震后快速钻探:历史、现状与未来

大地震发生后立即在断层带上进行钻探可以帮助我们获取更多的地震信息,尤其是可获得决定断层动态破裂的摩擦水平和强度,观测断层的愈合过程及可能触发余震的应力变化,并可获取控制破裂过程的重要的物理和化学属性。在2008年11月由国际大陆科学钻探项目（ICDP）和南加州地震中心（SCEC）联合在日本东京举办的为期3天的“震后快速钻探：历史、现状与未来”研讨会上,     

New Modes of Environmental Governance in Greater Sage-Grouse Conservation in Oregon

Abstract

Natural resource challenges often span administrative jurisdictions and include actors and processes operating at different spatial and political scales. We applied concepts of new environmental governance to analyze Oregon’s approach to greater sage-grouse conservation. Through one in-depth case study in Lake County, we traced features of new environmental governance (cross-scale interactions, decentralization, and capacities of actors) through different governance levels. Interviews and qualitative analysis revealed that decentralization of administrative functions facilitated cross-scale interactions and relied on intermediaries, gap-filling, and perceptions of legitimacy at lower levels. State and agency guidelines steered the effort and were accompanied by financial and technical resources from multiple arenas, which increased local capacity. This study adds to the understandings of environmental governance for implementing multi-actor, multi-level conservation arrangements in resource-dependent communities. Further exploration of connections between higher levels and local contexts will reveal important, new ways to link policies with on-the-ground outcomes.     

An analysis of failure mechanism constraints on pre-failure rock block deformation using TLS and roto-translation methods

Rockfall hazards increase the risk of train derailment along railway corridors in western Canada. In this study, repeated terrestrial laser scanning (TLS) datasets were collected every 2–3 months at three different sites along the Thompson and Fraser River corridors in British Columbia, referred to as the Goldpan, White Canyon, and Mile 109 sites. A total of 207 rockfall events occurring across all three sites between November 11, 2014 and October 18, 2016 were recorded in a database. For each of these rockfalls, pre-failure deformation was measured using a method of three-dimensional roto-translation block tracking. Each rockfall was classified by its deformation behaviour and further categorised based on failure mechanism, volume, lithology, and the roughness condition of the failure plane. Results reveal that detectable levels of deformation were measured in 33% of the total number of rockfall events using the present methods. Rotation deformation was most commonly observed in toppling failures with relatively steep joint orientations. Conversely, planar sliding blocks generally exhibited the least measurable deformation, with the majority not showing any precursory translation or rotation. It is postulated that overhanging rockfall configurations may suppress the expression of deformation in rockfall source blocks, though additional research is required to confirm this.     

A submillimetre survey of the kinematics of the Perseus molecular cloud – I. Data

We present submillimetre observations of the   J = 3 → 2  rotational transition of ¹²CO, ¹³CO and C¹⁸O across over 600 arcmin² of the Perseus molecular cloud, undertaken with the Heterodyne Array Receiver Programme (HARP), a new array spectrograph on the James Clerk Maxwell Telescope. The data encompass four regions of the cloud, containing the largest clusters of dust continuum condensations: NGC 1333, IC348, L1448 and L1455. A new procedure to remove striping artefacts from the raw HARP data is introduced. We compare the maps to those of the dust continuum emission mapped with the Submillimetre Common-User Bolometer Array (SCUBA; Hatchell et al.) and the positions of starless and protostellar cores (Hatchell et al.). No straightforward correlation is found between the masses of each region derived from the HARP CO and SCUBA data, underlining the care that must be exercised when comparing masses of the same object derived from different tracers. From the ¹³CO/C¹⁸O line ratio the relative abundance of the two species  ([¹³CO]/[C¹⁸O]∼ 7)  and their opacities (typically τ is 0.02–0.22 and 0.15–1.52 for the C¹⁸O and ¹³CO gas, respectively) are calculated. C¹⁸O is optically thin nearly everywhere, increasing in opacity towards star-forming cores but not beyond  τ₁₈∼ 0.9  . Assuming the ¹²CO gas is optically thick, we compute its excitation temperature, T _ex (around 8–30 K), which has little correlation with estimates of the dust temperature.     

汶川地震断裂作用研究新认识

2008年汶川地震后,人们不得不思考问题是:大地震是如何发生的?下一次大地震什么时候发生?也就是涉及地质学家和地球物理学家一直未解决的科学问题:断层是如何破裂的?震后断裂是如何愈合的?我们试图通过对汶川地震断裂带结构、断裂摩擦行为和断裂愈合过程的研究来回答这些问题。本文将介绍通过对地表露头和汶川地震断裂科学钻探一号孔(WFSD)岩心中汶川地震主滑移带的详细研究,以及钻孔中长期温度监测来分析有关汶川地震断裂动态弱化和摩擦行为,并结合钻孔中长期水文监测计算所得断裂带渗透率变化,分析震后断裂愈合过程,进而探讨和认识汶川地震断裂作用所涉及的上述问题。经过详细研究,确定了汶川地震断裂带(映秀—北川断裂带)宽105~240 m、具有五个不同断裂岩组合的内部结构,是一条经常发生大地震、具多种弱化机制的断裂带;发现了汶川地震不仅具有同震石墨化作用,而且测量到目前世界上最低的动态摩擦系数(≤0.02),同时首次记录到大地震后断裂快速愈合信息。这些研究结果不仅直接回答了一直困扰在地震地质和地震物理学领域几十年的关键问题,而且对完善地震断裂理论和认识汶川地震机制具有极其重要的意义,为防震减灾提供了理论依据。     

