The Arctic Coastal Dynamics Database: A New Classification Scheme and Statistics on Arctic Permafrost Coastlines     

Hugues Lantuit  Pier Paul Overduin  Nicole Couture  Sebastian Wetterich  Felix Aré  David Atkinson  Jerry Brown  Georgy Cherkashov  Dmitry Drozdov  Donald Lawrence Forbes  Allison Graves-Gaylord  Mikhail Grigoriev  Hans-Wolfgang Hubberten  James Jordan  Torre Jorgenson  Rune Strand ?deg?rd  Stanislav Ogorodov  Wayne H. Pollard  Volker Rachold  Sergey Sedenko  Steve Solomon  Frits Steenhuisen  Irina Streletskaya  Alexander Vasiliev 《Estuaries and Coasts》2012,35(2):383-400

Arctic permafrost coasts are sensitive to changing climate. The lengthening open water season and the increasing open water area are likely to induce greater erosion and threaten community and industry infrastructure as well as dramatically change nutrient pathways in the near-shore zone. The shallow, mediterranean Arctic Ocean is likely to be strongly affected by changes in currently poorly observed arctic coastal dynamics. We present a geomorphological classification scheme for the arctic coast, with 101,447?km of coastline in 1,315 segments. The average rate of erosion for the arctic coast is 0.5?m? year^?1 with high local and regional variability. Highest rates are observed in the Laptev, East Siberian, and Beaufort Seas. Strong spatial variability in associated database bluff height, ground carbon and ice content, and coastline movement highlights the need to estimate the relative importance of shifting coastal fluxes to the Arctic Ocean at multiple spatial scales.  相似文献   

Synoptic forcing of wave states in the southeast Chukchi Sea, Alaska, at an offshore location     

Oceana P. Francis  David E. Atkinson 《Natural Hazards》2012,62(3):1169-1189

A bottom-mounted Recording Doppler Current Profiler was placed at an offshore location (depth of 34 m) in the southeast Chukchi Sea, Alaska, from July through December 2007 (UTC) with the objective of linking observed wave activity—wind-sea and swells—to their synoptic drivers. A total of 47 intervals of elevated wave state were recorded: 29 exceeding 1 m significant wave height (SWH), 16 exceeding 2 m SWH, and 3 m exceeded on two occasions; during one of those, a SWH of 4 m was observed. Detailed analysis of the two large events, including comparison with high-resolution reanalysis wind data (North America Regional Reanalysis), showed wave direction from the east, varied about 15° to the north (counterclockwise) from the wind direction, and current flow in the opposite direction (from the west). This is thought to be the influence of a strong “wind-sea” presence. Regarding classic wave limitations, although the SE Chukchi Sea is a large embayment bordered by land to the east, fetch limitations from the northeast and southeast did not appear to be a constraint for the wind speeds indicated by reanalysis. These two events appeared to be driven by winds associated with cyclonic systems that moved into the eastern Bering Sea and stalled. Examination of smaller waves associated with these events suggested that waves of 1.5 m SWH or less are likely part of another regime and can either be swell or wind-sea, moving in from the open Chukchi Sea to the northwest or through the Bering Strait to the south.  相似文献   

