Wavefield reconstruction inversion for ambient seismic noise

<p>With the advent of large and dense seismic arrays, there is an opportunity for novel inversion methods that exploit the information captured by stations in close proximity to each other. Estimating surface waves dispersion is an interest for many geophysical applications using both active and passive seismic data. We present an inversion scheme that exploits the spatial and temporal relationships of the Helmholtz equation to estimate dispersion relations directly from surface wave ambient noise data, while reconstructing the full wavefield in space and frequency. The scheme is a PDE constrained inverse problem in which we jointly estimate the state and parameter spaces of the seismic wavefield. Key to the application on ambient seismic noise recordings is to remove the boundary conditions from the PDE constraint, which renders a conventional waveform inversion formulation singular. With synthetic acoustic and elastic data examples we show that using a variable projection scheme, we can iteratively update an initial estimate of the medium parameters and recover an estimate for the true underlying velocity field. Our examples show that the we can reconstruct the full wavefield even in the case of strong aliasing and irregular sampling. This works forms the basis for a new approach to inverting ambient seismic noise using large and dense seismic arrays.</p>

ASSESSMENT OF DOSE DUE TO AMBIENT Rn222/Rn220 PROGENY IN DIFFERENT DWELLINGS OF JAMMU AND KASHMIR STATE, INDIA

The un-attached part of radon (222Rn) progeny is one of the imperative variables for the definitive evaluation of the effective dose from the radon exposure perspective, and it might fluctuate enormously in various ecological conditions. Therefore, estimate dispersion of 222Rn/220Rn progeny, un-attached part and aerosol concentration was estimated in an indoor domain of Jammu and Kashmir State, India utilizing progeny deposition based sensors. Distinctive sorts of residence were picked up for this exploratory examination and maximum 222Rn and thoron (220Rn) descendants concentration was found in working environments or workplaces when contrasted from other abodes because of low ventilation rate. The average evaluated portions of an unattached for 222Rn and 220Rn are 0.29 and 0.26 and in addition, observed to be most extreme in work environments. The age-dependent dose has furthermore been determined utilizing attached and un-attached 222Rn/220Rn progeny concentrations. The dose to trachea-bronchial region and aerosol concentrations has additionally been estimated.

Hydraulic Conductivity of Sandy Soil with Varying Grain Size

A concept of mean particle size and size factor is presented in this paper and an attempt is made to relate the hydraulic conductivity to mean particle size, taking into account the optimum moisture content and maximum dry density. The distribution of particle size has a significant effect on hydraulic conductivity. It is possible to determine the mean particle size and size factor from the gradation curve. For the purpose of experimental analysis, three samples of soils were collected, local river sand available in market, coarse sand1.18mm sieve and quarry dust. For determining the hydraulic conductivity a constant head permeability test is conducted. A few exact conditions to compute water powered conductivity utilizing grain estimate dispersion of unconsolidated spring materials have been assessed in this examination. Evaluating examination of soil tests extricated from the test openings during ground water examination venture was performed to decide their arrangement and molecule measure dispersion attributes, from which pressure driven conductivities were figured. In particular, every single exact equation are to be utilized carefully inside the space of appropriateness

The Effect of Car Free Day (CFD) on Pollutant Emissions at Alternative Roads (Case Study: RE Martadinata Street, Bogor City)

Car Free Day (CFD) is a social campaign aimed to reduce the dependence of people on vehicle uses, which occurs once per week in Bogor. The idea intends to decrease the vehicle emissions. However, CFD is often to cause a new problem like the congestions, which are found on the nearby alternative roads, as happened in RE Martadinata Street, Bogor City. This study aims to compare the emission load and the concentrations of pollutants in ambient air during CFD (06.00-09.00 am) and non-CFD days in alternative road. We measured the following pollutants: CO, HC, NOx, PM10 and SO2. This research first applied Fixed-Box Model to estimate concentration of pollutants, then we used the Finite Length Line Source (FLLS) to estimate dispersion of pollutants. The results showed that there was no substantial difference in pollutant emissions between CFD and non-CFD days. But if we separate between weekdays and weekend, our analysis revealed that emissions during the weekend are bigger than that of weekdays. This was consistent with an increase of number of vehicles during the weekends by 17.2%. Based on our analysis, motorcycle contributes to an increased of CO, HC, PM10 pollutants, whereas SO2 and NOx pollutants were generated by cars. Our findings suggest that a short time of CFD does not contribute a lot to reduce the emissions.

