Automating adjoint wave-equation travel-time tomography using scientific workflow

Recent advances in commodity high-performance computing technology have dramatically reduced the computational cost for solving the seismic wave equation in complex earth structure models. As a consequence, wave-equation-based seismic tomography techniques are being actively developed and gradually adopted in routine subsurface seismic imaging practices. Wave-equation travel-time tomography is a seismic tomography technique that inverts cross-correlation travel-time misfits using full-wave Fréchet kernels computed by solving the wave equation. This technique can be implemented very efficiently using the adjoint method, in which the misfits are back-propagated from the receivers (i.e., seismometers) to produce the adjoint wave-field and the interaction between the adjoint wave-field and the forward wave-field from the seismic source gives the gradient of the objective function. Once the gradient is available, a gradient-based optimization algorithm can then be adopted to produce an optimal earth structure model that minimizes the objective function. This methodology is conceptually straightforward, but its implementation in practical situations is highly complex, error-prone and computationally demanding. In this study, we demonstrate the feasibility of automating wave-equation travel-time tomography based on the adjoint method using Kepler, an open-source software package for designing, managing and executing scientific workflows. The workflow technology allows us to abstract away much of the complexity involved in the implementation in a manner that is both robust and scalable. Our automated adjoint wave-equation travel-time tomography package has been successfully applied on a real active-source seismic dataset.     

Modeling of particle breakage in a smooth double roll crusher

A model has been developed to describe the breakage behavior of particle breakage in a smooth double roll crusher. In addition to this, an empirical relationship has been obtained between Hardgrove Grindability Index (HGI) of material and breakage parameters. The model uses matrix method of breakage process analysis. Experiments were carried out in a laboratory scale smooth double roll crusher using different materials. The model has been verified experimentally and gives product size distribution after breakage which matches with the experimental distribution well within the satisfactory range.     

A sewage and sludge treated lake and its impact on the environment, Mysore, India

Water, soil, suspended load and biomass samples were collected from a sewage and sludge treated lake (Lake Dalavayi) around Mysore, Karnataka, India. The polluted lake water is mainly used for irrigation and domestic purposes. The samples have been analysed for heavy metals (Cu, Cr, Co, Cd, Ni, Fe, Mn, V, Zn, Sr) and cations (Ca, Na, Mg) by Inductively Coupled Plasma Emission Spectrometer (ICP) model Labtam 8500. With the exception of water, all the matrices suspended particulate matter, lake bed sediment and biomass of the lake show high concentrations of heavy metals and cations when compared to the World Health Organization (WHO) standard, indicating metal toxicity in this lake. Additional inputs of soaps and detergents carried by sewage water are causing the eutrophication of the lake. Elevated levels of heavy metal toxicity, especially Co and Cd, are indicated by the bioindicator Eichornia cressepes (water hyacinth), which, using these metals as micronutrients, has grown luxuriously over the lake water, further augmenting the death of lifeforms in the lake.     

A Comparative Evaluation of the Geotechnical Index Properties of Clayey Sediments along the West Coast of India

Sediment core samples collected during geotechnical surveys along the West Coast of India in the near shore areas of Arabian Sea have generated data on the geotechnical index properties of clayey sediments up to nearly 5 m depth below seafloor. A comparative study of three sectors within themselves is attempted before carrying out a final evaluation between the sectors. Cohesive clayey sediments of Gujarat sector are comparable though widely variant in a few aspects; in the Maharashtra-Goa-Karnataka sector though, plasticity levels and clay type vary, and activity and consistency levels are quite similar. Though broadly comparable, the clayey sediments of Kerala-Tamilnadu sector have quite diverse characteristics that fail to conform to any particular pattern as each area has an exclusive set of geotechnical properties.     

A block Karhunen–Loève Transform based efficient lossy compression algorithm for optical remote sensing imagery

In present study, a block Karhunen–Loève Transform (KLT) based efficient lossy compression algorithm for optical remote sensing imagery is proposed. A Discrete Wavelet Transform (DWT) is performed on each band of the imagery to remove the spatial correlation. Each band of the imagery is decomposed into non-overlapping blocks of similar size and the transform coefficients of each block in the wavelet domain are treated as a single object. A rate-distortion optimization is introduced to perform rate allocation of multiple bands. Each band is partitioned into code-blocks. The embedded block coding with optimized truncation algorithm is executed on the code-blocks to produce final bit-stream. The complexity of the proposed algorithm is compared with global KLT-DWT. The result reports the complexity of JPEG 2000 (Part 1) is lowest with encoding time 114 ms as compared to global KLT-DWT (N = 1024), global DWT-KLT (N = 1024), block-based DWT-KLT (N = 512), block-based DWT-KLT (N = 256), block-based DWT-KLT (N = 128), block-based DWT-KLT (N = 64) and block-based DWT-KLT (N = 32).     

