Coordinate gauge conditions in theN-body equations of motion in the first-order post-Newtonian approximation of general relativity

The explicit forms of the metric as well as the equations of motion in the first-order post-Newtonian approximation are worked out under several gauge conditions. It is noted that the so-called EIH (Einstein, Infeld, and Hoffman) equation of motion for an assembly ofN finite mass points mutually interacting via gravitation is identically obtained under three different gauge conditions, namely the harmonic gauge, Chandrasekhar gauge and a composite Chandrasekhar gauge used by Misneret al. (1970), even though the solutions for the metric are found to be all different. In one case the metric has a component apparently diverging, but finally generates regular affine connections so that the equations of motions become free from any singularity. By use of the Chandrasekhar gauge and his formulation, the second-order contribution to the acceleration of planets in the limit of test particle motion around the Sun has been calculated, the inclusion of which in the EIH set of the equations of motion would extend the relative accuracy of computing the total acceleration of any planet to better than one part in 10¹⁷.     

Creep behaviour of intact and remoulded fibrous peat

This paper presents the creep behaviour of intact and remoulded specimens of fibrous peat obtained from a field site near Anzac, Alberta, Canada. The creep behaviour was investigated by means of long-term drained and undrained triaxial tests. The development of volumetric, axial, and undrained axial strain and strain rate during drained and undrained creep tests under variable stress conditions is presented. The stress _– strain _– strain rate (p′–ε _v–\(\dot{\varepsilon }_{\text{v}}\)) relationship is found to be unique for different stress and loading durations. The p′–ε _v–\(\dot{\varepsilon }_{\text{v}}\) relationship is analysed and represented by creep isotaches. The applicability of different creep models developed for normally consolidated clay is discussed and applied to define the development of creep strain in fibrous peat under varying isotropic and deviator stresses. The secondary consolidation coefficient for evaluating the volumetric strain rate of peat is found to be applicable with some limits. The drained creep behaviour of remoulded peat specimens differs from the behaviour shown by Shelby tube specimens, whereas the undrained creep behaviour in remoulded and Shelby tube specimens is similar.     

Holocene tectono-geomorphic evolution of Haryana plains,Western Ganga plain,India

Haryana plain is the drainage divide between the Ganga plain in the east and the Indus plain in the west. Being a part of the Himalayan foreland, its geomorphology, sedimentation processes, and tectonism are broadly controlled by the Himalayan tectonics. Soil and geomorphological mapping in Haryana plain bring out geomorphic features such as paleochannels, various active drainage patterns, and landforms such as old fluvial plains, floodplains, piedmonts, pediments, terminal fans, and eolian plains. Based on the degree of soil development, and Optical stimulated luminescence (OSL) ages, the soil-geomorphic units were grouped into six members (QIMS-I to VI) (Quaternary Indus Morphostratigraphic Sequence) of a morphostratigraphic sequence: QIMS-VI 9.86–5.38 Ka, QIMS-V 5.38–4.45 Ka, QIMS-IV 4.45–3.60 Ka, QIMS-III 3.60–2.91 Ka, QIMS-II <?2.91–1.52 Ka, and QIMS-I <?1.52 Ka. OSL chronology of different geomorphic features suggests six episodes of tectono-geomorphic evolution in the region since 10 Ka. Neotectonic features such as nine faults, two lineaments, and five fault-bounded tectonic blocks have been identified. Independent tilting and sagging of the blocks in response to neotectonics have resulted in modification of landforms, depositional processes, and hydro-geomorphology of the region. Major rivers like the Yamuna, the Ghaggar, and the Sutlej show different episodes of shifting of their courses. Lineament controlled few extinct channels have been recorded between 20 and 25 m depth below the surface in the ground-penetrating radar (GPR) profiles. These buried channels are aligned along the paleo-course of the Lost Saraswati River interpreted from the existing literature and hence are considered as the course of the lost river. Seven terminal fans have been formed on the downthrown blocks of the associated faults. The Markanda Terminal Fan, the first of such features described, is indeed a splay terminal fan and was formed by a splay distributary system of the Markanda River. Association of three terminal fans of different ages with the Karnal fault indicates the segment-wise development of the fault from west to east. Also, comparison with other such studies in the Ganga plain to further east suggests that the terminal fans formed by streams with distributary drainage pattern occur only in semiarid regions as in the present area and thus are indicators of semiarid climate/paleoclimate. Though the whole region is tectonically active, the region between the Rohtak fault and Hisar fault is most active at present signified by the concentration of earthquake epicenters.     

Estimation of tsunami hazard from volcanic activity — Suggested methodology with Augustine volcano,Alaska as an example

A general approach for the estimation of tsunami height and hazard in the vicinity of active volcanoes has been developed. An empirical relationship has been developed to estimate the height of the tsunami generated for an eruption of a given size. This relationship can be used to estimate the tsunami hazard based on the frequency of eruptive activity of a particular volcano. This technique is then applied to the estimation of tsunami hazard from the eruption of the Augustine volcano in Alaska. Modification of this approach to account for a less than satisfactory data base and differing volcanic characteristics is also discussed with the case of the Augustine volcano as an example. This approach can be used elsewhere with only slight modifications and, for the first time, provides a technique to estimate tsunami hazard from volcanic activity, similar to a well-established approach for the estimation of tsunami hazard from earthquake activity.     