Combination of Active and Passive Seismic Analyses for Embankment Characterization

Rayleigh wave dispersion is intensively used to determine near surface of shear wave velocity (Vs). The method has been known as non-invasive techniques which is costly effective and efficient to characterize subsurface. Acquisition of the Rayleigh wave can be approached in two ways, i.e. passive and active. Passive seismic is accurate to estimate dispersion curve in low frequency, although it is not accurate for high frequency. While active seismic is vice versa of passive seismic. The high frequency of Rayleigh wave dispersion reflects to near surface and vice versa. Therefore, we used the combination of both passive and active seismic method to overcome the limitations of each method. The Vs which is resulted by inversion of the combining data gives accurate model if compared to log and standard penetration test (N-SPT) data. Further, the approach has been used to characterize LUSI (Lumpur Sidoarjo) embankments. The result shows that embankment material (0-12 m) has higher Vs than that lower embankment material.

Averaged changes in the orbital elements of meteoroids due to Yarkovsky-Radzievskij force

Yarkovsky-Radzievskij effect exceeds the Poynting-Robertson effect in the perturbing action on particles larger than 100 μm. We obtained formulae for averaged changes in a meteoroid's Keplerian orbital elements and used them to estimate dispersion in the Geminid meteoroid stream. It was found that dispersion in semi-major axis of the model shower increased nearly three times on condition that meteoroids rotation is fast, and the rotation axis is stable.

Aerosol bolus dispersion in acinar airways—influence of gravity and airway asymmetry

The aerosol bolus technique can be used to estimate the degree of convective mixing in the lung; however, contributions of different lung compartments to measured dispersion cannot be differentiated unambiguously. To estimate dispersion in the distal lung, we studied the effect of gravity and airway asymmetry on the dispersion of 1 μm-diameter particle boluses in three-dimensional computational models of the lung periphery, ranging from a single alveolar sac to four-generation (g4) structures of bifurcating airways that deformed homogeneously during breathing. Boluses were introduced at the beginning of a 2-s inhalation, immediately followed by a 3-s exhalation. Dispersion was estimated by the half-width of the exhaled bolus. Dispersion was significantly affected by the spatial orientation of the models in normal gravity and was less in zero gravity than in normal gravity. Dispersion was strongly correlated with model volume in both normal and zero gravity. Predicted pulmonary dispersion based on a symmetric g4 acinar model was 391 ml and 238 ml under normal and zero gravity, respectively. These results accounted for a significant amount of dispersion measured experimentally. In zero gravity, predicted dispersion in a highly asymmetric model accounted for ∼20% of that obtained in a symmetric model with comparable volume and number of alveolated branches, whereas normal gravity dispersions were comparable in both models. These results suggest that gravitational sedimentation and not geometrical asymmetry is the dominant factor in aerosol dispersion in the lung periphery.

Use of lookout watches over forest to estimate detection, dispersion and density of hornbills, Great Argus and diurnal raptors at Bala forest, Thailand, compared with results from in-forest line transects and spot maps

SummaryWe estimated detection, dispersion and density of 10 hornbill, one pheasant and nine diurnal raptor species at Bala forest, southern Thailand, throughout 2004. We conducted 620 1-h lookout watches over the forest canopy from 14 elevated locations along 13.1 km of paved road through Bala, during which we recorded all detections and movements of target species. For a further 619 h, we also recorded all in-forest detections of target species during excursions along and adjacent to the road. Our records covered all months of the year and hours of the day, enabling us to estimate seasonal and diurnal patterns of detection for each target species. We found significant seasonal and diurnal variation for all commoner species in rates of overall detection, visual versus aural detection, and vociferousness. We related most monthly variation to the timing of nesting and most hourly variation to aspects of the behavioural ecology of each species. We used three techniques to estimate dispersion and density for each species, two from lookouts based on our counts of individuals or breeding units per unit area observed, and one from spot maps of core breeding units within 500 m of the road. Differences in our estimates of density varied within and between species, but were mostly lowest for the mean number of individuals detected from lookouts and highest for the maximum of breeding units, whether from lookout detections or core area counts from spot maps. These ranges of densities and their variance indicate upper and lower estimates for each species, and the differences between them and other survey techniques were explicable partly by the behavioural ecology of each species or apparent changes in density. Our density estimates never exceeded the highest comparative estimates for target species or near relatives in other forest habitats, although few were available for diurnal raptors. We suggest that 1-h lookout watches over forest, where feasible, offer alternative and efficient estimates of detection, dispersion and density to conventional distance-sampling techniques conducted from within forest. They will achieve optimum accuracy when conducted during the most detectable periods for target species, particularly for obvious and sparsely dispersed bird species.