Localization of water bearing fractured zones in a hard rock area using integrated geophysical techniques in Andhra Pradesh,India   总被引：1，自引：0，他引：1  

Sushobhan?DuttaEmail author  N.?S.?Krishnamurthy  T.?Arora  V.?A.?Rao  S.?Ahmed  J.?M.?Baltassat 《Hydrogeology Journal》2006,14(5):760-766

Knowledge of the existence of fracture zones, their extent, intensity and direction is very useful for assessing groundwater in hardrock regions and in this context geophysical methods are widely accepted as a powerful means of study. In the modern era of exploration, application of the Resistivity Imaging technique gives a new opportunity for groundwater study in hardrock regions. Exploration surveys were conducted at one of the important sites in Maheshwaram watershed, Andhra Pradesh, India with a multielectrode resistivity imaging system. To reduce the ambiguity of geophysical interpretation some complementary geophysical studies like ground Magnetic and VLF were also carried out.A number of 2D resistivity images were prepared in a grid pattern, which clearly show the weathered and fractured zones in different parts of the study area. With the help of all 2D profiles a quasi-3D image has been created, which indicates the orientation and extension of the fracture zone in a horizontal as well as vertical direction in the study area. Strong agreement exists among the anomalies identified using the ground magnetic, VLF and resistivity imaging methods. The litholog data available in the study area also helps to interpret geophysical results to find a potential groundwater bearing zone in that area.  相似文献   

Lineament fabric from airborne LiDAR and its influence on triggered earthquakes in the Koyna-Warna region,western India     

Kusumita Arora  R. K. Chadha  Y. Srinu  Adrien Selles  Srinagesh Davuluri  Vladimir Smirnov  Alexander Ponomarev  V. O. Mikhailov 《Journal of the Geological Society of India》2017,90(6):670-677

We present the results of the first airborne LiDAR survey flown in the Koyna-Warna region and examine the relationship between the lineament fabric and the ongoing seismicity in the region. Our studies reveal that earthquakes of M≥4.0 for the period 1968 to 2016 are strongly correlated with a 10 km wide N-S fracture zone, which not only represents the surface expression of seismically active basement faults, but also act as conduits for water percolation between the Koyna and Warna reservoirs. A decreasing trend in the annual distribution of earthquakes was observed from 1985. A new burst of seismic activity in 1993 followed the impoudment of the Warna reservoir. We report a change in annual seismicity pattern, where seismicity peaks during September and December in the pre-Warna period, with a new peak emerging during March-April subsequent to the impoundment of Warna reservoir. A model is proposed to explain the seismicity along dominant N-S lineaments and the impact of Warna reservoir impounding which altered the hydrogeologic regime in the region.  相似文献   

Signal-to-noise-ratio improvement of a linear seismic array     

J. R. Arora 《Pure and Applied Geophysics》1968,69(1):25-45

Summary The aim of this paper is improvement in signal-to-noise-ratio (SNR) through the use of a linear seismic array. The noise is considered to be composed of a coherent part with nature similar to that of incoming signals and an incoherent part having a constant power all across the array. All possible values of seismometer positions which minimise the coherent noise power are derived. Advantages of the delayed-summation processing technique, in so far as it enables us to obtain superior values of the signal-to-noise-ratio improvement, and furnishes unique values of signal wavelengths and signal amplitudes as compared to the simple-summation technique which gives relatively inferior values ofSNR, and enables us to obtain the signal wave-lengths as solutions of a trigonometric equation are brought out analytically. Being suitable for field work due to its simple nature, the simplesummation technique is studied in detail. Upper limit on the value of array aperture for actual improvement of all the expected signals are found. Requirements to be met for achieving the optimum value of theSNR improvement are deduced.  相似文献   

A magnetometer array study in northwest India     

F.E.M. Lilley  B.P. Singh  B.R. Arora  B.J. Srivastava  S.N. Prasad  M.N. Sloane 《Physics of the Earth and Planetary Interiors》1981,25(3):232-240

A magnetometer array study has been carried out in northwest India, from Rajasthan across the Indo-Gangetic Plain into the Himalayan foothills. Over the three months of operation, a wide variety of natural geomagnetic events has been recorded. The analysis of a simple substorm, polarized just west of north, shows a strong anomaly in the form of a reversal of the vertical component of the fluctuation, both in the Himalayan foothills and on the Ganga Plain.The magnetic fluctuations pattern observed is most directly interpreted in terms of a path of concentrated current flow in the Earth, striking across the Himalaya. It is evidently aligned with the Aravalli belt which outcrops further south, and may indicate that some geological structure in the sub-basement is of abnormally high electrical conductivity. The path of such a current concentration across the foothills raises the question whether some transverse structure in the Himalaya is not acting as a bridge to Peninsular India for current induced in the Tibetan plateau to the northeast.  相似文献   

