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Crustal And Uppermost Mantle Structure Beneath The Western United States From Usarray Regional Phase Analysis
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Book Synopsis Crustal and Uppermost Mantle Structure Beneath the Western United States from USArray Regional Phase Analysis by : Janine Sylvia Buehler
Download or read book Crustal and Uppermost Mantle Structure Beneath the Western United States from USArray Regional Phase Analysis written by Janine Sylvia Buehler and published by . This book was released on 2013 with total page 118 pages. Available in PDF, EPUB and Kindle. Book excerpt: The aim of this dissertation is to improve our understanding of the crust and uppermost mantle structure in the western United States, profiting from the wealth of regional phase data recorded at USArray stations. USArray, a transportable seismic array of ~400 seismometers, has greatly increased seismic data coverage across the United States in the past few years, and allows imaging of the lithosphere of the North American continent with better resolution and new methods. The regional phases are often challenging to analyze, especially in a tectonically-active region like the western United States, because of their sensitivities to the heterogeneities of the crust and uppermost mantle. However, knowledge of the seismic structure of the lithosphere is not only essential in order to accurately image the velocity structure at greater depths, but also for constraining geodynamic models that reconstruct the tectonic evolution of the continent, and hence the information that is carried by the regional phases is very valuable. The data set used in this study consists mostly of the regional seismic phases Pn and Sn, which propagate horizontally along the Moho in the mantle lid and constrain the seismic velocity structure at a confined depth. We applied traditional tomographic methods that profit from the improved ray coverage through USArray, but also employed array-based techniques that take advantage of the regular station spacing of the transportable array and don't depend on regularization. In addition, we used stacking methods to image the propagation efficiency of the Sn phase, which is often highly attenuated in tectonically active regions, on a regional scale. The results complement other seismic studies that average over greater depth intervals, such as surface- and body-wave tomographies and anisotropy analysis from shear-wave splitting, to provide information on temperature, composition, and tectonic processes at depth. Comparisons between Pn azimuthal anisotropy and fast polarization direction from shear wave splitting suggest significant vertical changes in anisotropy in several regions of the upper mantle beneath the western United States. Sn can in theory further constrain the nature of anisotropy in the mantle lid. However, we have so far been unable to resolve shear-wave splitting directly in the Sn waveforms as the phase is often attenuated and difficult to detect. Still, we obtained evidence for Sn propagation in several regions of the western United States such as the central Great Basin and the northeastern part of the Colorado Plateau. We found that there are enough quality Sn picks for joint Pn-Sn tomography and identified prominent Vp/Vs anomalies, such as large high Vp/Vs regions --- typically associated with partial melt --- below the Snake River Plain and the Colorado Plateau.
Book Synopsis Délégation bulgare à la conférence de la paix. A Son Excellence Monsieur Georges Clemenceau, président de la conférence de la paix, Paris by :
Download or read book Délégation bulgare à la conférence de la paix. A Son Excellence Monsieur Georges Clemenceau, président de la conférence de la paix, Paris written by and published by . This book was released on 19?? with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Regional Variations in Upper Mantle Structure Beneath North America by : Bruce Rene Julian
Download or read book Regional Variations in Upper Mantle Structure Beneath North America written by Bruce Rene Julian and published by . This book was released on 1979 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Structure of the Uppermost Mantle Beneath North America by : Stéphanie Godey
Download or read book Structure of the Uppermost Mantle Beneath North America written by Stéphanie Godey and published by . This book was released on 2002 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Crustal and Upper Mantle Structure Beneath the Southeastern United States from Joint Inversion of Rayleigh Wave Dispersion and Receiver Functions by : Qiuyue Yang
