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41.
Grant Heiken Napoleon Ramos Wendell Duffield John Musgrave Kenneth Wohletz Sue Priest James Aldrich Wilmer Flores Alexander Ritchie Fraser Goff Dean Eppler Carlos Escobar 《Journal of Volcanology and Geothermal Research》1991,45(1-2)
The Platanares geothermal area, Departamento de Copán, Honduras, is located within a graben that is complexly faulted. The graben is bounded on the north by a highland composed of Paleozoic (?) metamorphic rocks in contact with Cretaceous - Tertiary redbeds of unknown thickness. These are unconformably overlain by Tertiary andesitic lavas, rhyolitic ignimbrites, and associated sedimentary rocks. The volcanic rocks are mostly older than 14 Ma, and thus are too old to represent the surface expression of an active crustal magma body. Thermal fluids that discharge in the area are heated during deep circulation of meteoric water along faults in a region of somewhat elevated heat flow. Geothermometry based upon the chemical composition of thermal fluids from hot springs and from geothermal gradient coreholes suggests that the reservoir equilibrated at temperatures as high as 225 to 240°C, within the Cretaceous redbed sequence. Three continuously cored geothermal gradient holes have been drilled; fluids of about 165°C have been produced from two drilled along a NW-trending fault zone, from depths of 250 to 680 m. A conductive thermal gradient of 139°C/km, at a depth of 400 m, was determined from the third well, drilled 0.6 km west of that fault zone. These data indicate that the Platanares geothermal area holds considerable promise for electrical generation by moderate- to hightemperature geothermal fluids. 相似文献
42.
Two alternative approaches are investigated to compute the discrete Stokes integral for gravimetric geoid determination so that geographical grid subdivision and gridding is not required. The techniques are based on Voronoi and Delaunay structures, in which the target area is partitioned into polygons and triangles, respectively, and the computation is carried out by point-wise integration. In the Voronoi scheme, polygonal areas just contain the observed gravity anomalies, instead of the interpolated ones; thus no gridding process or data interpolation is necessary, and only the original data are used. In the Delaunay scheme, gridding is also not required, but observed anomalies are interpolated into triangular compartments whose vertices hold the gravity stations. Geoidal undulations are thus computed at the barycenters (centroids) of the triangles. Both schemes were applied to the local gravimetric geoid determination in two distinct areas of Brazil (municipality of Rio de Janeiro, and Resende). The gravity observations are almost uniformly distributed spatially at both sites, and their topographies are very rugged. The Stokes component was also computed by means of classical numerical integration (space-domain), and compared with the Voronoi and Delaunay schemes to give root-mean-square (RMS) differences of 0.022 and 0.024 m, respectively, at the Rio de Janeiro site. In Resende, the comparisons yielded RMS differences of 0.040 and 0.053 m. The largest difference did not exceed 0.100 m for both methods and datasets. The one-dimensional (1-D) FFT (spectral domain) technique was also used on the Rio de Janeiro dataset, which gave RMS differences of 0.031 m for the classical method, 0.039 m for the Voronoi scheme, and 0.047 m for the Delaunay scheme. Relative comparisons with 465 GPS-leveling baselines in the Rio de Janeiro site gave RMS differences of 0.069, 0.061, 0.071, and 0.071 m, for the Voronoi, Delaunay, classical, and 1-D FFT methods, respectively. Since the Voronoi and Delaunay schemes avoid the gridding step, the pre-processing time and labor are reduced. As with other methods, the dependence upon data quality and distribution is the main drawback of both schemes. Finally, the Voronoi and Delaunay schemes proved to be computationally as efficient as the 1-D FFT method for only the geoid height computation. 相似文献
43.
