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1.
The Mullipallam creek in Muthupet mangroves region is the only E-W trending coastal strip in the SE coast of India and is
very important, as the mangrove acts as a barrier to natural diasters. Natural, anthropogenic signals and accumulation of
elements were made by collecting sediment samples at various depths in a core. All sediments were analyzed for carbonates
(CaCO3), organic carbon (OC), major (Si, Al, Fe, Na, K, Ca, Mg, P), and trace (Mn, Cr, Cu, Ni, Co, Pb, Zn). Normalization with Al
values has been done for all the major and trace elements and enrichment factors have been calculated. The calculated enrichment
factors and comparison indicate that the trace metals (especially Pb) are enriched mainly due to the external (anthropogenic)
activities in the land as well as in the coastal zone (Palk Strait). 相似文献
2.
An integral transform, called in this study as Sundararajan transform, has been used to estimate the parameters of vertical magnetic effect of a fault structure. It differs from the well-known Hilbert transform in the property of phase shift as it yields a phase shift of 270° unlike the Hilbert transform, which is a 90° phase shifter. Other properties of the Sundararajan transform remain almost the same as the Hilbert transform. The transform has been tested on synthetic data and a field example of Lachlan Foldbelts, New South Wales, Australia. The results of this technique agree with the one published in the literature. The noise analysis has been examined and showed that it still provides acceptable results. The application of this transform to geophysical interpretation illustrates its potentiality, and it may be widely applied in various disciplines mainly in the field of communication engineering, signal, and image processing. An interesting property of this transform is that two successive transforms of a function return it to its original form unlike the Hilbert transform, which returns it to the negative of the original form. The procedure discussed may be automated. 相似文献
3.
The dispersive characteristics of Rayleigh type surface waves were utilized to estimate shear wave velocity (Vs) profile followed by imaging the shallow subsurface granitic layers in the heart of Hyderabad. The reliability of Multichannel Analysis of Surface Waves (MASW) depends on the accurate determination of phase velocities for horizontally traveling fundamental mode Rayleigh waves. Multichannel recording leads to effective identification and isolation of various factors of noise. Calculating the 1-D shear wave velocity (Vs) field from surface waves ensures high degree of accuracy irrespective of cultural noise. The main advantage of mapping the bed rock surface with shear wave velocity (Vs) is the insensitivity of MASW to velocity inversion besides being free from many constraints such as contrast in physical properties etc. Modeling of surface waves data results a shear wave velocity (Vs) of 250?C750 m/s covering the top soil to weathering and up to bedrock corresponding to a depth range of 10?C30 m. Further, the computed N values (which is an indicator of site characteristic) based on the harmonic shear wave velocity up to a depth of 5 m is found to be quite high (> 25?C30) well above 5 indicating the site to be safe and strong enough and not prone to liquefaction. A pair of selected set of results over granites are presented here as a case study highlighting the salient features of MASW. 相似文献
4.
El-Hussain I. Deif A. Al-Jabri K. Mohamed A. M. E. Al-Rawas G. Toksöz M. N. Sundararajan N. El-Hady S. Al-Hashmi S. Al-Toubi K. Al-Saifi M. Al-Habsi Z. 《Natural Hazards》2013,69(3):1919-1950
Natural Hazards - Site characterization was carried out for Muscat region using the ambient noise measurements applying the horizontal-to-vertical spectral ratio (HVSR) technique and using active... 相似文献
5.
N. Sundararajan I. Arun Kumar N. L. Mohan S. V. Seshagiri Rao 《Pure and Applied Geophysics》1990,133(1):117-126
Self-potential anomalies due to two-dimensional inclined sheet of finite depth extent are analysed from their horizontal and vertical derivatives via the Hilbert transform. The depths to the top and bottom of the sheet and the inclination are obtained by means of simple mathematical expressions. The method is applied to a theoretical example and to a field S.P. anomaly over a sulphide deposit in the Kalava fault zone of Cuddapah basin, India. The presence of random noise is analysed for various levels and its effect is discussed. This interpretation process can be automated for all practical purposes by simple programming. 相似文献
6.
An interpretation procedure is formulated using the Hilbert transform for analysing the gravity effect of (a) two-dimensional horizontal circular cylinder, (b) semi-infinite thin fault block, and (c) a geologic contact. In all three cases the abscissa of the point of intersection of the gravity anomaly curve or the horizontal derivative curve and its Hilbert transform yields directly the depth of the body. The proposed method is tested on theoretical models. Also, the method is applied to the field data of a geologic contact taken over the Himalayan foothills across the Brahmaputra valley. 相似文献
7.
N. Sundararajan Y. Srinivas M. Narasimha Chary G. Nandakumar A. Hanmantha Chary 《Journal of Earth System Science》2004,113(3):259-267
The contacts associated with an outlier in biotite gneiss and sandstones near Tiruvuru, Krishna district, Andhra Pradesh which
are generally favourable for groundwater occurrence were investigated employing refraction seismic method. Results were examined
by correlating the signals with local geology, bore well data and other available information in order to improve the reliability
of interpretation 相似文献
8.
N. Sundararajan Mansour A. Al-Garni G. Ramabrahmam Y. Srinivas 《Geophysical Prospecting》2007,55(6):901-910
Spectral analysis of the deformation of a homogenous electric field caused by a long, thin inclined bed, which is of considerable importance in the exploration of ground water and minerals, is presented using the Hartley transform. The Hartley transform is an alternative and real replacement for the well‐known complex Fourier transform in the field of spectral analysis. The thickness of the bed and the inclination are given as functions of frequency by simple expressions. A theoretical example illustrates the method while the applicability is demonstrated by the field examples from the fractured crystalline basement complex in Burkina Faso, Africa and the Precambrian limestones of the Cuddapah basin, Andhra Pradesh, India. The results obtained by this method agree well with those of the drilling. 相似文献
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10.
Shear wave velocity (V S) estimation is of paramount importance in earthquake hazard assessment and other geotechnical/geo engineering studies. In our study, the shear wave velocity was estimated from ground roll using multichannel analysis of surface wave (MASW) technique making use of dispersive characteristics of Rayleigh type surface waves followed by imaging the shallow subsurface basaltic layers in an earthquake-prone region near Jabalpur, India. The reliability of MASW depends on the accurate determination of phase velocities for horizontally traveling fundamental mode Rayleigh waves. Inversion of data from surface waves resulted in a shear wave velocity (V S) in the range of 200–1,200 m/s covering the top soil to weathering and up to bedrock corresponding to a depth of 10–30 m. The P-wave velocity (V P) obtained from refraction seismic studies at these locations found to be comparable with V S at an assumed specific Poisson’s ratio. A pair of selected set of V S profiles over basalt which did not result in a hazardous situation in an earthquake of moderate magnitude are presented here as a case study; in other words, the shear wave velocity range of more than 200 m/s indicate that the area is highly unlikely prone to liquefaction during a moderate or strong earthquake. The estimated depth to basalt is found to be 10–12 m in both the cases which is also supported by refraction studies. 相似文献