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21.
Clinton Rissmann Bruce Christenson Cynthia Werner Matthew Leybourne Jim Cole Darren Gravley 《Applied Geochemistry》2012
Carbon dioxide emissions and heat flow have been determined from the Ohaaki hydrothermal field, Taupo Volcanic Zone (TVZ), New Zealand following 20 a of production (116 MWe). Soil CO2 degassing was quantified with 2663 CO2 flux measurements using the accumulation chamber method, and 2563 soil temperatures were measured and converted to equivalent heat flow (W m−2) using published soil temperature heat flow functions. Both CO2 flux and heat flow were analysed statistically and then modelled using 500 sequential Gaussian simulations. Forty subsoil CO2 gas samples were also analysed for stable C isotopes. Following 20 a of production, current CO2 emissions equated to 111 ± 6.7 T/d. Observed heat flow was 70 ± 6.4 MW, compared with a pre-production value of 122 MW. This 52 MW reduction in surface heat flow is due to production-induced drying up of all alkali–Cl outflows (61.5 MW) and steam-heated pools (8.6 MW) within the Ohaaki West thermal area (OHW). The drying up of all alkali–Cl outflows at Ohaaki means that the soil zone is now the major natural pathway of heat release from the high-temperature reservoir. On the other hand, a net gain in thermal ground heat flow of 18 MW (from 25 MW to 43.3 ± 5 MW) at OHW is associated with permeability increases resulting from surface unit fracturing by production-induced ground subsidence. The Ohaaki East (OHE) thermal area showed no change in distribution of shallow and deep soil temperature contours despite 20 a of production, with an observed heat flow of 26.7 ± 3 MW and a CO2 emission rate of 39 ± 3 T/d. The negligible change in the thermal status of the OHE thermal area is attributed to the low permeability of the reservoir beneath this area, which has limited production (mass extraction) and sheltered the area from the pressure decline within the main reservoir. Chemistry suggests that although alkali–Cl outflows once contributed significantly to the natural surface heat flow (∼50%) they contributed little (<1%) to pre-production CO2 emissions due to the loss of >99% of the original CO2 content due to depressurisation and boiling as the fluids ascended to the surface. Consequently, the soil has persisted as the major (99%) pathway of CO2 release to the atmosphere from the high temperature reservoir at Ohaaki. The CO2 flux and heat flow surveys indicate that despite 20 a of production the variability in location, spatial extent and magnitude of CO2 flux remains consistent with established geochemical and geophysical models of the Ohaaki Field. At both OHW and OHE carbon isotopic analyses of soil gas indicate a two-stage fractionation process for moderate-flux (>60 g m−2 d−1) sites; boiling during fluid ascent within the underlying reservoir and isotopic enrichment as CO2 diffuses through porous media of the soil zone. For high-flux sites (>300 g m−2 d−1), the δ13CO2 signature (−7.4 ± 0.3‰ OHW and −6.5 ± 0.6‰ OHE) is unaffected by near-surface (soil zone) fractionation processes and reflects the composition of the boiled magmatic CO2 source for each respective upflow. Flux thresholds of <30 g m−2 d−1 for purely diffusive gas transport, between 30 and 300 g m−2 d−1 for combined diffusive–advective transport, and ?300 g m−2 d−1 for purely advective gas transport at Ohaaki were assigned. δ13CO2 values and cumulative probability plots of CO2 flux data both identified a threshold of ∼15 g m−2 d−1 by which background (atmospheric and soil respired) CO2 may be differentiated from hydrothermal CO2. 相似文献
22.
Local and regional minimum 1D models for earthquake location and data quality assessment in complex tectonic regions: application to Switzerland 总被引：1，自引：0，他引：1
One-dimensional (1D) velocity models are still widely used for computing earthquake locations at seismological centers or
in regions where three-dimensional (3D) velocity models are not available due to the lack of data of sufficiently high quality.
The concept of the minimum 1D model with appropriate station corrections provides a framework to compute initial hypocenter
locations and seismic velocities for local earthquake tomography. Since a minimum 1D model represents a solution to the coupled
hypocenter-velocity problem it also represents a suitable velocity model for earthquake location and data quality assessment,
such as evaluating the consistency in assigning pre-defined weighting classes and average picking error. Nevertheless, the
use of a simple 1D velocity structure in combination with station delays raises the question of how appropriate the minimum
1D model concept is when applied to complex tectonic regions with significant three-dimensional (3D) variations in seismic
velocities. In this study we compute one regional minimum 1D model and three local minimum 1D models for selected subregions
of the Swiss Alpine region, which exhibits a strongly varying Moho topography. We compare the regional and local minimum 1D
models in terms of earthquake locations and data quality assessment to measure their performance. Our results show that the
local minimum 1D models provide more realistic hypocenter locations and better data fits than a single model for the Alpine
region. We attribute this to the fact that in a local minimum 1D model local and regional effects of the velocity structure
can be better separated. Consequently, in tectonically complex regions, minimum 1D models should be computed in sub-regions
defined by similar structure, if they are used for earthquake location and data quality assessment. 相似文献
23.