阿尔泰南缘早泥盆世康布铁堡组的SIMS锆石U-Pb年龄及其向东向北延伸的范围   总被引：7，自引：2，他引：5  

刘伟  刘丽娟  刘秀金  尚海军  周刚 《岩石学报》2010,26(2):387-400

麦兹火山-沉积盆地康布铁堡组的年龄及其东界,以及阿尔泰南缘早泥盆世火山活动往东往北延伸的范围仍然没有确定;康布铁堡组火山岩的源岩及其形成的构造环境还有待阐明。近年来在麦兹盆地东侧发现了萨吾斯铅锌矿床,矿床赋存于康布铁堡组火山岩,与别斯萨拉玢岩体密切有关。本研究对萨吾斯铅锌矿床的康布铁堡组流纹岩和别斯萨拉玢岩进行了SIMS锆石U-Pb定年以及主微量元素组成测定,以期回答上述问题。流纹岩锆石的18个靶点给出了一致的谐和年龄和加权平均年龄(401Ma);花岗闪长玢岩锆石的15个靶点给出了一致的谐和年龄和加权平均年龄(401Ma)。因此,萨吾斯铅锌矿床康布铁堡组流纹岩和别斯萨拉玢岩是同期喷发/侵入的;康布铁堡组火山活动的时代在早泥盆世;麦兹火山-沉积盆地的东界应抵达卡拉先格尔断裂西侧。在～400Ma时期,阿尔泰地区不仅存在着广泛的花岗岩类深成岩浆活动,也发生了强烈的酸性火山喷发,两者共同构成了阿尔泰南缘的大陆边缘岩浆弧。但是,火山喷发主要集中于阿尔泰南缘,受断裂控制。花岗闪长玢岩的一些锆石给出513.8Ma和3134Ma的U-Pb年龄,反映区内陆壳由寒武纪—奥陶纪岩石组成,并且还有前寒武纪微陆块。硅-碱、SiO_2-K_2O、logτ-logσ、SiO_2-FeO/(FeO+MgO)图以及构造环境判别图表明,萨吾斯铅锌矿床的流纹岩、凝灰岩、石英闪长玢岩-花岗闪长玢岩以及阿尔泰南缘早泥盆世康布铁堡组火山岩形成于活动大陆边缘或岛弧环境。康布铁堡组中下段细碧角斑岩在岛弧海底环境喷发,上段流纹岩喷发于大陆边缘环境。原始地幔标准化的多元素蛛网图表明,萨吾斯矿床的三类岩石具有明显的Nb、Ta、Ti和Sr、P、Ba负异常,显著富集Th、U、K、La、Ce、Pr、Zr、Hf。结合锆石U-Pb年龄,作者认为它们的源岩应以寒武纪-奥陶纪的岛弧岩石为主;同时,可能还含有一定比例的前寒武纪古老陆壳岩石。冲乎尔、克兰、麦兹三个火山-沉积盆地在所属构造单元、陆壳基底、火山岩岩石地球化学以及沉积岩的比例上都表现出系统变化,这些变异控制了阿尔泰南缘块状硫化物矿床从西部到中部到东部的成矿元素组合上的变化。  相似文献   

The significance of dilution in evaluating possible impacts of wastewater discharges from large cruise ships   总被引：1，自引：0，他引：1  

Loehr LC  Beegle-Krause CJ  George K  McGee CD  Mearns AJ  Atkinson MJ 《Marine pollution bulletin》2006,52(6):681-688

In response to public concerns about discharges from large cruise ships, Alaska's Department of Environmental Conservation (ADEC) sampled numerous effluents in the summer of 2000. The data showed that basic marine sanitation device (MSD) technology for black water (sewage) was not performing as expected. Untreated gray water had high levels of conventional pollutants and surprisingly high levels of bacteria. Both black water and gray water discharges sometimes exceeded state water quality standards for toxicants. The state convened a Science Advisory Panel (the Panel) to evaluate impacts associated with cruise ship wastewater discharges. The effluent data received wide media coverage and increased public concerns. Consequently, legislative decisions were made at the State and Federal level, and regulations were imposed before the Panel completed its evaluation. The Panel demonstrated that following the rapid dilution from moving cruise ships, the effluent data from the Summer of 2000 would not have exceeded water quality standards, and environmental effects were not expected.  相似文献   

The possibilities and pitfalls presented by a pragmatic approach to ecosystem service valuation in an arid biodiversity hotspot     

P.J. O’Farrell  W.J. De LangeD.C. Le Maitre  B. ReyersJ.N. Blignaut  S.J. MiltonD. Atkinson  B. EgohA. Maherry  C. ColvinR.M. Cowling 《Journal of Arid Environments》2011,75(6):612-623

