DETERMINATION OF PHOSPHOROUS IN FIFTY-NINE GEOCHEMICAL REFERENCE SAMPLES BY EXTRACTIVE SPECTROPHOTOMETRY

A digestion procedure with sequential use of HF-HCl and HNO₃-HClO₄ involving yellow vanadium molybdophosphate complex and its extraction into isobutylmethylketone (IBMK) has been employed for estimation of phosphorus in 59 geochemical reference samples. The agreement between the results obtained from IBMK-extraction and the recommended values has been found to be better than those available from the usual procedures (i.e., estimation in the aqueous phase).     

Influence of microscopic particle interaction models on the flux of atmospheric antiprotons

We study the effect of particle interaction models on the theoretical estimates of atmospheric antiproton flux by comparing the BESS observations of antiproton spectra with the spectra obtained by means of a full three dimensional Monte Carlo simulation program. For such a purpose, we use two popular microscopic interaction models, namely FLUKA and UrQMD, to simulate antiproton spectra at multiple observation levels. In this article, we further compare the atmospheric antiproton fluxes predicted by a few popular microscopic high energy particle interaction models with each other to get an idea about the influence of such models at energies beyond the BESS upper cutoff up to about 100 GeV. We find that the simulated antiproton flux has strong dependence on the choice of interaction models. The present analysis seems to further indicate that the theoretical prediction of galactic antiproton spectrum may be uncertain by an appreciable amount due to our limited knowledge of particle interaction characteristics.     

Geology and geochemistry of Pachmarhi dykes and sills,Satpura Gondwana Basin,central India: problems of dyke-sill-flow correlations in the Deccan Traps

Many tholeiitic dyke-sill intrusions of the Late Cretaceous Deccan Traps continental flood basalt province are exposed in the Satpura Gondwana Basin around Pachmarhi, central India. We present field, petrographic, major and trace element, and Sr–Nd–Pb isotope data on these intrusions and identify individual dykes and sills that chemically closely match several stratigraphically defined formations in the southwestern Deccan (Western Ghats). Some of these formations have also been identified more recently in the northern and northeastern Deccan. However, the Pachmarhi intrusions are significantly more evolved (lower Mg numbers and higher TiO₂ contents) than many Deccan basalts, with isotopic signatures generally different from those of the chemically similar lava formations, indicating that most are not feeders to previously characterized flows. They appear to be products of mixing between Deccan basalt magmas and partial melts of Precambrian Indian amphibolites, as proposed previously for several Deccan basalt lavas of the lower Western Ghats stratigraphy. Broad chemical and isotopic similarities of several Pachmarhi intrusions to the northern and northeastern Deccan lavas indicate petrogenetic relationships. Distances these lava flows would have had to cover, if they originated in the Pachmarhi area, range from 150 to 350 km. The Pachmarhi data enlarge the hitherto known chemical and isotopic range of the Deccan flood basalt magmas. This study highlights the problems and ambiguities in dyke-sill-flow correlations even with extensive geochemical fingerprinting.     

Theoretical development of the differential scattering decomposition for the 3D resistivity experiment

In any numerical solution of the DC resistivity experiment, care must be taken to deal with strong heterogeneity of electrical conductivity. In order to examine the importance of conductivity contrasts, we develop a scattering decomposition of the DC resistivity equation in the sparse differential domain as opposed to the traditional dense integral formulation of scattering‐type equations. We remove the singularity in the differential scattered series via separation of primary and secondary conductivity, thereby avoiding the need to address the singularity in a Green's function. The differential scattering series is observed to diverge for large conductivity contrasts and to converge for small contrasts. We derive a convergence criterion, in terms of matrix norms for the weak‐form finite‐volume equations, that accounts for both the magnitude and distribution of heterogeneity of electrical conductivity. We demonstrate the relationship between the differential scattering series and the Fréchet derivative of the electrical potential with respect to electrical conductivity, and we show how the development may be applied to the inverse problem. For linearization associated with the Fréchet derivative to be valid, the perturbation in electrical conductivity must be small as defined by the convergence of the scattered series. The differential scattering formulation also provides an efficient tool for gaining insight into charge accumulation across contrasts in electrical conductivity, and we present a derivation that equates accumulated surface charge density to the source of scattered potential.     