Physically based models are useful frameworks for testing intervention strategies designed to reduce elevated sediment loads in agricultural catchments. Evaluating the success of these strategies depends on model accuracy, generally established by a calibration and evaluation process. In this contribution, the physically based SHETRAN model was assessed in two similar U.K. agricultural catchments. The model was calibrated on the Blackwater catchment (18 km2) and evaluated in the adjacent Kit Brook catchment (22 km2) using 4 years of 15 min discharge and suspended sediment flux data. Model sensitivity to changes in single and multiple combinations of parameters and sensitivity to changes in digital elevation model resolution were assessed. Model flow performance was reasonably accurate with a Nash–Sutcliffe efficiency coefficient of 0.78 in Blackwater and 0.60 in Kit Brook. In terms of event prediction, the mean of the absolute percentage of difference (μAbsdiff) between measured and simulated flow volume (Qv), peak discharge (Qp), sediment yield (Sy), and peak sediment flux (Sp) showed larger values in Kit Brook (48% [Qv], 66% [Qp], 298% [Sy], and 438% [Sp]) compared with the Blackwater catchment (30% [Qv], 41% [Qp], 106% [Sy], and 86% [Sp]). Results indicate that SHETRAN can produce reasonable flow prediction but performs less well in estimation of sediment flux, despite reasonably similar hydrosedimentary behaviour between catchments. The sensitivity index showed flow volume sensitive to saturated hydraulic conductivity and peak discharge to the Strickler coefficient; sediment yield was sensitive to the overland flow erodibility coefficient and peak sediment flux to raindrop/leaf soil erodibility coefficient. The multiparameter sensitivity analysis showed that different combinations of parameters produced similar model responses. Model sensitivity to grid resolution presented similar flow volumes for different digital elevation model resolutions, whereas event peak and duration (for both flow and sediment flux) were highly sensitive to changes in grid size. 相似文献
44.
Llanes Francesca V. Eco Rodrigo Herrero Tatum Miko Briones Jo Brianne Louise Escape Carmille Marie Sulapas Jolly Joyce Galang Jan Albert Macario Ortiz Iris Jill Sabado Jasmine May Lagmay Alfredo Mahar Francisco Rodolfo Kelvin 《Natural Hazards》2022,114(1):665-690
Natural Hazards - In October 2015, heavy rains brought by Typhoon Koppu generated landslides and debris flows in the municipalities of Bongabon, Laur, and Gabaldon in Nueva Ecija province.... 相似文献
45.
Abstract Using daily suspended sediment and water discharge data, we calculated the current mean annual runoff and Specific Suspended Sediment Yield (SSY) for 66 mountainous and piedmont catchments in Chile. These catchments are located from the extreme north of Chile to Southern Patagonia and cover an exceptionally wide range of climates, slopes, and vegetation. The SSY ranges mainly between 0 and 700 t km-2 year-1 with some exceptions as high as 1780 t km-2 year-1. The SSY increases between the extreme north and 33°S and then decreases toward the south. Sediment and water discharge north of 33°S occur mainly during summer. Farther south the contribution of winter precipitation increases and predominates. When the SSY database is correlated with topographic, climatic and vegetation indices, it is found to correlate significantly with runoff and mean slope only. In order to concentrate on erosion processes in the mountain range, 32 mountainous catchments were selected along a strong north–south SSY gradient between 27°S and 40°S. From north to south, SSY increases strongly with runoff and then decreases, even while runoff keeps increasing. In catchments where SSY is low, although runoff is high, the mean slope is less than 40% and the vegetation cover is greater than 8%. For the other catchments, runoff variations explain 67% of the variance in sediment yields. Thus, SSY seems to be controlled by vegetation cover and slope thresholds. In addition, SSY also correlates with glacier cover. However, a correlation between SSY and seismicity, although possible, is ambiguous. Citation Pepin, E., Carretier, S., Guyot, J. L. & Escobar, F. (2010) Specific suspended sediment yields of the Andean rivers of Chile and their relationship to climate, slope and vegetation. Hydrol. Sci. J. 55(7), 1190–1205. 相似文献
46.
This paper demonstrates the applicability of a black‐and‐white visible‐infrared sensitive video camera, filtered to record radiation in the 1.45–2.0 μm mid‐infrared (MIR) spectral region, for detecting burning wood coals. Airbome imagery of a burned rangeland area and a wood fire at a dump site showed that hot spots (smoldering wood coals) could be delineated from other landscape features. MIR video imagery should be useful to detect burning wood coals at temperatures as low as 900K. These results indicate that the MIR video system may be a potential tool to aid wild‐land managers in the thermal analysis of wildfires. 相似文献
47.
