Fifty topsoil samples collected from 12 different regions of East China have been analyzed for rare earth elements (REEs).
The average REE concentrations of the 50 topsoil samples are much higher than world average and are characterized by LREE-enrichment,
HREE-depletion, Eu-depletion and Ce-enrichment. However, the REE concentration is not strongly affected by the climate of
the sampling site; it is controlled mainly by parent materials. The plot of Ce/Eu against Eu/Sm is proved to be useful to
distinguish different parent materials of topsoil. Each element in the 50 topsoil has a good correlation with its neighboring
element. Seven of the 13 values are above 0.987. 相似文献
Summary Based on 90 accurately localized earthquakes in and around North-East India and the local crustal velocity model of Gupta
et al. [4], the travel times of P-waves have been determined from the foci of these earthquakes at arbitrarily selected depths
of 5, 13, 25, 41 and 50 km to the sites of the seismic stations operated by the Regional Research Laboratory, Jorhat and the
National Geophysical Research Institute, Hyderabad, and also to the sites of the Shillong and Tura seismic stations run by
the India Meteorological Department, New Delhi. The travel times of P-waves fit a straight line very well with velocities
of 5·97 ± 0·31, 6·18 ± 0·01, 6·41 ± 0·03, 7·82 ± 0·07 and 7·95 ± 0·01 km/sec at each of the depths under study. Similar investigations
of P* and Pg-waves of 16 earthquakes at a depth of 10 km have revealed velocities of 6·53 ± 0·31 and 5·64 ± 0·34 km/sec, respectively.
A simplified two-layered crustal model consisting of an average crustal thickness of 41·5 km with 22·2 and 19·3 km thick layers
has been obtained. 相似文献
The rainfall interception losses from Cashew trees were quantified, based on the records of 105 selected storms within the range 25.0 mm, occurring in a humid tropical region at Kottamparamba, India.
The storage capacity of the Cashew trees was worked out as 0.8 mm and the throughfall coefficient as 0.391. The trees under observation were 15–20 years of age with a leaf area index of 1.0–1.25.
About 31% of the storm rainfall for storms 25.0 mm was intercepted by the Cashew trees and lost to the atmosphere.
The measured interception losses from the trees were compared with the estimated interception losses using the analytical model of Gash (1979). The predicted interception losses from the Cashew trees were within ± 10% for storms with total rainfall 10.0 mm and within ± 22% for storms with a rainfall of 10.1–25.0 mm. 相似文献
The variation in the density of sediments with depth in a sedimentary basin can be represented by a hyperbolic function. Gravity anomaly expressions for a 2D vertical prism and an asymmetric trapezium with a hyperbolic density distribution are derived in a closed form. These are used in inverting the gravity anomaly of a sedimentary basin with variable density. Firstly, the basin is viewed as a series of prisms juxtaposed with each other. The initial thickness of each prism is obtained from the gravity anomaly at its centre, based on the gravity anomaly of an infinite slab with a hyperbolic density contrast. These thicknesses are improved, based on the differences between the observed and the calculated anomalies. For an improved rate of convergence of the solution, these thicknesses may alternatively be refined using the well-known ridge regression technique. Secondly, the basin is approximated by an asymmetric trapezium and its anomalies are inverted for the parameters of the trapezium using the ridge regression. Since this approximation serves to oversimplify the floor of the basin, it must be used only when the sediment-basement interface has minor undulations. The results of a hypothetical case and two field cases (the San Jacinto Graben, California and the Godavari Graben, southern India) are presented. In both field cases, the interpreted depths are comparable with the real ones, proving the validity of the assumption of a hyperbolic density distribution of the sediments in the two basins considered. 相似文献
Coastal flooding induced by storm surges associated with tropical cyclones is one of the greatest natural hazards sometimes
even surpassing earthquakes. Although the frequency of tropical cyclones in the Indian seas is not high, the coastal region
of India, Bangladesh and Myanmar suffer most in terms of life and property caused by the surges. Therefore, a location-specific
storm surge prediction model for the coastal regions of Myanmar has been developed to carry out simulations of the 1975 Pathein,
1982 Gwa, 1992 Sandoway and 1994 Sittwe cyclones. The analysis area of the model covers from 8° N to 23° N and 90° E to 100° E.
