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171.
1 STUDIEDREGIONANDANALYSISMETHODLocatedatnorthwesternmarginofTenggerDesertand70kmnortheastofMinqinCountyinGansuProvince,QingtuLakebelongstotheShiyangRiverDryDelta,andthealtitudeis1292-1310m.Theregionhasthecharacteroftemperatecontinentalariddesertcli… 相似文献
172.
Björn Heincke Thomas Günther Einar Dalsegg Jan Steinar Rønning Guri Venvik Ganerød Harald Elvebakk 《Journal of Applied Geophysics》2010,70(4):292-306
We present a combined 3-D geoelectric and seismic tomography study conducted on the large Åknes rockslide in western Norway. Movements on the slope are strongly influenced by water infiltration, such that the hydrogeological regime is considered as a critical factor affecting the slope stability. The aim of our combined geophysical study was to identify and visualize the main shallow tension fractures and to determine their effect on hydraulic processes by comparing the geophysical results with information from borehole logging and tracer tests. To resolve the complex subsurface conditions of the highly fractured rock mass, a three-dimensional set-up was chosen for our seismic survey. To map the water distribution within the rock mass, a pattern of nine intersecting 2-D geoelectric profiles covered the complete unstable slope. Six of them that crossed the seismic survey area were considered as a single data set in a 3-D inversion. For both methods, smoothing-constraint inversion algorithms were used, and the forward calculations and parameterizations were based on unstructured triangular meshes. A pair of parallel shallow low-velocity anomalies (< 1400 m/s) observed in the final seismic tomogram was immediately underlain by two anomalies with resistivities <13 kΩm in the resistivity tomogram. In combination with borehole logging results, the low-velocity and resistivity anomalies could be associated with the drained and water-filled part of the tension fractures, respectively. There were indications from impeller flowmeter measurements and tracer tests that such tension fractures intersected several other water-filled fractures and were responsible for distinct changes of the main groundwater flow paths. 相似文献
173.
174.
Record of enhanced late Pliocene tectono‐volcanic activity in the Lesser Antilles forearc basin: Insights into the long‐term behaviour of the Lesser Antilles subduction zone
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Jean‐Len Léticée Mélody Philippon Jean‐Jacques Cornée Philippe Münch Lyvane De Min Mélanie Noury Auran Randrianasolo Jean‐Frédéric Lebrun 《地学学报》2017,29(4):245-252
In this study, we investigate the Lesser Antilles forearc basin, focusing on the late Pliocene to Pleistocene sedimentary archives in order to track the occurrence of extreme events triggered by enhanced subduction‐related tectono‐volcanic activity. We identify late Piacenzian deposits covering a major regional erosional surface, displaying sedimentary dykes and large marine boulders embedded in a mixed continental–marine matrix, characteristic of tsunamites. We interpret this episode of platform emersion and the successive cataclysmic deposits as resulting from enhanced tectonic activity at the interface of the subduction zone, synchronous with the initiation of the Lesser Antilles volcanic arc. We then discuss the implications in terms of the mechanical behaviour of the Lesser Antilles subduction zone. 相似文献
175.
Two killifish common in east coast U.S.A. salt marshes,Cyprinodon variegatus Lacepede andFundulus heteroclitus Walbaum, differ in their ability to assimilate nitrogen from and grow on detritus.C. variegatus grew on a diet of detritus ofSpartina alterniflora Loisel, whileF. heteroclitus did not. In addition, when the fish were fed15N-labeledS. alterniflora detritus,15N:14N ratios inC. variegatus were higher than were ratios inF. heteroclitus. Therefore, even though both species ingest large amounts of detritus,C. variegatus makes more effective use of this portion of its diet. These dietary differences are corroborated by anatomical differences that suggest thatC. variegatus should make better use of detrital or plant tissues thanF. heteroclitus. In the label experiment, the degree of label in both fish was directly proportional to the degree of label in the food treatments. In previously published experiments designed to compare plant substrate with attached microbes as nitrogen sources for detritivores, %15N incorporated by a polychaete was also directly proportional to %15N in the detrital food. Therefore, it is difficult to distinguish between plant substrate and microbes as nitrogen sources for this detritivore. 相似文献
176.
The paper deals with the application of the telluric method and of magnetotelluric soundings including experimental and model
data on the localization of tectonic disturbances in connection with the selection of appropriate sites for nuclear plants. 相似文献
177.
Water samples were collected from 18 natural springs within the West Fork of the Obey River watershed. Overton County, Tennessee,
to determine if groundwater was adversely affected by runoff from abandoned surface coal mines Six springs were found to be
affected severely and deemed unfit as a source of potable water Water quality of the remaining springs was essentially unaffected
it appeared that proximity to surface mines, elevation at the outflow, and geology of the surrounding strata determined the
quality of the groundwater
The unit is jointly supported by Tennessee Technological University, the Tennessee Wildlife Resource Agency, and the US. Fish
and Wildlife Service 相似文献
178.
179.
In September 1984, the freshwater input to the Eastmain River (James Bay, Canada) was increased by a factor of 50 over a 6-d period during a controlled reservoir discharge. Changes to the current, salinity and turbidity regimes were monitored during the peak runoff. Estuarine salinity values fell rapidly with increasing mean flow, as did the amplitude of the semi-diurnal tidal currents. A large increase in bottom shear stress dispersed the settled suspension layer into the water column, raising concentrations of suspended matter in the estuary by a factor of 4 in 3 d. The peak values exceeded 150 mg I?1. This led to erosion of the river silt deposits, with the export of an estimated 6 × 104 metric tons of sediments. After the reduction of discharge, current values returned to their normal range within a day, whereas upstream salinity intrusion occurred at a slower rate. Horizontal diffusivities of about 100 m2 s?1 were required to match the observed lag. 相似文献
180.
Eighty-nine juvenile Atlantic sturgeon,Acipenser oxyrhynchus oxyrhynchus, including 10 recaptures, were collected, tagged and released in the upper tidal Delaware River between July 1981 and December 1984. All were captured in the river channel between Roebling and Trenton, New Jersey, using bottom-set experimental gill nets during daylight hours. The species was present from July through December and collected in increased numbers in the past two years. The fork lengths ranged from 284 to 862 mm (mean±SD = 516 mm±106 mm) and the weights from 140 to 4,250 g (mean±SD = 1,369 g±815 g). Ten juvenile Atlantic sturgeon were recaptured between September 1983 and December 1984 and were at large from one to 418 d. Recapture data suggest that these sturgeon utilize this area annually from July through December, possibly as a nursery. Juvenile Atlantic sturgeon appear to utilize the upper tidal portion of the Delaware River for a much longer period of time and at lower temperatures than in other river systems. 相似文献