GIS-based MCDA–AHP modelling for avalanche susceptibility mapping of Nubra valley region,Indian Himalaya

Avalanches are behind the majority of fatalities and heavy damage to property in snow-covered mountainous terrain like Himalaya. Recognizing avalanche susceptible areas and publication of avalanche susceptibility maps assist decision-makers and planners to execute suitable measures to reduce the avalanche risk. The present study is an attempt to prepare an avalanche susceptibility map of the Nubra valley region using multi-criteria decision analysis–analytical hierarchy process model in GIS environment. The most prominent avalanche occurrence factors used in this model are slope, aspect, curvature, elevation, terrain roughness and ground cover. ASTER GDEM V2 and Landsat 8 satellite imagery were used to generate considered factors. For validation of the results, prediction rate/accuracy is calculated using the avalanche inventory map of documented avalanche locations. To calculate the prediction accuracy, area under the ROC curve (ROC-AUC) method has been used. The prediction accuracy of the validation results using ROC-AUC shows 91%.     

Study of stream temperature dynamics and corresponding heat fluxes within Miramichi River catchments (New Brunswick,Canada)

Water temperature is a key physical habitat determinant in lotic ecosystems as it influences many physical, chemical, and biological properties of rivers. Hence, a good understanding of the thermal regime of rivers and river heat fluxes is essential for effective management of water and fisheries resources. This study dealt with the modelling of river water temperature using a deterministic model. This model calculated the different heat fluxes at the water surface and from the streambed using different hydrometeorological conditions. The water temperature model was applied on two watercourses of different sizes and thermal characteristics, but within a similar meteorological region, namely, the Little Southwest Miramichi River and Catamaran Brook (New Brunswick, Canada). The model was also applied using microclimate data, i.e. meteorological conditions within the river environment (1–2 m above the water surface), for a better estimation of river heat fluxes. Water temperatures at different depths within the riverbed were also used to estimate the streambed heat fluxes. Results showed that microclimate data were essential to get accurate estimates of the surface heat fluxes. Results also showed that for larger river systems, the surface heat fluxes were generally the dominant component of the heat budget with a correspondingly smaller contribution from the streambed. As watercourses became smaller and groundwater contribution more significant, the streambed contribution became important. For instance, approximately 80% of the heat fluxes occurred at the surface for Catamaran Brook (20% from the streambed) whereas the Little Southwest Miramichi River showed values closer to 90% (10% from the streambed). As was reported in previous studies, the solar radiation input dominated the contribution to the heat gain at 63% for Catamaran Brook and 89% for Little Southwest Miramichi River. Copyright © 2011 John Wiley & Sons, Ltd.     

Delineation of fresh aquifers in tannery belt for sustainable development — A case study from southern India

The tannery effluents discharged by the existing units on either side of the Palar river at Ambur town (known for tannery industry), has resulted in vertical and lateral spread of pollution. The study area of 55.3 km² is situated on a granitic terrain of Archaean age with undulating topography and hillocks. The shallow aquifers, in flood plain and valley fills of the river are highly polluted (with EC: 15340 μS/cm) by tannery effluents making groundwater unfit for any use, hence the local population (20000) face health hazards and shortage of potable water. Hydrogeological, geophysical and in-situ groundwater quality measurement were carried out to demarcate fresh groundwater zones and to delineate lateral and vertical extent of pollution. The results show, brackish aquifer was characterized by low order of resistivity (<20 Ω-m) with a thickness of 8.5 to 28 m located in the flood plains, valley fills, and partially in hard rock formations, whereas the fresh water aquifer resistivity varying from 23 to 216 Ω-m in hard rock. Further, these results were correlated with the water quality data and Ground Penetrating Radar (GPR) signals. The integrated studies revealed that pollution due to tannery effluents has spread over an area of 33.4 km² (60.4 %) on either side of the river and only a small area of 21.9 km² (39.6 %) was identified as fresh groundwater zone, which has to be conserved and exploited in sustainable manner for future generations.     

Hyperspectral Radiometry to Characterise Dunite Alteration and Magnesite Deposits of Salem,South India

This work reports the results of insitu surveys, hyperspectral-radiometry and geochemistry for dunite-alteration and magnesite mapping in the Salem, southern India. Spectral parameters such as the strength of absorption in the 865 nm and 2,300 nm range for Fe²⁺ and CO3^2- respectively, and the position of absorption trough were derived from the laboratory spectra for 13 samples. It is observed that dunite alteration and conversion to magnesite produce measurable changes in the VIS-NIR-SWIR spectra due to a transition from the silicate-dominated rocky composition to carbonate-dominated industrial mineral composition. Relationship between the spectra and mineralogy suggests that we can identify the varieties of magnesite using hyperspectral radiometry.