Structural model of the eastern Achara-Trialeti fold and thrust belt using seismic reflection profiles
Victor AlaniaAlexander ChabukianiOnise EnukidzeAlexander RazmadzeMarc SossonNino TsereteliOtar Varazanashvili
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PreviousNext No AccessSEG Technical Program Expanded Abstracts 1998Shallow seismic reflection investigations of neotectonic activity in the Lower Mississippi ValleyAuthors: James B. HarrisSeth A. BermanWilliam C. BeardRon L. StreetRandel T. CoxJames B. HarrisMillsaps College, Seth A. BermanMississippi Office of Geology, William C. BeardMillsaps College, Ron L. StreetUniversity of Kentucky, and Randel T. CoxArkansas State Universityhttps://doi.org/10.1190/1.1820619 SectionsAboutPDF/ePub ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinked InRedditEmail Permalink: https://doi.org/10.1190/1.1820619FiguresReferencesRelatedDetailsCited ByQuaternary deformation and fault structure in the Northern Mississippi Embayment as imaged by near-surface seismic reflection data27 May 2014 | Tectonics, Vol. 33, No. 5Application of shallow shear-wave seismic reflection methods in earthquake hazards studiesJames B. Harris10 August 2010 | The Leading Edge, Vol. 29, No. 8Hammer-impact SH-wave seismic reflection methods in neotectonic investigations: General observations and case histories from the Mississippi Embayment, U.S.A.23 June 2009 | Journal of Earth Science, Vol. 20, No. 3Mapping an aquitard breach using shear-wave seismic reflection2 December 2008 | Hydrogeology Journal, Vol. 17, No. 3SH-Wave Seismic Reflection Images of Anomalous Foundation Conditions at the Mississinewa Dam, IndianaEdward W. Woolery27 April 2012 | Journal of Environmental and Engineering Geophysics, Vol. 7, No. 4Known and suggested quaternary faulting in the midcontinent United StatesEngineering Geology, Vol. 62, No. 1-3 SEG Technical Program Expanded Abstracts 1998ISSN (print):1052-3812 ISSN (online):1949-4645Copyright: 1998 Pages: 2092 publication data© 1998 Copyright © 1998 Society of Exploration GeophysicistsPublisher:Society of Exploration Geophysicists HistoryPublished: 06 Jan 2005 CITATION INFORMATION James B. Harris, Seth A. Berman, William C. Beard, Ron L. Street, and Randel T. Cox, (1998), "Shallow seismic reflection investigations of neotectonic activity in the Lower Mississippi Valley," SEG Technical Program Expanded Abstracts : 848-851. https://doi.org/10.1190/1.1820619 Plain-Language Summary PDF DownloadLoading ...
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Accretionary wedge
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In 1986, 1181 km of marine seismic reflection data was collected to 18–20 s of two-way traveltime in the Gulf of St. Lawrence area. The seismic profiles sample all major surface tectono-stratigraphic zones of the Canadian Appalachians. They complement the 1984 deep reflection survey northeast of Newfoundland. Together, the seismic profiles reveal the regional three-dimensional geometry of the orogen.Three lower crustal blocks are distinguished on the seismic data. They are referred to as the Grenville, Central, and Avalon blocks, from west to east. The Grenville block is wedge shaped in section, and its subsurface edge follows the form of the Appalachian structural front. The Grenville block abuts the Central block at mid-crustal to mantle depths. The Avalon block meets the Central block at a steep junction that penetrates the entire crust.Consistent differences in the seismic character of the Moho help identify boundaries of the deep crustal blocks. The Moho signature varies from uniform over extended distances to irregular with abrupt depth changes. In places the Moho is offset by steep reflections that cut the lower crust and upper mantle. In other places, the change in Moho elevation is gradual, with lower crustal reflections following its form. In all three blocks the crust is generally highly reflective, with no distinction between a transparent upper crust and reflective lower crust.In general, Carboniferous and Mesozoic basins crossed by the seismic profiles overlie thinner crust. However, a deep Moho is found at some places beneath the Carboniferous Magdalen Basin.The Grenville block belongs to the Grenville Craton; the Humber Zone is thrust over its dipping southwestern edge. The Dunnage Zone is allochthonous above the opposing Grenville and Central blocks. The Gander Zone may be the surface expression of the Central block or may be allochthonous itself. There is a spatial analogy between the Avalon block and the Avalon Zone. Our profile across the Meguma Zone is too short to seismically distinguish this zone from the Avalon Zone.
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Imaging the architecture of the shallow crust of the South Portuguese Zone fold-and-thrust belt is essential to extend surface mapped geological information to depth and to help in developing models of the ore-bearing Iberian Pyrite Belt part of the Variscan orogeny. The recently acquired IBERSEIS seismic-reflection data set provides, for the first time, detailed images of the entire crust, but source-generated noise masks the earliest reflections and limits the shallowest observed signals to depths >500 m. We inverted P- and SV first-arrival traveltimes for the smoothest minimum-structure velocity models, imaging the shallowest few hundreds of metres along four in total ∼60-km-long profiles. A comparison of a 2-D and 2.5-D (3-D forward and 2-D inverse problem) crooked-line inversion scheme revealed that the crooked-line geometry has a negligible effect on the final images. Resolution of the final preferred models was assessed on the basis of an extensive series of checkerboard tests, showing a slightly lower resolution capability of the SV-data due to greater data uncertainty, fewer number of picks and more limited source–receiver offsets compared with the P-data. The preferred final models compare favourably with the mapped surface geology, showing relatively high and uniform velocities (>5.25 km s−1) for the flysch group in the southern part of the investigation area. Low velocities (∼4.5 km s−1) are found for the 'La Puebla de Guzman antiform' in the centre of the investigation area, where the phyllite–quartzite group is exposed. Velocities fluctuate the most along the northernmost ∼20 km. Velocity variations reflect more the state of tectonic deformation than being directly correlated with the mapped lithologies. Based on a comparison with coincident seismic-reflection data along the southern half of the area, we suggest that two areas of low to intermediate ratios (∼1.85–1.9) correspond to occurrences of thick and less deformed flysch-group units, whereas high ratios (∼1.95) are interpreted to indicate increased porosity due to intense fracturing.
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The crustal model has been created from the integration of potential field data and complemented by multichannel reflection seismic profiles, allowing the interpretation of five tectono-stratigraphy provinces of Deepwater Fold and Thrust Belt, Sabah Trough, Dangerous Grounds Province and Thrust Sheet Zone. The free-air and magnetic anomaly was published from satellite altimetry data. Seismic interpretation displays structural anticline that indicate fold and thrust zone as the Sabah Trough frontier to the southeast. The formation of half-grabens and normal faults was clearly indicated extension in the entire Dangerous Grounds which subducted beneath to the Sabah Trough. The crustal modelling was used to describe and determine the Moho thickness and the configuration of deeper crustal layer by using the GM-SYS Profile Modelling software. The range of Moho thickness shows slightly variable between 33 and 26 km across of the study area. Analytical signal analysis estimated the depth of magnetic source range between 26 and 33 km disclosed to upper crust. The high density surrounded by low density body at Thrust Sheet Zone interpreted as a thrust block built of Palaeogene Crocker sediment.
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