Download or read book Time Term Analysis of Seismic Data from the East Pacific Rise Project ROSE written by Carlos Angel Q. Mortera Gutierrez and published by . This book was released on 1984 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Masters Theses in the Pure and Applied Sciences written by Wade H. Shafer and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 407 pages. Available in PDF, EPUB and Kindle. Book excerpt: Masters Theses in the Pure and Applied Sciences was first conceived, published, and disseminated by the Center for Information and Numerical Data Analysis and Synthesis (CINDAS) * at Purdue University in 1 957, starting its coverage of theses with the academic year 1955. Beginning with Volume 13, the printing and dissemination phases of the activity were transferred to University Microfilms/Xerox of Ann Arbor, Michigan, with the thought that such an arrangement would be more beneficial to the academic and general scientific and technical community. After five years of this joint undertaking we had concluded that it was in the interest of all con cerned if the printing and distribution of the volumes were handled by an interna tional publishing house to assure improved service and broader dissemination. Hence, starting with Volume 18, Masters Theses in the Pure and Applied Sciences has been disseminated on a worldwide basis by Plenum Publishing Cor poration of New York, and in the same year the coverage was broadened to include Canadian universities. All back issues can also be ordered from Plenum. We have reported in Volume 29 (thesis year 1984) a total of 12,637 theses titles from 23 Canadian and 202 United States universities. We are sure that this broader base for these titles reported will greatly enhance the value of this important annual reference work. While Volume 29 reports theses submitted in 1984, on occasion, certain univer sities do report theses submitted in previous years but not reported at the time.
Download or read book Le Pacifique Sud written by Frédéric Angleviel and published by Presses Univ de Bordeaux. This book was released on 1991 with total page 294 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bibliography and Index of Geology written by and published by . This book was released on 1988 with total page 1178 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Seismic Attenuation Structure of the East Pacific Rise written by William Sam Douglas Wilcock and published by . This book was released on 1992 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: Studies of seismic propagation through oceanic crust have contributed enormously to our understanding of the generation and evolution of oceanic crust However, such work has largely been confined to the seismic velocity structure. In this thesis we present results from a study of seismic attenuation using a data set collected for three-dimensional tomographic imaging of a fast-spreading ridge. The experiment location at 9°30'N on the East Pacific Rise is the site of a strong mid-crustal seismic reflector which has been inferred to be the roof of a small axial magma chamber at about 1.6 km depth. A spectral method is used to estimate t*, a measure of the integrated attenuation along a wave path. Such a method asswnes that the dominant frequency-dependent component of propagation is intrinsic attenuation. A logarithmic parameterization is then used to invert t* measurements for Q-1 structure asswning that the velocity structure is given from earlier studies. To evaluate the method of Q tomography a full-waveform finitedifference technique which does not include attenuation is used to calculate solutions for seismic propagation through a two-dimensional velocity model. The results show a complex pattern of seismic propagation in the vicinity of the axial magma chamber. The first arrival always passes above the magma chamber. However, for paths of significant length that cross the rise axis the amplitude of this arrival is very small, and the first phase with significant amplitude is a diffraction below the magma chamber. High-amplitude Moho turning and PP arrivals may also be important secondary arrivals. Synthetic inversions show the importance of selecting time windows for power spectral estimation which are dominated by a single phase and of using wave paths which closely corresponds to that of the selected phase. A comparison of the finite difference solutions and the predictions of the a twodimensional, exact ray-tracing algorithm with record sections obtained during the tomography experiment significantly improves our understanding of seismic propagation across the East Pacific Rise. The results enable an objective choice of the position and length of the time window fort* estimation. Moreover, additional constraints are incorporated into an approximate three-dimensional ray-tracing algorithm used in the inversion so that the wave paths more closely correspond to those of the desired phase. The full data set to be inverted comprises about 3500 t* estimates and includes crustal paths which do not cross the rise axis, diffractions above and below the axial magma chamber, and Moho-turning phases. Wave paths for the Moho-turning phases cross the rise axis at a wide range of lower crustal depths. The Q-1 models resulting from two-dimensional and three-dimensional tomographic inversions show that the attenuation of seismic waves on the East Pacific Rise is dominated by two regions of low Q; one in the upper 1 km of crust, and one at depths greater than about 2 km below the rise axis. While the data do not resolve the details of vertical variations in near-surface Q-1, the results show a substantial variation in shallow attenuation within 0.05 My of the rise axis. On-axis, Q values averaged over the upper 1 km are about 100, while off-axis the average value rapidly decreases to about 30. Measurements of the seismic velocity suggest that the thickness of the surficial highporosity extrusive layer increases substantially off-axis. If such thickening is entirely responsible for the observed change in near-surface attenuation then Q within the extrusive layer must be much less than 20. Alternatively, in situ changes in porosity may also contribute to the observed increase in attenuation. Since significant tectonic activity is apparently restricted to locations well off-axis we suggest that such variations in porosity may result from hydrothermal activity. Regions of hydrothermal downwelling located off-axis will be subject to cooling and thermally-induced cracking while upwelling regions on-axis may be accompanied by rapid infilling of existing pores by hydrothermal deposits. Estimates of t* for all phases propagating below the magma chamber are markedly higher than those for other phases, resulting in Q-1 models which include a region of low Q extending from 2 to 7 km depth below the rise axis. The lowest Q values resolved are about 25-30 both immediately below the magma chamber and within the lower crust. While there is some evidence for a small decrease in attenuation with depth in the lower crust, axial Q values at depths ranging from less than 2.5 to 6 km are relatively constant, always lying below 50. Laboratory measurements at seismic frequencies suggest that Q values of 25-50 require only very small fractions of partial melt. The attenuation observations thus place constraints on the dimensions of the axial magma chamber and strongly suggest that the thickness of the region containing more than a few percent of partial melt is no more than 1 km.
Download or read book Yearbook written by Hawaii Institute of Geophysics and published by . This book was released on 1982 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book References to Anisotropy Attenuation Low Velocity Zones and Poisson s Ratio in the Earth s Crust written by and published by . This book was released on 1990 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summaries of Projects Completed written by National Science Foundation (U.S.) and published by . This book was released on with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book South Pacific Bibliography written by and published by . This book was released on 1992 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summaries of Projects Completed in Fiscal Year written by and published by . This book was released on 1979 with total page 718 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Marine Seismic Study of the East Pacific Rise 8 50 N to 13 30 N written by Ginger Anne Barth and published by . This book was released on 1991 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Baseline for Upper Crustal Velocity Variations Along the East Pacific Rise written by Mary Elizabeth Kappus and published by . This book was released on 1991 with total page 358 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Summaries of Projects Completed in Fiscal Year written by National Science Foundation (U.S.) and published by . This book was released on 1979 with total page 720 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book East Pacific Rise Data Synthesis Petrology data base written by Stacey Tighe and published by . This book was released on 1988 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book East Pacific Rise Data Synthesis Introduction written by Stacey Tighe and published by . This book was released on 1988 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fine Scale Seismic Structure of Upper Crust on the East Pacific Rise written by Chin Chen and published by . This book was released on 1985 with total page 326 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Marine Seismic Study of the East Pacific Rise 8 50 N to 13 30 N written by Ginger Anne Barth and published by . This book was released on 1991 with total page 474 pages. Available in PDF, EPUB and Kindle. Book excerpt:
