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  • 1
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    Inverse Q-filtering by Fourier transform (1987)
    Soc. Explorat. Geophys.
    In:  57th Annual International of SEG, Univ. Minnesota, Minneapolis, Soc. Explorat. Geophys., vol. 10, no. 421, pp. 61-63, (ISBN 3-933346-037)
    Details
    Publication Date: 1987
    Keywords: Filter- ; Fourier transform ; Inversion ; Attenuation ; Quality factor
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
    Electronic Resource
    Electronic Resource
    Archaean subduction inferred from seismic images of a mantle suture in the Superior Province (1995)
    [s.l.] : Nature Publishing Group
    Nature 375 (1995), S. 670-674 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Superior Province of Canada consists of an alternating sequence of granite-greenstone belts and metasedimentary sub-provinces that decrease in age from 3,100 Myr in the north to 2,650 Myr in the south (Fig. 1). This sequence probably arose through the amalgamation of ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/375670a0
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Seismic evidence for a magma chamber beneath the slow-spreading Mid-Atlantic Ridge (1995)
    [s.l.] : Nature Publishing Group
    Nature 377 (1995), S. 410-414 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The axial valley of the MARK (Mid-Atlantic Ridge at Kane) area lies south of the Kane fracture zone and has been the object of a number of geological, geochemical and geophysical surveys. These have included dredging15, submersible dives16, fluid sampling14, side-scan sonar17, ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/377410a0
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    Paper (German National Licenses)
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  • 4
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    Seismic waveform tomography across the Seattle Fault Zone in Puget Sound: resolution analysis and effectiveness of visco-acoustic inversion of viscoelastic data (2013)
    Oxford University Press
    Details
    Publication Date: 2013-04-11
    Description: Visco-acoustic waveform tomography was applied to marine seismic reflection data across the Seattle fault zone in Puget Sound in the northwestern USA. Using the recovered velocity and attenuation models, we performed a set of synthetic visco-acoustic and viscoelastic checkerboard tests, and compared the results to verify the effectiveness of applying visco-acoustic waveform tomography to viscoelastic field data. Visco-acoustic waveform tomography produces higher resolution velocity and attenuation models than ray-based tomography, but artefacts due to elastic effects such as mode conversion are present at layer interfaces where the velocity contrast is high. Elastic effects also affect attenuation values, which can be too high or too low in places because visco-acoustic inversion compensates the loss of amplitude due to mode conversion by inadequately estimating the attenuation. A comparison of the attenuation models inverted from viscoelastic and visco-acoustic synthetic data suggests that inverted attenuation values can be reliable when the velocity gradient is low, and the quality of the inversion improves in a highly attenuating medium or in a medium with high attenuation contrasts. Joint interpretation of the derived velocity and attenuation models enables us to identify Quaternary (glacial and postglacial Pleistocene) sedimentary, Tertiary sedimentary and Eocene volcanic rocks. Several shallow faults, anticlines and a syncline are identified across the Seattle uplift and the Seattle fault zone. Our interpretation of faults using the velocity model, attenuation model and migrated seismic section is consistent with two possible published models of the Seattle Fault Zone: either a thrust fault that accommodates north–south shortening by forming a fault-propagation fold with a forelimb breakthrough, or part of a passive roof duplex in which the Seattle Fault Zone is located at the leading edge of a triangle zone that is propagating into the Seattle basin.
    Print ISSN: 0956-540X
    Electronic ISSN: 1365-246X
    Topics: Geosciences
    Published by Oxford University Press on behalf of The Deutsche Geophysikalische Gesellschaft (DGG) and the Royal Astronomical Society (RAS).