For certain porous media and initial conditions, constant flux infiltrations show a saturation profile which exhibits overshoot. This overshoot is the cause of gravity driven fingering, cannot be described by standard models of unsaturated flow, and is likely controlled by the exact nature of the pore filling at the initial front. Here we report synchrotron X-ray micro-tomography measurements of the porous medium and measure which pores are filled by water and air at the initial wetting front as a function of flux. We find that at high fluxes all the pores are filled with water; for intermediate fluxes, the pores along the edge of the column remain unsaturated; and for low fluxes the pores in the bulk of the experimental column remain unsaturated. This suggests that the unsaturated overshoot conditions observed at higher fluxes are primarily an edge effect of the column. The results can help delineate the correct continuum models that can capture overshoot and gravity driven fingering. 相似文献
24.
Carlo?CauzziEmail author Yannik?Behr Thomas?Le?Guenan John?Douglas Samuel?Auclair Jochen?Woessner John?Clinton Stefan?Wiemer 《Bulletin of Earthquake Engineering》2016,14(9):2495-2512
Based on our experience in the project REAKT, we present a methodological framework to evaluate the potential benefits and costs of using earthquake early warning (EEW) and operational earthquake forecasting (OEF) for real-time mitigation of seismic risk at nuclear facilities. We focus on evaluating the reliability, significance and usefulness of the aforementioned real-time risk-mitigation tools and on the communication of real-time earthquake information to end-users. We find that EEW and OEF have significant potential for the reduction of seismic risk at nuclear plants, although much scientific research and testing is still necessary to optimise their operation for these sensitive and highly-regulated facilities. While our test bed was Switzerland, the methodology presented here is of general interest to the community of EEW researchers and end-users and its scope is significantly beyond its specific application within REAKT. 相似文献
25.
A litter of eight near‐term shortfin mako (Isurus oxyrinchus Rafinesque 1810) embryos is described from a 317.5 cm total length (TL) female caught off Hawke Bay, south‐east North Island, New Zealand on 5 February 1999. The embryos (3 males and 5 females) were 67.2–77.0 cm TL. Embryo length, condition, hepato‐somatic indices, and mass of yolk in their stomachs all indicate they were close to birth. This is the first shortfin mako litter reported from New Zealand and is outside the late winter‐early spring parturition period predicted from estimated embryonic and juvenile growth rates. Uterine width data from four mature non‐pregnant females and age‐0+ length‐at‐capture data suggest parturition occurs from September to late February (late winter‐mid summer) but is infrequent after January. We suggest that shortfin makos have an extended parturition period, possibly year‐round, with peak parturition occurring in late winter‐spring. 相似文献
26.
Tobias Diehl John Clinton Nicolas Deichmann Carlo Cauzzi Philipp Kästli Toni Kraft Irene Molinari Maren Böse Clotaire Michel Manuel Hobiger Florian Haslinger Donat Fäh Stefan Wiemer 《Swiss Journal of Geoscience》2018,111(1-2):221-244
This report summarizes the seismicity in Switzerland and surrounding regions in the years 2015 and 2016. In 2015, the Swiss Seismological Service detected and located 735 earthquakes in the region under consideration. With a total of 20 earthquakes of magnitude ML ≥ 2.5, the seismic activity of potentially felt events in 2015 was close to the average of 23 earthquakes over the previous 40 years. Seismic activity was above average in 2016 with 872 located earthquakes of which 31 events had ML ≥ 2.5. The strongest event in the analyzed period was the ML 4.1 Salgesch earthquake, which occurred northeast of Sierre (VS) in October 2016. The event was felt in large parts of Switzerland and had a maximum intensity of V. Derived focal mechanisms and relative hypocenter relocations of aftershocks image a SSE dipping reverse fault, which likely also hosted an ML 3.9 earthquake in 2003. Another remarkable earthquake sequence in the Valais occurred close to Sion with four felt events (ML 2.7–3.2) in 2015/16. We associate this sequence with a system of WNW-ESE striking fault segments north of the Rhône valley. Similarities with a sequence in 2011, which was located about 10 km to the NE, suggest the existence of an en-echelon system of basement faults accommodating dextral slip along the Rhône-Simplon line in this area. Another exceptional earthquake sequence occurred close to Singen (Germany) in November 2016. Relocated hypocenters and focal mechanisms image a SW dipping transtensional fault segment, which is likely associated with a branch of the Hegau-Bodensee Graben. On the western boundary of this graben, micro-earthquakes close to Schlattingen (TG) in 2015/16 are possibly related to a NE dipping branch of the Neuhausen Fault. Other cases of earthquakes felt by the public during 2015/16 include earthquakes in the region of Biel, Vallorcine, Solothurn, and Savognin. 相似文献
27.