Arid regions are home to unique fauna, flora, and vulnerable human populations, and present a challenge for sustainable land-use management. We undertook an assessment and valuation of three key services, grazing, tourism and water supply in the arid Succulent Karoo biome in western South Africa - a globally recognised biodiversity hotspot. We were looking for ways and values that could be used to promote conservation in this region through the adoption of sustainable land-use practices which have human welfare benefits. Our study adopted a variety of methods in valuing these services in developing ranges of values for these services. At the biome level, total annual values ranged from $ 19-114 million for grazing, $ 2-$ 20 million for tourism, and $ 300-3120 million for water. These values are generally low compared with values derived for other biomes and regions and do not adequately reflect known dependence and the importance of ecosystem services to the residents of this biome. The ecosystems here provide small but critical benefits enabling communities to sustain themselves and small changes in service levels can have major welfare effects. Highlighting these sensitivities will require finding more appropriate ways to link ecological and social factors.  相似文献   

Image fusion by spatially adaptive filtering using downscaling cokriging     

E. Pardo-Iguzquiza  V.F. Rodríguez-Galiano  M. Chica-Olmo  Peter M. Atkinson   《ISPRS Journal of Photogrammetry and Remote Sensing》2011,66(3):337-346

The aim of this paper was to extend the method of downscaling cokriging for image fusion by making the method spatially adaptive in that the filter parameters (cokriging weights) can change across the image. The method can adapt itself to the usual statistical non-homogeneity (spatially variable mean, variance and correlation length) of a satellite sensor image that covers an area with different spatial patterns of geographical objects or different terrain types. The solution adopted was to estimate the models of covariances and cross-covariances (or semivariograms and cross-semivariograms) by the same procedure as described in Pardo-Iguzquiza et al. (2006) but with the method applied locally instead of globally. The correct implementation of this local estimation is the key for computational feasibility and prediction efficiency. Two parameters to be taken into account are the grid of locations on which a moving window is centred (local modelling is performed inside this window) and the size of this moving window. With respect to the latter parameter, there is a trade-off between a size small enough to make the procedure locally adaptive and large enough to produce reliable statistical estimates. The computational burden will impose limits to the distance between grid points on which the local moving window is centred. A case study with Landsat ETM+ images was used to show the implementation of the method and the result was evaluated using several statistics widely used for assessing the quality of a fused image, apart from its visual appearance.  相似文献   

Implications of the 2011 M9.0 Tohoku Japan earthquake for the treatment of site effects in large earthquakes     

Hadi Ghofrani  Gail M. Atkinson  Katsuichiro Goda 《Bulletin of Earthquake Engineering》2013,11(1):171-203

Site response in Japan is characterized using thousands of surface and borehole recordings from events of moment magnitude $(\mathbf{M}) > 5.5$ collected by the KiK-net network, including the 2011 M9.0 Tohoku earthquake. Site amplification is defined by the ratio of motions at the surface to those at depth (within the borehole), corrected for the depth effect due to destructive interference using a technique based on cross-spectral ratios between surface and down-hole motions. Site effects were particularly strong at high frequencies, despite the expectation that high-frequency response may be damped by nonlinear effects. In part, the large amplitudes at high frequencies are due to the prevalence of shallow soil conditions in Japan. We searched for typical symptoms for soil nonlinearity, such as a decrease in the predominant frequency and/or amplification, using spectral ratios of weak to strong ground motions. Localized nonlinearity occurred at some recording sites, but was not pervasive. We developed a general empirical model to express site amplification for the KiK-net sites as a function of common site variables, such as the average shear-wave velocity in the uppermost 30 m ( $\text{ V}_\mathrm{S30})$ and the horizontal-to-vertical (H/V) spectral ratio. We use the model to estimate site-corrected ground-motions for the Tohoku mainshock for a reference site condition; these motions are in reasonable agreement with the predictions of some of the published ground motion prediction equations for subduction zones.  相似文献   

Incorporating spatial association into statistical classifiers: local pattern-based prior tuning     

Hexiang Bai  Feng Cao  M. Peter Atkinson  Qian Chen  Jinfeng Wang 《International journal of geographical information science》2020,34(10):2077-2114