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  • 5
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    Application of waveform tomography to marine seismic reflection data from the Queen Charlotte Basin of western Canada (2011)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2011-03-01
    Description: To obtain a higher resolution quantitative P-wave velocity model, 2D waveform tomography was applied to seismic reflection data from the Queen Charlotte sedimentary basin off the west coast of Canada. The forward modeling and inversion were implemented in the frequency domain using the visco-acoustic wave equation. Field data preconditioning consisted of F-K filtering, 2D amplitude scaling, shot-to-shot amplitude balancing, and time windowing. The field data were inverted between 7 and 13.66 Hz, with attenuation introduced for frequencies miss data to improve the final velocity model; two different approaches to sampling the frequencies were evaluated. The limited maximum offset of the marine data (3770 m) and the relatively high starting frequency (7 Hz) were the main challenges encountered during the inversion. An inversion strategy that successively recovered shallow-to-deep structures was designed to mitigate these issues. The inclusion of later arrivals in the waveform tomography resulted in a velocity model that extends to a depth of approximately 1200 m, twice the maximum depth of ray coverage in the ray-based tomography. Overall, there is a good agreement between the velocity model and a sonic log from a well on the seismic line, as well as between modeled shot gathers and field data. Anomalous zones of low velocity in the model correspond to previously identified faults or their upward continuation into the shallow Pliocene section where they are not readily identifiable in the conventional migration.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
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  • 6
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    Seismic velocity and attenuation structures of the Queen Charlotte Basin from full-waveform tomography of seismic reflection data (2012)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2012-05-01
    Description: We applied viscoacoustic waveform tomography to four seismic reflection lines from the central and northern part of the Queen Charlotte sedimentary basin and, using frequencies of 7–12 Hz, we estimated the compressional velocity and attenuation above a depth of approximately 1.2 km. We refined our previously published inversion strategy by alternating between phase-only and amplitude-plus-phase velocity inversion for the first two pairs of frequencies used, and added a second step, in which we inverted for attenuation from the lowest frequency using the final recovered velocity model and an initial homogeneous QP-model. Our recovered velocity and attenuation models demonstrated an overall good correlation with the available sonic and gamma-ray logs. Modeled seismic data matches the field data well and 1D velocity and attenuation profiles extracted at line intersections show a good correlation, thus demonstrating the robust nature of the results. Recovered velocities aid in interpreting shallow structures not readily identifiable on the conventional migration such as Quaternary strata and Pliocene faulting. Recovered attenuation values in the sedimentary rocks are generally consistent with saturated sandstones and consistent with the geology interpreted from well logs. Localized regions of elevated attenuation and associated low velocities correlate with siltstones and shales, the presence of hydrocarbons, or inferred increases in porosity due to fracturing. Seafloor pockmarks, where venting of gas occurs, are underlain by low velocities and an anomalous attenuation variation, and pipe-like gas chimneys are interpreted in two other areas of Hecate Strait. Igneous basement is associated with high velocity and high attenuation in its uppermost part, suggesting the presence of volcanic rocks, but the elevated attenuation may also be due to scattering and elastic mode conversions not included in the viscoacoustic inversion.
    Print ISSN: 0016-8033
    Electronic ISSN: 1942-2156
    Topics: Geosciences , Physics
    Published by Society of Exploration Geophysicists (SEG)
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  • 7
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    Frugal full-waveform inversion: From theory to a practical algorithm (2013)
    Society of Exploration Geophysicists (SEG)
    Details
    Publication Date: 2013-09-05
    Description: As conventional oil and gas fields are maturing, our profession is challenged to come up with the next-generation of more and more sophisticated exploration tools. In exploration seismology this trend has let to the emergence of wave-equation-based inversion technologies such as reverse time migration and full-waveform inversion. While significant progress has been made in wave-equation-based inversion, major challenges remain in the development of robust and computationally feasible workflows that give reliable results in geophysically challenging areas that may include ultralow shear-velocity zones or high-velocity salt. Moreover, subsalt production carries risks that need mitigation, which raises the bar from creating subsalt images to inverting for subsalt overpressure.
