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81.
82.
In this paper, we present a seismic hazard scenario for the Garhwal region of the north-western Himalayan range, in terms of the horizontal Peak Ground Acceleration. The scenario earthquake of moment magnitude M w 8.5 has a 10% exceedance probability over the next 50 years. These estimates, the first for the region, were calculated through a stepwise process based on:
相似文献
- An estimation of the Maximum Credible Earthquake from the seismicity of the region and Global Seismic Hazard Assessment Program considerations, and
- four seismotectonic parameters abstracted from near field weak-motion data recorded at five stations installed in Chamoli District of the Garhwal region in the aftermath of the 1999 Chamoli earthquake. The latter include
- The frequency dependent power law for the shear wave quality factor, Q S
- the site amplification at each station using horizontal-to-vertical-spectral ratio and generalized inversion technique
- source parameters of various events recorded by the array and application of the resulting relations between the scalar seismic moment M 0 (dyne-cm) and moment magnitude M w and the corner frequency, ? c (Hz) and moment magnitude M w to simulate spectral acceleration due to higher magnitude events corresponding to the estimated Maximum Credible Earthquake, and
- regional and site specific local spectral attenuation relations at different geometrically central frequencies in the low, moderate and high frequency bands.
83.
84.
J. N. Pattan G. Parthiban C. Moraes R. Rajalakshmi S. Lekshmi S. Athira S. Jai Sankar 《Journal of the Geological Society of India》2016,87(1):62-68
Pumice are explosive volcanic product, occur as uncoated or coated with ferromanganese (Fe-Mn) oxide and resides in association with ferromanganese nodules on the seabed in Central Indian Ocean Basin (CIOB). The older Fe-Mn oxide coated and younger uncoated pumice clasts were leached with 6N HCl to remove Fe-Mn oxide coatings as well as the calcium carbonate present within the vesicles. The main objective of the present study is to understand the origin of these pumice by utilizing their chemical composition. Both coated and uncoated pumice samples are rhyoliteand medium K calc-alkaline series. Major, trace, rare earth elements (∑REE) concentration and chondrite-normalized REE patterns of both coated and uncoated pumice are nearly similar to each other suggesting a same source. Tectonomagmatic discrimination diagrams (Nb vs Y: Yb vs. Ta), triangular plot (TiO2-Zr-Y) and High Field Strength Element ratios (La/Ta- 25; Ta/Hf- 0.2; Nb/Ta- 9; Zr/Nb- 22 and Ba/Ta-1084) indicate volcanic arc origin. These were probably sourced from the nearest Indonesian volcanic arc and drifted to the CIOB by currents. 相似文献
85.
Hydrochemical and hydrogeological studies were carried out in the groundwater of Dhaligaon refinery area, Bongaigoan district, Assam. The study revealed that the area is underlain by alluvial deposits of thickness varying from 67 to 142 meters and the groundwater occurs in unconfined alluvial formations. Transmissivity values of the formations range from 2100 to 3800 m2/day. The effluents from the refinery are disposed off into a natural drain, “Tunia nala”, which contaminates the groundwater. The effluents contain constituents like phenol, nitrite, sulphide, iron etc, which subsequently seep into the dug well zone, but the phenol concentrations get naturally attenuated during the contaminant transport to the depths below. The probable reasons leading to natural attenuation of phenol as per in-situ hydrogeological and environmental conditions have been discussed. 相似文献
86.
87.
Shreeram Suman Sahu Sahendra Singh Jyoti Sankar Satapathy 《Journal of the Geological Society of India》2018,92(3):291-297
Emerald, the green gem variety of beryl (Be3Al2Si6O18), is the third most valuable gemstone after diamond and ruby. The green colour appearance of the crystal is due to trace of Cr3+ and V3+, which replaces Al3+ ions in the crystal lattice of beryl. The hue of green colour of emerald depends on the quantity of Cr3+ and V3+ present in the crystal. Be is incorporated along with Cr and/or V during the process of crystallization. Since Be is relatively rare in the upper continental crust, therefore specific geological and geochemical parameters are required for Be to be incorporated in the crystal lattice of emerald.The present work was carried out to understand the lithological and structural control of emerald occurrences in and around Gurabanda area within the Singhbhum shear zone (SSZ) of Singhbhum crustal province, eastern India. The biotite and serpentine schist belong to the Paleoproterozoic Dhanjori Group and constitute the major lithology of the area. Pegmatite and biotite schist contains a variety of gem minerals in abundance in the area and the gem quality emerald occur at the contact zone of quartz vein and mica-schist. Lithology and structure are the main controlling factors of gem-mineralization in the study area. The study indicates that regional metamorphism and deformation processes along the shear zone played a significant role in the formation of emerald deposits. It is inferred that Singhbhum shear zone facilitated a favourable condition, where the Be bearing pegmatites interacted with Cr bearing mica schist or ultramafic rocks to produce emerald crystal. 相似文献
88.
High Mg-Al spinel-sapphirine granulites, orthopyroxene-bearing quartzofeldspathic granulites, two pyroxene-bearing mafic granulites
and metapelitic gneisses are exposed around Paderu, Eastern Ghats Belt. Geothermobarometry in orthopyroxene-bearing quartzofeldspathic
granulites and mafic granulites indicate near isobaric cooling through 90°C from ca. 720°C to 630°C, at 8.0 kbar. However,
signatures of ultrahigh temperature metamorphism are recorded from the mineralogy and reaction textures in the high Mg-Al
granulites. Mineral reactions deduced in this work, when combined with others described by Lalet al (1987) from the same area and plotted in an appropriate petrogenetic grid in the system FMASO indicate an ACW path comprising
a high dT/dP prograde arm reaching Pmax − Tmax = 9.5 kbar, ∼ 1000°C, followed by near-isobaric cooling down to 9 kbar, 900°C and subsequent decompressive reworking. 相似文献
89.
A moment method for analysing the stochastic stability of the surge motion of a tethered buoyant platform (TBP) in a random sea is examined. In the differential equation describing the surge motion the variation of tether tension caused by the vertical component of the wave forces is random-time dependent in form. The asymptotic moment behaviour of the solution is determined and approximated in terms of an integral equation. Under the assumption of a narrow band process imposed upon the random coefficient, the stability results are obtained with the aid of deterministic stability theory. The mean square stability is studied and criteria for stability are obtained in terms of the damping coefficient and the auto-correlation function of the random sea. 相似文献
90.
R. S. Dwivedi K. Sreenivas K. V. Ramana P. R. Reddy G. Ravi Sankar 《Journal of the Indian Society of Remote Sensing》2006,34(4):351-367
Realizing the potential of spaceborne multispectral measurements in providing spatial information on natural resources, and
of Geographic Information System (GIS) in integrating such information with the socio-economic data and other collateral information
to arrive at derivative information, we report here the results of a study which was taken up in a watershed in Charkhari
block of Mahoba district, northern India, to generate the information on natural resources from Indian Remote Sensing Satellite
(IRS-1B) Linear Imaging Self-scanning Sensor (LISS-II) images through a systematic visual interpretation, and its subsequent
integration with the collateral information in a GIS environment to develop optimal land use plan/action plan for sustainable
development of its land resources. Since permanent vegetation cover in the watershed has been dwindling due to population
pressure, the need for establishing more vegetation cover has been stressed. 相似文献