Characterizing and classifying urban watersheds with compositional and structural attributes

Current land-use classifications used to assess urbanization effects on stream water quality date back to the 1980s when limited information was available to characterize watershed attributes that mediate non-point source pollution. With high resolution remote sensing and widely used GIS tools, there has been a vast increase in the availability and precision of geospatial data of built environments. In this study, we leverage geospatial data to expand the characterization of developed landscapes and create a typology that allows us to better understand the impact of complex developed landscapes across the rural to urban gradient. We assess the ability of the developed landscape typology to reveal patterns in stream water chemistry previously undetected by traditional land-cover based classification. We examine the distribution of land-cover, infrastructure, topography and geology across 3876 National Hydrography Dataset Plus catchments in the Piedmont region of North Carolina, USA. From this dataset, we generate metrics to evaluate the abundance, density and position of landscape features relative to streams, catchment outlets and topographic wetness metrics. While impervious surfaces are a key distinguishing feature of the urban landscape, sanitary infrastructure, population density and geology are better predictors of baseflow stream water chemistry. Unsupervised clustering was used to generate a distinct developed landscape typology based on the expanded, high-resolution landscape feature information. Using stream chemistry data from 37 developed headwater catchments, we compared the baseflow water chemistry grouped by traditional land-cover based classes of urbanization (rural, low, medium and high density) to our composition and structure-based classification (a nine-class typology). The typology based on 22 metrics of developed landscape composition and structure explained over 50% of the variation in NO₃⁻-N, TDN, DOC, Cl⁻, and Br⁻ concentration, while the ISC-based classification only significantly explained 23% of the variation in TDN. These results demonstrate the importance of infrastructure, population and geology in defining developed landscapes and improving discrete classes for water management.     

Farming ‘practice’ as temporally and spatially situated intersections of biography,culture and social structure

This paper brings anthropological, sociological and geographical perspectives to bear on the problem of farm sustainability and, in particular, the legitimation of sustainable farm practices. It attempts to lay some theoretical foundations for explanation of the adoption of farming practices which may, or may not, promote sustainability. A brief survey of the literature surrounding these issues finds many of the current theoretical perspectives incapable of fully accounting for the complexity of farming practice. Reductionist decision/rational‐action models, in particular, are found wanting for their lack of both cultural consistency and social/spatial specificity. Instead, this paper promotes a generative structuralist approach directed towards an analysis of social and economic practice in lived space; that is, firmly anchored in long‐term ethnographic research.     

Engagement in the Third U.S. National Climate Assessment: commitment,capacity, and communication for impact

This paper examines the dynamics of energy investments and clean energy Research and Development (R&D) using a scenario-based modeling approach. Starting from the global scenarios proposed in the RoSE model ensemble experiment, we analyze the dynamics of investments under different assumptions regarding economic and population growth as well as availability of fossil fuel resources, in the absence of a climate policy. Our analysis indicates that economic growth and the speed of income convergence across countries matters for improvements in energy efficiency, both via dedicated R&D investments but mostly through capital-energy substitution. In contrast, fossil fuel prices, by changing the relative competitiveness of energy sources, create an economic opportunity for radical innovation in the energy sector. Indeed, our results suggest that fossil fuel availability is the key driver of investments in low carbon energy innovation. However, this innovation, by itself, is not sufficient to induce emission reductions compatible with climate stabilization objectives.     

Magnetostratigraphy of mid-Cretaceous limestones from the Sierra Madre of northeastern Mexico

We present the results of a palaeomagnetic study of four mid-Cretaceous limestone sections exposed in northeastern Mexico. The limestones are weakly magnetized and exhibit two- to three-component magnetizations. These magnetization components appear to be carried by both a sulphide mineral and a magnetite-titanomagnetite mineral. The sulphide mineral carries a reverse polarity overprint that often makes it difficult to isolate definitively the higher-unblocking-temperature component. The high-unblocking-temperature component is well defined in the upper portion of the Santa Rosa Canyon section and in the Cienega del Toro section and passes the fold test. The characteristic remanent magnetization (ChRM) inclinations agree well with predicted mid-Cretaceous inclinations for these sites, although the declinations differ by more than 100°. The relative rotation between these two sites probably occurred as the thrust sheets were emplaced during Laramide deformation. At two of the sections, namely Cienega del Toro and the overturned Los Chorros sections, only normal polarity directions are observed. The La Boca Canyon and Santa Rosa Canyon sections exhibit zones of both normal and reverse polarity magnetization. Correlation of these polarity zones with the geomagnetic polarity timescale provides a time framework for lithostratigraphic and palaeoceanographic studies of these sections.