Download or read book Processing and Interpretation of Seismic Data in the Northern Gulf of Alaska Offshore Yakutat written by Julie K. Zweig and published by . This book was released on 1985 with total page 246 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Acoustic Full waveform to Elastic Pre stack Seismic Inversion of the Yakutat Terrane Gulf of Alaska written by Hala Alqatari and published by . This book was released on 2018 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Yakutat-North American collision in the Gulf of Alaska has developed a complex subduction zone followed by major deformations such as the Chugach-St Elias mountain range creation, intensified exhumation, fold and thrust-fault formation. I generate a compressional velocity model of the Yakutat microplate using two-dimensional acoustic and isotropic time-domain full waveform inversion (FWI) of marine seismic reflection and refraction data from the STEEP project (ST. Elias Erosion/tectonics Project). FWI is a non-linear data-fitting algorithm that aims to recover subsurface parameters from the recorded seismic wavefield. Seismic wave propagation along the Yakutat terrane is simulated using a staggered-grid finite difference modeling scheme. Drawbacks associated with FWI is cycle skipping during the minimization process, which results in converging to the wrong velocity model. Starting with a good initial model that contains the low-frequency information can help mitigate this issue. The starting velocity model input to FWI in this case is generated by a traveltime tomographic inversion of ocean-bottom seismometer and streamer seismic data. Data preconditioning includes muting, filtering, noise removal and amplitude rescaling of the field seismic data to match the corresponding amplitudes of the synthetic traces. The forward model is able to produce a good match between the observed and the modeled wavefield within half the propagated wavelength. I use the FWI result, which shows good correlation with the industry well, as an input to two additional seismic inversion methods: acoustic post-stack and elastic pre-stack seismic inversion in order to recover shear impedance and density models along the seismic line. Extending the problem to the elastic medium is important to support more advanced seismic interpretation. Both techniques were able to produce higher-resolution images of the Yakutat terrane that are well correlated with the well response. Structural complexities identified in the generated models include the northwest-dipping Pamplona fault system, the offshore folding zone, thickening of the Yakutat basement and, lastly, significantly lower velocities in the Poul Creek formation compared to the younger Yakataga formation, which may be attributed to high-fluid pressure within that formation.
Download or read book Seismic and Morphologic Analysis of the Gulf of Alaska Yakutat Margin written by John Marshall Swartz and published by . This book was released on 2014 with total page 104 pages. Available in PDF, EPUB and Kindle. Book excerpt: The active St. Elias Orogen in southern Alaska was created by collision of the offshore Yakutat Terrane with North America. These mountains exhibit the highest coastal relief in the world and also are home to temperate tidewater glaciers, one of the most powerful erosive agents known. Glaciation in Southern Alaska has occurred since the Miocene, but climatic shifts associated with the intensification of Northern Hemisphere glaciation at ~2.5 Ma and the mid-Pleistocene transition at ~1 Ma have led to drastic increases in glacial erosion and associated offshore sediment transport and deposition. The Yakutat continental shelf has hosted ice streams during glacial advances since the mid-Pleistocene, but it is only recently that ice has reached the continental shelf edge itself. Quantitative morphologic analysis finds significant variability along the slope, with an relatively gentle gradient trough mouth fan building off the Yakutat Sea Valley, a shelf-crossing glacial trough, due to massive sediment supply from the heart of the St. Elias Orogen, while farther to the east the extremely steep continental margin is heavily gullied and sediment bypasses the slope reaching the offshore Surveyor fan. Seismic stratigraphy indicates that ice streams first reached the shelf edge with the mid-Pleistocene climate transition, a shift from 41 ka to 100 ka glacial-interglacial climate cycles. This increase in glacial durations allowed not only the ice to sustain advances to the shelf edge, but led to amplified erosion and climate-tectonic feedback effects.
Download or read book Seismogenic and Tsunamigenic Processes in Shallow Subduction Zones written by Jeanne Sauber and published by Birkhäuser. This book was released on 2012-12-06 with total page 373 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthquakes in shallow subduction zones account for the greatest part of seismic energy release in the Earth and often cause significant damage; in some cases they are accompanied by devastating tsunamis. Understanding the physics of seismogenic and tsunamigenic processes in such zones continues to be a challenging focus of ongoing research. The seismologic and geodetic work reported in this volume highlights the recent advances made toward quantifying and understandig the role of shallow plate coupling in the earthquake generation process. The relation between regional seismotectonics, features in the downgoing plate, and the slip distribution in earthquakes are examined for recent and great historical events. In addition to papers reporting new results, review articles on tsunami and tsunamigenic earthquakes and depth dependent plate interface properties are presented. These observational results, along with complementary laboratory and theoretical studies, can assist in assessing the seismic potential of a given region.
Download or read book Geological Survey Circular written by and published by . This book was released on 1982 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quaternary Glacial and Climatic History of Southern Alaska Using High resolution Seismic Reflection Records written by Bryce Arthur Willems and published by . This book was released on 2009 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The ultra and high-resolution seismic reflection data in a temperate glacimarine environment provides insight into glacimarine, marine, climatic, and tectonic processes of the Gulf of Alaska margin. Objectives of the dissertation were to improve our understanding of: (1) modern depositional processes operating within temperate glacimarine systems and (2) the glacial dynamics of the Cordilleran Ice Sheet. These objectives have been met from investigations in Disenchantment Bay and Muir Inlet, as well as the Bering Trough and Yakutat Sea Valley areas on the Alaskan shelf. Disenchantment Bay is similar to other glacimarine systems that have high sediment flux and rates of denudation despite the advance of Hubbard Glacier. Glacimarine varves can be recognized in Huntec seismic reflection profiles within proximal portions of the fjord and provide a high-resolution chronology from which depositional processes can be described. Annual accumulations of sediment measured from Huntec seismic reflection data cannot be used as a proxy of climate variability due to inadequate vertical resolution. Outburst sediments from the 1986 and 2002 outburst floods in Disenchantment Bay deposited laminated mud, thin beds of sand, and beds of diamicton. Depositional processes and sedimentary volumes are similar between the two outburst flood events. Their volumes are of similar magnitude to marine sediments derived from Icelandic jokulhlaups and are potentially analogous to marine ending outburst events. Fjord strata reveal differences in sediment preservation and fjord geometry and may collectively represent glacial processes throughout the glacial cycle from alpine to coastal settings. LIA, Neoglacial, and LGM deposits are thought to occur within Muir Inlet and provide new insight into the past glacial history. Strata in Disenchantment Bay reveal the dynamic nature of Hubbard Glacier and the dominance of Malaspina Glacier within the depositional system of Yakutat Bay. Glacimarine sequences on the shelf are dominantly composed of ice-proximal and ice-contact sediments. Sequence geometries reveal transition from aggradational to progradational style that is interpreted to represent the shift into the 100 k climate cycle. This transition is marked by a steady shift into shelf-edge progradation and subsequent ice streaming conditions as opposed to an abrupt transition"--Abstract.
Download or read book U S Geological Survey Circular written by and published by . This book was released on 1976 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Impact of Climate and Tectonics on Sedimentary and Deformational Processes Gulf of Alaska written by Robert Sherman Reece and published by . This book was released on 2012 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt: Collision of the Yakutat Terrane with North America in southern Alaska has driven growth of the Chugach-St. Elias orogen. Glaciation of the St. Elias Range has periodically increased since the Miocene, but began dominating erosion and spurred enhanced exhumation since the mid-Pleistocene transition at ~1 Ma. Ice associated with this glacial intensification carved cross-shelf sea valleys that connect the St. Elias Range to the deep-sea Surveyor Fan. A newly increased terrigenous sediment flux into the fan triggered the formation and growth of the Surveyor Channel. The change in geomorphology observed throughout Fan sequences allows us to characterize the influence that a glaciated orogen can have in shaping margin processes and the sediment pathways from source to sink. Seismic data also reveal an isolated, large, short runout, mass-transport deposit (MTD) buried in the Surveyor Fan. The MTD geometry, size and location on a convergent margin lend support to recent studies suggesting seismic strengthening and infrequent sediment failure on active margins. This study provides insight into the magnitude and scope of events required to cause submarine mega-slides and overcome higher than normal sediment shear strength, including the influence of climate and sea level change. Beneath the Surveyor Fan, integrated geophysical data reveals massive intraplate shearing, and a lack of oceanic crust magnetic lineaments in regions of Pacific Plate crust. We argue that stress from the Yakutat-North America collision transferred outboard to the Pacific Plate is the major driver for the deformation causing these features. This stress would have resulted in significant strain in the NE corner of the Pacific Plate, creating pathways for sill formation in the crust and Surveyor Fan. The collision further intensified as the thickest Yakutat portion began to subduct during the Pleistocene, possibly providing the impetus for the creation of the Gulf of Alaska Shear Zone, a >200 km zone of shear extending out into the Pacific Plate. This study highlights the importance of farfield stress from complex tectonic regimes in consideration of large-scale oceanic intraplate deformation.
Download or read book Publications of the Geological Survey written by and published by . This book was released on 1971 with total page 536 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book High resolution Seismic Survey of an Offshore Area Near Nome Alaska written by A. R. Tagg and published by . This book was released on 1973 with total page 32 pages. Available in PDF, EPUB and Kindle. Book excerpt: Additional title page description: Description and interpretation of data from seismic records and bathymetric charts.
Download or read book The United States Geological Survey in Alaska written by Edward Huntington Cobb and published by . This book was released on 1976 with total page 72 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This report of the activities of the U.S. Geological Survey in Alaska is organized in four parts (1) services and responsibilities; (2) organization; (3) current activities; and (4) cooperative projects with Federal, State, and local agencies.
Download or read book Earth s Glacial Record written by M. Deynoux and published by Cambridge University Press. This book was released on 1994 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book discusses glacial or glacially-controlled sequences as markers of the Earth's geodynamic and climatic history.
Download or read book Publications of the U S Geological Survey 1971 1981 written by and published by . This book was released on 1986 with total page 544 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book U S Geological Survey Professional Paper written by and published by . This book was released on 1968 with total page 672 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book 1992 Proceedings International Conference on Arctic Margins written by Dennis K. Thurston and published by . This book was released on 1994 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geological Survey Professional Paper written by and published by . This book was released on 1979 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Selected Water Resources Abstracts written by and published by . This book was released on 1979 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
