Propagation of Love type waves in a non-homogeneous layer lying over a vertically semi-infinite homogeneous isotropic medium

Summary The aim of this paper is to study the propagation of love-type waves in a homogeneous half-space overlain by a heterogeneous crust with various types of heterogenety. Frequency equations are obtained in each of the cases and numerical calculations are done in some cases and the results thus obtained are compared with those done byJeffreys andMitra [3]²).     

GaRiRO: Gradient and residual integrated rank ordering of stations in rainfall monitoring network

This paper presents a new method that integrates gradient and residual values for rank ordering of stations in a monitoring network (GaRiRO). The innovation is derived from the fact that the parameter (dependent variable) gauged through the monitoring network is modelled using independent variables that influence its measured quantity. And the dependent variable exhibit non-stationary spatial gradient with respect to the independent variables, particularly in complex terrain. GaRiRO technique was developed to prioritize the rain gauge stations for optimizing the existing network and selection of the best locations for relocation or installation of gauges. Although initially aimed to assist hydrologists with a ranking scheme for rain gauge stations, it can be applied to any environmental, meteorological or hydro-meteorological monitoring network. The new procedure is based on deriving gradient and residual value at each station by modeling the spatial relationship of dependent-independent variable using geographically weighted regression (GWR) technique. For the prospective stations with no record, the gradient value is estimated using GWR model and the residual value is derived from the residual map generated by applying kriging technique on the residual derived at all gauged locations. The method combines the decision factor with analytical strength of GIS for prioritizing the stations which results in limited number of trials for installation or relocation of gauges to yield optimized network configuration.     

Behaviour of radiogenic Pb in zircon during ultrahigh-temperature metamorphism: an ion imaging and ion tomography case study from the Kerala Khondalite Belt,southern India

Zircon crystals from a locally charnockitized Paleoproterozoic high-K metagranite from the Kerala Khondalite Belt (KKB) of southern India have been investigated by high-spatial resolution secondary ion mass spectrometry analysis of U–Th–Pb and rare earth elements (REE), together with scanning ion imaging and scanning ion tomography (depth-profiled ion imaging). The spot analyses constrain the magmatic crystallization age of the metagranite to ca. 1,850 Ma, with ultrahigh-temperature (UHT) metamorphism occurring at ca. 570 Ma and superimposed charnockite formation at ca. 520–510 Ma, while the ion imaging reveals a patchy distribution of radiogenic Pb throughout the zircon cores. Middle- to heavy-REE depletion in ca. 570 Ma zircon rims suggests that these grew in equilibrium with garnet and therefore date the UHT metamorphism in the KKB. The maximum apparent ²⁰⁷Pb/²⁰⁶Pb age obtained from the unsupported radiogenic Pb concentrations is also consistent with formation of the Pb patches during this event. The superimposed charnockitization event appears to have caused additional Pb-loss in the cores and recrystallization of the rims. The results of depth-profiling of the scanning ion tomography image stack show that the Pb-rich domains range in size from <5 nm to several 10 nm (diameter if assumed to be spherical). The occurrence of such patchy Pb has previously been documented only from UHT metamorphic zircon, where it likely results from annealing of radiation-damaged zircon. The formation of a discrete, heterogeneously distributed and subsequently immobile Pb phase effectively arrests the normal Pb-loss process seen at lower grades of metamorphism.     

Effect of biochar on desiccation of marine soils under constant and cyclic temperatures

Acta Geotechnica - Biochar has recently been gaining increasing attention as a stable and sustainable soil amendment material. However, the effect of biochar amendment on the desiccation behaviour...     

Evaluation of seismic events detection algorithms

Identification of seismic events from continuously recorded seismic data in real-time through a Digital Seismic Data Recording system is a difficult task. Despite the vast amount of research in this field, the signal processing and event parameters discrimination algorithms have not yet fully come of age. Presently, we have a wide spectrum of trigger algorithms, ranging from a very simple amplitude threshold type to the sophisticated ones based on pattern recognition approaches. Some of the other approaches use adaptive technique and neural network methods. Researchers are continuously making efforts for the development of algorithms using various techniques, which produce minimum false trigger. Some approaches have been reported which are accurate for detecting first phase of events and take minimum possible computational time. In this paper several approaches for detecting event signals in background noise are presented and their precision evaluation is discussed.     

