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51.
Ram Bichar Singh Yadav Jayant Nath Tripathi Bal Krishna Rastogi Mridul Chandra Das Sumer Chopra 《Pure and Applied Geophysics》2010,167(11):1331-1342
Northeast India and adjoining regions (20°–32° N and 87°–100° E) are highly vulnerable to earthquake hazard in the Indian
sub-continent, which fall under seismic zones V, IV and III in the seismic zoning map of India with magnitudes M exceeding 8, 7 and 6, respectively. It has experienced two devastating earthquakes, namely, the Shillong Plateau earthquake
of June 12, 1897 (M
w
8.1) and the Assam earthquake of August 15, 1950 (M
w
8.5) that caused huge loss of lives and property in the Indian sub-continent. In the present study, the probabilities of
the occurrences of earthquakes with magnitude M ≥ 7.0 during a specified interval of time has been estimated on the basis of three probabilistic models, namely, Weibull,
Gamma and Lognormal, with the help of the earthquake catalogue spanning the period 1846 to 1995. The method of maximum likelihood
has been used to estimate the earthquake hazard parameters. The logarithmic probability of likelihood function (ln L) is estimated
and used to compare the suitability of models and it was found that the Gamma model fits best with the actual data. The sample
mean interval of occurrence of such earthquakes is estimated as 7.82 years in the northeast India region and the expected
mean values for Weibull, Gamma and Lognormal distributions are estimated as 7.837, 7.820 and 8.269 years, respectively. The
estimated cumulative probability for an earthquake M ≥ 7.0 reaches 0.8 after about 15–16 (2010–2011) years and 0.9 after about 18–20 (2013–2015) years from the occurrence of
the last earthquake (1995) in the region. The estimated conditional probability also reaches 0.8 to 0.9 after about 13–17
(2008–2012) years in the considered region for an earthquake M ≥ 7.0 when the elapsed time is zero years. However, the conditional probability reaches 0.8 to 0.9 after about 9–13 (2018–2022)
years for earthquake M ≥ 7.0 when the elapsed time is 14 years (i.e. 2009). 相似文献
52.
The carbonate concretions occurring at the bottom of Talchir fissile shale facies preserved signatures of various trace fossils
along with a cast of doubtful organisms and cyanobacterial mat structures. The host shale deposited under glacial melt water
fed lacustrine condition. The concretions, formed in poorly oxygenated conditions, are either of syndepositional origin and/or
deposited a little below the sediment water interface and were later exhumed to the depositional surface due to erosion of
soft mud overlying them.
The trace fossils are both megascopic and microscopic in nature. The megascopic trace fossils are identified on the basis
of their morphology as Monocraterion and Rhizocorallium. Some of the megascopic structures described remain problematic at present. The microscopic trace fossils are formed due
to the activity of marine meiofauna (possibly by nematodes), which, although produced morphologically show similar traces
of known larger ichnogeneras but much smaller than them. The discovery of these trace fossils apparently indicate the influx
of saline water into a lacustrine domain during the Talchir sedimentation at Giridih basin. Moreover, presence of the above
two megascopic trace fossils in the marine lacustrine carbonate concretions may lead researchers to consider their much wider
environmental significance than hitherto believed. 相似文献
53.
The tannery industry influences the gross domestic product/economic activity of any country, but the uncontrolled release of tannery effluents causes environmental degradation and increases health risks to human. The reason for the toxicity of tannery effluents is the presence of high concentrations of organic and inorganic chemicals used in the production of leather goods. Untreated or partially treated effluents discharged into surface water results in an increase in both chemical and biological oxygen demand as well as in an increase in the levels of total suspended solids, dissolved solids, and toxic metals in environmental bodies, especially in soil, water bodies, and water sediments. Various treatment techniques, such as physicochemical, biological, and advanced oxidation methods, which include chemical precipitation, electrocoagulation, aerobic or anaerobic treatment, wetland construction, and Fenton, electro-Fenton, and photo-Fenton processes are also described. This review also discusses the technical appropriateness and economic feasibility of reducing the effluent pollution load and solid waste emanating from the tannery industry. Considering the enhanced health risks in the tannery waste treatment and management regime, some green and advanced technologies should be explored. A sustainable green technology that avoids the use of toxic chemicals in the tanning process is seen well for ecological health. 相似文献
54.
Effect of overtaking disturbances on the propagation of a spherical shock wave in self gravitating gas has been studied by the technique developed by the first author [Mod. Meas. Cont. B,46(4), 1 (1992)]. The analytical expressions for modified shock velocity and shock strength have been obtained for an initial density distribution0 =r
–w, where is the density at the axis of symmetry andw is a constant; simultaneously, for the two cases viz.; (i) when the shock is strong and ii) when it is weak. The results accomplished here have been compared with those for freely propagation of shock.It is observed that the conclusions arrived at here agree with experimental observations. Finally, the modified expressions for the pressure, the density and the particle velocity immediately behind the shock have also been derived from, for both cases. 相似文献
55.
Denny P. Alappattu D. Bala Subrahamanyam P. K. Kunhikrishnan K. M. Somayaji G. S. Bhat R. Venkatesan C. B. S. Dutt A. Bagavath Singh V. K. Soni A. S. Tripathi 《Journal of Earth System Science》2008,117(1):281-291
Detailed measurements were carried out in the Marine Atmospheric Boundary Layer (MABL) during the Integrated Campaign for Aerosols, gases and Radiation Budget (ICARB) which covered both Arabian Sea and Bay of Bengal during March to May 2006. In this paper, we present the meteorological observations made during this campaign. The latitudinal variation of the surface layer turbulent fluxes is also described in detail. 相似文献
56.
