Effect of pore connectivity on reflection amplitudes of an inhomogeneous wave in a composite porous solid saturated by two immiscible fluids     

Neeru Bala  Ashish Arora 《Journal of Earth System Science》2018,127(4):59

Present paper aims to study the phenomenon of reflection and transmission when an inhomogeneous wave strikes some discontinuity in a composite porous medium saturated by two immiscible viscous fluids. The incident wave splits into six reflected and six transmitted waves at the interface. All reflected and transmitted waves are inhomogeneous in nature with different directions of propagation vector and attenuation vector. A dimensionless parameter \(\varsigma \in [0, 1]\) is introduced to represent the extent of connection among the pores at the interface. Expression of Umov–Poynting vector is derived to obtain energy flux vector. Continuity of energy flux vector at the interface gives the required boundary conditions for the system. Connecting parameter \(\varsigma \) is also employed in boundary conditions to model the partial connection of pores at the interstices of two media. For numerical discussion we consider a porous medium composed of sandstone and ice, saturated with oil and water. The effect of parameter \(\varsigma \) and angle of incidence is determined numerically on the amplitude and the energy ratios of reflected and transmitted waves.  相似文献   

Use of site amplification and anelastic attenuation for the determination of source parameters of the Sikkim earthquake of September 18, 2011, using far-field strong-motion data     

A. Joshi  Parveen Kumar  Sandeep Arora 《Natural Hazards》2014,70(1):217-235

An earthquake of magnitude 6.9 (M _w) occurred in the Sikkim region of India on September 18, 2011. This earthquake is recorded on strong-motion network in Uttarakhand Himalaya located about 900 km away from the epicenter of this earthquake. In this paper acceleration record from six far-field stations has been used to compute the source parameters of this earthquake. The acceleration spectra of ground motion at these far-field stations are strongly affected by both local site effects and near-site anelastic attenuation. In the present work the spectrum of S-phase recorded at these far-field stations has been corrected for anelastic attenuation at both source and site and the site amplification terms. Site amplifications at different stations and near-site shear wave attenuation factor have been computed by the technique of inversion of acceleration spectra given by Joshi et al. (Pure Appl Geophys 169:1821–1845, 2012a). For estimation of site amplification and shear wave quality factor [Q _β (f)] at the recording sites, ten local events recorded at various stations between July 2011 and December 2011 have been used. The obtained source spectrum from acceleration records is compared with the theoretical source spectrum defined by Brune (J Geophys Res 76:5002, 1970) at each station for both horizontal components of the records. Iterative forward modeling of theoretical source spectrum gives the average estimate of seismic moment (M _o), source radius (r _o) and stress drop (Δσ) as (3.2 ± 0.8) × 10²⁶ dyne cm, 13.3 ± 0.8 km and 59.2 ± 8.8 bars, respectively, for the Sikkim earthquake of September 18, 2011.  相似文献   

The effect of the variability of wind forcing on ENSO simulation in an OGCM: case of canonical and protracted event     

Arora  Anika 《Theoretical and Applied Climatology》2022,147(1-2):265-281

Theoretical and Applied Climatology - This study is an attempt to understand the onset and the evolution of canonical (typical length ~ 18–24 months; CE) and protracted...  相似文献   

Bottom Boundary Layer Characteristics in the Hooghly Estuary Under Combined Wave-Current Action     

Chitra Arora  B. Prasad Kumar  Indu Jain  Ashoke Bhar  A. C. Narayana 《Marine Geodesy》2013,36(2-3):261-281

The development of a theoretical model for estimating bottom boundary layer characteristics in the Hooghly estuary, located in the east coast of India, under combined effects of waves and currents is reported. Three numerical models, viz a depth averaged hydrodynamic model, SWAN wave model, and bottom boundary layer model, were integrated. In the bottom boundary layer parameters, maximum bottom stress, effective friction factor, and near-bed velocity both during ebb and flood phases of the tidal forcing are investigated and validated for the Haldia channel. The close match seen from results signifies applicability of this model for entire Hooghly basin.  相似文献   

On the Dynamics of the Seasonal Components of Induced Seismicity in the Koyna–Warna Region,Western India     

V. B. Smirnov  V. O. Mikhailov  A. V. Ponomarev  K. Arora  R. K. Chadha  D. Srinagesh  M. G. Potanina 《Izvestiya Physics of the Solid Earth》2018,54(4):632-640

