Numerical simulation of the 1992 Flores tsunami: Interpretation of tsunami phenomena in northeastern Flores Island and damage at Babi Island

Numerical analysis of the 1992 Flores Island, Indonesia earthquake tsunami is carried out with the composite fault model consisting of two different slip values. Computed results show good agreement with the measured runup heights in the northeastern part of Flores Island, except for those in the southern shore of Hading Bay and at Riangkroko. The landslides in the southern part of Hading Bay could generate local tsunamis of more than 10 m. The circular-arc slip model proposed in this study for wave generation due to landslides shows better results than the subsidence model, It is, however, difficult to reproduce the tsunami runup height of 26.2 m at Riangkroko, which was extraordinarily high compared to other places. The wave propagation process on a sea bottom with a steep slope, as well as landslides, may be the cause of the amplification of tsunami at Riangkroko. The simulation model demonstrates that the reflected wave along the northeastern shore of Flores Island, accompanying a high hydraulic pressure, could be the main cause of severe damage in the southern coast of Babi Island.     

Kinetics of silica sorption and clay dissolution reactions at 1 and 670 atm

Rates of reactions between clay minerals and silica-spiked seawater and the effect of pressure on the direction, extent and rate of such reactions have been studied. Kinetic behavior of short-term, clay-silica reaction indicates that diffusion is the rate controlling process in both clay dissolution and clay reconstitution reactions. Rate constants of these reactions are of the order of 10^?13 moles/ sec^{$\text{1}\text{2}$}cm². No significant pressure effect on the rate of clay dissolution was observed. Estimates of diffusion coefficient of silicic acid for clay dissolution and silica sorption reactions indicate that the true value lies within the range, 10^?13–10^?17cm²/sec, thus reflecting the semicrystalline or amorphous nature of the reaction product through which diffusion is occurring.     

Late Cretaceous mafic dykes in the Dharwar craton

Palaeomagnetic, geochemical and geochronological studies have been conducted on a set of dolerite dykes intruding the Peninsular gneisses near Huliyurdurga town, Karnataka, as a reconnaissance survey indicated a Cretaceous age for them. The dykes are mainly tholeiitic in composition with their 87Sr/86Sr ratios tightly clustered around 0·7045. Their palaeomagnetic data (D _m =329°,I _m =−55°) and the corresponding palaeopole coordinates (λ _p = 34°S,L _p =108°E) are strikingly close to those of the Deccan Traps to the north. Whole rock K-Ar ages of these dykes ranging between 69 and 84 Ma are also similar to the range of K-Ar ages of the Deccan basalts. The chemical, palaeomagnetic and temporal coherence between the dykes and the Deccan basalts indicate that they may indeed be tectonically related events.     

On the response of flexible risers to loads imposed by hydraulic collars

Even though hydraulic collars are largely used to install flexible risers, neither the loads imposed by this equipment nor the response of the risers to these loads have been previously studied. Hence, this paper presents a three-dimensional nonlinear finite element (FE) model to predict the response of flexible risers to loads imposed by hydraulic collars and also provides a set of equations to predict these loads. The FE model relies on an analogy between helical tendons and orthotropic shells to simulate the inner carcass and the pressure armour of flexible risers. Shell elements are used to represent the polymeric layers and three-dimensional beam elements simulate the wires of the tensile armours. Material, geometric and contact nonlinearities are addressed. Contact interactions between the layers of the riser are handled by surface to surface contact elements with a contact detection algorithm based on the pinball technique and contact forces evaluated with the augmented Lagrangian method. A 9.5″ flexible riser is analyzed and the numerical results are compared to those from the experimental tests. The agreement between all results indicates that the proposed FE model is an efficient approach to predict the response of flexible risers to loads imposed by hydraulic collars and, moreover, may be used to analyze the response of such structures to other types of loads.     

The behavior of iron,manganese and silicon in the Peconic River estuary,New York

The behavior of dissolved and particulate iron and manganese and dissolved silicon has been studied as a function of chlorinity in the Peconic River estuary, New York. This study sought to identify important geochemical processes in a relatively pristine estuary facing increasing anthropogenic impact.Dissolved iron behaved in the classical non-conservative manner exhibiting removal of nearly 80% at very low chlorinities, while particulate iron increased by a corresponding amount over the same chlorinity range. Dissolved manganese was enriched by up to 200% over its predicted concentration at low and intermediate chlorinities by desorption from suspended particulates and by a probable benthic flux. Dissolved silicon was enriched by up to 100% at low and intermediate chlorinities also from a probable benthic flux. These fluxes were estimated to be 5 μg cm^?2 day^?1 for dissolved manganese and 70 μg cm^?2 day^?1 for dissolved silicon.The quantity of both particulate iron and manganese increased at high chlorinities due to an influx of suspended inorganic particulates. In the intermediate to high chlorinity region, oxidation of sediment-derived manganese is believed to contribute to the observed increase in particulate manganese.Total iron was essentially conservative throughout most of the estuary, while total manganese was non-conservative presumably due to extensive remobilization of dissolved manganese from the sediments.     

