Narrow associated quasi-stellar object absorbers: clustering, outflows and the line-of-sight proximity effect

Using data from the Sloan Digital Sky Survey data release 3 (SDSS DR3), we investigate how narrow (<700 km s⁻¹) C  iv and Mg  ii quasar absorption-line systems are distributed around quasars. The C  iv absorbers lie in the redshift range 1.6 < z < 4 and the Mg  ii absorbers in the range 0.4 < z < 2.2. By correlating absorbers with quasars on different but neighbouring lines of sight, we measure the clustering of absorbers around quasars on comoving scales between 4 and 30 Mpc. The observed comoving correlation lengths are   r _o∼ 5 h ⁻¹Mpc  , similar to those observed for bright galaxies at these redshifts. Comparing correlations between absorbers and the quasars, in whose spectra they are identified, then implies: (i) that quasars destroy absorbers to comoving distances of ∼300 kpc (C  iv ) and ∼800 kpc (Mg  ii ) along their lines of sight; (ii) that ≳40 per cent of C  iv absorbers within 3000 km s⁻¹ of the quasi-stellar object are not a result of large-scale clustering but rather are directly associated with the quasar itself; (iii) that this intrinsic absorber population extends to outflow velocities of the order of 12 000 km s⁻¹; (iv) that this outflow component is present in both radio-loud and radio-quiet quasars and (v) that a small high-velocity outflow component is also observed in the Mg  ii population. We also find an indication that absorption systems within 3000 km s⁻¹ are more abundant for radio-loud quasars than for radio-quiet quasars. This suggests either that radio-loud objects live in more massive haloes, or that their radio activity generates an additional low-velocity outflow, or both.     

Mine Overburden Dump Failure: A Case Study

In any open cast mine, the management of stripped spoil during mining is crucial to the mine’s successful operation. The improper management of the overburden (OB) dump can result in stability issues which may affect safety and production of the mine. Various literatures have reported the failure of open pit dumps and the consequences in loss of life, production and impact on neighbouring amenities. Recently, the failure of an out-of-pit OB dump at an Indian Colliery was reported. The failed OB dump displaced spoil approximately 70 m from the original location of the dump toe and impacted on neighbouring amenities. This paper back analyse material properties and investigates the probable mechanism of this OB failure. Well established tools including limiting equilibrium and continuum numerical methods have been used to understand and identify the failure kinematics of this dump. It has been found that the residual friction angle of the material comprising the dump structural unit dominates stability. Mobilisation of residual strength can occur by operational induced strains and/or the presence of water. The shear strength of the foundation was fully mobilised and provided a slip surface for the overlying dump material. The resultant failure is manifest as a bilinear wedge movement of two ridged blocks defined by linear rupture planes.     

A Novel Intelligent ELM-BBO Technique for Predicting Distance of Mine Blasting-Induced Flyrock

Natural Resources Research - Blasting is an economical technique for rock breaking in hard rock excavation. One of its complex undesired environmental effects is flyrock, which may result in human...     

Major and trace element geochemistry of olivine from an ENE-trending picrite dyke,genetically linked to the ca. 1.89–1.88 Ga Hampi swarm,western Dharwar craton: Implications for plume induced melting of a mixed peridotite-pyroxenite source

The presence of recycled crust in the lithospheric mantle of the Dharwar craton has been investigated using trace element geochemistry of olivine grains from an ENE-trending Paleoproterozoic picrite dyke (associated with the ca. 1.89–1.88 Ga Hampi dyke swarm) emplaced in the western Dharwar craton. Olivine grains are purely magmatic, formed as early phenocrysts in a fractionated basaltic melt. They exhibit enrichment in NiO contents (0.32–0.43 wt%) and depletion in Ca (1366–2105 ppm), Mn (1578–2663 ppm) and 100 1 Mn/Fe (1.28–1.48). Further, the compiled whole-rock geochemical data of the picrite dyke and associated dyke swarm illustrates relatively low CaO/MgO (0.55–1.78), intermediate FeO/MnO (47–54), negative to positive PX# (?0.34 to +1.86), and high values of FC3MS (0.24–0.90) and FCKANTMS (0.19–1.11). These chemical markers are not consistent with the derivation of the primary melt from a pure peridotite or a pyroxenite source; therefore, contribution from a mixed type of source having both peridotite and pyroxenite end members (pyroxene rich and olivine poor lithology) is suggested. The amount of pyroxenite and recycled crust varies from 46% to 86% and 14% to 44%, respectively. The Al-in-olivine based thermometer estimates the maximum crystallization temperature as 1407 °C, which is 137 °C higher than the average temperature of MORB and accordant with several well-established plume-induced large igneous provinces (LIPs) worldwide. Therefore, it is suggested that the studied picrite dyke is derived from a primary melt generated by plume-induced melting of a peridotite-pyroxenite mixed source. The ca. 1.89–1.88 Ga Hampi dyke swarm, being genetically linked with the studied dyke, could also be derived from this same source. Further, the recycled crust in the subcontinental lithospheric mantle of the western Dharwar craton may have generated the pyroxene rich mafic source during the Neoarchean convergence between eastern and western Dharwar craton.     