Download or read book Crustal and Upper Mantle Structure Beneath the Southeastern United States from Joint Inversion of Rayleigh Wave Dispersion and Receiver Functions written by Qiuyue Yang and published by . This book was released on 2021 with total page 186 pages. Available in PDF, EPUB and Kindle. Book excerpt: "In spite of numerous geophysical investigations have been conducted in southeastern United States, the structure and evolution of the crust and lithospheric mantle remain controversial due the thick sedimentary covers atop the crust of the coastal plains there. In this study, we use data from 186 broadband seismic stations belonging to the USArray Transportable Array to construct a 3-D shear wave velocity model for the southeastern United States for the top 180 km by a joint inversion of Rayleigh wave phase velocity dispersion and receiver functions. Our results show a clear spatial correspondence with major surficial geological features. A prominent low velocity anomaly observed in the depth range of 0 to 25 km beneath the eastern Gulf Coastal Plain suggests the existence of thick sediments atop the crystalline crust. The eastern side of the southern Appalachian Mountains is characterized by low crustal Vp/Vs, thin crust, and slow lower crustal velocities, which may be caused by lower crustal delamination followed by relamination. Beneath the Osceola intrusive complex located at the central Suwannee Terrane, our results show low Vp/Vs measurements and seismically fast lower crust, which are attributable to eclogites in the lower crust. The Grenville Province and a narrow zone to its east possess relatively higher Vp/Vs values comparing with the surrounding areas, which can be attributed to mafic intrusion associated with crustal extension in the recently recognized eastern arm of the Proterozoic Midcontinent Rift. According to the isostasy theory, we estimate the density variations from the resulting velocity anomalies in the top 180 km, which indicate that contributions from density anomalies in greater depths are required to reach isostatic balance"--Abstract, page iv.
Book Synopsis Plates, Plumes, and Planetary Processes by : Gillian R. Foulger
Download or read book Plates, Plumes, and Planetary Processes written by Gillian R. Foulger and published by Geological Society of America. This book was released on 2007 with total page 1012 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presents a collection of papers discussing various hypotheses and models of planetary plumes.
Book Synopsis Crustal Structure of the Western United States by : C. Prodehl
Download or read book Crustal Structure of the Western United States written by C. Prodehl and published by . This book was released on 1979 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: A reinterpretation of seismic-refraction measurements made from 1961 to 1963 and a comparison with the crustal structure of central Europe.
Book Synopsis Regional Variations in Upper Mantle Structure Beneath North America by : Bruce Rene Julian
Download or read book Regional Variations in Upper Mantle Structure Beneath North America written by Bruce Rene Julian and published by . This book was released on 1976 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Earth's Crust and Upper Mantle by : Pembroke J. Hart
Download or read book The Earth's Crust and Upper Mantle written by Pembroke J. Hart and published by American Geophysical Union. This book was released on 1969 with total page 801 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis The Earth's Inner Core by : Hrvoje Tkalčić
Download or read book The Earth's Inner Core written by Hrvoje Tkalčić and published by Cambridge University Press. This book was released on 2017-02-02 with total page 237 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first comprehensive review of past and contemporary research on the Earth's inner core from a seismological perspective. Providing a detailed account of how seismology is used in inner core research, and suggesting avenues for further study, it is an essential resource for researchers and students studying seismology and deep Earth processes.
Book Synopsis Mantle Convection and Surface Expressions by : Hauke Marquardt
Download or read book Mantle Convection and Surface Expressions written by Hauke Marquardt and published by John Wiley & Sons. This book was released on 2021-07-07 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: A multidisciplinary perspective on the dynamic processes occurring in Earth's mantle The convective motion of material in Earth's mantle, powered by heat from the deep interior of our planet, drives plate tectonics at the surface, generating earthquakes and volcanic activity. It shapes our familiar surface landscapes, and also stabilizes the oceans and atmosphere on geologic timescales. Mantle Convection and Surface Expressions brings together perspectives from observational geophysics, numerical modelling, geochemistry, and mineral physics to build a holistic picture of the deep Earth. It explores the dynamic processes occurring in the mantle as well as the associated heat and material cycles. Volume highlights include: Perspectives from different scientific disciplines with an emphasis on exploring synergies Current state of the mantle, its physical properties, compositional structure, and dynamic evolution Transport of heat and material through the mantle as constrained by geophysical observations, geochemical data and geodynamic model predictions Surface expressions of mantle dynamics and its control on planetary evolution and habitability The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.