Polarimetry and spectroscopy of RX J1141.3−6410: a single‐pole AM Her system

We present polarimetric and spectroscopic observations of the ROSAT source RX J1141.3−6410, recently identified as a polar. The detection of circular polarization variations, with an amplitude of 10 per cent, over a 3.16-h period confirms that the system is a polar (AM Herculis star). Supporting evidence comes from the nature of the emission lines and their radial velocity variability. In addition, we observe continuum slope changes in the far-red spectral region (∼6000–8200 Å), indicative of phase dependent cyclotron emission. Polarimetric modelling at two wavelengths establishes RX J1141.3−6410 as a single-pole system, with i ∼ β ∼70°. The accretion region is extended in magnetic longitude, and is totally self-occulted for ∼25 per cent of the orbit. The radial velocity curves derived from the emission lines show a phasing with maximum blueshift occurring with Δ φ ∼0.05 of maximum intensity and circular polarisation. In addition, the broader component of the lines exhibit a substantial radial velocity phase shift with respect to the narrower component, in the sense that the broad component preceeds the narrow. This can be readily understood if the narrower component is principally a result of orbital motion of the stream material and the broad component mainly a result of streaming motion near the coupling region. The phasing of the Ca  ii near-infrared line radial velocities also supports this general picture.     

Light hydrocarbons geochemistry of surface sediments from Pranhita-Godavari Basin,Andhra Pradesh

A geochemical study of surface sediments from Pranhita-Godavari Basin, Andhra Pradesh, India was carried out using light hydrocarbon compounds to assess the hydrocarbon potential of the basin. Suite of 80 soil samples were collected from the depth of 2.5 m and analyzed for adsorbed light gaseous hydrocarbons namely methane (CH₄), ethane (C₂H₆) and propane (C₃H₈) in Gas chromatograph. Compound specific Carbon isotope ratios for CH₄ and C₂H₆ were also determined using GC-C IRMS (Gas Chromatograph Combustion Isotope Mass Spectrometer). The presence of moderate to low concentrations of methane (C_CH4 C_{CH_4 } : 1 to 138 ppb), ethane (H₄{H_4 }: 1 to 35 ppb) and propane (C_{C3 H8} C_{C_3 H_8 } : 1 to 20 ppb) was measured in the soil samples. Carbon isotopic composition of d¹³ C_CH4 \delta ^{13} C_{CH_4 } ranges between −27.9 to −47.1 ‰ and d¹³ C_{C2 H6} \delta ^{13} C_{C_2 H_6 } ranged between −36.9 to −37.2 ‰ (V-PDB) indicating that these gases are of thermogenic origin. Study of soil samples suggests the area has good potential for hydrocarbon.     

Three-Dimensional Particle Acceleration in Electromagnetic Cylinder and Torus

Particle acceleration via Poynting vector with toroidal magnetic field is studied in 3D PIC simulation of electron-positron plasma. We choose two different initial magnetic field configurations to compare how the particle acceleration is affected by the expansion of electromagnetic wave. In the cylindrical case, the electromagnetic field strength decays as (ct)⁻², and particles are accelerated in the radial direction as well as the axial direction. Rayleigh-Taylor instability is also observed at the center of the cylinder. In the torus case, the field strength decays as (ct)⁻³, making the acceleration less efficient. Particles accelerated in the axial direction by E × B force creates strong charge separation.     

Geochemical characterization of adsorbed light gaseous alkanes in near surface soils of the eastern Ganga basin for hydrocarbon prospecting

This study aims to assess the hydrocarbon potential of Ganga basin utilizing the near surface geochemical prospecting techniques. It is based on the concept that the light gaseous hydrocarbons from the oil and gas reservoirs reach the surface through micro seepage, gets adsorbed to soil matrix and leave their signatures in soils and sediments, which can be quantified. The study showed an increased occurrence of methane (C₁), ethane (C₂) and propane (C₃) in the soil samples. The concentrations of light gaseous hydrocarbons determined by Gas Chromatograph ranged (in ppb) as follows, C₁: 0–519, C₂: 0–7 and C₃: 0–2. The carbon isotopic (VPDB) values of methane varied between ?52.2 to ?27.1‰, indicating thermogenic origin of the desorbed hydrocarbons. High concentrations of hydrocarbon were found to be characteristic of the Muzaffarpur region and the Gandak depression in the basin, signifying the migration of light hydrocarbon gases from subsurface to the surface and the area’s potential for hydrocarbon resources.