5%.在这些活性菌株中,红树源菌株拮抗比例为30.2%,非红树源菌株拮抗比例为69.8%.具有抗菌活性的菌株主要分布于15个属中,包括木霉Trichoderma、青霉Penicillium、拟青霉Paecilomyces和一些不产孢的分类群.某些稀有真菌如盘多毛孢Pestalotia、茎点霉Phoma也具有一定的抗菌活性.  相似文献   

江苏岸外辐射沙脊群东沙稳定性研究   总被引：8，自引：0，他引：8  

陈君  王义刚  张忍顺  林祥 《海洋工程》2007,25(1):105-113

东沙是江苏岸外辐射沙脊群中的第二大沙洲,具有独特的地形地貌和水动力条件,对它进行稳定性研究为揭示整个辐射沙洲及其邻近岸滩的动态演变都非常有益。通过利用多年遥感卫片资料、1998年取得的现场水文泥沙观测资料和东沙滩面表层沉积物资料等,对东沙的地形地貌特征、沉积特征和东沙两侧潮汐通道的水流泥沙特征等进行了详细分析。研究结果表明,东沙的沙脊偏于西侧,西侧滩面较窄、高程较高且岸线较为顺直,东侧滩面较宽、高程较低且岸线较为破碎;西洋和陈家坞槽均处于冲刷状态,净输沙的主要方向为输向槽外或输向条子泥;东沙近三十年来面积有所缩小且有外围向中央收缩的趋势,尤其以向东、向南方向的迁移最为明显。  相似文献   

大亚湾的环境研究     

温伟英  何悦强  郑庆华  林燕棠  叶能权 《热带海洋学报》1992,(2)

大亚湾自然条件优越,生物资源丰富,是当前广东经济开发的“热点”。本文从生态环境的角度讨论大亚湾的环境质量问题,并指出今后大亚湾的经济开发应注意环境保护问题。  相似文献   

鳜亚科SINIPERCINAE鱼类的LDH同工酶的比较研究     

孔晓瑜  周才武 《中国海洋大学学报(自然科学版)》1992,(1)

对鳜亚科9种鱼类的LDH同工酶进行了比较研究。结果表明9种鱼的LDH同工酶表型具有明显的种间差异;同种的个体及性别之间没有明显差异。根据LDH同工酶表型所得的分类结果与形态分类基本一致。鉴于9种鱼具有基本相同的相对迁移率,提出鳜亚科的种类可能是单系起源。在暗鳜(Siniperca obscura Nichols,1930);鳜(S.chuatsi Basilew-sky,1855)的晶体里,发现了C基因控制的区带,暗鳜、斑鳜(S.scherzeri Steindachner,1892)及大眼鳜(S.knerni Garmar,1912)的肝组织中酶谱存在多态现象。  相似文献