Attenuation Tomography Based on Strong Motion Data: Case Study of Central Honshu Region, Japan

Three-dimensional frequency dependent S-wave quality factor (Q_β(f)) value for the central Honshu region of Japan has been determined in this paper using an algorithm based on inversion of strong motion data. The method of inversion for determination of three-dimensional attenuation coefficients is proposed by Hashida and Shimazaki (J Phys Earth. 32, 299–316, 1984) and has been used and modified by Joshi (Curr Sci. 90, 581–585, 2006; Nat Hazards. 43, 129–146, 2007) and Joshi et al. (J. Seismol. 14, 247–272, 2010). Twenty-one earthquakes digitally recorded on strong motion stations of Kik-net network have been used in this work. The magnitude of these earthquake ranges from 3.1 to 4.2 and depth ranging from 5 to 20 km, respectively. The borehole data having high signal to noise ratio and minimum site effect is used in the present work. The attenuation structure is determined by dividing the entire area into twenty-five three-dimensional blocks of uniform thickness having different frequency-dependent shear wave quality factor. Shear wave quality factor values have been determined at frequencies of 2.5, 7.0 and 10 Hz from record in a rectangular grid defined by 35.4°N to 36.4°N and 137.2°E to 138.2°E. The obtained attenuation structure is compared with the available geological features in the region and comparison shows that the obtained structure is capable of resolving important tectonic features present in the area. The proposed attenuation structure is compared with the probabilistic seismic hazard map of the region and shows that it bears some remarkable similarity in the patterns seen in seismic hazard map.     

Overview of the potential of microalgae for CO2 sequestration

An economic and environmentally friendly approach of overcoming the problem of fossil CO₂ emissions would be to reuse it through fixation into biomass. Carbon dioxide (CO₂), which is the basis for the formation of complex sugars by green plants and microalgae through photosynthesis, has been shown to significantly increase the growth rates of certain microalgal species. Microalgae possess a greater capacity to fix CO₂ compared to C₄ plants. Selection of appropriate microalgal strains is based on the CO₂ fixation and tolerance capability together with lipid potential, both of which are a function of biomass productivity. Microalgae can be propagated in open raceway ponds or closed photobioreactors. Biological CO₂ fixation also depends on the tolerance of selected strains to high temperatures and the amount of CO₂ present in flue gas, together with SO_x and NO_x. Potential uses of microalgal biomass after sequestration could include biodiesel production, fodder for livestock, production of colorants and vitamins. This review summarizes commonly employed microalgal species as well as the physiological pathway involved in the biochemistry of CO₂ fixation. It also presents an outlook on microalgal propagation systems for CO₂ sequestration as well as a summary on the life cycle analysis of the process.     

Evaluation of the exact conditional spectrum and generalized conditional intensity measure methods for ground motion selection

Two existing, contemporary ground motion selection and modification procedures – (i) exact conditional spectrum (CS‐exact) and (ii) generalized conditional intensity measure (GCIM) – are evaluated in their ability to accurately estimate seismic demand hazard curves (SDHCs) of a given structure at a specified site. The amount of effort involved in implementing these procedures to compute a single SDHC is studied, and a case study is chosen where rigorous benchmark SDHCs can be determined for evaluation purposes. By comparing estimates from ground motion selection and modification procedures with the benchmark, we conclude that estimates from CS‐exact are unbiased in many of the cases considered. The estimates from GCIM are even more accurate, as they are unbiased for most – but not all – of the cases where estimates from CS‐exact are biased. We find that it is possible to obtain biased SDHCs from GCIM, even after employing a very diverse collection of intensity measures to select ground motions and implementing its bias‐checking feature, because it is usually difficult to identify intensity measures that are truly ‘sufficient’ for the response of a complex, multi‐degree‐of‐freedom system. Copyright © 2015 John Wiley & Sons, Ltd.