A seismic event on August 20, 1983: double explosion or a single earthquake     

S. K. Arora  T. K. Basu 《Physics of the Earth and Planetary Interiors》1985,40(4):309-315

An interesting weak seismic event occurred on August 20, 1983 in the Caspian Sea region in southwestern U.S.S.R., which produced at Gauribidanur array two distinct seismic signals, viz. the leading P signal and a similar signal after an interval of nearly 12 s. Preliminary data corresponding to these two signals led to an initial assumption that the event was a double underground nuclear explosion. However, the focal depth of this event from P arrival-time data of 21 stations was found to be 45 km. Further processing of the Gauribidanur array seismograms confirmed that the second signal, detected exactly 11.85 s after the first arrival, was none other than the surface-reflected P pulse which lent excellent support to the source depth estimate. By using three discriminants, viz. signal complexity, third moment of frequency and relative efficiency of generation of core-reflected P, the event was objectively compared with 10 small presumed underground nuclear explosions in southwestern U.S.S.R. to conclude that the August 20, 1983 event was a shallow-focus small earthquake in the Caspian Sea area.  相似文献   

The two-component extreme value distribution for flood frequency analysis: Derivation of a new estimation method   总被引：1，自引：0，他引：1  

M. Fiorentino  K. Arora  V. P. Singh 《Stochastic Environmental Research and Risk Assessment (SERRA)》1987,1(3):199-208

The two component extreme value (TCEV) distribution has recently been shown to account for most of the characteristics of the real flood experience. A new method of parameter estimation for this distribution is derived using the principle of maximum entropy (POME). This method of parameter estimation is suitable for application in both the site-specific and regional cases and appears simpler than the maximum likelihood estimation method. Statistical properties of the regionalized estimation were evaluated using a Monte Carlo approach and compared with those of the maximum likelihood regional estimators.  相似文献   

Rock magnetism and palaeomagnetism of the Oddanchatram anorthosite, Tamil Nadu, South India   总被引：1，自引：0，他引：1  

K. V. V. Satyanarayana  Baldev R. Arora  A. S. Janardhan 《Geophysical Journal International》2003,155(3):1081-1092

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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   

On the photo-gravitational restricted four-body problem with variable mass     

Amit Mittal  Rajiv Agarwal  Md Sanam Suraj  Monika Arora 《Astrophysics and Space Science》2018,363(5):109

This paper deals with the photo-gravitational restricted four-body problem (PR4BP) with variable mass. Following the procedure given by Gascheau (C. R. 16:393–394, 1843) and Routh (Proc. Lond. Math. Soc. 6:86–97, 1875), the conditions of linear stability of Lagrange triangle solution in the PR4BP are determined. The three radiating primaries having masses \(m_{1}\), \(m_{2}\) and \(m_{3}\) in an equilateral triangle with \(m_{2}=m_{3}\) will be stable as long as they satisfy the linear stability condition of the Lagrangian triangle solution. We have derived the equations of motion of the mentioned problem and observed that there exist eight libration points for a fixed value of parameters \(\gamma (\frac{m \ \text{at time} \ t}{m \ \text{at initial time}}, 0<\gamma\leq1 )\), \(\alpha\) (the proportionality constant in Jeans’ law (Astronomy and Cosmogony, Cambridge University Press, Cambridge, 1928), \(0\leq\alpha\leq2.2\)), the mass parameter \(\mu=0.005\) and radiation parameters \(q_{i}, (0< q_{i}\leq1, i=1, 2, 3)\). All the libration points are non-collinear if \(q_{2}\neq q_{3}\). It has been observed that the collinear and out-of-plane libration points also exist for \(q_{2}=q_{3}\). In all the cases, each libration point is found to be unstable. Further, zero velocity curves (ZVCs) and Newton–Raphson basins of attraction are also discussed.  相似文献   

Elastic waves along a cylindrical borehole in a poroelastic medium saturated by two immiscible fluids     

Ashish Arora  S. K. Tomar 《Journal of Earth System Science》2007,116(3):225-234

The propagation of elastic waves along a cylindrical borehole filled with/without liquid and embedded in an infinite porous medium saturated by two immiscible fluids has been studied. The theory of porous media saturated by two immiscible fluids developed by Tuncay and Corapcioglu (1997) is employed. Frequency equations determining the phase velocity of axial symmetric waves are obtained. It is found that the surface waves along cylindrical borehole are dispersive. The dispersion equation of Rayleigh-type surface waves along the boundary of a poroelastic solid half-space saturated by two immiscible fluids is also obtained. Some special cases have been deduced and the dispersion curves are obtained numerically for a peculiar model. It is found that the density of fluids affects the Rayleigh mode.  相似文献   

Semi-annual modulation of earth's magnetic field in the equatorial electrojet region     

B.N. Bhargava  D.R.K. Rao  B.R. Arora 《Planetary and Space Science》1973,21(7):1251-1255

Autospectra in the 2–13 month range, computed from mean monthly horizontal intensity on quiet days at Trivandrum, situated close to the dip equator, suggest an exceedingly large semi-annual modulation of the field confined to an interval of about 5 hr centred at 1000 LT. The amplitude of the semi-annual oscillation at this station, derived from power density, is greater than 19 γ at 1000 LT. Between 1900 and 0500 LT, spectral lines, corresponding to a period of six months, are not observed above the continuum. Spectral densities from observations at two other electrojet stations in India, Kodaikanal and Annamalainagar, and at Alibag, outside the electrojet, establish the existence of an appreciable enhancement of the semi-annual oscillation of the field in the equatorial electrojet belt. Similar computations of spectra using observations on all days, however, suggest a secondary component in the evening sector. This component is not enhanced in the equatorial electrojet belt. It is concluded that while in low latitudes the daytime component is largely associated with the modulation of Sq currents, in the electrojet belt it appears to be due entirely to a semi-annual modulation of the equatorial electrojet. It is also concluded that the secondary component, observed in the evening sector in low latitude and equatorial stations, is associated purely with the modulation of the ring current by disturbance. The two components of the semi-annual variation observed at the Indian stations have also been noticed at several stations between geomagnetic latitudes N54.6° and S41.8°. It is also observed that the association of the semi-annual component with geomagnetic latitude is confined to the evening-night component.  相似文献   

Reactive transport codes for subsurface environmental simulation     

C. I. Steefel  C. A. J. Appelo  B. Arora  D. Jacques  T. Kalbacher  O. Kolditz  V. Lagneau  P. C. Lichtner  K. U. Mayer  J. C. L. Meeussen  S. Molins  D. Moulton  H. Shao  J. Šimůnek  N. Spycher  S. B. Yabusaki  G. T. Yeh 《Computational Geosciences》2015,19(3):445-478

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Utility of Hyperspectral Data for Potato Late Blight Disease Detection   总被引：1，自引：0，他引：1  

Shibendu Shankar Ray  Namrata Jain  R. K. Arora  S. Chavan  Sushma Panigrahy 《Journal of the Indian Society of Remote Sensing》2011,39(2):161-169

The study was carried out to investigate the utility of hyperspectral reflectance data for potato late blight disease detection. The hyperspectral data was collected for potato crop at different level of disease infestation using hand-held spectroradiometer over the spectral range of 325–1075 nm. The data was averaged into 10-nm wide wavebands, resulting in 75 narrowbands. The reflectance curve was partitioned into five regions, viz. 400–500 nm, 520–590 nm, 620–680 nm, 770–860 nm and 920–1050 nm. The notable differences in healthy and diseased potato plants were noticed in 770–860 nm and 920–1050 nm range. Vegetation indices, namely NDVI, SR, SAVI and red edge were calculated using reflectance values. The differences between the vegetation indices for plants at different levels of disease infestation were found highly significant. The optimal hyperspectral wavebands to discriminate the healthy plants from disease infested plants were 540, 610, 620, 700, 710, 730, 780 and 1040 nm whereas upto 25% infestation could be discriminated using reflectance at 710, 720 and 750 nm.  相似文献