The spatial and time dynamics are analyzed for the seasonal components of induced seismicity in the Koyna–Warna region of Western India. The peculiarities of the variations in these components are compared to the changes in the local tectonic regime inferred from the focal mechanism data of the earthquakes. Based on this, the hypotheses about the probable nature of the dynamics in the seasonal components of seismicity are suggested. It is noted that the variations in the seasonal seismic activity after the impoundment of the Koyna reservoir in the north are caused by the spatial migration of the induced seismicity and activation of the normal faults in the south. It is hypothesized that the process of fracture migration from the north to the south at this stage advanced the diffusion of the fluid from the Koyna reservoir, and as the water front reached the southern zone of normal faulting, this caused reactivation of the seasonal seismicity. An explanation is suggested for the stronger response of the seasonal activity in the region of Warna reservoir compared to the Koyna area: in contrast to Koyna, filling the Warna reservoir was geographically close to the area of activated seismicity. It is shown that the localization and sizes of the areas of the instantaneous and delayed components in the seasonal activity of the induced seismicity are determined by the localization and sizes of the areas of high stresses created by the increase in the pore pressure in highly permeable fault zones.  相似文献   

Comparison of Electrostatic and Non‐Electrostatic Models for U(VI) Sorption on Aquifer Sediments          下载免费PDF全文

Bhavna Arora  James A. Davis  Nicolas F. Spycher  Wenming Dong  Haruko M. Wainwright 《Ground water》2018,56(1):73-86

A non‐electrostatic generalized composite surface complexation model (SCM) was developed for U(VI) sorption on contaminated F‐Area sediments from the U.S. Department of Energy Savannah River Site, South Carolina. The objective of this study was to test if a simpler, semi‐empirical, non‐electrostatic U(VI) sorption model (NEM) could achieve the same predictive performance as a SCM with electrostatic correction terms in describing U(VI) plume evolution and long‐term mobility. One‐dimensional reactive transport simulations considering key hydrodynamic processes, Al and Fe minerals, as well as H⁺ and U surface complexation, with and without electrostatic correction terms, were conducted. The NEM was first calibrated with laboratory batch H⁺ and U(VI) sorption data on F‐Area sediments, and then the surface area of the NEM was adjusted to match field observations of dissolved U(VI). Modeling results indicate that the calibrated NEM was able to perform as well as the previously developed electrostatic model in predicting the long‐term evolution of H⁺ and U(VI) at the site, given the variability of field‐site data. The electrostatic and NEM models yield somewhat different results for the time period when basin discharge was active; however, it is not clear which modeling approach may be better to model this early time period because groundwater quality data during this period were not available. A key finding of this study is that the applicability of NEM (and thus robustness of its predictions) to the field system evolves with time and is strongly dependent on the pH range that was used to develop the model.  相似文献   

Changing river temperatures in northern Germany: trends and drivers of change          下载免费PDF全文

Roshni Arora  Klement Tockner  Markus Venohr 《水文研究》2016,30(17):3084-3096

Climate change is one of the main drivers of river warming worldwide. However, the response of river temperature to climate change differs with the hydrology and landscape properties, making it difficult to generalize the strength and the direction, of river temperature trends across large spatial scales and various river types. Additionally, there is a lack of long‐term and large‐scale trend studies in Europe as well as globally. In this study, we investigated the long‐term (25 years; 132 sites) and the short‐term (10 years; 475 sites) river temperature trends, patterns and underlying drivers within the period 1985–2010 in seven river basins of Germany. The majority of the sites underwent significant river warming during 1985–2010 (mean warming trend: 0.03 °C year^?1, SE = 0.003), with a faster warming observed during individual decades (1985–1995 and 2000–2010) within this period. Seasonal analyses showed that, while rivers warmed in all seasons, the fastest warming had occurred during summer. Among all the considered hydro‐climatological variables, air temperature change, which is a response to climate forcing, was the main driver of river temperature change because it had the strongest correlation with river temperature, irrespective of the period. Hydrological variables, such as average flow and baseflow, had a considerable influence on river temperature variability rather than on the overall trend direction. However, decreasing flow probably assisted in a faster river temperature increase in summer and in rivers in NE basins (such as the Elbe basin). The North Atlantic Oscillation Index had a greater significant influence on the winter river temperature variability than on the overall variability. Landscape and basin variables, such as altitude, ecoregion and catchment area, induced spatially variable river temperature trends via affecting the thermal sensitivity of rivers, with the rivers in large catchments and in lowland areas being most sensitive. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Rayleigh wave dispersion equation for a layered spherical earth with exponential function solutions in each shell     

