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A combination of ray theory and diffraction theory has been used to simulate reflections of seismic pulses from a full plane and reflections and diffractions from a half plane buried horizontally in earth models with linear increase of velocity with depth. Wave forms of signals reflected from a full plane in this case are modifications of the source pulse, even if the medium is assumed to be perfectly elastic. The extent of pulse modification increases with increase of the velocity gradient. The duration of the reflected pulse is always longer than that of the source pulse. The pulses diffracted from the edge of the half plane in such cases do not lie along hyperbolic curves in the time-offset plane. Diffracted signals can be observed only up to a limited distance from the edge of the half plane equalling half the horizontal range of the ray which is tangential to the half plane and has its end points at the level of the source and the receiver. 相似文献
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SANTANU ACHARJEE JYOTISANKAR RAY PAYEL DEY DEBAPRIYA BHATTACHARYYA MOUSUMI BANERJEE BASAB CHATTOPADHYAY SHYAMAL SENGUPTA A K BHATT D CHOWDHURY A K DWIVEDI SANJOY MAHATO ARKA RANJAN JANA P B MAITHANI P V RAMESH BABU 《Journal of Earth System Science》2016,125(8):1681-1696
The area of investigation at and around Mashak Pahar, Bankura district, West Bengal, India comprises a number of rock types namely: granite gneiss, migmatized quartz tourmaline gneiss, quartz pebble conglomerate, ferruginous quartzite, quartz tourmaline veins (as veins) and graphite schists. Interestingly, the study area lies in the region extending South Purulia Shear Zone (～Tamar–Porapahar Shear Zone) which marks the boundary between two contrasting tectonic blocks of eastern India, namely, the Chhotanagpur Gneissic Terrane (CGC) to the north and Singhbhum Group of rocks to the south. The rocks of the study area are poly-phasedly deformed by three phases of folding, namely, F1, F2 and F3. All the tourmalines are classified to be of ‘Alkali Group’. Chemistry of tourmalines from migmatized quartz tourmaline gneiss and those from quartz tourmaline veins are in conformity with their relation to (earthquake induced) shear system evolution in this terrain. In general, the compositional evolution of tourmaline during prograde metamorphism (～400°–730°C) has been supported by both petrographic and chemical evidences. Assessment of mineral–chemical data of constituent tourmaline grains clearly suggests compositional variations across zonal boundaries within tourmaline that was controlled by changing metamorphic milieu in this terrane. Field and petrographic evidences clearly indicate activation of earlier and later shears in this region accompanied by infiltration of boron and formation of zoned tourmaline crystals. 相似文献
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Analytical data on 34 geochemically significant trace elements (Sc, V, Cr, Co, Ni, Cu, Zn, Ga, Rb, Sr, Y, Zr, Nb, Cs, Ba, Hf, Ta, Pb, The, U and REE) by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS), for 13 reference rock samples obtained from the Geological Survey of Finland are presented. For many elements, especially most of the heavy-REE, concentrations are reported here for the first time. 相似文献
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R. CHANDER 《Geophysical Prospecting》1977,25(1):120-124
A polygonal ray path connects the seismic source and detector positions when the intervening medium consists solely of constant velocity layers with plane interfaces which may have arbitrary orientation. The coordinates of the ray vertices satisfy a system of coupled equations resulting from the requirement that Fermat's principle be satisfied along the ray path. Solving the system of equations is equivalent to tracing the ray numerically. A notable feature of this approach is that a ray which is critically refracted over a segment of its path requires no special handling. 相似文献
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RAMESH P. SINGH 《Geophysical Prospecting》1985,33(3):369-376
In tectonically active regions electrical conductivity anisotropies are the dominating features. The importance of conductivity anisotropy in the interpretation of magnetotelluric data is well known. In the present study numerical results presented which show the effect of a substratum with inclined anisotropy on the magnetotelluric response. The pronounced change on the magnetotelluric response is found for the models in which the substratum underlies (i) conductive and (ii) resistive overburden. 相似文献
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Long-term climate data records (CDR) are often constructed using observations made by multiple Earth observing sensors over
a broad range of spectra and a large scale in both time and space. These sensors can be of the same or different types operated
on the same or different platforms. They can be developed and built with different technologies and are likely operated over
different time spans. It has been known that the uncertainty of climate models and data records depends not only on the calibration
quality (accuracy and stability) of individual sensors, but also on their calibration consistency across instruments and platforms.
Therefore, sensor calibration inter-comparison and validation have become increasingly demanding and will continue to play
an important role for a better understanding of the science product quality. This paper provides an overview of different
methodologies, which have been successfully applied for sensor calibration inter-comparison. Specific examples using different
sensors, including MODIS, AVHRR, and ETM+, are presented to illustrate the implementation of these methodologies. 相似文献