Book Synopsis Mapping Crust and Upper Mantle Structure Beneath Southern Eurasia by :
Download or read book Mapping Crust and Upper Mantle Structure Beneath Southern Eurasia written by and published by . This book was released on 1993 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study of lateral variations in compressional velocity in the uppermost mantle underneath the Tibetan plateau, 353 Pn travel times were collected for 44 Tibetan earthquakes at 46 seismic stations. The inverse method and procedures in this study differ from previous Pn tomography studies in that corrections were applied to the biases caused by (1) event mislocation by ISC, (2) mantle velocity gradient, and (3) large-scale variations in crustal thicknesses. Main results to date are: (1) the average P velocity value for the uppermost mantle in Tibet is 7.93+/-0.17 km/s; (2) the average P velocity gradient in the upper 150 km of the mantle is 3.1 x 10(exp-3)1/s; (3) the 2D P velocity image of the region includes a low velocity zone in the north central Tibet, and two high velocity zones in the western and eastern flanks of Tibet; and (4) in much of the area inside Tibet, the crustal thickness exceeds 70 km. Another important finding of this study is that event relocation (see the bias 1) plays a very important role in reliably retrieving the detailed lateral variations in 2D P velocity image. Corrections to biases 2 and 3, seem to have a greater effect on the average of the velocity image, causing over-estimations.
Book Synopsis Layered Crustal and Mantle Structure and Anisotropy Beneath the Afar Depression and Malawi Rift Zone by : Cory Alexander Reed
Download or read book Layered Crustal and Mantle Structure and Anisotropy Beneath the Afar Depression and Malawi Rift Zone written by Cory Alexander Reed and published by . This book was released on 2017 with total page 215 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Although a wealth of geophysical data sets have been acquired within the vicinity of continental rift zones, the mechanisms responsible for the breakup of stable continental lithosphere are ambiguous. Eastern Africa is host to the largest contemporary rift zone on Earth, and is thus the most prominent site with which to investigate the processes which govern the rupture of continental lithosphere. The studies herein represent teleseismic analyses of the velocity and thermomechanical structure of the crust and mantle beneath the Afar Depression and Malawi Rift Zone (MRZ) of the East African Rift System. Within the Afar Depression, the first densely-spaced receiver function investigation of crustal thickness and inferred velocity attenuation across the Tendaho Graben is conducted, and the largest to-date study of the topography of the mantle transition zone (MTZ) beneath NE Africa is provided, which reveals low upper-mantle velocities beneath the Afar concordant with a probable mantle plume traversing the MTZ beneath the western Ethiopian Plateau. In the vicinity of the MRZ, a data set comprised of 35 seismic stations is employed that was deployed over a two year period from mid-2012 to mid-2014, belonging to the SAFARI (Seismic Arrays For African Rift Initiation) experiment. Accordingly, the first MTZ topography and shear wave splitting analyses were conducted in the region. The latter reveals largely plate motion-parallel anisotropy that is locally modulated by lithospheric thickness abnormalities adjacent to the MRZ, while the former reveals normal MTZ thicknesses and shallow discontinuities that support the presence of a thick lithospheric keel within the MRZ region. These evidences strongly argue for the evolution of the MRZ via passive rifting mechanisms absent lower-mantle influences"--Abstract, page iv.