Clinton M. Rowe 《自然地理学》2013,34(2):93-114
Over the past decade, the climatic impact of changes in terrestrial albedo has been studied using numerous climate models, ranging from simple, one-dimensional energy balance climate models to the more sophisticated, three-dimensional general circulation models of the atmosphere. In most of these, however, the land-surface albedos have been prescribed both spatially and temporally from albedo observations. To overcome the limitations of using prescribed land-surface albedos, a model of radiation transfer in plant canopies was used to predict vegetation albedos. Because of the model's reliance on the physical properties of the land-surface cover, it is able to account explicitly for albedo variations caused by factors both internal to and external from the vegetation canopy. The model is described and the results of simulations for three representative canopy types are discussed. The dependence of albedo on irradiance distribution predicted by the model agrees well with established theory. [Key words: albedo, modeling, vegetation canopy, climatology.] 相似文献
28.
Amber Wutich Melissa Beresford Julia C. Bausch Weston Eaton Kathryn J. Brasier Clinton F. Williams 《社会与自然资源》2020,33(7):941-948
AbstractThis study compares the efficiency of two analytic approaches—qualitative and quantitative—to social network analysis for identifying stakeholder groups. Social network data were collected from 23 water and agriculture stakeholders in Arizona, USA, and analyzed quantitatively and qualitatively. Analysis of the sample in the original order of data collection found qualitative analysis was more efficient, in that it yielded a stable result—the identification of four stakeholder groups—within 16 interviews. In contrast, the quantitative analysis did not produce a stable result after 23 interviews. Repeated analyses with randomized order and reverse order samples found qualitative approaches yielded more stable results, took about the same number of interviews to yield results, and produced slightly fewer stakeholder groups compared to quantitative approaches. Our findings suggest that, in resource-constrained projects, qualitative social network analysis for identifying stakeholder groups can provide an efficient alternative to conventional quantitative social network analysis. 相似文献
29.
Molly M. Miller Scott W. Phipps Clinton S. Major Kelly M. Major 《Estuaries and Coasts》2011,34(6):1182-1193
This study was designed to investigate non-point source nutrient pollution and its influences on submerged aquatic plant community
structure and biological invasion in the Weeks Bay National Estuarine Research Reserve (WBNERR). A monthly vegetation survey
was conducted to document plant abundance and changes in community structure; physicochemical data and water samples were
collected on a bi-monthly basis to monitor environmental conditions (i.e., pH, salinity, dissolved oxygen, light intensity,
and attenuation) and water column nutrient (NO2−/NO3− and NH4+) and chlorophyll a concentrations. A total of seven submerged aquatic species were identified at the WBNERR with the occurrence of only one
non-native species (Hydrilla verticillata). Statistical analyses suggest that water column nitrogen concentrations along with variations in dissolved oxygen (0.6–11.5 mg L−1), light attenuation, pH (5.6–8.6), and temperature (11–33°C) play key roles in determining the aquatic plant abundance and
distribution in the WBNERR. 相似文献
30.
Chloe Winant Arnoldo Valle-Levinson Aurelien Ponte Clinton Winant Guillermo Gutierrez-de-Velasco Kraig Winters 《Estuaries and Coasts》2014,37(6):1319-1328
Time series of current velocity profiles and thermistor chains were obtained throughout a cross-bay transect for ~90 days for the purpose of comparing observed wind-driven stratified flows to theory. This study concentrates on the synoptic scale wind and its influence on the bay’s circulation. The maximum water column stratification was 3–4 °C/m throughout the deployment and influenced wind-driven flows. Low-pass filtered flows showed more complicated structures than those expected from theory: a depth-dependent recirculating structure with the along-bay flow over one half of the transect moving in opposite direction to the other half. Analysis of complex empirical orthogonal functions indicated that the first six modes explained 80 % of the flow variability. Therefore, there was no predominantly energetic mode of variability. All modes exhibited a rich spatial structure with vertical and lateral variations. For all modes there was vertically sheared bidirectional flow, as expected from theory, with the largest eigenvector (mode value) asymmetrically influenced by Earth’s rotation and advection of momentum. 相似文献