Pradeep Srivastava Jayant K. Tripathi R. Islam Manoj K. Jaiswal 《Quaternary Research》2008,70(1):68-80
We study the aggradation and incision of the Alaknanda River Valley during the late Pleistocene and Holocene. The morphostratigraphy in the river valley at Deoprayag shows the active riverbed, a cut terrace, and a fill terrace. The sedimentary fabric of the fill terrace comprises four lithofacies representing 1) riverbed accretion, 2) locally derived debris fan, 3) the deposits of waning floods and 4) palaeoflood records. The sedimentation style, coupled with geochemical analysis and Optically Stimulated Luminescence (OSL) dating, indicate that this terrace formed in a drier climate and the river valley aggraded in two phases during 21–18 ka and 13–9 ka. During these periods, sediment supply was relatively higher. Incision began after 10 ka in response to a strengthened monsoon and aided by increase of the tectonic gradient. The cut terrace formed at ~ 5 ka during a phase of stable climate and tectonic quiescence. The palaeoflood records suggest wetter climate 200–300 yr ago when the floods originated in the upper catchment of the Higher Himalaya and in the relatively drier climate ~ 1.2 ka when locally derived sediments from the Lesser Himalaya dominated flood deposits. Maximum and minimum limits of bedrock incision rate at Deoprayag are 2.3 mm/a and 1.4 mm/a. 相似文献
57.
58.
Kavita Tripathi Koushik Sen A. K. Dubey 《International Journal of Earth Sciences》2012,101(3):761-772
The present day South Tibetan Detachment (STD) of Higher Himalaya is a system of low-angle normal faults. In the Himachal
High Himalaya, the STD hanging wall is characterized by the presence of S-type per-aluminous Paleozoic (~475 Ma) granite called
the Kinnaur Kailash Granite (KKG). This granite is later intruded by Cenozoic leucogranites (~18 Ma) in vicinity of the STD
zone. In this work, microstructures, anisotropy of magnetic susceptibility (AMS), and U–Pb geochronology were carried out
on the KKG and the leucogranites with an aim to (a) understand the conditions of fabric development and (b) decipher the tectonic
relationship between deformation along the STD and the evolution of these granites. Microstructural features and magnetic
anisotropy indicate that the granites are intensely deformed in vicinity of the STD and preserve their emplacement-related
fabric in the interior parts. It is inferred that close to the STD zone, fabrics of both the KKG and the leucogranite are
tectonic and are modified by the Cenozoic (~20 Ma) right-lateral slip and extensional tectonics. Magnetic fabric in the interior
parts of the KKG is related to its emplacement indicating that original fabric was preserved. U–Pb geochronology of zircons
from two samples of the KKG yields crystallization age of 477.6 ± 3.4 and 472 ± 4 Ma. The leucogranite gives a crystallization
age of 18.5 ± 0.6 Ma. Zircons from the KKG also reveal signatures of a deformation event (20.6 ± 2.3 Ma) at its rim. It is
inferred that deformation of the external rim of the KKG and crystallization of the leucogranites are synchronous and triggered
by ductile deformation along the STD. 相似文献
59.
Neeraj Singh Bankoti Navin Chandra Joshi Seema Pande Bimal Pande Kavita Pandey 《New Astronomy》2010,15(6):561-568
A study on north–south (N–S) asymmetry of different solar activity features (DSAF) such as solar proton events, solar active prominences [total, low (?40°) and high (?50°) latitudes], Hα flare indices, soft X-ray flares, monthly mean sunspot areas and monthly mean sunspot numbers carried out from May 1996 to October 2008. Study shows a southern dominance of DSAF during this period. During the rising phase of the cycle 23 the number of DSAF approximately equals on both, the northern and the southern hemispheres. But these activities tend to shift from northern to southern hemisphere during the period 1998–1999. The statistical significance of the asymmetry time series using a χ2-test of goodness of fit indicates that in most of the cases the asymmetry is highly significant, meaning thereby that the asymmetry is a real feature in the N–S distribution of DSAF. 相似文献
60.
In the previous study (Dabas et al. in Solar Phys.
250, 171, 2008), to predict the maximum sunspot number of the current solar cycle 24 based on the geomagnetic activity of the preceding
sunspot minimum, the Ap index was used which is available from the last six to seven solar cycles. Since a longer series of the aa index is available for more than the last 10 – 12 cycles, the present study utilizes aa to validate the earlier prediction. Based on the same methodology, the disturbance index (DI), which is the 12-month moving
average of the number of disturbed days (aa≥50), is computed at thirteen selected times (called variate blocks 1,2,…,13; each of them in six-month duration) during the
declining portion of the ongoing sunspot cycle. Then its correlation with the maximum sunspot number of the following cycle
is evaluated. As in the case of Ap, variate block 9, which occurs exactly 48 months after the current cycle maximum, gives the best correlation (R=0.96) with a minimum standard error of estimation (SEE) of ± 9. As applied to cycle 24, the aa index as precursor yields the maximum sunspot number of about 120±16 (the 90% prediction interval), which is within the 90%
prediction interval of the earlier prediction (124±23 using Ap). Furthermore, the same method is applied to an expanded range of cycles 11 – 23, and once again variate block 9 gives the
best correlation (R=0.95) with a minimum SEE of ± 13. The relation yields the modified maximum amplitude for cycle 24 of about 131±20, which
is also close to our earlier prediction and is likely to occur at about 43±4 months after its minimum (December 2008), probably
in July 2012 (± 4 months). 相似文献