Download or read book Seismic Wave Attenuation of the Crust and Upper Mantle in the Himalaya and South Central Tibetan Plateau written by Patrick W. Monigle and published by . This book was released on 2014 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent geophysical and geological investigations of the Tibetan plateau have given rise to conflicting models of plateau growth and deformation, where the presence and extent of partial melt in the crust could be a determining factor. Here we investigate the attenuation structure of the crust and upper mantle, as attenuation is particularly sensitive to temperature and fluids, both aqueous and melts. We present 3D Qp and Qs results of attenuation structure beneath the HiCLIMB array using local earthquakes recorded between 2004 July and 2005 August. Additional synthetic data analysis shows our ability to expand attenuation analysis beyond the traditional use of first-arriving seismic phases to include reflected and refracted arrivals from the Moho and a persistent upper crust velocity interface. Synthetic analysis also reveals a bandwidth-limited window over which source and attenuation can be uniquely determined, improving the precision of attenuation measurements. Results indicate a high Qp, s upper crust, interrupted by moderate to low Qp faulting and evidence for partial fluid saturation to depths of 15 km and full saturation before 30 km depth. Middle and lower crust attenuation is broadly low Qp, s, with evidence for limited partial melt and interrupted by high Qp, s bodies near the termination of the subducting Indian plate and coincident with a sharp decrease in upper mantle Qp. We find little evidence for extensive partial melt in the crust and the sharpness of Q transitions at depth coincident with changes in faulting style in the upper crust suggest strike-slip motion penetrates the crust and upper mantle at the terminus of subduction.
Download or read book Investigating the Tibetan Crust Through Automatic S Wave Detection and Travel time Tomography Using the Hi CLIMB Seismic Array written by Evan Riddle and published by . This book was released on 2015 with total page 95 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Hi-CLIMB broadband seismic experiment (2002-2005) operated 233 stations along an 800 km long north-south line from the Himalayan foreland into the central Tibetan Plateau and in a 350x350 km sub-array within southern Tibet and central and eastern Nepal. Station spacing was approximately 8 km along the line and 50 km within the sub-array. The experiment spanned the Himalayan range, Lhasa Block, Qiangtang Block and crossed the Yarlung Tsangpo Suture (YTS) and the Banggong-Nujiang Suture (BNS). From June 2004 to August 2005, over 22,500 local and regional seismic events were recorded throughout the south-central Tibetan Plateau based on automated arrival time picks. This dataset provides an opportunity to jointly invert for crust and upper mantle velocity structure along with earthquake locations using both P and S waves. Automated P and S wave picks, however, were originally determined from vertical component data using short term average to long term average (STA/LTA) windows, resulting in relatively few S picks of generally low quality. To increase the number of accurate S arrivals, we implemented an automatic S-wave picker, which uses signal attributes from three-component seismic data. The signal attributes used are rectilinearity, directivity relative to incoming P wave, ratio of transverse to overall energy and transverse amplitude. An S pick is declared when the combination of signal attributes reaches a noise dependent threshold. We used manual picks and S phase observations from events throughout south-central Tibet to adjust picking parameters and thresholds to optimize automatic S picks. For shallow events we found S[subscript g] can be picked reliably to the S[subscript g]/S[subscript n] crossover distance of approximately 3° while S[subscript n] arrivals are absent. Deep events beneath the southern Tibetan Plateau and the High Himalayas produce clear S arrivals that can be picked to about 7° distance. Applying the S-picker to over 5,700 larger (M[subscript L]≥2.7), well-recorded events