Deep seismic soundings along Hirapur-Mandla profile, central India

Summary. The crustal depth section along Hirapur-Mandla profile has been computed in two steps from Deep Seismic Sounding (DSS) data. The shallow section up to the crystalline basement is derived by inverting first arrival refraction travel times. The upper Vindhyan sediments (velocity 4.5 km s⁻¹) have a maximum thickness of about 1.5 km at Bakshaho. The lower Vindhyan sediments (velocity 5.4 km s⁻¹) were deposited north of Narmada-Son lineament between Katangi and Narsinghgarh in a graben developed in crystalline basement. The thickness of the lower Vindhyans increases from north to south towards Katangi and the depth to the basement reaches 5.5 km near Jabera. The depth to the Moho boundary varies from 39.5 km near Tikaria to 45 km at Narsinghgarh. The narrow block between Katangi and Jabalpur forms a horst feature which represents the Narmada-Son lineament forming the southern boundary of the Vindhyan basin. Two-dimensional ray tracing was performed generating travel time curves from various shot points which were matched with observed travel time data.     

Auto-correlation analysis of ocean surface wind vectors

The nature of the inherent temporal variability of surface winds is analyzed by comparison of winds obtained through different measurement methods. In this work, an auto-correlation analysis of a time series data of surface winds measuredin situ by a deep water buoy in the Indian Ocean has been carried out. Hourly time series data available for 240 hours in the month of May, 1999 were subjected to an auto-correlation analysis. The analysis indicates an exponential fall of the autocorrelation in the first few hours with a decorrelation time scale of about 6 hours. For a meaningful comparison between satellite derived products andin situ data, satellite data acquired at different time intervals should be used with appropriate ‘weights’, rather than treating the data as concurrent in time. This paper presents a scheme for temporal weighting using the auto-correlation analysis. These temporal ‘weights’ can potentially improve the root mean square (rms) deviation between satellite andin situ measurements. A case study using the TRMM Microwave Imager (TMI) and Indian Ocean buoy wind speed data resulted in an improvement of about 10%.     

Inorganic arsenic sorption by drinking-water treatment residual-amended sandy soil: effect of soil solution chemistry

Previous studies in our laboratory have demonstrated that drinking-water treatment residuals are effective sorbents of arsenic V. However, the effect of soil solution chemistry on arsenic V sorption by drinking-water treatment residuals-amended soils remains to be explored. The current study uses a batch incubation experimental set up to evaluate the effect of soil solution pH, competing ligands, and complexing metal on arsenic V sorption by a sandy soil (Immokalee series) amended with two rates (25 and 50 g kg^?1) of aluminum and iron-based drinking-water treatment residuals. Experiments were conducted at three initial arsenic loads (125, 1,875, 3,750 mg kg^?1) and a constant solid: solution ratio of 200 g L^?1. An optimum equilibration time of 8 days, obtained from kinetic studies, was utilized for sorption experiments with both aluminum and iron drinking-water treatment residual-amended soil. Presence of phosphate decreased arsenic V sorption by both aluminum and iron drinking-water treatment residual amended soils, with a strong dependence on pH, drinking-water treatment residual types, drinking-water treatment residual application rates, and phosphate concentrations. Addition of sulfate had no effect on arsenic V sorption by aluminum or iron drinking-water treatment residual-amended soil. A complementing effect of calcium on arsenic V sorption was observed at higher pH. Results elucidating the effect of soil solution chemistry on the arsenic V sorption will be helpful in calibrating drinking-water treatment residual as a sorbent for remediation of arsenic-contaminated soils.     