    Print ISSN: 1070-485X
    Electronic ISSN: 1938-3789
    Topics: Geosciences
    Published by Society of Exploration Geophysicists (SEG)
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  • 8
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    Seismic interpretation of crustal-scale extension in the Intermontane Belt of the northern Canadian Cordillera (2016)
    Geological Society of America (GSA)
    In: Geology
    Details
    Publication Date: 2016-05-24
    Description: The crustal thickness of the Canadian Cordillera, which may have reached 50–65 km during the Cretaceous, is now only 32–38 km along its length. In the south, postorogenic extension during the Eocene resulted in the formation of core complexes and crustal-scale extensional shear zones, whereas in the north evidence for postorogenic extension is either limited to relatively minor basin formation in a transtensional environment or has not been recognized. Using new images of Lithoprobe seismic reflection line 2a in northern British Columbia, which has been previously interpreted in terms of terrane accretion, I make an alternative interpretation of crustal-scale postaccretion extension in the middle and upper crust. As early as the late Permian to Early Triassic, the Quesnellia and Stikinia arc terranes were accreted to ancestral North America along a crustal ramp, which is imaged in the lower crust. An extensional shear zone, which extends from close to the surface to 20 km depth, is identified from the geometry of reflections in the overlying structural basin and a lateral change in seismic velocity. The oceanic Cache Creek terrane, which is 〈4 km thick in the vicinity of line 2a, was preserved, because it was imbricated with its overlap assemblage and dropped into the 10-km-deep structural half-graben, which may correspond approximately to the combined extent of the Whitehorse trough and the Cache Creek terrane in southern Yukon and northern British Columbia.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
    Published by Geological Society of America (GSA)
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  • 9
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    Distribution of Paleogene and Cretaceous rocks around the Nazko River belt of central British Columbia from 3-D long-offset first-arrival seismic tomography (2014)
    National Research Council Canada (NRC)
    Details
    Publication Date: 2014-06-14
    Description: Across the Nechako–Chilcotin plateau of British Columbia, the distribution of Cretaceous sedimentary rocks, which are considered prospective for hydrocarbon exploration, is poorly known due to the surface cover of glacial deposits and Tertiary volcanic rocks. To constrain the subsurface distribution of these Cretaceous rocks, in 2008 Geoscience BC acquired seven long, up to 14.4 km, offset vibroseis seismic reflection lines across a north-northwest-trending belt of exhumed sedimentary rocks inferred to be part of the Taylor Creek Group. P-wave velocity models, which are consistent with sonic logs from nearby wells, have been estimated using three-dimensional first-arrival tomography to depths ranging from 1 to 4 km. Igneous basement can be identified on most lines using the 5.5 km/s isovelocity contour, which locates the top of the basement to an accuracy of ~400 m where its depth is known in exploration wells. There is no general distinction on the basis of seismic velocity between Cretaceous sedimentary and Paleocene–Eocene volcanic–volcaniclastic rocks, both of which appear to be characterized in the tomographic models by velocities of 3.0–5.0 km/s. The geometry of the igneous basement inferred from the velocity models identifies north-trending basins and ridges, which correlate with exposed rocks of the Jurassic Hazelton Group. Identified Cretaceous sedimentary rocks occur beneath less negative Bouguer gravity anomalies, but the original distribution of these rocks has been disrupted by later Tertiary extension that created north-trending basins associated with the most negative gravity anomalies. We suggest that Cretaceous sedimentary rocks, if deposited, could be preserved within these basins if the rocks had not been eroded prior to Tertiary extension.
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
    Published by National Research Council Canada (NRC)
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  • 10
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    Deep seismic reflection constraints on Paleogene crustal extension in the south-central Intermontane belt, British Columbia (2014)
    National Research Council Canada (NRC)
    Details
    Publication Date: 2014-06-14
    Description: Following growth of the Canadian Cordillera during the Mesozoic, the southern Cordillera was subject to extension during the Paleocene and Eocene that correlated with widespread volcanic activity in south-central British Columbia, including across much of the Nechako–Chilcotin plateau. In 2008, Geoscience BC acquired 330 km of deep vibroseis reflection profiles on the plateau, mostly over the Stikinia arc terrane, but also over its eastern contact with the oceanic Cache Creek terrane. All seven seismic reflection lines reveal a strongly reflective lower crust that extends from 7 to 9 s down to the Moho, which is defined by the downward termination of reflectivity at 11–12 s. In the uppermost crust, extension occurred by block faulting with faults soling into subhorizontal to shallowly dipping detachments above 10 km depth. Extension in the deeper upper and middle crust, which was partly controlled by antiforms likely related to earlier shortening, was accommodated on a network of anastomosing shear zones that sole out into the top of the reflective lower crust. The lower crustal reflections correlate with seismic P-wave velocities of 6.45–6.98 km/s, indicating that the reflective lower crust has a more mafic composition than the middle crust. As in other extensional settings, we suggest that this pervasive fabric of reflectors arises from the intrusion of mantle-derived basaltic magma into zones of ductile shearing, and that differentiation of these melts resulted in the widespread Paleocene to Eocene volcanism. Reflector dips indicate that extension was approximately east–west, consistent with north-northwest-trending horsts separated by basins filled with Paleocene to Eocene volcanic and volcaniclastic rocks.
    Print ISSN: 0008-4077
    Electronic ISSN: 1480-3313
    Topics: Geosciences
    Published by National Research Council Canada (NRC)
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