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201.
Sandeep Panda Anil Kumar Satyabrata Das Rahul Devrani Santosh Rai Kuldeep Prakash Pradeep Srivastava 《地球表面变化过程与地形》2020,45(11):2495-2511
This study explores paleoflood deposits of the Siang River, known as the Tsangpo in Tibet. The river that often experiences large floods brings down huge amount of sediment and water that adversely affect the downstream regions with large human populations in the states of northeast Himalaya and its foreland. Along it's ~300 km mountainous stretch we collected samples for sedimentological, petrographic and Sr–Nd isotopic study to explore sediment provenance and dated the paleofloods (via optically stimulated luminescence, OSL). Geomorphic indices including precipitation and a geomorphic swath profile across the Brahmaputra catchment were studied to understand the interplay of mountain relief and rainfall that determine potential zones of high erosion and sediment supply. The OSL technique indicated the Siang River experienced at least eight large floods between 7 and 1 ka, possibly under the influence of warm and wet climatic conditions. The petrographic and isotopic data suggests that the eastern Himalayan syntaxis, which has the highest uplift and exhumation rate in the area, is not always the highest sediment producing zone. In some instances, the Tibetan plateau produces higher fluxes of sediments via glacial and landslide lake outburst floods (GLOFs and LLOFs). © 2020 John Wiley & Sons, Ltd. 相似文献
202.
Soil characterization using electrical resistivity tomography and geotechnical investigations 总被引:1,自引:0,他引:1
Electrical Resistivity Tomography (ERT) has been used in association with Standard Penetration Test (SPT) and Dynamic Cone Penetration Test (DCPT) for Geotechnical investigations at two sites, proposed for thermal power plants, in Uttar Pradesh (UP), India. SPT and DCPT tests were conducted at 28 points and two ERT profiles, each measuring 355 m long, were recorded using 72 electrodes deployed at 5 m spacing. Electrical characterization of subsurface soil was done using borehole data and grain size analysis of the soil samples collected from boreholes. The concept of electrical resistivity variation with soil strength related to the grain size distribution, cementation, porosity and saturation has been used to correlate the transverse resistance of soil with the number of blow counts (N-values) obtained from SPT and DCPT data. It was thus observed that the transverse resistance of soil column is linearly related with the number of blow counts (N-values) at these sites. The linear relationships are site-specific and the coefficients of linear relation are sensitive to the lithology of subsurface formation, which was verified by borehole data. The study demonstrates the usefulness of the ERT method in geotechnical investigations, which is economic, efficient and less time consuming in comparison to the other geotechnical methods, such as SPT and DCPT, used for the purpose. 相似文献
203.
204.
Kossitse Venyo Akpataku Shive Prakash Rai Masamaéya Dadja-Toyou Gnazou Lallébila Tampo Limam Moctar Bawa Gbandi Djaneye-Boundjou 《水文科学杂志》2019,64(8):983-1000
Hydrochemical, inverse geochemical modelling and isotopic approaches are used to assess the hydrogeochemical evolution of groundwater from the basement aquifers in the southeastern part of the Plateaux Region, Togo. Groundwater originates from present-day rainwater infiltration and is mostly fresh and slightly acidic to neutral. Hydrochemical facies are predominantly mixed cations-HCO3 associated with Ca/Mg-Cl, Na-HCO3 and Na-Cl water types in equilibrium with kaolinite and Ca/Mg-smectites. They are related to silicates hydrolysis, anthropogenic contamination, nitrification/denitrification, mixing along flowpaths and dissolution/precipitation of secondary minerals. The pattern of flow paths is in accordance with an increasing trend in total dissolved solids (TDS) toward the potentiometric depression located in the central and southern parts of the aquifer system. Inverse geochemical modelling using the NETPATH-WIN model showed the relative importance of biotite, plagioclase and amphibole weathering and dissolution of secondary carbonate minerals along the flowpath, suggesting that an abundance of minerals is not necessarily the main factor controlling the groundwater chemistry evolution. 相似文献
205.
Manisha Rai Adrian Rodriguez-Marek Domniki Asimaki 《Bulletin of Earthquake Engineering》2016,14(11):2959-2975
We use 2D numerical analyses at ground motion stations from the NGA-West2 dataset to develop parameters to predict the effect of surface topography on response spectra. The simplistic numerical analyses use sinusoidal input motions, uniform soil profiles, elastic soil properties, and absorbing boundary conditions. We define several topographic parameters for stations using the natural logarithm of 2D amplifications in peak ground acceleration of a sinusoidal input motion in different orientations. The natural log of 2D amplifications when averaged over multiple orientations is found to have the most predictive power among the studied parameters. We also explore the relationship between the topographic parameters developed in this study, and the topographic parameters developed at the same sites in an earlier study (Rai et al. in Earthq Spectra, 2016b). 相似文献
206.
Arjun Kumar S. S. Rai Anand Joshi Himanshu Mittal Rajiv Sachdeva Rohtash Kumar Vandana Ghangas 《地震科学(英文版)》2013,26(2):99-105
Earthquakes began to occur in Koyna region (India) soon after the filling of Koyna Dam in 1962. In the present study, three datasets 1964–1993, 1993–1995, and 1996–1997 are analyzed to study the b-value and fractal dimension. The b-value is calculated using the Gutenberg–Richter relationship and fractal dimension D corr. using correlation integral method. The estimated b-value and D corr. of this region before 1993 are found to be in good agreement with previously reported studies. In the subsequent years after 1995, the b-value shows an increase. The estimated b-values of this region are found within the limits of global average. Also, the pattern of spatial clustering of earthquakes show increase in clustering and migration along the three zones called North-East Zone, South-East Zone (SEZ), and Warna Seismic Zone. The earthquake events having depth ≤5 km are largely confined to SEZ. After 1993, the D corr. shows decrease, implying that earthquake activity gets clustered. This seismic clustering could be helpful for earthquake forecasting. 相似文献
207.
J. J. Galiana-Merino A. K. Mahajan C. Lindholm J. Rosa-Herranz A. K. Mundepi Nitesh Rai 《Bulletin of Earthquake Engineering》2011,9(5):1309-1325
In recent years, seismic noise array measurements have emerged as a promising way for estimating Vs profiles and characterizing
the corresponding soil structure. Although methods based on analysis of seismic noise are simpler, cheaper and faster than
conventional soil penetrating techniques, array deployment requires the use of several stations which are not always available
for all the research groups. Broadband stations are expensive, but even short-period sensors can require a significant economical
effort as it is necessary to use several. In this paper, the results from broadband stations and vertical geophones using
the f-k method have been compared. Circular arrays with both types of instruments were installed north and south of the Himalayan
Frontal Thrust (HFT) also known as Mohand Thrust, with different soil characteristics. The comparison carried out in terms
of dispersion curves shows an excellent agreement between broadband stations and geophones recordings in the frequency range
of applicability of the arrays used. These results indicate the possibility of using seismic refraction equipments for the
f-k analysis in the frequency band of geotechnical engineering interest. This has potentially great importance since the same
equipment is indicated to be applicable for both seismic noise measurements as well as for active reflection seismic surveys. 相似文献