Volcanic activity and large earthquakes

Several investigators have noted an increase in volcanic activity prior to several large interplate earthquakes in the circum-Pacific area. From these data, I have examined the temporal relationship between the beginning of this increased volcanic activity and the occurrence of large earthquakes. I find that the time (year) of the beginning of enhanced volcanic activity depends on the magnitude of the subsequent large earthquake, for earthquakes with magnitude > 7.5. The volcanoes which exhibit this enhanced activity are situated on the landward side of the rupture zone of the large earthquake, and this study therefore suggests a casual physical relationship between the two phenomena. I also find that this increase in volcanic activity occurs a few years before an increase in the occurrence of smaller earthquakes, noted by several invesigators, in the rupture zones of large earthquakes.     

Effect of surface stress on magneto-elastic surface waves in finitely conducting media

This paper deals with the investigation of the effect of surface stress and conductivity on the propagation of surface wave in isotropic, homogeneous, elastic media under the action of a primary magnetic field. Formulation of the general surface wave propagation problem has been made, and the corresponding frequency equation has been derived. Frequency equations for Rayleigh wave, surface shear wave and Stoneley wave have been deduced from that of general surface wave as special cases. The effects of surface stress and magnetic field on the wave velocities and attenuation factors of Rayleigh wave and surface shear wave are shown by numerical calculations and graphs. Some important wave velocity equations, as obtained by other authors, have been deduced as special cases from the wave velocity equation for Stoneley wave. It is found that the combined effect of surface stress and magnetic field modulates the wave velocity ratios and attenuation factors of Rayleigh wave and surface shear wave to a considerable extent.     

Approaches for modeling longitudinal dispersion in pore-networks

The purpose of this study is to quantify the dispersivity in the longitudinal direction by upscaling pore scale mixing over a network domain and to verify the dispersivity with that obtained through the more rigorous upscaling technique, the Brownian particle tracking model (BPTM). We model a porous medium with a network of pore-units that are comprised of pore bodies and bonds of finite volume. Such a pore-unit is assumed to be a mixing cell with the steady state flow condition for a single fluid. Dispersivity can be obtained by solving the mixing cell model (MCM) for the concentration in each pore-unit and by averaging the concentrations for a large number of pore units (as a function of time and space). A minimal size of network that ascertains an asymptotic value of dispersivity was determined and verified with large size pore networks. This numerically computed dispersivity is compared with the results from the BPTM for the same porous medium and flow conditions. We show that the dispersivity obtained from the MCM is equally reliable for the heterogeneous pore-networks and can be estimated as a function of pore size heterogeneity. For homogeneous networks with the MCM, the iteration time step plays an important role. On the other hand, for networks with the BPTM, the assumption of intra-bond velocity profile affects the results.     

Using magnetic susceptibility to find Precambrian impact ejecta: A proposal

Layers with high magnetic susceptibility contain heavy minerals that are the most likely to preserve signatures of impact in metamorphosed Precambrian rocks. The following impact indicators are resistant to alteration and metamorphism and are likely to be found in heavy mineral layers: impact diamond, SiC, shocked zircon, high-pressure TiO₂ phases, reidite, and high-pressure chromite. Coesite and stishovite could also be present but are not likely to be preserved in rocks metamorphosed above the greenschist facies. Looking for layers with high magnetic susceptibility will also identify layers that might contain concentrations of zircon for dating.     

Monthly prediction of rainfall over India and its homogeneous zones during monsoon season: a supervised principal component regression approach on general circulation model products

A supervised principal component regression (SPCR) technique has been employed on general circulation model (GCM) products for developing a monthly scale deterministic forecast of summer monsoon rainfall (June–July–August–September) for different homogeneous zones and India as a whole. The time series of the monthly observed rainfall as the predictand variable has been used from India Meteorological Department gridded (1°?×?1°) rainfall data. Lead 0 (forecast initialized in the same month) monthly products from GCMs are used as predictors. The sources of these GCMs are International Research Institute for Climate and Society, Columbia University, National Center for Environmental Prediction, and Japan Agency for Marine Earth Science and Technology. The performance of SPCR technique is judged against simple ensemble mean of GCMs (EM) and it is found that over almost all the zones the SPCR model gives better skill than EM in June, August, and September months of monsoon. The SPCR technique is able to capture the year to year observed rainfall variability in terms of sign as well as the magnitude. The independent forecasts of 2007 and 2008 are also analyzed for different monsoon months (Jun–Sep) in homogeneous zones and country. Here, 1982–2006 have been considered as development year or training period. Results of the study suggest that the SPCR model is able to catch the observational rainfall over India as a whole in June, August, and September in 2007 and June, July, and August in 2008.