led to about 100,000 S picks, significantly increasing the number of arrivals and improving their accuracy. Compared to STA/LTA picks, the new automatic S picks show a decrease in average arrival time residual by over 30 percent. This new polarization picking process allowed us to increase ray coverage, which is crucial for P and S wave structural inversions. With the new automatic arrival time picks we use tomoDD double-difference tomography to invert for crust and uppermost mantle structure beneath the Tibetan Plateau. We use the same subset of over 5,700 best-recorded local events containing over 200,000 P and 100,000 S wave arrivals to conduct the inversion. In the upper crust we observe extensive low velocity zones extending to 25 km depth. Based on Vp and Vp/Vs results we suggest this material is quartzite and highly felsic granite. Beneath the BNS we image low Vp values and increased seismicity, indicating a possible fault zone down to 25 km depth. In the lower crust beneath the Qiangtang Block we image high Vp and increased seismicity, suggesting an area of increased crustal strength to the north. Beneath the High Himalaya, south of YTS, the Moho depth decreases from 55 to 75 km depth as the Indian plate subducts beneath Tibetan crust. Along the Moho we observe Vp values upwards of 8.5 km/s extending to 31°N. We attribute these high velocities to the formation of eclogite along the base of the Indian plate, which terminates at 31°N as upper mantle velocities drop to 8.2 km/s. In the lower crust beneath the Lhasa Block low Vp values, around 6.5 km/s, extend to near Moho depth. A lack of seismicity is also present, which could indicate a weak and possibly ductile lower crust in the Lhasa Block. Nowhere in the lower crust does the Vp/Vs ratio exceed 1.8 suggesting extensive areas of partial melt are unlikely.
Download or read book Heterogeneity in the Crust and Upper Mantle written by John A. Goff and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of our knowledge about the physical structure and the chemical composition of the Earth's deep interior is inferred from seismic data. The interpretation of seismic waves generally follows the assumption that the Earth's physical structure is grossly layered and that fluctuations of the physical parameters within individual layers are smooth in structure and small in magnitude. While this view greatly facilitates the analytic and interpretative procedure, it is clearly at odds with evidence from outcrops and boreholes, which indicates that compositional, structural and petrophysical heterogeneity in the Earth prevails over a wide range of scales. This book is the first to unify three different views of crustal and upper mantle heterogeneity. It brings together the geological view, which is derived from the analysis of crustal exposures and deep boreholes; the stochastic view, which attempts to find order and structure in these seemingly chaotic data; and the seismological view, which considers the end product of the complex interaction of seismic energy with the heterogeneous structure at depth. John Goff and Klaus Holliger have compiled chapters that explore and quantify the relationship between geological and petrophysical heterogeneity and its seismic response, and use seismic data to probe the fabric of the Earth's interior. Geologists, geostaticians, and geophysicists alike will benefit from the integrative perspective presented in Heterogeneity in the Crust and Upper Mantle: Nature, Scaling, and Seismic Properties, making this text an unparalleled reference for professionals and students in Earth science fields.
Download or read book Channel Flow Ductile Extrusion and Exhumation in Continental Collision Zones written by Richard D. Law and published by Geological Society of London. This book was released on 2006 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume includes sections on: Evolution of ideas on channel flow and ductile extrusion in the Himalaya-Tibetan Plateau system; Modeling channel flow and ductile extrusion processes; Geological constraints on channel flow and ductile extrusion as an important orogenic process in the Himalaya-Tibetan Plateau, the Hellenides and Appalachians, and the Canadian Cordillera.