Assessment of Vulnerability of Rock Slope Considering Material and Seismic Variability

The Ghawar anticline (GA) is the super-giant anticline belonging to a set of giant anticlines called the Rayn anticlines (RA) developed in the Eastern Province (EP), Saudi Arabia. The RA is situated within the Arabian block microplate forming the distant foreland of the Zagros. For the first time, using the ‘Reviewed ISC Earthquake Catalogue’ for the period of 1970-2010, it is demonstrated that the EP crust is seismogenic down to a depth of ～15 km or more and has a typical surface width of ～220 km; this width is ostensibly six-times wider than that of GA. The Saudi Geological Survey (SGS) Earthquake Network Catalogue is utilized to study local seismicity. The GA is locally seismically active such that 826 events have occurred during the period of 2005-2010, with a maximum magnitude of ML 4.24. Magnitude completeness (Mc) analysis, based on the assumption of self-similarity, suggests that all local earthquakes above a cut-off magnitude of ³2.7 have been detected in EP. Certain basic estimates on the average depth of origin of the induced events and histogram plot on the frequency of induced and ambient (natural) seismicity are illustrated. The induced events came almost in equal proportions from the Uthmaniyah-Hawaiyah and Haradh production divisions belonging to the central and southern oil/gas Fields in GA. Poroelastic parameters of the reservoir are reviewed with respect to the induced seismicity. Focal-depth distribution of events along the strike direction of seismic zones follows the ‘En-Nala axis’ in the GA and is used, together with ISC data, to broadly define the seismogenic crust from a 3D-perspective. Seismic activity below both production divisions is supposedly triggered by hydrocarbon fluid-extraction; locally triggered seismicity shows better correlation to mutually opposite reverse faults transgressing the Haradh and Uthmaniyah-Hawaiyah production divisions under the influence of regional compressive stress oriented along N40°E. Results from four composite focal mechanism solutions also support this contention.     

Antioxidant Enzymes Response in Vetiver Grass: A Greenhouse Study for Chelant‐Assisted Phytoremediation of Lead‐Contaminated Residential Soils

In a previous study we have demonstrated the suitability of using vetiver grass (Vetiveria zizanioides L.) for the phytostabilization of lead‐based paint contaminated residential soils. Vetiver did not show any growth retardation or toxicity symptoms despite high soil Pb levels. Antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) reportedly allow plants to combat metal stress. Thus, we hypothesized that in vetiver, these antioxidant enzymes can play an important role in combating Pb induced stress, and that chelant‐bound Pb is less toxic to vetiver compared to free Pb in soil. The response of antioxidant enzymes was studied in vetiver grass grown in Pb paint‐contaminated residential soils collected from San Antonio, Texas and Baltimore, Maryland. Chelating agents such as ethylenediaminetetraacetic acid (EDTA) and ethylenediaminedisuccinic acid (EDDS) were used to mobilize Pb from bound fractions to the labile pool, facilitating Pb uptake by vetiver. Although the Pb concentration in vetiver from these treatments was significantly higher than those grown in the absence of a chelant, the antioxidant enzymes activities were lower compared to the latter. Antioxidant enzymes activity of vetiver plants grown in the presence of chelants is lower compared to those in without chelant treatment, while they tended to increase with dose in treatments with varying chelant concentrations. Data obtained support the proposed hypothesis.     

Seismic behavior of batter pile groups embedded in liquefiable soil

A comparative study of the seismic performance of 2×1 pile groups considering different degrees of batter(0° for vertical, 10° and 20°) embedded in single homogeneous liquefiable sand through fully coupled three-dimensional dynamic analyses is presented. The effects of inertial interaction are considered with structures having two different periods. The performance of pile groups is investigated for the fixed and pinned pile to cap connections for both floating and end bearing types of pile groups. Slenderness ratios of piles were also varied to enable a comprehensive understanding. Investigations have been carried out for three earthquake motions having varied dominant frequencies. It is observed that batter pile groups in liquefiable soils provide beneficial effects on piles and superstructure responses for both fixed and pinned head pile to cap connections for long period structures. However, for short period structures, a beneficial effect is most evident for fixed head connection.     

Remnants of vertical and lateral migration of the entrapped volatiles and gases in the Deccan Trap basalts at Bhaja,Maval Taluka of Pune district,Maharashtra

The present paper records some of the remnant vertical and horizontal to sub-horizontal gas migration channels in the Deccan Trap basalts from the vertical escarpment face at Bhaja Caves. These could have developed during the eruption, migration, inflation and overriding of the basaltic lava flows. The accumulated entrapped gases and volatiles of the lower flows migrated vertically and laterally into offshoots along the upper contacts or within the flow itself. In most cases, the vesicles are found to be empty as well as filled with the secondary minerals.