Studies of normal fault systems in modern extensional regimes (e.g. Basin and Range), and in exhumed, ancient rift basins (e.g. Gulf of Suez Rift) have shown a link between the evolution of fault‐related footwall topography and associated erosional drainage systems. In this study, we use 3D seismic reflection data to image the footwall crest of a gravity‐driven fault system developed during late Middle Jurassic to Early Cretaceous rifting on the Halten Terrace, offshore Mid‐Norway. This 22‐km‐long fault system lacks significant footwall uplift, with hangingwall subsidence accommodating throw accumulation on the fault system. Significant erosion has occurred along the length of the footwall crest and is defined by 96 catchments characterized by erosional channels. These erosional channels consist of small, linear systems up to 750 m long located along the front of the fault footwall. Larger, dendritic channel systems extend further back (up to 3 km normal to fault strike) into the footwall. These channels are up to 7 km long, up to 50 m deep and up to 1 km wide. Fault throw varies along strike, with greatest throw in the centre of the fault decreasing towards the fault tips; localized throw minima are interpreted to represent segment linkage points, which were breached as the fault grew. Comparison of the catchment location to the throw distribution shows that the largest catchments are in the centre of the fault and decrease in size to the fault tips. There is no link between the location of the breached segment linkage points and the location and size of the footwall catchments, suggesting that the first‐order control on footwall erosion patterns is the overall fault‐throw distribution. 相似文献
Linking meteorites to their asteroid parent bodies remains an outstanding issue. Space-based dust characterization using impact ionization mass spectrometry is a proven technique for the compositional analysis of individual cosmic dust grains. Here we investigate the feasibility of determining asteroid compositions via cation mass spectrometric analyses of their dust ejecta clouds during low (7–9 km s−1) velocity spacecraft flybys. At these speeds, the dust grain mass spectra are dominated by easily ionized elements and molecular species. Using known bulk mineral volume abundances, we show that it is feasible to discriminate the common meteorite classes of carbonaceous chondrites, ordinary chondrites, and howardite–eucrite–diogenite achondrites, as well as their subtypes, relying solely on the detection of elements with ionization efficiencies of ≤700 or ≤800 kJ mol−1, applicable to low (~7 km s−1) and intermediate (~9 km s−1) flyby speed scenarios, respectively. Including the detection of water ion groups enables greater discrimination between certain meteorite types, and flyby speeds ≥10 km s−1 enhance the diagnostic capabilities of this technique still further. Although additional terrestrial calibration is required, this technique may allow more unequivocal asteroid-meteorite connections to be determined by spacecraft flybys, emphasizing the utility of dust instruments on future asteroid missions. 相似文献
Stakeholders in natural resource management decisions are also multifaceted individuals and members of communities; as such, they bring complex histories, experiences, values, aspirations, and relationships to public participation processes. When these processes fail to take this social context into account, multiple problems can result, including a perceived lack of process trustworthiness; perceived focus on issues that seem immaterial or irrelevant; failure to equitably represent and take account of diverse voices; and failure to engage participants in productive dialogue. In this article we evaluate the Community Voice Method (CVM) as a way of addressing those problems by better situating public participation in place. CVM is a mixed-method approach to public participation in which stakeholders are interviewed and the interview data is presented through a film, which is then screened at public meetings to catalyze dialogue. We draw on 14 years of CVM projects addressing natural resource management issues in the United States, the United Kingdom, and the Caribbean. Through an overview of nine projects and their results, and more in-depth consideration of three, we elucidate how this method fosters trustworthy, relevant, representative, and productive public participation that has resulted in community capacity-building, institutional capacity-building, and stakeholder-guided policymaking.
Governments and development organisations consider the involvement of poor forest managers in global value chains and markets as a most promising approach for resolving the social and environmental challenges of the Amazon. This paper intends to provide a clearer picture about opportunities and potentials of this market-approach, by analysing integrated forest based development initiatives in the Bolivian, Brazilian, Ecuadorian and Peruvian Amazon. Findings suggest that the externally promoted initiatives seldom correspond to local realities and that they suffer from limited financial viability due to competitive disadvantages of locals in comparison to more capitalized actors. Success stories remain isolated without replication, and depend on external support for continuation. Only a limited number of families provided with privileged support have been able to overcome the technical, institutional and financial hurdles and to benefit from existing market opportunities. In some cases, interventions have generated conflicts and even weakened social organisation. Instead of simply copying the mistakes of the past regarding the emerging markets for environmental services, it is deemed essential to question the current market focus and search for alternatives placing greater emphasis on the interests, cultures and capacities of local people. 相似文献
In weather forecasting, current and past observational data are routinely assimilated into numerical simulations to produce ensemble forecasts of future events in a process termed “model steering”. Here we describe a similar approach that is motivated by analyses of previous forecasts of the Working Group on California Earthquake Probabilities (WGCEP). Our approach is adapted to the problem of earthquake forecasting using topologically realistic numerical simulations for the strike-slip fault system in California. By systematically comparing simulation data to observed paleoseismic data, a series of spatial probability density functions (PDFs) can be computed that describe the probable locations of future large earthquakes. We develop this approach and show examples of PDFs associated with magnitude M > 6.5 and M > 7.0 earthquakes in California. 相似文献
Climate models with biogeochemical components predict declines in oceanic dissolved oxygen with global warming. In coastal regimes oxygen deficits represent acute ecosystem perturbations. Here, we estimate dissolved oxygen differences across the global tropical and subtropical oceans within the oxygen minimum zone (200–700-dbar depth) between 1960–1974 (an early period with reliable data) and 1990–2008 (a recent period capturing ocean response to planetary warming). In most regions of the tropical Pacific, Atlantic, and Indian Oceans the oxygen content in the 200–700-dbar layer has declined. Furthermore, at 200 dbar, the area with O2 <70 μmol kg?1, where some large mobile macro-organisms are unable to abide, has increased by 4.5 million km2. The tropical low oxygen zones have expanded horizontally and vertically. Subsurface oxygen has decreased adjacent to most continental shelves. However, oxygen has increased in some regions in the subtropical gyres at the depths analyzed. According to literature discussed below, fishing pressure is strong in the open ocean, which may make it difficult to isolate the impact of declining oxygen on fisheries. At shallower depths we predict habitat compression will occur for hypoxia-intolerant taxa, with eventual loss of biodiversity. Should past trends in observed oxygen differences continue into the future, shifts in animal distributions and changes in ecosystem structure could accelerate. 相似文献
Decline onset times were measured in long-term visual light curves for five R Coronae Borealis (RCB) variable stars. These included RY Sgr and V854 Cen, the two RCB stars previously reported to have a relationship between dust formation events and pulsational variations. Analysis of the decline epochs showed that all decline onsets for a given star obey a linear ephemeris tied to the object's dominant radial pulsation period. Thus, in addition to confirming the pulsation–decline correlation for RY Sgr and V854 Cen, this same behaviour was demonstrated in UW Cen, R CrB and S Aps for the first time. This general result firmly establishes the connection between radial pulsation and mass loss in the RCB stars. The dominant pulsation period of ≈40 d for all of these objects therefore represents the characteristic time-scale on which these stars produce dust. 相似文献