Ranchi mega lineament and its correlation with geological and geophysical data

Remotely-sensed satellite data of Landsat 5 (TM) and IRS-1A (LISS II) covering parts of central portion of Chotanagapur plateau have been analysed visually to delineate some prominent lineaments in Ranchi district and its adjoining area. One of the most prominent lineament “Ranchi mega lineament? has been analysed in this paper. This lineament is a potential site for base metal mineralisation at some places, and it acts as good groundwater conduit in the region. No earlier attempt to map this entire structural unit as a separate entity is known. Geophysical bouguer gravity anomaly map, lithological and structural maps have some remarkable correlation with this lineament. In the present paper authors have tried to analyse the lineament with respect to its tectonic, mineralisation and groundwater prospects. Resistivity survey carried in close proximity of this lineament at selected sites, indicate that rocks are well fractured at depth. Available lithological and structural map support this lineament as a shear near Purulia (W.B.) and also having base-metal mineralisation potential in this area. Authors opine that existing gravity anomaly map may be further augmented in the light of present study.     

Sunspots and physics of magnetic flux tubes overstability and Kelvin-Helmholtz instability in a magnetic field

We have studied the dynamical properties of convective overstability and Kelvin-Helmholtz instability in a vertical magnetic field with a downdraft. The Kelvin-Helmholtz instability and overstability produce the upward downward propagating Alfvén waves depending upon the magnitudes of the kinematic viscosity coefficient (eddy viscosity) ν, and thermometric conductivity κ. It is found that the instability may be driven by the density stratification and the effect of the eddy viscosity is to make the system stable. We discuss also the interaction of the overstability inx<0 and the downdraft inx>0, and the overstability at a vertical boundary of the field.     

Statistical parameters of Bhuj earthquake sequence of January 26th, 2001

An intraplate earthquake of magnitude (M _c) 6.9 (Anon 2001a) struck Bhuj and the adjoining region of Kachchh in Gujarat on January 26th, 2001 at about 0316 hrs (GMT) and was followed by a number of aftershocks. The epicentre of this earthquake was located at 23.4‡N and 70.28‡E close to the Kachchh mainland fault. The intensity observed around the epicenter was X on the MSK scale. A study of 531 aftershocks, in the magnitude range of 3.0–5.7, recorded at Vadodara Seismological Observatory till March 31st, 2001 has been carried out and various statistical parameters calculated. The total energy released during the study period is calculated to be 8.2 × 10¹⁴ joule. Sudden occurrence of the main shock without any foreshock in the same tectonic system is a unique feature of this sequence. Theb- value (0.86), value of M₀-M₁ (1.2), high M₁/M₀ (0.89) and high value of the decay constanth (0.91), all support the tectonic origin of the present study.     

Identification of Suitable Hydrological Models for Streamflow Assessment in the Kangsabati River Basin,India, by Using Different Model Selection Scores

The increasing demand for water in developing countries, like India, requires efficient water management and resource allocation. This is crucial to accurately assess and predict hydrological processes such as streamflow, drought, and flood. However, simulations of these hydrologic processes from various hydrological models differ in their accuracy. By analyzing different characteristics of hydrological models, selection scores can be used to select the best model for the intended purpose based on their inherit strengths (i.e., some models are better for streamflow prediction). In this study, 13 different criteria were used for the model selection scores including temporal and spatial resolutions, and processes involved. Thereafter, based on different scores, we selected two different hydrological models for streamflow prediction in the Kangsabati River Basin (KRB) in eastern India, namely (1) Génie Rural à 4 paramètres Journalier (GR4J), a conceptual model, and (2) Variable Infiltration Capacity (VIC), a semi-distributed model. The models were calibrated against the daily observed streamflow at upper KRB (Reservoir) and lower KRB (Mohanpur) from 2000 to 2006 and validated during the period from 2008 to 2010. Despite the differences in model structure and data used, both models simulated streamflow at a daily time scale with Nash–Sutcliffe coefficient of 0.71–0.82 for the VIC model and 0.63–0.71 for the GR4J. Due to the simpler structure, parsimonious nature, fewer parameters, and reasonable accuracy, the results suggest that a conceptual rainfall—runoff model like GR4J can be used in data-deficient conditions.

     

Assessment of flood inundation mapping of Surat city by coupled 1D/2D hydrodynamic modeling: a case application of the new HEC-RAS 5

Surat city of India, situated 100 km downstream of Ukai Dam and 19.4 km upstream from the mouth of River Tapi, has experienced the largest flood in 2006. The peak discharge of about 25,770 m³ s^?1 released from the Ukai Dam was responsible for a disaster. To assess the flood and find inundation in low-lying areas, simulation work is carried out under the 1D/2D couple hydrodynamic modeling. Two hundred ninety-nine cross sections, two hydraulic structures and five major bridges across the river are considered for 1D modeling, whereas a topographic map at 0.5 m contour interval was used to produce a 5 m grid, and SRTM (30 and 90 m) grid has been considered for Surat and the Lower Tapi Basin. The tidal level at the river mouth and the release from the Ukai Dam during 2006 flood are considered as the downstream and upstream boundaries, respectively. The model is simulated under the unsteady flow condition and validated for the year 2006. The simulated result shows that 9th August was the worst day in terms of flooding for Surat city and a maximum 75–77% area was under inundation. Out of seven zones, the west zone had the deepest flood and inundated under 4–5 m. Furthermore, inundation is simulated under the bank protection work (i.e., levees, retaining wall) constructed after the 2006 flood. The simulated results show that the major zones are safe against the inundation under 14,430 m³ s^?1 water releases from Ukai Dam except for the west zone. The study shows the 2D capability of new HEC-RAS 5 for flood inundation mapping and management studies.     