Bearing of plate geometry and rheology on shallow-focus mega-thrust seismicity with special reference to 26 December 2004 Sumatra event

We propose a model pertaining to the generation of 26th December 2004 off Sumatra mega-event in the backdrop of other similar type earthquakes along subduction zones around the world. Reconstructions of Benioff trajectories through the hypocenters of historical earthquakes including six mega-earthquakes indicate (i) confinement of hypocenters right within the descending lithosphere, and (ii) natural coincidence of foci of the mega-events around the zones of plate flexing. These observations are discussed in detail with special emphasis on the Sumatra margin considering the role of rheological anomaly across the cross-section of the descending lithosphere; yield strength envelope and residual stress accumulation through time. The intraplate origin of shallow mega-thrust earthquakes allowed us to advocate the ‘zone of flexing’ along the profiles of the subducting plates as nodal area for stress concentration. We propose here that at elevated confining pressure and temperature, loading of unidirectional cyclic stress on time-average bending stress enhanced the material yield strength (i.e., strain-hardening), and leads the semi-brittle portion of the lithosphere into near-brittle condition through rheological transformation. Under subsequent rise in neutral surface and increase in compressive stress field, non-coaxial deformation triggered shear failure on 26th December 2004 preferably at the rheological interface between strain-hardened near-brittle layer and deformed ductile layer within the sub-oceanic mantle.A two-stage fracture mechanism viz. a slow (～1.1 km/s) bilateral initiation in an essentially strain-hardened near-brittle domain and a follow-up very rapid progression (3.3 km/s) in the brittle, crustal domain was mainly involved in the generation of 2004 off Sumatra mega-event. Estimation shows an amount of 3.38 × 10²² to 4.50 × 10²² N m seismic moment (M_o) and 8.95–9.03 moment magnitude (M_w) for the southern part of the 1300 km extended rupture i.e. between the North Andaman to the north and the Sumatra at its south. The study necessitates the reassessment of other shallow-focus mega-thrust earthquakes along the subduction margins around the globe.     

Fractal study of seismicity in order to characterize the various tectonic blocks of North-east Himalaya,India

Three major projects initiated by the European Commission within its 7th Framework Programme that have studied the weather phenomena and their projections to the future in relation to their impacts and implications to the European transport systems have recently been concluded. All of the transport modes were covered, as well as all of the critical phenomena present within the European area. The three projects (that ran from 2009 and 2012) are as follows: (1) EWENT (Extreme Weather impacts on European Networks of Transport—www.ewent.vtt.fi); (2) ECCONET (Effects of climate change on the inland waterway networks—www.ecconet.eu); (3) WEATHER (Weather Extremes: Assessment of Impacts on Transport and Hazards for European Regions—www.weather-project.eu). In this Foreward to the Special Issue on “Vulnerability of Transportation to Extreme Weather and Climate Change,” the key results of the above three projects are addressed concisely, offering the reader a broader view of their findings; since some of these are enveloped in the research papers hosted in this volume, they will not be covered in detail. However, the rich output of these projects in the form of “Project Deliverables” and “Reports” is also an important source of information on the findings and results from these three projects which are publicly available on the projects’ Web sites. The purpose of this Foreward is to bring to the attention of the interested reader these sources and overview briefly some of the projects’ outcomes. Also, a short comparative discussion on selected findings is made, outlining agreements and disagreements between the projects.     