Download or read book Treatise on Geomorphology written by and published by Academic Press. This book was released on 2013-02-27 with total page 6392 pages. Available in PDF, EPUB and Kindle. Book excerpt: The changing focus and approach of geomorphic research suggests that the time is opportune for a summary of the state of discipline. The number of peer-reviewed papers published in geomorphic journals has grown steadily for more than two decades and, more importantly, the diversity of authors with respect to geographic location and disciplinary background (geography, geology, ecology, civil engineering, computer science, geographic information science, and others) has expanded dramatically. As more good minds are drawn to geomorphology, and the breadth of the peer-reviewed literature grows, an effective summary of contemporary geomorphic knowledge becomes increasingly difficult. The fourteen volumes of this Treatise on Geomorphology will provide an important reference for users from undergraduate students looking for term paper topics, to graduate students starting a literature review for their thesis work, and professionals seeking a concise summary of a particular topic. Information on the historical development of diverse topics within geomorphology provides context for ongoing research; discussion of research strategies, equipment, and field methods, laboratory experiments, and numerical simulations reflect the multiple approaches to understanding Earth’s surfaces; and summaries of outstanding research questions highlight future challenges and suggest productive new avenues for research. Our future ability to adapt to geomorphic changes in the critical zone very much hinges upon how well landform scientists comprehend the dynamics of Earth’s diverse surfaces. This Treatise on Geomorphology provides a useful synthesis of the state of the discipline, as well as highlighting productive research directions, that Educators and students/researchers will find useful. Geomorphology has advanced greatly in the last 10 years to become a very interdisciplinary field. Undergraduate students looking for term paper topics, to graduate students starting a literature review for their thesis work, and professionals seeking a concise summary of a particular topic will find the answers they need in this broad reference work which has been designed and written to accommodate their diverse backgrounds and levels of understanding Editor-in-Chief, Prof. J. F. Shroder of the University of Nebraska at Omaha, is past president of the QG&G section of the Geological Society of America and present Trustee of the GSA Foundation, while being well respected in the geomorphology research community and having won numerous awards in the field. A host of noted international geomorphologists have contributed state-of-the-art chapters to the work. Readers can be guaranteed that every chapter in this extensive work has been critically reviewed for consistency and accuracy by the World expert Volume Editors and by the Editor-in-Chief himself No other reference work exists in the area of Geomorphology that offers the breadth and depth of information contained in this 14-volume masterpiece. From the foundations and history of geomorphology through to geomorphological innovations and computer modelling, and the past and future states of landform science, no "stone" has been left unturned!
Download or read book Growth and Collapse of the Tibetan Plateau written by Richard Gloaguen and published by Geological Society of London. This book was released on 2011 with total page 272 pages. Available in PDF, EPUB and Kindle. Book excerpt: Despite agreement on first-order features and mechanisms, critical aspects of the origin and evolution of the Tibetan Plateau, such as the exact timing and nature of collision, the initiation of plateau uplift, and the evolution of its height and width, are disputed, untested or unknown. This book gathers papers dealing with the growth and collapse of the Tibetan Plateau. The timing, the underlying mechanisms, their interactions and the induced surface shaping, contributing to the Tibetan Plateau evolution are tightly linked via coupled and feedback processes. We present interdisciplinary contributions allowing insight into the complex interactions between lithospheric dynamics, topography building, erosion, hydrological processes and atmospheric coupling. The book is structured in four parts: early processes in the plateau formation; recent growth of the Tibetan Plateau; mechanisms of plateau growth; and plateau uplift, surface processes and the monsoon.
Download or read book Seismic Velocity Radial Anisotropy in the Crust and Upper Mantle of Northeastern Tibetan Plateau from Surface Wave Tomography written by Lun Li and published by . This book was released on 2013 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The northeastern (NE) Tibetan Plateau with complex interaction between mountain building and strike-slip faulting is a prime site to study the growth of the plateau and to understand the dynamic processes at its boundaries. This dissertation research investigates the crust and upper mantle structure in the NE Tibetan Plateau using surface wave tomography from teleseismic data recorded at the 36 seismic stations of NorthEast Tibet Seismic (NETS) array. The first part of this dissertation is to construct a 3-D SV velocity (VSV) model using Rayleigh wave data in the NE Tibetan Plateau. The average and 2-D variations of phase velocities were obtained at 14 periods from 20 to 100 s and then used to constrain 1-D and 3-D VSV models. The entire region is characterized by relatively low absolute velocity, indicating a weak upper mantle. One pronounced slow anomaly centered at ~120 km depth is imaged right beneath a restraining bend of the Kunlun fault and is probably caused by anomalously high temperature and partial melting resulted from localized asthenosphere upwelling after the delamination of a thick lithosphere root beneath the bend. In the second part of the dissertation, a 3-D SH velocity (VSH) model was obtained from the Love wave phase velocities at 13 periods from 20 to 91 s, and then used to construct a 3-D radial anisotropic model combined with the VSV model. The lower crust is characterized with positive anisotropy (VSH>VSV). The large positive anisotropy can be explained by horizontal alignment of anisotropic minerals such as mica at the formation of lower crust. The mantle lithosphere above 90 km is largely isotropic while weak positive anisotropy appears beneath 90 km, which probably marks the lithosphere-asthenosphere boundary. The Kunlun restraining bend and its surrounding region are distinguished by a relatively negative radial anisotropy in the entire lithosphere, providing evidence for coherent lithosphere deformation in this area where local compression stress is high. Such coherent lithosphere deformation is not observed in the eastern portion of the Kunlun neither in the Qinling and Qilian orogens, suggesting that the lithosphere shortening in most of the NE Tibet is not as strong as in the interiors of the plateau.