Holocene Dune Activity in the Thar Desert,India

The Thar Desert dune system in north-west India and eastern Pakistan provides a rich archive of past environmental, geomorphological and climatic change. Much of the knowledge about the timing of dune accumulation in the Thar stems from scattered and sporadic records, based on older luminescence dating protocols. If the Thar dune record is to be incorporated within a growing multiproxy framework of past climate and environmental dynamics, it is necessary to generate a systematic record of the timing of dunefield accumulation. From this, relationships to climate and other drivers of dune activity may then be better established. To this end, an intensive programme of field sampling and optically stimulated luminescence (OSL) dating was carried out from a dunefield in the east-central Thar Desert. This study presents the first detailed Holocene dune accumulation history from the region, and sheds light on the development of the multi-generational parabolic dune systems. In contrast to previously published work, we identify the importance of the Holocene and the last millennium as periods with a number of preserved accumulation phases. OSL ages suggest that accumulation was persistent during the early and mid-Holocene (within 11.7-5.5 ka), late Holocene (2-1 ka), as well as two major phases in the last millennium (600 – 200 a and within the last 70 a). Potential drivers of dune mobility in the last century include a strong anthropogenic dimension. Rapid net accumulation is recorded in the last 70 years, with rates varying between 2 and 5 m/year, in an environment where agricultural pressures have increased dramatically with the advent of irrigation schemes expanding into dunefield areas. © 2019 John Wiley & Sons, Ltd.     

Hyper-spectral data based investigations for snow wetness mapping

Spatial information on snow wetness content (SWC) is important for hydrology, climatology applications. Limited work is available on estimation of SWC using optical sensors. In present work, spectral signature characteristics of snow (~145 samples) acquired in winters of three years, using field spectral-radiometer (350–2500 nm) were correlated with synchronized SWC measurements. Correlation is found stronger in Near-Infra-Red (NIR) and Short-Wave-Infrared (SWIR) regions than Visible (VIS). Spectral peak width at 905 and 1240 nm is found negatively correlated with SWC, while positively correlated at 1025 nm. Asymmetry tends towards right as SWC increases and has stable positive correlations as compared to other characteristics. Sensitivity of widely used snow-related indices to SWC is also analyzed. Based on analysis, new ratio method at selected wavelengths is proposed to discriminate dry and wet snow zones using air/ground borne sensors. Proposed methodology is evaluated on air-borne hyper-spectral (AVIRIS-NG) data and 88% overall accuracy with kappa coefficient 77.6 observed after validation with reference observations.     

Evolution and paleobiogeography of mangroves

We reviewed the geological record of mangroves based on fossil pollen, fruits, and wood evidence of Nypa, Avicennia, Sonneratia, Rhizophoraceae, and mangrove associates to trace the origin, distribution, extinction, and range contraction of paleo‐mangroves during the Late Cretaceous–Miocene time. Our study region covers paleocoastal areas of Indo‐West Pacific (IWP) and Atlantic East Pacific (AEP) region. First, we compiled the mangrove fossil records from the Late Cretaceous till Miocene and identified the migration pattern for Nypa, Avicennia, Sonneratia, Rhizophoraceae members, and mangrove associates such as Acrostichum, Wetherellia, Pelliciera, Aegiceras, Heritiera, Excoecaria, and Barringtonia. Second, we interpreted the paleoclimate shifts which caused the dispersal/extinction of this specialized ecosystem. Lastly, we proposed the future consequences of mangrove diversity for restoration and conservation strategies. First mangroves appeared during the Late Cretaceous, 100–65 Ma, since then their evolution is closely related to sea‐level changes in geological times. The oldest geological record of Nypa palm which prefers broad ecological tolerance is a good example for pantropical distribution of mangroves. High sea‐level and humid climate offered sufficient coastal regions and climate for the development of 12 genera of mangroves in nine families and subsequent proliferation into newer areas during early to middle Eocene (~50–40 Ma). The Eocene/Oligocene boundary crisis heralds the beginning of a biogeographical split between the present‐day eastern and western provinces of mangroves with records of Sonneratia, Rhizophora, Pelliciera, Barringtonia, and Acrostichum. However, during Oligocene and Middle Miocene mangroves occupied the present geographical position with addition of Nypa, Avicennia, and Excoecaria species. Re‐evaluation of Cenozoic records suggests that the climatic conditions of Late Paleocene, end of Eocene, and middle Pliocene were the driving force that led to the evolution and expansion of mangrove flora. During the Neogene, latitudinal contraction, extinction, and migration of mangroves led to the present bipartite distribution. The Himalayan uplift and establishment of Asian summer monsoon toward Late Neogene further affected the coastal dynamics which tailored the mangrove distribution of the Indian subcontinent. Loss of ecological habitats and local extinction forming disjunct distribution of mangroves during the Quaternary have also affected its overall biogeography.     

Halo orbit of regularized circular restricted three-body problem with radiation pressure and oblateness

In this paper, computation of the halo orbit for the KS-regularized photogravitational circular restricted three-body problem is carried out. This work extends the idea of Srivastava et al. (Astrophys. Space Sci. 362: 49, 2017) which only concentrated on the (i) regularization of the 3D-governing equations of motion, and (ii) validation of the modeling for small out-of-plane amplitude (\(A_z =110000\) km) assuming the third-order analytical approximation as an initial guess with and without differential correction. This motivated us to compute the halo orbits for the large out-of-plane amplitudes and to study their stability analysis for the regularized motion. The stability indices are described as a function of out-of-plane amplitude, mass reduction factor and oblateness coefficient. Three different Sun–planet systems: the Sun–Earth, Sun–Mars and the Sun–Jupiter are chosen in this study. Stable halo orbits do not exist around the \(L_{1}\) point, however, around the \(L_{2}\) point stable halo orbits are found for the considered systems.