Download or read book Treatise on Geophysics written by and published by Elsevier. This book was released on 2015-04-17 with total page 5604 pages. Available in PDF, EPUB and Kindle. Book excerpt: Treatise on Geophysics, Second Edition, is a comprehensive and in-depth study of the physics of the Earth beyond what any geophysics text has provided previously. Thoroughly revised and updated, it provides fundamental and state-of-the-art discussion of all aspects of geophysics. A highlight of the second edition is a new volume on Near Surface Geophysics that discusses the role of geophysics in the exploitation and conservation of natural resources and the assessment of degradation of natural systems by pollution. Additional features include new material in the Planets and Moon, Mantle Dynamics, Core Dynamics, Crustal and Lithosphere Dynamics, Evolution of the Earth, and Geodesy volumes. New material is also presented on the uses of Earth gravity measurements. This title is essential for professionals, researchers, professors, and advanced undergraduate and graduate students in the fields of Geophysics and Earth system science. Comprehensive and detailed coverage of all aspects of geophysics Fundamental and state-of-the-art discussions of all research topics Integration of topics into a coherent whole
Book Synopsis Crustal and Upper-mantle Structure Beneath the Colorado Plateau and Basin and Range Province as Determined from Rayleigh-wave Dispersion by : Robert Louis Bucher
Download or read book Crustal and Upper-mantle Structure Beneath the Colorado Plateau and Basin and Range Province as Determined from Rayleigh-wave Dispersion written by Robert Louis Bucher and published by . This book was released on 1971 with total page 212 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Proterozoic Crustal Evolution by : K.C. Condie
Download or read book Proterozoic Crustal Evolution written by K.C. Condie and published by Elsevier. This book was released on 1993-02-03 with total page 553 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a final product of the International Geological Correlation Program (IGCP) Project 217, this volume brings together significant advances in the understanding of Proterozoic crustal evolution. This IGCP Project focussed on nine research objectives: 1) Comparison of Archean and Proterozoic supracrustal assemblages to more fully understand differences between Archean and post-Archean tectonic regimes; 2) To more fully understand the geochemical differences between Archean and post-Archean sediments and to evaluate the various factors that control sediment composition; 3) From combined U/Pb zircon and whole-rock Sm/Nd studies, to see if the apparent 2.4-2.0 continental crust "generation gap" is real; 4) To employ new techniques in the dating of individual zircons to more fully understand Proterozoic tectonic history and the role of crustal reworking; 5) From trace element ratios and Nd isotopic data from basalts, to better understand Proterozoic mantle evolution; 6) To encourage more detailed studies of the anorogenic granite-anorthosite association to better understand its origin and significance in terms of crustal evolution; 7) From combined Nd, Pb, and Sr isotopic data, to more precisely estimate the amount of new continental crust formed during the Proterozoic; 8) To encourage joint P-T and geochronological studies of Proterozoic and high-grade terranes to better understand Proterozoic orogenesis: and 9) To try and understand why hydrothermal precious metal deposits are relatively rare in the Proterozoic compared to both the Archean and the Phanerozoic. The book should be of interest to professionals in the geosciences (especially geochemists, petrologists and structural geologists) and graduate students in the same fields.
Book Synopsis Variations in Crust and Upper Mantle Structure Beneath Diverse Geologic Provinces in Asia by :
Download or read book Variations in Crust and Upper Mantle Structure Beneath Diverse Geologic Provinces in Asia written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents results of a two year effort to determine crust and mantle lithospheric structure beneath Eurasia and to explore the effects that structural variations have on regional wave propagation. First, variations in crust and lid structure on Pn and Lg propagation are investigated using regionalized velocity models previously determined under China. While explosion Pn/Lg ratios are higher than earthquake ratios for all of the regionalized Chinese velocity models, this difference is much smaller than the variations in Pn/Lg ratios caused by propagation differences. This emphasizes the importance of resolving crust and upper mantle structure for successful discrimination. The second part of this report describes detailed regional wave modeling studies to determine crustal and mantle lithospheric structure beneath Tibet. We find low average crustal P-wave velocities (5.9-6.1 km/s), thick crust (68-76 km) and fast lithospheric mantle (8.2-8.25 km/s) beneath the Lhasa Terrane in southern Tibet. Crustal and mantle lithospheric structure to the north in the Qiangtang Terrane differs dramatically with average crustal P and S-wave velocities 4% faster and 2% slower, respectively relative to the Lhasa Terrane. These differences are too large to be explained by temperature differences alone and require a partially molten uppermost mantle lithosphere in the Qiangtang Terrane.