Jennifer?M.?GarrisonEmail authorView author&#;s OrcID profile Kenneth?W.?W.?Sims Gene?M.?Yogodzinski Ricardo?D.?Escobar Sean?Scott Patricia?Mothes Minard?L.?Hall Patricio?Ramon 《Contributions to Mineralogy and Petrology》2018,173(1):6
Sumaco Volcano is located in the rear-arc of Ecuador and produces phonolitic alkaline lavas hosting a unique assemblage of minerals including haüyne and titanaugite. The most mafic lavas are picrobasalts that contain titanaugite as the primary mineral phase; the most evolved tephri-phonolite lavas contain titanaugite?+?anorthoclase?+?haüyne. Titanaugite forms at middle to deep crustal pressures, whereas haüyne is only stable at shallow depths in highly oxidizing conditions. The Sumaco mineral assemblages and geochemistry indicate that fractionation of the titanaugite- and haüyne-bearing assemblage took place over a range of pressures from 5 to 25 kbar (14–75 km), with at least 50% of differentiation taking place at shallow crustal levels. Minerals record multiple cycles of recharge and mixing accompanied by an increase in fO2 and sulfur concentration during differentiation. Mantle-like Sr and Nd isotope values (87Sr/86Sr = 0.70406–0.70423; 143Nd/144Nd = 0.512880–0.512913) indicate minimal crustal assimilation. Sumaco’s unique geochemical composition is not observed in the nearby volcanoes Antisana, Pan de Azucar or El Reventador suggesting that its unique magma source is confined to this volcano. The high temperature and sulfate-saturated conditions at shallow depths suggest that magma ascends rapidly to a shallow reservoir where the majority of crystallization and recharge takes place prior to eruption. An important conclusion of this research is that Sumaco does not represent typical rear-arc subduction processes, and caution should be used when using Sumaco as an end-member to evaluate across-arc processes in the Northern Volcanic Zone. 相似文献
48.
The Paper presents the regional perspective on the conditions and efforts for the integrated coastal management (ICM) that exist in the Wider Caribbean Region (WCR).The Caribbean Action Plan was adopted in 1981 with an initial workplan of activities of evaluation and control of marine pollution, evaluation of impacts on the coastal area, fishing studies, watershed management, evaluation of natural hazard effects, energy accounting systems studies, urbanisation of the coastal area, building capacity and training. The Convention for the Protection and Development of the Marine Environment of the WCR is the only regional legal framework for the protection and sustainable development of marine resources.The Paper describes some region-wide ICM-related programme initiated or supported by the CEP as well as actions at the national level. Other ICM-related general activities and training programmes of CEP are also presented.Trends in national policies in ICM and current developments and issues are also highlighted and recommendations made. 相似文献
49.
Elva Escobar Briones Javier Alcocer Edith Cienfuegos Pedro Morales 《International Journal of Salt Lake Research》1998,7(4):345-355
Carbon stable isotope ratios were determined in dominant biotic components of pelagic and littoral systems in Alchichica crater-lake.
Results showed that carbon signatures were significantly different between both systems. The pelagic environment was more
depleted (−26.15 to −15.14 per mille) than the littoral zone (−21.03 to −17.91 per mille). The potential source end-point
in the simplified pelagic community was established to be diatomaceous phytoplankton; its predicted value was −21.7 per mille.
There is a clear evidence thatNodularia does not sustain the pelagic food chain. In contrast, the highly diverse littoral community was sustained by epiphytes. No
allochthonous sources seemed to influence this food web.13C enrichment was observed along the components of both systems with fractionations of 0.8 to 1.4 per mille. The contribution
of the seagrassRuppia maritima is probably associated with the detritus pathway. Carbon source partitioning between both systems was not recorded. The δ13C in Alchichica crater-lake was more enriched than in other saline lakes and could be attributed to different salinity and
CO2 concentrations among lakes. 相似文献
50.
J.M. Torrelles A. Alberdi A. Rius J.M. Paredes X. Barcons F. Briones J. Cepa J. Vilchez C. Eiroa J.M. Marcaide J.M. Mas 《Astrophysics and Space Science》1998,263(1-4):381-388
The Spanish participation as an Associate Member in the Millimeter Array (MMA) project - led by the U.S. National Radio Astronomy
Observatory (NRAO) - has been recently proposed to the Spanish Science and Technology Bureau (OCYT). This request to the Spanish
Government is based on two key factors: (1) The high scientific interest and support of the Spanish scientific community,
for whom major new fields of research--inaccessible with other instruments--will become available. (2) An industrial return
that will clearly benefit Spanish companies developing cutting-edge technology and providing them with a high international
profile.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献