Download or read book Tectonic Evolution of the Himalayas and Tibet written by Royal Society (Great Britain). Discussion Meeting and published by . This book was released on 1988 with total page 350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Crust Mantle Thermal Structure and Tectonothermal Evolution of the Tibetan Plateau written by Xianjie Shen and published by VSP. This book was released on 1996-12 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt: This monograph deals with systematic studies of all relevant thermal aspects of the Tibetan Plateau, including terrestrial heat flow measures, distribution pattern of observed heat flow along a N-S profile, crust-mantle thermal structure, and North-Middle-South triple heterogeneity across the whole plateau. Main emphasis has been put on the close correlation between thermal and comprehensive geophysical fields and the intrinsic genetic linkage between tectonic deformation of terranes and thereby induced deep-seated and superficial theral activities and responses. This new approach, in combination with available geoscientific research results, has led to a synthetic idea of integrated tectonothermal evolution of the Tibetan Plateau.
Download or read book Upper Mantle Heterogeneities from Active and Passive Seismology written by K. Fuchs and published by Springer Science & Business Media. This book was released on 2013-03-14 with total page 365 pages. Available in PDF, EPUB and Kindle. Book excerpt: 600 km giving insight into the 3D structure of the upper mantle. These data are confronted with the requirements of the CTBT for 3D regional seismic models of the lithosphere-asthenosphere system. The two primary purposes of the present work are, first, to present these seismic observations on super long-range profiles in digitised format, using peaceful nuclear explosions (PNE) in the former USSR, and, second, to present the joint thoughts of experts from the deep seismic sounding (DSS) and the comprehensive test ban treaty (CTBT) communities. Implications for petrological and other earth science disciplines are presented. Audience: The CTBT community and earth scientists interested in the 3D structure of the lithosphere-asthenosphere system.
Download or read book Heterogeneity in the Crust and Upper Mantle written by John A. Goff and published by Boom Koninklijke Uitgevers. This book was released on 2003 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Most of our knowledge about the physical structure and the chemical composition of the Earth's deep interior is inferred from seismic data. The interpretation of seismic waves generally follows the assumption that the Earth's physical structure is grossly layered and that fluctuations of the physical parameters within individual layers are smooth in structure and small in magnitude. While this view greatly facilitates the analytic and interpretative procedure, it is clearly at odds with evidence from outcrops and boreholes, which indicates that compositional, structural and petrophysical heterogeneity in the Earth prevails over a wide range of scales. This book is the first to unify three different views of crustal and upper mantle heterogeneity. It brings together the geological view, which is derived from the analysis of crustal exposures and deep boreholes; the stochastic view, which attempts to find order and structure in these seemingly chaotic data; and the seismological view, which considers the end product of the complex interaction of seismic energy with the heterogeneous structure at depth. John Goff and Klaus Holliger have compiled chapters that explore and quantify the relationship between geological and petrophysical heterogeneity and its seismic response, and use seismic data to probe the fabric of the Earth's interior. Geologists, geostaticians, and geophysicists alike will benefit from the integrative perspective presented in Heterogeneity in the Crust and Upper Mantle: Nature, Scaling, and Seismic Properties, making this text an unparalleled reference for professionals and students in Earth science fields.