Resolution analysis of geophysical images: Comparison between point spread function and region of data influence measures

Practical decisions are often made based on the subsurface images obtained by inverting geophysical data. Therefore it is important to understand the resolution of the image, which is a function of several factors, including the underlying geophysical experiment, noise in the data, prior information and the ability to model the physics appropriately. An important step towards interpreting the image is to quantify how much of the solution is required to satisfy the data observations and how much exists solely due to the prior information used to stabilize the solution. A procedure to identify the regions that are not constrained by the data would help when interpreting the image. For linear inverse problems this procedure is well established, but for non‐linear problems the procedure is more complicated. In this paper we compare two different approaches to resolution analysis of geophysical images: the region of data influence index and a resolution spread computed using point spread functions. The region of data influence method is a fully non‐linear approach, while the point spread function analysis is a linearized approach. An approximate relationship between the region of data influence and the resolution matrix is derived, which suggests that the region of data influence is connected with the rows of the resolution matrix. The point‐spread‐function spread measure is connected with the columns of the resolution matrix, and therefore the point‐spread‐function spread and the region of data influence are fundamentally different resolution measures. From a practical point of view, if two different approaches indicate similar interpretations on post‐inversion images, the confidence in the interpretation is enhanced. We demonstrate the use of the two approaches on a linear synthetic example and a non‐linear synthetic example, and apply them to a non‐linear electromagnetic field data example.     

Impact of LULC change on the runoff,base flow and evapotranspiration dynamics in eastern Indian river basins during 1985–2005 using variable infiltration capacity approach

As a catchment phenomenon, land use and land cover change (LULCC) has a great role in influencing the hydrological cycle. In this study, decadal LULC maps of 1985, 1995, 2005 and predicted-2025 of the Subarnarekha, Brahmani, Baitarani, Mahanadi and Nagavali River basins of eastern India were analyzed in the framework of the variable infiltration capacity (VIC) macro scale hydrologic model to estimate their relative consequences. The model simulation showed a decrease in ET with 0.0276% during 1985–1995, but a slight increase with 0.0097% during 1995–2005. Conversely, runoff and base flow showed an overall increasing trend with 0.0319 and 0.0041% respectively during 1985–1995. In response to the predicted LULC in 2025, the VIC model simulation estimated reduction of ET with 0.0851% with an increase of runoff by 0.051%. Among the vegetation parameters, leaf area index (LAI) emerged as the most sensitive one to alter the simulated water balance. LULC alterations via deforestation, urbanization, cropland expansions led to reduced canopy cover for interception and transpiration that in turn contributed to overall decrease in ET and increase in runoff and base flow. This study reiterates changes in the hydrology due to LULCC, thereby providing useful inputs for integrated water resources management in the principle of sustained ecology.     

Outcrop signatures of relative sea level fall on a siliciclastic shelf: Examples from the Rewa Group of Proterozoic Vindhyan basin

The Rewa Group of the Vindhyan Supergroup in the Son valley begins with a thick (∼200m) dominantly shaly, shelfal succession, occurring between the Dhandraul Formation of the Kaimur Group (fluvial sandstone) below and Drammondganj Formation of the Rewa Group (marginal marine sandstone) above. Such a stratigraphic disposition indicates a sharp rise in relative sea level at the onset of Rewa sedimentation, inducing a shelfal depth to the Vindhyan basin. However, a number of wedge-shaped, sandstone/conglomerate bodies (maximum thickness 23.5 m) occur at multiple stratigraphic levels within the aforesaid deeper water shale succession, which appear to be of much shallow water origin representing regressive deposits. Though these bodies do not define a single physically continuous unit, either vertically or laterally, they are still designated by a single term ‘Asan Sandstone’ in the literature. On the other hand, the encasing shelfal shales are termed as Panna and Jhiri Shales, in accordance with their occurrence below or above the so-called ‘Asan Sandstone’. The present study reveals that in different sections spread over the Son valley, there are several discrete regressive wedges occurring vertically, and their depositional environment is also variable, ranging between braided fluvial, shoreface fan and braid delta. The features common to most of the regressive coarser clastic bodies are: