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  • Other Sources  (10)
  • American Institute of Physics
  • München : Bayerisches Landesvermessungsamt
  • Springer Nature
  • Wien : Geolog. Bundesanst.
  • 2005-2009  (7)
  • 1990-1994  (3)
  • 1
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    Geo- and hydro-acoustic manifestations of shallow gas and gas seeps in the Dnepr paleodelta, northwestern Black Sea (2009)
    American Institute of Physics
    In:  The Leading Edge, 28 (9). pp. 1030-1040.
    Details
    Publication Date: 2016-05-24
    Description: Shallow gas occurs between 0 and 1000 m below the sea floor. It consists mainly of microbial-formed or thermogenic methane or a combination of both, sometimes with a limited admixture of higher hydrocarbons (propane, butane, etc.).
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  • 2
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    Noise reduction in 2D and 3D seismic imaging by the CRS method (2008)
    American Institute of Physics
    In:  The Leading Edge, 27 (2). pp. 258-265.
    Details
    Publication Date: 2015-12-16
    Description: The definition of noise and signal in seismic data will vary widely with the viewer's perspective and methods to process and visualize the data. Thus we begin with our definition from the perspective of presenting structural subsurface information.
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  • 3
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    A new equation for the accurate calculation of sound speed in all oceans (2008)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 124 (5). pp. 2774-2782.
    Details
    Publication Date: 2020-07-16
    Description: A new equation is proposed for the calculation of sound speed in seawater as a function of temperature, salinity, depth, and latitude in all oceans and open seas, including the Baltic and the Black Sea. The proposed equation agrees to better than ±0.2m∕s with two reference complex equations, each fitting the best available data corresponding to existing waters of different salinities. The only exceptions are isolated hot brine spots that may be found at the bottom of some seas. The equation is of polynomial form, with 14 terms and coefficients of between one and three significant figures. This is a substantial reduction in complexity compared to the more complex equations using pressure that need to be calculated according to depth and location. The equation uses the 1990 universal temperature scale (an elementary transformation is given for data based on the 1968 temperature scale). It is hoped that the equation will be useful to those who need to calculate sound speed in applications of marine acoustics.
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  • 4
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    Fracture properties from seismic scattering (2007)
    American Institute of Physics
    In:  The Leading Edge, 26 (9). pp. 1186-1196.
    Details
    Publication Date: 2019-04-29
    Description: The seismic trace is a complex aggregate of reflected and scattered signals from subsurface formation interfaces and heterogeneities. Although many varieties of random noise may also be present in the trace, we know from reacquiring the same seismic survey that seismic data are highly repeatable, indicating that significant information about the subsurface is contained in the trace but not yet used by our standard analysis methods. Seismic scattering is a type of signal contained in the data that is generally not utilized.
    Type: Article , PeerReviewed
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  • 5
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    Seismic characterization and continuity analysis of gas-hydrate horizons near Mallik research wells, Mackenzie Delta, Canada (2006)
    American Institute of Physics
    In:  The Leading Edge, 25 (5). pp. 599-604.
    Details
    Publication Date: 2015-11-25
    Description: Gas-hydrate accumulations located onshore in Arctic permafrost regions are seen as a potential source of natural gas. Surprisingly, most of the gas hydrate found in the Mackenzie Delta and Beaufort Sea areas was indirectly discovered or inferred from conventional hydrocarbon exploration programs. One of these occurrences, the Mallik gas-hydrate field (Figure 1), has received particular attention over the last 10 years. Two internationally partnered research well programs have intersected three intervals of gas hydrates and have allowed successful extraction of subpermafrost core samples with significant gas hydrates. The gas-hydrate intervals are up to 40 m thick and have high gas-hydrate saturation, sometimes exceeding 80% of pore volume of unconsolidated clastic sediments with average porosities from 25–40%. At Mallik, the gas-hydrate intervals are located at depths of 900–1100 m and are localized on the crest of an anticline.
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  • 6
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    Seafloor reflectivity—An important seismic property for interpreting fluid/gas expulsion geology and the presence of gas hydrate (2006)
    American Institute of Physics
    In:  The Leading Edge, 25 (5). pp. 620-628.
    Details
    Publication Date: 2020-01-20
    Description: A bottom-simulating reflection (BSR) is a seismic reflectivity phenomenon that is widely accepted as indicating the base of the gas-hydrate stability zone. The acoustic impedance difference between sediments invaded with gas hydrate above the BSR and sediments without gas hydrate, but commonly with free gas below, are accepted as the conditions that create this reflection. The relationship between BSRs and marine gas hydrate has become so well known since the 1970s that investigators, when asked to define the most important seismic attribute of marine gas-hydrate systems, usually reply, “a BSR event.” Research conducted over the last decade has focused on calibrating seafloor seismic reflectivity across the geology of the northern Gulf of Mexico (GoM) continental slope surface to the seafloor. This research indicates that the presence and character of seafloor bright spots (SBS) can be indicators of gas hydrates in surface and near-surface sediments (Figure 1). It has become apparent that SBSs on the continental slope generally are responses to fluid and gas expulsion processes. Gas-hydrate formation is, in turn, related to these processes. As gas-hydrate research expands around the world, it will be interesting to find if SBS behavior in other deepwater settings is as useful for identifying gas-hydrate sites as in the GoM.