Download or read book Geological Evolution of Central Asian Basins and the Western Tien Shan Range written by Marie-Franc̦oise Brunet and published by Geological Society of London. This book was released on 2017-10-10 with total page 605 pages. Available in PDF, EPUB and Kindle. Book excerpt: The geological evolution of Central Asia commenced with the formation of a complex Precambrian–Palaeozoic orogen. Cimmerian blocks were then accreted to the southern margin in the Mesozoic, leading to tectonic reactivation of older structures and discrete episodes of basin formation. The Indian and Arabian blocks collided with Asia in the Cenozoic, leading to renewed structural reactivation, intracontinental deformation and basin development. This complex evolution resulted in the present-day setting of an elongated Tien Shan range flanked by large Mesozoic–Cenozoic sedimentary basins with smaller intramontane basins distributed within the range. This volume presents multidisciplinary results and reviews from research groups in Europe and Central Asia that focus on the western part of the Tien Shan and some of the adjacent large sedimentary basins. These works elucidate the Late Palaeozoic–Cenozoic tectono-sedimentary evolution of the area. Emphasis is given to the collision of terranes and continents and the ensuing fault reactivations. The impact of climatic changes on sedimentation is also examined.
Download or read book 4 D Framework of Continental Crust written by Robert D. Hatcher and published by Geological Society of America. This book was released on 2007 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This book contains landmark papers on the processes of formation of continental crust from its beginnings in the Archean to modern processes, as well as discussions of several ancient and modern orogenic belts. The book is international in scope, with contributions from geoscientists dealing with crustal processes on five continents, and articles from more than 50 non-U.S. authors and co-authors."--Publisher's website.
Download or read book Seismicity Tectonics and Lithospheric Structure of the Tibetan Plateau written by William Robert Langin and published by . This book was released on 2003 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seismic wave Attenuation and the State of the Upper Mantle written by Sean C. Solomon and published by . This book was released on 1971 with total page 642 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monitoring the Comprehensive Nuclear Test Ban Treaty written by H.J. Patton and published by Springer Science & Business Media. This book was released on 2001-09-01 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Regional seismograms are dominated by the phases Pn, Pg, Sn, and Lg. More often Sn and Lg are used to infer the attenuation structure of the lithosphere. The seismic phase Sn is a high-frequency shear-wave (typically from 1 to 4 Hz and occasionally higher) that travels in the lithospheric mantle above the negative velocity gradient which usually marks the lithosphere-asthenosphere boundary. Sn has been reported out to distances of 35° (e. g. , MOLNAR and OLIVER, 1969; HUESTIS et aI. , 1973). Sn arrives as a high-frequency wave train lasting tens of seconds and up to 1 to 2 minutes. Sn velocities are typically 4. 7 km/s in stable continental and oceanic lithosphere (HUESTIS et al. , 1973) and as low as 4. 3 km/s (KADINSKY-CADE et al. , 1981) in more tectonically active regions. Lg is a complex short period guided wave consisting of high-frequency P and S energy which travels primarily in the earth's crust at frequencies typically between 0. 5 and 5 Hz. It has been modeled as higher-mode Love and Rayleigh waves as well as a sequence of multiply reflected post-critical S waves trapped in a crustal guide (BOUCHON, 1982; KENNETT, 1986; BOSTOCK and KENNETT, 1990). Lg has been observed not to propagate in oceanic or very thin continental crust (PRESS and EWING, 1952; SEARLE, 1975; ZHANG and LAY, 1995).
Download or read book Tectonics of the Western Himalayas written by Lawrence L. Malinconico and published by Geological Society of America. This book was released on 1989 with total page 331 pages. Available in PDF, EPUB and Kindle. Book excerpt: Papers from a symposium held in San Antonio, Texas, 1986. Contributors consider problems of crustal and lithospheric scales in this area. Contains a folded map of the Salt Range, Pakistan. Annotation copyright Book News, Inc. Portland, Or.