Hydromagnetic flow between two parallel planes,one oscillating and the other fixed     

P. R. Gupta  K. L. Arora 《Pure and Applied Geophysics》1974,112(2):498-505

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Choice of a teleseismicP-wave travel-time model and the associated source corrections     

S. K. Arora  C. A. Krishnan 《Pure and Applied Geophysics》1972,101(1):74-89

Summary Among various trial models ofP-wave travel times, there exists at least one model which best predicts the times of first arrivals from a certain region at a set of recording stations even if no attempt is made to correct the travel-time standards against known station errors and source bias. In teleseismic distance range (25°100°) and surface-focus case, the possibility of statistically establishing which of the twoP models, viz. Jeffreys-Bullen and Herrin, is more appropriate for each of the four source regions, viz. Southern Nevada, Aleutian Islands, Eastern Kazakh and Novaya Zemlya, is discussed in this paper. Data corresponding to a set of underground explosions from these regions form the basis of such an analysis. The Herrin model is found to be better applied to Aleutian Islands region while the Jeffreys-Bullen model seems more appropriate for each of the remaining three regions.As a result of the study of the travel-time models, numerical estimates of space and time corrections pertaining to the above mentioned regions, based on the most appropriate model and directly applicable to the computed source parameters, are obtained. On applying these corrections, the size of source location error ellipse and the source-time error reduce to very small representative values, viz. 4 km×6 km (area 75 km²) and ±0.2 sec respectively.  相似文献   

Space-time seismicity and earthquake swarms: Certain observations along the slow-spreading mid-Indian Ocean ridges     

M. Radha Krishna  S. K. Arora 《Journal of Earth System Science》1998,107(2):161-173

The slow spreading mid-Indian Ocean ridge system containing the Carlsberg, Central and Southwest Indian ridges is seismically very active. In the present study, a detailed analysis has been carried out of the data of earthquake sources along different ridge segments in order to investigate the spatial and temporal clustering patterns and to evaluate crustal processes related to the swarm occurrences along these ridges. The spatial and temporal clustering pattern of the recent earthquakes (1980–1990) pertaining to nine major spreading segments and eight fracture zones suggests that the events cluster in greater proportion along the spreading segments than along the fracture zones. We performed a systematic search of earthquake catalogue during the period 1964–1990 by examining the spatio-temporal hypocentral clusters in order to identify the swarm occurrences along these ridges. The search included eighteen prominent sequences, of which, thirteen were earthquake swarms. Except two, all other swarms were found to be occurring mainly on the spreading segments. The maximum magnitude observed in these swarms is m_b = 5.4 and have many events predominantly showing normal faulting mechanisms. The spatial disposition and temporal activity of the events in swarms is much similar to the foreshock-mainshock-aftershock sequences observed along the spreading rift valley zones. These characteristics help us to support that swarms along the slow spreading mid-Indian Ocean ridges are the result of extensional tectonic activity, leading to the development of the median valley topography, a mechanism similar to that proposed by Bergman and Solomon (1990) for the Mid-Atlantic Ridge.  相似文献   

Visco-plastic response of deep tunnels based on a fractional damage creep constitutive model     

Xu  Guowen  Gutierrez  Marte  Arora  Ketan  Wang  Xin 《Acta Geotechnica》2022,17(2):613-633

Acta Geotechnica - Hard rock tunnels under high geo-stresses, and weak, soft rock tunnels show evident continued deformation after excavation, which is closely associated with the time-dependent...  相似文献   

A reactive transport benchmark on heavy metal cycling in lake sediments     

Bhavna Arora  S. Sevinç Şengör  Nicolas F. Spycher  Carl I. Steefel 《Computational Geosciences》2015,19(3):613-633

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Separation of diffracted waves in transversely isotropic media     

Yogesh Arora  Ilya Tsvankin 《Studia Geophysica et Geodaetica》2016,60(3):487-499

Imaging diffracted waves can provide useful information about complex subsurface geology and fracture networks. Separation of diffractions from typically more intensive reflected events can be done based on specularity, which measures deviation from Snell’s law. Here, we analyze two formulations of specularity and their applicability to diffraction processing in the presence of anisotropy. We show that the most common definition of specularity, originally introduced for pure modes in isotropic media, remains valid for both pure and converted waves in arbitrarily anisotropic models. The other formulation operates directly with the difference between the slowness projections onto the reflector for the incident and reflected waves. Testing on a VTI (transversely isotropic with a vertical symmetry axis) diffraction ramp model demonstrates that both formulations produce satisfactory results for anisotropic media with appropriate tapering of the specularity gathers. Then separation and imaging of diffractions is performed for the structurally complex VTI Marmousi model. We also analyze the sensitivity of diffractions in the specularity gathers to errors in the symmetry-direction velocity and anellipticity parameter η.  相似文献