Chrome-diopside Megacryst-bearing Lamprophyre from the Late Cretaceous Mundwara Alkaline Complex,NW India: Petrological and Geodynamic Implications

The occurrence of a rare mantle-derived chrome-diopside megacryst (～8 mm), containing inclusions of olivine, in a lamprophyre dyke from the late Cretaceous polychronous (～100 – 68 Ma) Mundwara alkaline complex of NW India is reported. The olivine inclusions are forsteritic (Fo: 85.23) in composition, and their NiO (0.09 wt%) and CaO (0.13 wt%) contents imply derivation from a peridotitic mantle source. The composition of the chrome diopside (Cr₂O₃: 0.93 wt ) (Wo_45.27 En_48.47 Fs_5.07 and Ac_1.18) megacryst is comparable to that occurring in the garnet peridotite xenoliths found in diamondiferous kimberlites from Archaean cratons. Single pyroxene thermobarometry revealed that this chrome diopside megacryst was derived from a depth range of ～100 km, which is relatively much deeper than that of the chrome-diopside megacrysts (～40–50 km) reported in spinellherzolite xenoliths from the alkali basalts of Deccan age (ca. 66–67 Ma) from the Kutch, NW India. This study highlights that pre- Deccan lithosphere, below the Mundwara alkaline complex, was at least ～100 km thick and, likely, similar in composition to that of the cratonic lithosphere.     

Morphometric and rheological study of lunar domes of Marius Hills volcanic complex region using Chandrayaan-1 and recent datasets

Marius Hills volcanic complex is one of the most important regions on the lunar surface having an abundant number of volcanic features like domes and cones. Systematic mapping of 106 domes/cones in the Marius Hills region was carried out in this study using high-resolution orthoimage and digital elevation models of Chandrayaan-1 and Kaguya missions. Various morphometric parameters like diameter, height, volume, flank slope, circularity index and form factor are derived for all the mapped domes. The rheological parameters, such as viscosity and eruption rate are estimated for isolated domes and cones superimposed over low domes. The morphometric and rheological properties of these domes are comparable to those located in the area near to Hortensius crater and other mare regions. Surface ages derived for a selected region in NW portion of the Marius Hills volcanic complex using crater size-frequency distribution technique yields ages of 2.98 and 1.91 Ga. It suggests that the domes in this region formed at about 2.98 Ga ago, and then, the younger mare basalts likely embayed this region about 1.98 Ga ago. Stratigraphic sequence of rilles, wrinkle ridge and domes shows that wrinkle ridges are the oldest, while the rilles are younger than the domes.     

Multivariate statistical analysis approach for prediction of blast-induced ground vibration

Excavation of coal, overburden, and mineral deposits by blasting is dominant over the globe to date, although there are certain undesirable effects of blasting which need to be controlled. Blast-induced vibration is one of the major concerns for blast designers as it may lead to structural damage. The empirical method for prediction of blast-induced vibration has been adopted by many researchers in the form of predictor equations. Predictor equations are site specific and indirectly related to physicomechanical and geological properties of rock mass as blast-induced ground vibration is a function of various controllable and uncontrollable parameters. Rock parameters for blasting face and propagation media for blast vibration waves are uncontrollable parameters, whereas blast design parameters like hole diameter, hole depth, column length of explosive charge, total number of blast holes, burden, spacing, explosive charge per delay, total explosive charge in a blasting round, and initiation system are controllable parameters. Optimization of blast design parameters is based on site condition and availability of equipment. Most of the smaller mines have predesigned blasting parameters except explosive charge per delay, total explosive charge, and distance of blast face from surface structures. However, larger opencast mines have variations in blast design parameters for different benches based on strata condition: Multivariate predictor equation is necessary in such case. This paper deals with a case study to establish multivariate predictor equation for Moher and Moher Amlohri Extension opencast mine of India. The multivariate statistical regression approach to establish linear and logarithmic scale relation between variables to predict peak particle velocity (PPV) has been used for this purpose. Blast design has been proposed based on established multivariate regression equation to optimize blast design parameters keeping PPV within legislative limits.     