Swarn Arora  S. N. Bhattacharya  M. L. Gogna 《Pure and Applied Geophysics》1996,147(3):515-536

We consider the second-order differential equations ofP-SV motion in an isotropic elastic medium with spherical coordinates. We assume that in the medium Lamé's parameters , r ^p and compressional and shear-wave velocities , r, wherer is radial distance. With this regular heterogeneity both the radial functions appearing in displacement components satisfy a fourth-order differential equation which provides solutions in terms of exponential functions. We then consider a layered spherical earth in which each layer has heterogeneity as specified above. The dispersion equation of the Rayleigh wave is obtained using the Thomson-Haskel method. Due to exponential function solutions in each layer, the dispersion equation has similar simplicity, as in a flat-layered earth. The dispersion equation is further simplified, whenp=–2. We obtain numerical results which agree with results obtained by other methods.  相似文献   

Benthic coverage and bottom topography of coral reef environment over Pirotan reef,Gulf of Kachchh region,India     

Mohit Arora  Nandini Ray Chaudhury  Ramesh Chander Patel 《国际地球制图》2019,34(10):1089-1097

Remote sensing measurements in coral reef environments commonly confront the problem of overlying atmosphere and modification of spectral signal due to water column over the bottom substrates. In order to correct these problems, hyperspectral observations offer an advantage over multispectral observations. Airborne hyperspectral remote sensing data from Airborne Visible Infrared Imaging Spectrometer- Next Generation (AVIRIS-NG) sensor was acquired during low tidal condition on 14 February 2016 at Pirotan reef, Gulf of Kachchh region, India. The objective of this study is to map benthic coverage and bottom topography over Pirotan reef. The methodology involved atmospheric correction, simultaneous retrieval of water parameters, bathymetry, water column correction and mapping. Atmospheric correction was performed by removing path radiance and aerosol contribution and dividing by atmospheric transmittance and incoming solar irradiance to obtain remote sensing reflectance. Model derived error minimization technique was used for simultaneous retrieval of water parameters and bathymetry. Derived water parameters were used to account for water column attenuation and retrieve concomitant true bottom signature.  相似文献   

Study of soil gas radon variations in the tectonically active Dharamshala and Chamba regions,Himachal Pradesh,India     

Arvind Kumar  Vishal Arora  Vivek Walia  Bikramjit Singh Bajwa  Surinder Singh  Tsanyao Frank Yang 《Environmental Earth Sciences》2014,72(8):2837-2847

Soil gas radon measurements were made in Chamba and Dharamshala regions of Himachal Pradesh, India, to study the correlation, if any, between the soil gas radon, radium activity concentration of soil, and the geology/active tectonics of the study region. Soil gas radon surveys were conducted around the local fault zones to check their tectonic activities using the soil gas technique. Soil gas radon activity concentration at thirty-five different locations in Dharamshala region has been found to be varying from 13.2 ± 1.5 to 110.8 ± 5.0 kBq m^?3 with a geometrical mean of 35.9 kBq m^?3 and geometrical standard deviation of 1.8. Radon activity concentration observed in the thirty-seven soil gas samples collected from the Chamba region of Himachal Pradesh varies from 5.2 ± 1.0 to 35.6 ± 2.5 kBq m^?3, with geometrical mean of 15.8 kBq m^?3 and geometrical standard deviation of 1.6. Average radium activity concentrations in thirty-four soil samples collected from different geological formations of Dharamshala region and Chamba region are found to be 40.4 ± 17 and 38.6 ± 1.7 Bq kg^?1, respectively. It has been observed that soil gas radon activity concentration has a wide range of variation in both Dharamshala and Chamba regions, while radium activity concentrations in soil samples are more or less same in both the regions. Moreover, soil gas radon activity concentration has a better positive correlation with the radium activity concentration in soil samples collected from Chamba region as compared to Dharamshala region.  相似文献