ABSTRACT

This paper proposes a new classification method for spatial data by adjusting prior class probabilities according to local spatial patterns. First, the proposed method uses a classical statistical classifier to model training data. Second, the prior class probabilities are estimated according to the local spatial pattern and the classifier for each unseen object is adapted using the estimated prior probability. Finally, each unseen object is classified using its adapted classifier. Because the new method can be coupled with both generative and discriminant statistical classifiers, it performs generally more accurately than other methods for a variety of different spatial datasets. Experimental results show that this method has a lower prediction error than statistical classifiers that take no spatial information into account. Moreover, in the experiments, the new method also outperforms spatial auto-logistic regression and Markov random field-based methods when an appropriate estimate of local prior class distribution is used.  相似文献   

Non‐iterative equivalent linearization of inelastic SDOF systems for earthquakes in Japan and California     

Katsuichiro Goda  Gail M. Atkinson 《地震工程与结构动力学》2010,39(11):1219-1238

The seismic performance of existing structures can be assessed based on nonlinear static procedures, such as the Capacity Spectrum Method. This method essentially approximates peak responses of an inelastic single‐degree‐of‐freedom (SDOF) system using peak responses of an equivalent linear SDOF model. In this study, the equivalent linear models of inelastic SDOF systems are developed based on the constant strength approach, which does not require iteration for assessing the seismic performance of existing structures. To investigate the effects of earthquake type and seismic region on the equivalent linear models, four ground‐motion data sets—Japanese crustal/interface/inslab records and California crustal records—are compiled and used for nonlinear dynamic analysis. The analysis results indicate that: (1) the optimal equivalent linear model parameters (i.e. equivalent vibration period ratio and damping ratio) decrease with the natural vibration period, whereas they increase with the strength reduction factor; (2) the impacts of earthquake type and seismic region on the equivalent linear model parameters are not significant except for short vibration periods; and (3) the degradation and pinching effects affect the equivalent linear model parameters. We develop prediction equations for the optimal equivalent linear model parameters based on nonlinear least‐squares fitting, which improve and extend the current nonlinear static procedure for existing structures with degradation and pinching behavior. Copyright © 2010 John Wiley & Sons, Ltd.  相似文献   

Ground Motion Prediction Equations in the San Jacinto Fault Zone: Significant Effects of Rupture Directivity and Fault Zone Amplification     

I. Kurzon  F. L. Vernon  Y. Ben-Zion  G. Atkinson 《Pure and Applied Geophysics》2014,171(11):3045-3081

We present a new set of Ground Motion Prediction Equations (GMPEs) for horizontal Peak Ground Acceleration, Peak Ground Velocity, and 5 % damped pseudo-spectral acceleration (PSA), developed for the San Jacinto Fault Zone (SJFZ) area. Besides using these equations to quantify seismic shaking in the area, the results allow us to examine the physics and local properties controlling the observed ground motions. The analyzed dataset includes ~30,000 observations from ~800 events spanning a magnitude range of 1.5 < M < 6.0 and recorded by up to 140 stations at epicentral distances ranging from essentially zero to 150 km. The local GMPE is developed for the SJFZ by applying classical regression techniques with predictive variables that include first distance and magnitude, and then site characteristics, rupture directivity, and fault zone amplification. The significance of these effects is determined by measuring the uncertainty-reduction of the GMPE due to each factor. The results show that, in contrast to many regional studies, traditional site characteristic has a relatively minor effect on peak amplitudes in our study area. However, rupture directivity is a significant factor controlling the amplitudes of ground motion even for small events. The dense seismic network and newly developed directivity tool enable us to extract efficiently directivity effects with statistical significance, using the ground-motion dataset during the regression analysis process. The obtained rupture directivities are consistent with the main focal mechanism orientations and surface trace orientations, known from other studies, and predictions for bimaterial ruptures in the trifurcation area of the SJFZ. Fault zone amplification is a second important factor, showing strong impact on the peak ground motion values, with increasing role for the lower frequency range (<10 Hz) examined in the 5 % damped PSA values. We also observe signatures of large amplitude-variances, which indicate additional source-related control on the distribution of amplitudes (besides rupture directivity) for aftershocks close in time and location to the M _L 5.1 earthquake of March 2013. Using the full set of records we present the most complete set of GMPEs for the SJFZ area, including a higher-amplitude prediction for regions in the direction of rupture.  相似文献