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  • 7
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    ‘Lophenteropneust’ hypothesis refuted by collection and photos of new deep-sea hemichordates (2005)
    Springer Nature
    In:  Nature, 434 (7031). pp. 374-376.
    Details
    Publication Date: 2021-09-07
    Description: The deep ocean is home to a group of broad-collared hemichordates—the so-called ‘lophenteropneusts’—that have been photographed gliding on the sea floor1,2,3,4,5,6,7,8 but have not previously been collected. It has been claimed that these worms have collar tentacles and blend morphological features of the two main hemichordate body plans, namely the tentacle-less enteropneusts and the tentacle-bearing pterobranchs. Consequently, lophenteropneusts have been invoked as missing links to suggest that the former evolved into the latter5. The most significant aspect of the lophenteropneust hypothesis is its prediction that the fundamental body plan within a basal phylum of deuterostomes was enteropneust-like. The assumption of such an ancestral state influences ideas about the evolution of the vertebrates from the invertebrates9,10,11,12,13,14. Here we report on the first collected specimen of a broad-collared, deep-sea enteropneust and describe it as a new family, genus and species. The collar, although disproportionately broad, lacks tentacles. In addition, we find no evidence of tentacles in the available deep-sea photographs (published and unpublished) of broad-collared enteropneusts, including those formerly designated as lophenteropneusts. Thus, the lophenteropneust hypothesis was based on misinterpretation of deep-sea photographs of low quality and should no longer be used to support the idea that the enteropneust body plan is basal within the phylum Hemichordata.
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  • 8
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    High‐frequency bottom backscattering: Roughness versus sediment volume scattering (1992)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 92 (2). pp. 962-977.
    Details
    Publication Date: 2020-07-16
    Description: High‐frequency bottom acoustic and geoacoustic data from three well‐characterized sites of different bottom composition are compared with scattering models in order to clarify the roles played by interface roughness and sediment volume inhomogeneities. Model fits to backscattering data from two silty sites lead to the conclusion that scattering from volume inhomogeneities was primarily responsible for the observed backscattering. In contrast, measured bottom roughness was sufficient to explain the backscattering seen at a sandy site. Although the sandy site had directional ripples, the model and data agree in their lack of anisotropy.
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  • 9
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    Foraging behaviour of emperor penguins as a resource detector in winter and summer (1992)
    Springer Nature
    In:  Nature, 360 (6402). pp. 336-339.
    Details
    Publication Date: 2021-04-22
    Description: The emperor penguin (Aptenodytes forsteri), which feeds only at sea, is restricted to the higher latitudes of the antarctic sea-ice habitat1–3. It breeds on the winter fast ice when temperatures are−30 °C and high winds are frequent3. Assuming entirely the task of incubating the single egg, the male fasts for about 120 days in the most severe conditions. When it is relieved by the female around hatching time, the distance between the colony and the open sea may be 100km or more4,5, but where emperors go to forage at that time or during the summer is unknown. The polynias are areas of open water in sea-ice and during winter, with the under-ice habitats at any time of the year, they are among the most difficult of all Antarctic areas to sample. Here we monitor by satellite the routes taken by emperor penguins for foraging and compare them with satellite images of sea-ice. Winter birds walking over fast ice travelled up to 296 km to feed in polynias, whereas those swimming in light pack-ice travelled as far as 895km from the breeding colony. One record of diving showed that although most dives are to mid-water depths, some are near the bottom. Obtaining such detailed information on foraging in emperor penguins means that this bird now offers a unique opportunity to investigate the Antarctic sea-ice habitat.
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  • 10
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    Classification of heterogeneous seafloor topography through surface slope distributions (1991)
    American Institute of Physics
    In:  Journal of the Acoustical Society of America, 90 (4, Pt. 2). pp. 2255-2256.
    Details
    Publication Date: 2020-07-16
    Description: Seafloor topography is neither spatially homogeneous, nor does it obey Gaussian statistics; deviations from both of these assumptions are important from a geological and acoustic point of view. It has been found that the distribution of topographic slopes can be used as a primary tool for understanding the sources and extent of spatial heterogeneities and patterns on the seafloor. The covariance function has been widely used to characterize seafloor topography, but requires the assumption of Gaussian joint probability statistics to be valid. For heterogeneous topography characterized by large transient signals such as steep scarps and volcanoes, the covariance becomes dominated by the transients; in contrast the family slope distributions can still be used to derive stable descriptors for regions with large transient signals, as well as regions containing asymmetric features, and regions with only limited sampling. Knowledge of slopes is useful because a direct relation exists between the covariance and the slope distributions at different spatial scales. Studies of the slope distribution provide a means of identifying the presence of the non‐Gaussian elements in the topography, and flagging their spatial locations. The methods used here are demonstrated by applying them to three small patches of topography located within 20 km of each other in the Eastern Pacific. It is found that dominant azimuthal directions and dip angles differ widely between the patches. In addition, asymmetries in the cross‐sectional shapes of faulted abyssal hills are documented. [Work supported by ONR.]
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