Investigation on spectral behavior of Solar transients and their interrelationship

We probe the spectral hardening of solar flares emission in view of associated solar proton events (SEPs) at earth and coronal mass ejection (CME) acceleration as a consequence. In this investigation we undertake 60 SEPs of the Solar Cycle 23 along with associated Solar Flares and CMEs. We employ the X-ray emission in Solar flares observed by Reuven Ramaty Higly Energy Solar Spectroscopic Imager (RHESSI) in order to estimate flare plasma parameters. Further, we employ the observations from Geo-stationary Operational Environmental Satellites (GOES) and Large Angle and Spectrometric Coronagraph (LASCO), for SEPs and CMEs parameter estimation respectively. We report a good association of soft-hard-harder (SHH) spectral behavior of Flares with occurrence of Solar Proton Events for 16 Events (observed by RHESSI associated with protons). In addition, we have found a good correlation (R=0.71) in SEPs spectral hardening and CME velocity. We conclude that the Protons as well as CMEs gets accelerated at the Flare site and travel all the way in interplanetary space and then by re-acceleration in interplanetary space CMEs produce Geomagnetic Storms in geospace. This seems to be a statistically significant mechanism of the SEPs and initial CME acceleration in addition to the standard scenario of SEP acceleration at the shock front of CMEs.     

FLAC Based Numerical Studies on Dynamic Interference of Two Nearby Embedded Machine Foundations

This paper emphasizes on the dynamic interaction of two closely spaced embedded square or rectangular foundations under the action of machine vibration. One of the foundations is excited with a known vibration source placed on the top of it, called the active foundation. The objective is to study the effect of dynamic motion of the active foundation on the nearby passive foundation through a layered soil medium. The analysis is performed numerically by using the explicit finite difference code FLAC ^3D . The soil profile is assumed to obey the Mohr–Coulomb yield criteria with non-linear failure envelope. The analysis is performed under sinusoidal dynamic loading with varying amplitude. Under the dynamic excitation, the settlement behavior of the interacting foundations is studied by varying the spacing between the foundations. In addition, the variation of vertical normal and shear stress developed beneath the interacting foundations is also explored. The present theoretical investigation indicates that the settlement and vertical normal stress below the active foundation is generally found to be higher than that obtained for the passive foundation, whereas the shear stress response below the foundations follows the reverse trend.     

Seismic analysis of nailed vertical excavation using pseudo-dynamic approach

An attempt has been made to study the behavior of nailed vertical excavations in medium dense to dense cohesionless soil under seismic conditions using a pseudo-dynamic approach. The effect of several parameters such as angle of internal friction of soil(Φ), horizontal(k_h) and vertical(k_v) earthquake acceleration coefficients, amplification factor(f_a), length of nails(L), angle of nail inclination(α) and vertical spacing of nails(S_v) on the stability of nailed vertical excavations has been explored. The limit equilibrium method along with a planar failure surface is used to derive the formulation involved with the pseudo-dynamic approach, considering axial pullout of the installed nails. A comparison of the pseudo-static and pseudo-dynamic approaches has been established in order to explore the effectiveness of the pseudo-dynamic approach over pseudo-static analysis, since most of the seismic stability studies on nailed vertical excavations are based on the latter. The results are expressed in terms of the global factor of safety(FOS). Seismic stability, i.e., the FOS of nailed vertical excavations is found to decrease with increase in the horizontal and vertical earthquake forces. The present values of FOS are compared with those available in the literature.     

Interaction Effect of Group of Helical Anchors in Cohesive Soil Using Finite Element Analysis

In this paper, the interaction effect of a group of two and four symmetrical as well as asymmetrical helical anchors resting in homogeneous cohesive soil deposit with different helix configurations is determined using finite element analysis. The anchors were pulled to its ultimate failure controlling the displacement. Eight different types of anchor configuration were considered in the analysis, where mainly the number of helical plates, the depth of upper- and lower-most helical plates and the ratio of spacing between the helical plates to the diameter of the plate were varied. The variation of load–displacement curve for each anchor in the group was obtained and subsequently, the ultimate uplift capacity of each anchor was determined. The soil was assumed to follow Mohr–Coulomb failure criteria. The present theoretical observations are generally found in good agreement with those theoretical and experimental results available in the literature for single isolated helical anchor.     

