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Topic: Seismic tomography

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	Seismic Tomography Structures Of Source Areas Of The Two Recent Devastating Earthquakes In Peninsular India. (Site not responding. Last check: 2007-10-11)
		Seismic tomography structures of source areas of the 1993 Killari earthquake (mb 6.3) in central India and the 2001 Bhuj earthquake (MW 7.5) in western India are studied.
		In this paper we shall be discussing tomography structures of the source areas of the two recent devastating intraplate earthquakes in peninsular India; the 1993 Killari earthquake, body wave magnitude mb 6.3, in central India, and the 2001 Bhuj earthquake, moment magnitude MW 7.5, in western India (Figure 1).
		The tomography structure at a depth of 6 km, at the main shock source area, is illustrated in Figure 3b.
	www.virtualexplorer.com.au /journal/2003/12/kayal (1937 words)

	Seismic Techniques
		Due to the dependence of seismic velocity on the elasticity and density of the material through which the energy is passing, seismic refraction surveys provide a measure of material strengths and can consequently be used as an aid in assessing rippability and rock quality.
		The travel times of the first-arrival seismic waves are measured at regular intervals down the hole using a string of hydrophones or, in the case of S-wave surveys, a single clamped triaxial geophone that is gradually moved down the hole.
		The travel times of the seismic waves are derived from the first-arrivals identified on the seismic trace for each shot-receiver position and are used with the known distance(s) between the shot/receiver boreholes to calculate the apparent velocities (P and S) for each depth interval.
	www.geophysics.co.uk /mets3.html (3087 words)

	Seismology
		Seismic wave speeds are different in different kinds of rocks, and in addition increase with pressure (which is very nearly a function of depth alone) and decrease with temperature.Through seismic wave speeds, we know of Earth’s major vertical subdivisions and their approximate compositions:
		Seismic tomography is much more difficult than X-ray tomography, because the ray paths are curved and initially unknown, and in some cases the locations of the sources are poorly known.
		The main methods for studying Earth structure in a way that is useful in the search for plumes include seismic tomography, studying the transit times and attenuation of individual waves that penetrate the volume of interest, and the use of receiver functions to study topography on the boundaries of the transition zone.
	www.mantleplumes.org /Seismology.html (2972 words)

	Seismic tomography applied to diamond pipes prospecting
		Seismic tomography may be applied to diamond kimberlite pipes prospecting using 2D and 3D seismic data.
		Seismic tomography method is divided into ray tomography and diffraction tomography.
		Transmission tomography is applicable for cross-hole data and is for use on detailed exploration stage (not considered).
	www.webstructor.net /geotomo/paper_seg99 (935 words)

	GEOPHYSICS: ON SEISMIC NOISE
		The technique of "seismic tomography" uses the same principles, with the difference that the travel-times of the signals, rather than their attenuation, are observed.
		Thus, the technique of seismic tomography may be described as the 3-dimensional modeling of the velocity distribution of seismic waves in the Earth.
		Seismic tomography, which emerged in the early 1980s, has provided a major probe of the dynamical system of which plates are just the surface veneer.
	scienceweek.com /2005/sw050506-2.htm (1540 words)

	Tomography - Seismology Research - KNMI
		Seismic tomography is a method to determine (to some level of accuracy) the internal structure (in terms of velocity) of the Earth.
		Local, regional and global tomography may differ in scale and approach but essentially refer to the same goal to image (part of) the interior of the Earth.
		Arrival time (or travel time) tomography is the technique to map the arrival time information in seismograms into a velocity model of the interior.
	www.knmi.nl /research/seismology/tomography.html (280 words)

	Integrated Seismic Tomography and Correction of Back Projection Algorithm
		On the contrary, the geometrical conditions of the seismic survey do not enable to apply the conventional convolution – back projection algorithm and that is why iterative algorithms are commonly used in the seismic tomography even though the resolution power of the algorithms is not high enough.
		Many of existing seismic tomography techniques are oriented toward processing specific to travel times of amplitude data, which doesn’t enable to use the whole scope of seismic information.
		Usually, the results of seismic tomography inversion are distorted with artifacts induced by the irregularity of the most of seismic data collection geometries, which makes it difficult to perform the geological interpretation of the obtained sections.
	www.webstructor.net /geotomo/paper_moscow2003 (1479 words)

	Seismic tomography - Wikipedia, the free encyclopedia
		Seismic tomography uses digital seismographic records to image the interior of the Earth.
		Seismic tomography is considered as an inversion problem in which the seismic data are given and the goal is to determine the attributes of the medium such as wave speed and medium density.
		Seismic tomography is a nonlinear inversion problem where the traveltime tomography is much less nonlinear than the full-waveform tomography.
	en.wikipedia.org /wiki/Seismic_tomography (207 words)

	Passive Seismic: Something Old, Something New, by Peter M. Duncan, #40154 (2005).
		Movement on the fault causes a seismic signal that is recorded on the surface array.
		The seismic energy recorded by the array over a period of observation time is displayed as colors in the cube, hotter colors representing higher energy levels.
		The most straight-forward approach is to observe and record the direct arrivals of the seismic waves from these events and to map the distribution of hypocenter locations.
	www.searchanddiscovery.com /documents/2005/duncan/index.htm (1107 words)

	Prospecting for Jurassic slabs
		Seismic tomography, named in analogy to medical imaging, is a child of the early 1980s now grown to vigorous adulthood.
		Furthermore, this work shows that seismic tomography is a powerful tool for palaeogeography, providing a fresh source of information about the history of global plate motions and the processes of continental growth.
		Seismic tomography is providing similar insights into the fates of other subducted slabs.
	cas.bellarmine.edu /tietjen/images/prospecting_for_jurassic_slabs.htm (1569 words)

	IPY: International Polar Year
		The seismic studies also demonstrated that the inner core is rotating relative to the Earth mantle and surface.
		The main target of the proposed experiment is to deploy a temporary seismic array in the area with latitudes from 66N to 70N and longitudes from 24E to 30E and to collect seismic waveforms from events containing seismic phases travelling through the inner core.
		The SVEKALAPKO Deep Seismic Tomography project was a passive seismic array research in southern and central Finland aiming at studying the lithosphere-asthenosphere system at the suture of Archean and Proterozoic domains of the Fennoscandian Schield.
	www.ipy.org /development/eoi/details.php?id=34 (974 words)

	Seismic tomography of central Eurasia
		Seismic tomography is the most powerful instrument for determination of 3D structure of deep Earth's interiors.
		First quantitative tomographic model was obtained by Alekseev et al., 1971 The seismic structure of the upper mantle beneath a broad area located in the center of Euroasian continent is described in the paper.
		A large negative seismic anomalies was obtained under the regional depression of Ubsu-Nur lake and under Hubsugul lake.
	geology.uiggm.nsc.ru /homepages/geophysics/ris/index.html (2442 words)

	UNR Mathematics Colloquium, 9 Nov. 1995 (Site not responding. Last check: 2007-10-11)
		Tomography is a model-building process, controlled by synthetic times forward-projected through proposed velocity models and compared with the observed times.
		As seismic rays never sample all of our models, the singularity found by linearized inversions is expressed in SA as indeterminance among the low-error models.
		Most seismic tomography problems are exploratory in purpose, so choosing an initial model is difficult and would add bias.
	www.seismo.unr.edu /ftp/pub/louie/talks/math/math95.html (1894 words)

	Mantle dynamics and seismic tomography -- Tanimoto and Lay 97 (23): 12409 -- Proceedings of the National Academy of ...
		Mantle dynamics and seismic tomography -- Tanimoto and Lay 97 (23): 12409 -- Proceedings of the National Academy of Sciences
		Seismic tomography emerged in the early 1980s, providing a major probe of the dynamical system of which plates are just the
		Seismic tomography also has revealed complex structure in the boundary layer at the base of the mantle, where heat from the
	www.pnas.org /cgi/content/full/97/23/12409 (1091 words)

	Applications of finite frequency tomography
		The existence of the African and Pacic superplumes (vast piles of material with lowered seismic velocity and probably a higher density) was uncontested, but as recently as 2003 Ritsema and Allen concluded: Whole-mantle plumes are well established through both numerical and analog experiments, but conclusive evidence for their existence remains elusive on Earth.
		One of the major hurdles is the (presumed) narrow conduit of plumes, which makes it easy for seismic waves to diffract around them, thus masking any delay acquired by the wave energy that actually travels through the plume by earlier arrivals that have found a way around the low velocities.
		Karin Sigloch solved this problem in a way that is as elegant as efficient (Sigloch and Nolet, 2006), and efforts are now under way by Karin, and new graduate student Yue Tiang, to measure frequency-dependent delay times and amplitudes for all major events in the IRIS data base.
	geoweb.princeton.edu /people/faculty/nolet/born.html (942 words)

	Borehole Geophysics: Seismic Cross Well at the TAN Site
		Seismic tomography was conducted to attempt imaging of the geologic conditions (mainly fracturing) controlling the contaminant spread.
		Correlation to borehole geophysical logs indicates that low velocity zones delineated by seismic tomography correlate to fractured intervals known to contain elevated levels of 137Cs and 60Co.
		Seismic crosshole tomography as demonstrated at the TAN site has provided a cost-effective method for delineating the volume and distribution of highly contaminated fracture zones.
	www-esd.lbl.gov /GG/CCS/tan.shtml (322 words)

	Seismic Tomography at Toba (Site not responding. Last check: 2007-10-11)
		The reservoir contracts in size with depth, and appears to merge in the 10-24 km depth range with a narrow, tabular-shaped region of low Vp that is elongate ENE below volcano Pusubukit.
		Seismic velocities of the middle and deep crust are also anomalously low farther south, below the Pardepur domes at the southern end of the SR.
		The low-velocity regions below Pusubukit and Pardepur each extend to mantle depths.
	www.rpi.edu /~warkd/toba/toba_tomography.html (226 words)

	Oilfield Glossary: Term 'tomography'
		A technique to measure and display the three-dimensional distribution of velocity or reflectivity of a volume of the Earth by using numerous sources and receivers.
		There are several types of tomography used by geophysicists, including transmission tomography (which uses measurements between boreholes, surface-to-surface, or between a borehole and the surface), reflection or seismic tomography (based on standard reflection seismology), and diffraction tomography (using Fermat's principle for computations instead of Snell's law).
		Variations in velocity can be attributed to changes in density and elastic properties of rocks, which in turn are affected by the increasing temperature with depth in the Earth.
	www.glossary.oilfield.slb.com /Display.cfm?Term=tomography (152 words)

	Global Seismic Tomography: A Snapshot of Convection in the Earth
		It is important that we study the nature of this convective flow in order to understand the thermal history of the Earth, its internal composition, and the forces that drive plate motions.
		The differences in data sampling between the two studies are large, which means it is unlikely that systematic errors common to both studies contribute to the agreement in their results.
		The shear wave study uses multiple bounce seismic phases to study the shallow mantle beneath regions where structures cannot be constrained by direct P- or S-wave data.
	geo.web.ru /sbmg/sbor/tomography/Grand/grand.html (434 words)

	[No title]
		It was operated between August 1998 and May 1999, when 85 short period and 39 broad band stations were installed in a regular 50x50 km grid covering an area of 600 by 400 km.
		The array was on the largest size (110 stations) from the end of November 1998 till the middle of March 1999.
		High-Resolution body wave tomography beneath the SVEKALAPKO array: I. A-priori 3D crustal model and associated traveltime effects on teleseismic wavefronts.
	www.gf.oulu.fi /Sveka/SSTWG/index.html (599 words)

	Eurasian Tomography
		Levshin, A.L., M.H. Ritzwoller, and L. Ratnikova, The nature and cause of polarization anomalies of surface waves crossing northern and central Eurasia, Geophys.
		Levshin, A.L. and M.H. Ritzwoller, Surface wave group velocity measurements across Eurasia, Proceedings of the 17th Seismic Research Symposium on Monitoring a CTBT, 226-236, 1995.
		Levshin, A.L., M.H. Ritzwoller, and S.S. Smith, Group velocity variations across Eurasia, Proceedings of the 18th Seismic Research Symposium on Monitoring a CTBT, 70 - 79, 1996.
	phys-geophys.colorado.edu /geophysics/eurasia_old.dir/eurasia.html (447 words)

	Table of contents for Library of Congress control number 2005384444
		Conclusion 295 Outline of the Chapter 297 Seismic evidence for a low-velocity zone in the upper crust beneath Mount Vesuvius 299 A.
		Seismic evidence of an extended magmatic sill under Mt. Vesuvius 309 E.
		Lomax Locating and quantifying the seismic discontinuities in a complex rhedium through the migration and AVA analysis of reflected and converted waves: An application to Mt. Vesuvius Volcano 481 E.
	www.loc.gov /catdir/toc/fy0604/2005384444.html (727 words)

	Tomography - Wikipedia, the free encyclopedia
		A device used in tomography is called a tomograph, while the image produced is a tomogram.
		In most cases it is based on the mathematical procedure called tomographic reconstruction.
		Magnetic resonance imaging (MRI), formerly known as magnetic resonance tomography (MRT) or nuclear magnetic resonance tomography
	en.wikipedia.org /wiki/Tomography (131 words)

	Geol 775 - Refraction, Tomography, and Surface Waves (Site not responding. Last check: 2007-10-11)
		Achauer, Evans, and Stauber, High-Resolution Seismic tomography of Compressional Wave Velocity Structure at Newberry Volcano, Oregon Cascade Range, J. Geophys.
		Foulger and Toomey, Structure and Evolution of the Hengill-Grensdalur Volcanic Complex, Iceland: Geology, Geophysics, and Seismic Tomography, J. Geophys.
		Lee, D. Stevenson, V. Mullen, C. Time-lapse crosswell seismic tomography to characterize flow structure in the reservoir during the thermal stimulation.
	www.seismo.unr.edu /ftp/pub/louie/class/775/tomorefs.html (2657 words)

	Harmen Bijwaard's global seismic tomography page
		In short: seismic tomography is a technique to image the interior of the Earth with (pressure) waves that are generated by earthquakes.
		The method is comparable to that of the CT scan that is used to image the interior of the human body.
		In 1999 I completed a PhD thesis on global seismic tomography at the Faculty of Earth Sciences of Utrecht University.
	www.geo.uu.nl /~bijwaard (856 words)

	Colin Zelt Presentations
		Zelt, C. Sawyer, and E. Knoll, Seismic velocity structure of the Iberia margin from simultaneous wide-angle and zero-offset traveltime inversion, EOS, 80, F674, 1999.
		Zelt, C. A., Seismic velocity structure of the central Chilean margin near the subducting Juan Fernandez ridge: effective inversion of traveltime data across complex, laterally varying structure, 7th International Symposium, Deep Seismic profiling of the continents, Asilomar, CA, 1996.
		Zelt, C. A., and P. Barton, 3D seismic refraction tomography: comparison of methods applied to OBS data from the Faeroe basin, 7th International Symposium, Deep Seismic profiling of the continents, Asilomar, CA, 1996.
	zephyr.rice.edu /department/faculty/zelt/presentations.html (1664 words)

	Seismic Tomography
		In the earth, we can apply the method using seismic waves.
		Imagine you had no way of finding out where Missouri was except by plotting the paths of satellites and knowing they had either passed over Missouri (red) or not passed over it (blue).
		Here's an example that is actually a little closer to the way seismic tomography is actually done.
	www.uwgb.edu /dutchs/PLATETEC/seistom.HTM (580 words)

	RAYFRACT Seismic Refraction Tomography
		Investigation of a landfill with Seismic Refraction, Resistivity and Electromagnetic methods (William E. Doll et al.
		Seismic traveltime tomography using Fresnel volume approach (Toshiki Watanabe 1999; purchase Adobe Acrobat)
		Improving modelling and inversion in refraction seismics with a first-order Eikonal solver (Isabelle Lecomte et al.
	rayfract.com (731 words)

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