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31.
Casey R. Remmer Tanner Owca Laura Neary Johan A. Wiklund Mitchell Kay Brent B. Wolfe Roland I. Hall 《水文研究》2020,34(2):303-320
Hydrological monitoring in complex, dynamic northern floodplain landscapes is challenging, but increasingly important as a consequence of multiple stressors. The Peace-Athabasca Delta in northern Alberta, Canada, is a Ramsar Wetland of International Importance reliant on episodic river ice-jam flood events to recharge abundant perched lakes and wetlands. Improved and systematic monitoring of landscape-scale hydrological connectivity among freshwater ecosystems (rivers, channels, wetlands, and lakes) is needed to guide stewardship decisions in the face of climate change and upstream industrial development. Here, we use water isotope compositions, supplemented by measurements of specific conductivity and field observations, from 68 lakes and 9 river sites in May 2018 to delineate the extent and magnitude of spring ice-jam induced flooding along the Peace and Athabasca rivers. Lake-specific estimates of input water isotope composition (δI) were modelled after accounting for influence of evaporative isotopic enrichment. Then, using the distinct isotopic signature of input water sources, we develop a set of binary mixing models and estimate the proportion of input to flooded lakes attributable to river floodwater and precipitation (snow or rain). This approach allowed identification of areas and magnitude of flooding that were not captured by other methods, including direct observations from flyovers, and to demarcate flow pathways in the delta. We demonstrate water isotope tracers as an efficient and effective monitoring tool for delineating spatial extent and magnitude of an important hydrological process and elucidating connectivity in the Peace-Athabasca Delta, an approach that can be readily adopted at other floodplain landscapes. 相似文献
32.
Headless submarine canyons and fluid flow on the toe of the Cascadia accretionary complex 总被引:1,自引:0,他引:1
Daniel L. Orange Brian G. McAdoo J. Casey Moore Harold Tobin Elizabeth Screaton Hank Chezar Homa Lee Mark Reid & Rick Vail 《Basin Research》1997,9(4):303-312
Headless submarine canyons with steep headwalls and shallowly sloping floors occur on both the second and third landward vergent anticlines on the toe of the Cascadia accretionary complex off central Oregon (45 °N, 125° 30′W). In September 1993, we carried out a series of nine deep tow camera sled runs and nine ALVIN dives to examine the relationship between fluid venting, structure and canyon formation. We studied four canyons on the second and third landward vergent anticlines, as well as the apparently unfailed intercanyon regions along strike. All evidence of fluid expulsion is associated with the canyons; we found no evidence of fluid flow between canyons. Even though all fluid seeps are related to canyons, we did not find seeps in all canyons, and the location of the seeps within the canyons differed. On the landward facing limb of the second landward vergent anticline a robust cold seep community occurs at the canyon’s inflection point. This seep is characterized by chemosynthetic vent clams, tube worms and extensive authigenic carbonate. Fluids for this seep may utilize high-permeability flow paths either parallel to bedding within the second thrust ridge or along the underlying thrust fault before leaking into the overriding section. Two seaward facing canyons on the third anticlinal ridge have vent clam communities near the canyon mouths at approximately the intersection between the anticlinal ridge and the adjacent forearc basin. No seeps were found along strike at the intersection of the slope basin and anticlinal ridge. We infer that the lack of seepage along strike and the presence of seeps in canyons may be related to fluid flow below the forearc basin/slope unconformity (overpressured by the impinging thrust fault to the west?) directed toward canyons at the surface. 相似文献
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Numerical modelling of finite-amplitude similar folds developing under general deformation histories
A simple model of similar folds in homogeneous materials with anisotropic properties is proposed and it is shown that the model is applicable to a wide range of natural examples of folds. A mathematical derivation is given which allows the instantaneous deformation of the folds to be calculated for any imposed bulk deformation. A means of projecting the effects of the deformation over a finite time interval is described. The modelling is illustrated by simulations of folds observed in the Morcles nappe, western Switzerland, based on the assumption that the folds formed under simple shear bulk deformation. Folds with geometrical features remarkably similar to those natural folds are produced in the modelling by varying the parameters. 相似文献
36.
The Canadian design for the Square Kilometre Array radio telescope includes a large multi-tethered aerostat to support the telescope’s receiver. To validate this design concept, two parallel tracks have been undertaken: a numerical simulation of the multi-tethered aerostat system has been assembled, and a one-third scale prototype of the system has been constructed. This paper describes the experimental facility, presents results from initial tests of the uncontrolled system and compares these results to the predictions of the computer model of the system. Generally, the results compare very favourably. Using the simulation, we arrive at two important design philosophies to be used in the design of the full-scale system: (a) perturbations on the confluence point should be minimized, and (b) the system stiffness should be maximized to ensure minimum response to disturbances. 相似文献
37.