Hydrochemical characterization and suitability assessment of groundwater in Baga–Calangute stretch of Goa,India

The present study is the first attempt to determine the suitability of groundwater for drinking and irrigation in the Baga–Calangute stretch of Goa. The suitability of groundwater for potable use was assessed by comparing observed values against standards prescribed by the Bureau of Indian Standards, and the quality was classified based on the Weighted Arithmetic Water Quality Index. Most of the groundwater samples (90%) were found to be suitable for drinking except for hardness, chlorides, and nitrates. The percent sodium (%Na), residual sodium carbonate, soluble sodium percentage, sodium adsorption ratio, Kelly’s ratio, and Permeability Index were found to be within the prescribed limits for irrigation purposes. The major mechanism controlling groundwater chemistry, i.e., rock–water interaction, was also studied, and it was found that silicate weathering plays a major role in the dissolution of minerals. Based on the hydrochemical characterization, the water was observed to be of the Ca–Na–SO₄ composition type except for one sample which was of the Na–Cl composition type. Classification of the meteoric genesis suggested that the groundwater in surficial aquifers in the region had a deep meteoric percolation, and its chemistry is regulated by rock–water interaction.     

Probabilistic Assessment of Earthquake Recurrence in Northeast India and Adjoining Regions

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).     

Trace fossils from Talchir carbonate concretions,Giridih basin,Jharkhand

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.     

A review of the ～1600 Ma sedimentation, volcanism, and tectono-thermal events in the Singhbhum craton, Eastern India

The Palaeoproterozoic–Mesoproterozoic transition (～1600 Ma) is a significant event in the Earth history as a global thermal perturbation affected the pre-1600 Ma landmasses. Like other cratonic blocks of the world, lithospheric thinning, sedimentation, magmatism, metamorphism and crustal melting/anatexis are associated with this significant geological event in the Singhbhum cratonic province of India. This paper is a review of sedimentological, magmatic and tectono-thermal events in the Singhbhum craton at ～1600 Ma. The Palaeo-Mesoproterozoic sedimentation and volcanism in the Singhbhum craton took place in a terrestrial intracontinental rift setting. The available geochronological data are indicative of late Palaeoproterozoic to Neoproterozoic tectono-thermal events in the Chhotanagpur Granite Gneissic Complex (CGGC), an east–west trending arcuate belt of granite gneisses, migmatites and metasedimentary rocks. A detailed multidisciplinary geo-scientific investigation of the Dalma volcanic belt and the area to its north (Chandil Formation) and further north in CGGC will enable us to constrain the extant surface processes and crust-mantle interactions, the collision events between the North and South Indian cratonic blocks, and the position of India in the Columbia supercontinent.     

Spherules from the Late Cretaceous Phosphorite of the Fatehgarh Formation, Barmer Basin, India

A first report of discovery of spherules, glassy balls, highly magnetic fine dust and microbracciated matrix in the Fatehgarh Formation of Barmer Basin, Rajasthan, India is being presented in this paper. The Fatehgarh Formation is a mixed siliciclastic, carbonate and phosphorite formation of Cretaceous age in the Barmer Basin that comprises sediments of Middle Jurassic to Lower Eocene age. The phosphorite zone in the Fatehgarh Formation is 8 metre-thick zone that comprises phosphatic sandstone, bone bed, bedded phosphorite and phosphatic and non phosphatic gastropod beds. The spherules occur in a thin phosphatic-clay mud and silt band of bone bed, which also yielded a very rich and diverse microvertebrate assemblage with a dominant Late Cretaceous (Maastrichtian) form of Igdabatis along with forms comprising of Semionodontid, Lapisosteum and Enchodontid. The end Cretaceous is marked for a mass extinction of numerous species including dinosaurs. An extraterrestrial impact is interpreted as the reason for this mass extinction. Whether these spherules are related to the volcanic source or K/T Boundary impact ejecta found at Caribbean and Gulf of Mexico region needs detailed chemical and age characterization for which study is in progress.     

Characterization of bauxite deposits from Kachchh Area,Gujarat

The bauxites deposits of Kachchh area in Gujarat are investigated to characterize them based on mineralogical and petrographic studies. The major bauxitic mineral in these occurrences is gibbsite, with minor concentration of boehmite and diaspore. Apart from the bauxitic minerals, the other associate minerals are kaolin, calcite, alunite and the iron ore minerals such as hematite and goethite and titanium rich anatase. The iron ore minerals (hematite and goethite) are 10-50microns in size and are disseminated throughout the oolitic and pisolitic bauxitic minerals. At places the goethite exhibits colloform texture. The preservation of basaltic texture in some of the samples indicate that the insitu nature of these bauxites, which are formed by the alteration of calcic plagioclase from the parent basalt. Although, the basalt occurs as the main parent rock for these bauxites, the presence of calcite in some of the samples represent the possibility of having a limestone parent rock at least in some of the bauxite occurrences.