A uniform grid distance of about 9 km is taken along latitudinal and longitudinal directions. The coastal boundaries in the
model are represented by orthogonal straight line segments. Using this model, numerical experiments are performed to simulate
the storm surge heights associated with past severe cyclonic storms which struck the coastal regions of Myanmar. The model
results are in agreement with the limited available surge estimates and observations. 相似文献
Demand for groundwater for drinking, agricultural and industrial purposes has increased due to uncertainty in the surface water supply. Agriculture is the main occupation of the rural people in Guntur district, Andhra Pradesh, India. Development of groundwater in the district is very less, indicating a lot of scope for further development of groundwater resources. However, assessment of groundwater conditions, particularly in a crystalline terrain, is a complex task because of variations in weathering and fracturing zones from place to place. Systematic studies for evaluation of groundwater potential zones have been carried out in a crystalline terrain of the district. Information on soils, geological formations and groundwater conditions is collected during the hydrogeological survey. Topographical and drainage conditions are derived from the Survey of India topographical maps. Geomorphological units and associated landform features inferred and delineated from the Indian remote sensing satellite imagery (IRS ID LISS III FCC) are moderately buried pediplain (BPM), shallow buried pediplain (BPS), valley fills (VF), structural hill (SH), residual hills (RH), lineaments and land use/land cover. A groundwater potential index (GPI) is computed for relative evaluation of groundwater potential zones in the study area by integrating all the related factors of occurrence and movement of groundwater resources. Accordingly, the landforms, BPM, BPS, VF, SH and RH, of the area are categorized as very good groundwater potential zone, good to moderate groundwater potential zone, moderate to poor groundwater potential zone, poor to very poor groundwater potential zone and very poor groundwater potential zone, respectively, for development and utilization of both groundwater and surface water resources for eliminating water scarcity. This study could help to improve the agrarian economy for better living conditions of the rural people. Taking the total weight-score of the GPI into account, a generalized classification of groundwater potential zones is evaluated for a quick assessment of the occurrence of groundwater resources on regional scale. 相似文献
Summary The dolerite dyke of post-lower Gondwana age reported earlier by the authors [5]2) has been taken for detailed magnetic study. Seven magnetic traverses have been taken across the dyke using Schmidt vertical force variometer. Negative anomalies varying from 1400 to 2200 gammas have been observed. Magnetic susceptibility of samples from the dyke has been determined on both cores and crushed material, using the Model MS-3 susceptibility bridge. The average susceptibility of 20 samples has been found to be 1930x10–6 C.G.S. units. Direction and intensity of remanence on 10 oriented samples have been determined by an Astatic magnetometer. The average intensity of remanence has been found to be 3.13x10–3 C.G.S. units and the average direction has a declination of 323° and inclination-68° (up dip). The Koenigsberger ratio varies from 1.6 to 5.6. The high negative magnetic anomalies have been explained in terms of remance-that more than 80% of the anomaly is due to remance and that negative anomalies are due to negative inclination of remanent direction of the rocks. The magnetic direction for the dyke gave the position for Dhanbad as 51° south latitude in Jurassic period. This is in conformity with the deductions made by other workers from the palaeomagnetic studies of the Deccan and Rajmahal traps. The virtual geomagnetic pole in Jurassic period as deduced from the palaeomagnetism of the dyke has a position of latitude 8 1/2°N and longitude 71°W, in the southern Carribean. On palaeomagnetic evidence this dyke has been correlated with Rajmahal traps of eastern Bihar. 相似文献
This paper attempts to make a systematic comparison of all important criteria for the selection of either scandium-46 or iridium-192 as the radioisotopic glass tracer for bed-load transport studies in rivers and estuaries. This study has been restricted to only these two tracers as they are found to be the only strong contenders for long-range quantitative studies.The discussion leads the authors to the conclusion that except for the transport problem, scandium-46 is preferable to iridium-192 in all other respects. 相似文献