Casey R 《Irish geography : bulletin of the Geographical Society of Ireland》2010,43(3):211-232
There is a growing body of research in racial and ethnic studies on the processes of identity construction within minority ethnic populations. This article seeks to build on this work by analysing emerging collective identity formations in an ‘invisible’ minority ethnic group. Based upon focus groups and in-depth interviews with Irish people in Sheffield, the article aims to advance three key arguments. First, the concept of community is central to an Irish collective identity, but is negotiated in a multiplicity of ways. Second, Irish collective identity has been shaped not only by demographic differences but by shared experiences of non-recognition and stereotyping. Third, there is a simultaneous assertion of an Irish identity running parallel with a perception that the ‘traditional’ Irish community may have to re-invent itself in response to changing demographics at the local level. The paper concludes by considering the implications of these arguments for an understanding of Irish ethnicity in multicultural Britain. 相似文献
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39.
Borehole image analysis of the Nankai Accretionary Wedge, ODP Leg 196: Structural and stress studies 总被引:2,自引:0,他引:2
Masanori Ienaga Lisa C. McNeill Hitoshi Mikada Saneatsu Saito David Goldberg J. Casey Moore 《Tectonophysics》2006,426(1-2):207
Electrical images recorded with Resistivity-At-Bit (RAB) from two sites drilled during Ocean Drilling Program (ODP) Leg 196 were analyzed to study the effects of subduction at the Nankai margin. For the first time in the history of scientific deep-sea drilling in ODP, in situ complete borehole images of the décollement zone were obtained. Analyses of all drilling-induced fracture data indicated that the maximum horizontal compressive stress (SHmax) axes have an azimuth of 303°, and analyses of breakout data from RAB images indicated an azimuth of 310°. These azimuths approximate the convergence direction of the Philippine Sea plate towards the Eurasian plate. The frontal thrust at Site 808 was encountered at about 389 mbsf. Density, porosity, resistivity, and gamma ray data change across the frontal thrust. The décollement zone at the deformation front was identified between 937 and 965 mbsf. The base of the décollement is sharply defined as the maximum extent of conductive fracturing and is marked by abrupt changes in physical properties [Mikada, H., Becker, K., Moore, J.C., Klaus, A., Austin, G.L., Bangs, N.L., Bourlange, S., Broilliard, J., Brückmann, W., Corn, E.R., Davis, E.E., Flemings, P.B., Goldberg, D.B., Gulick, S.S., Hansen, M.B., Hayward, N., Hills, D.J., Hunze, S., Ienaga, M., Ishiguro, H., Kinoshita, M., Macdonald, R.D., McNeill, L., Obana, S., Hong, O.S., Peacock, S., Pettigrew, T.L., Saito, S., Sawa, T., Thaiprasert, N., Tobin, H.J., Tsurumi, H., 2002. Proc. ODP, Initial Rep., 196, College Station, TX, (Ocean Drilling Program)]. The upper boundary of the décollement is marked by several sets of conductive fractures and by high variability in physical properties. The décollement zone is characterized by intense brittle fracturing. These fractures are considered to be the consequence of cyclic stresses and high fluid pressures in this zone. We analyzed fracture dips and their orientations at both sites and found that they are all consistent with a unique stress field model surrounding the two sites. 相似文献
40.
Jerome V. DeGraff David L. Wagner Alan J. Gallegos Margie DeRose Casey Shannon Todd Ellsworth 《Landslides》2011,8(3):343-353
On July 12, 2008, two convective cells about 155 km apart produced a brief period of intense rainfall triggering large debris
flows in the southern Sierra Nevada. The northernmost cell was centered over Oak Creek Canyon, an east-flowing drainage, and
its tributaries near Independence, CA, USA. About 5:00 p.m., debris flows passed down the South Fork and North Fork of Oak Creek to merge into a large single feature whose passage affected
the historic Mt. Whitney Fish hatchery and blocked California State Highway 395. At about the same time, the southernmost
cell was largely centered over Erskine Creek, a main tributary of the west-flowing Kern River. Debris flows issued from several
branches to coalesce into a large debris flow that passed along Erskine Creek, through the town of Lake Isabella, CA, USA
and into the Kern River. It was observed reaching Lake Isabella about 6:30 p.m. Both debris flows caused significant disruption and damage to local communities. 相似文献