Mooring forces in horizontal interlaced moored floating pipe breakwater with three layers

The paper presents the results from model scale experiments on the study of forces in the moorings of horizontally interlaced, multi-layered, moored floating pipe breakwaters. The studies are conducted with breakwater models having three layers subjected to waves of steepness H_i/L (H_i is the incident wave height and L the wavelength) varying from 0.0066 to 0.0464, relative width W/L (W is the width of breakwater) varying from 0.4 to 2.65, and relative spacing S/D (S is the spacing of pipes and D the diameter of pipe) of 2 and 4. The variation of measured normalized mooring forces on the seaward side and leeward side are analyzed by plotting non-dimensional graphs depicting f/γW² (f is the force in the mooring per unit length of the breakwater, γ the weight density of sea water) as a function W/L for various values of H_i/d (d is the depth of water). It is found that the force in the seaward side mooring increases with an increase in H_i/L for d/W values ranging between 0.081 and 0.276. The experimental results also reveal that the forces in the seaward side mooring decrease as W/L increases, up to a value of W/L=1.3, and then increases with an increase in W/L. It is also observed that the wave attenuation characteristics of breakwater model with relative spacing of 4 is better than that of the model with relative spacing of 2. The maximum force in the seaward side mooring for model with S/D=4 is lower compared to that for the breakwater model with S/D=2. A multivariate non-linear regression analysis has been carried out for the data on mooring forces for the seaside and leeside.     

Residual-state creep behavior of typical clayey soils

There are few places in the world to monitor aseismic creep. One of them is the Ismetpasa segment of the North Anatolian Fault. The observations in the Ismetpasa showed that the creep rate progressively decreased along the 40 years before the 1999 Kocaeli-Golcuk (Mw = 7.6) earthquake and then started increasing. This phenomenon might be a systematic of the creeping segments. If it is the case, this behavior can be utilized for early warning before the expected major earthquake in the Marmara Sea. In this study, the creep rate of the segment has been studied by GPS and InSAR technologies. The results showed that the rate has decreased to 1.3 cm a year. This result might be an indication of stress starting increase. If the segment retains the decreasing trend and it is ceased by a major earthquake, it would be a proof of the relationship between the creep process and the earthquakes. Then, the creep process might be utilized for early warning.     

Systematic precipitation redistribution following a strong hurricane landfall

The 2017 and 2018 Atlantic hurricane seasons poignantly illustrated the dangers tropical cyclones pose to US, Central American, and Caribbean coastlines. In particular, Hurricane Maria inflicted widespread damage, including catastrophic defoliation, to Puerto Rico, altering surface heat fluxes and possibly modifying precipitation patterns. This study assesses whether defoliation-driven changes to surface energy fluxes redistribute precipitation in the months following a powerful hurricane landfall. Remote sensing analyses of Maria-related vegetation reduction and recovery from Puerto Rico were adapted to the Georgia coastline. In this novel methodology, the resulting landscape evolution, characterized by an instantaneous vegetation reduction with a gradual recovery, was assimilated into the Weather Research and Forecasting model at a convection-allowing a 3-km grid spacing for the 1 June–1 August 2017 period. The experiment revealed that Maria-scale defoliation reduced precipitation by 14% during the month following landfall within a 50 × 50 km zone containing the hypothetical landfall location. A maximum deficit of 20.0% was reached 4 weeks after landfall. For June 2017, the modeled 14% deficit would have shifted the precipitation total from the 61st to the 47th percentile for years 1981–2016. Meanwhile, precipitation totals were unchanged on the domain scale. The near-landfall drying was also evident in three less-severe defoliation simulations, suggesting that systematic precipitation redistribution near the landfall location is possible following storms considerably weaker than Hurricane Maria. Analyses of the temperature and wind fields suggest that coastal kinematic flow is altered by the introduction of a thermally driven pressure gradient in the defoliated zone.