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  • 1
    Electronic Resource
    Electronic Resource
    The time—frequency characteristics of quarry blasts and calibration explosions recorded in Kazakhstan, USSR (1989)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 99 (1989), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: In this paper we consider two fundamentally different processes that can be responsible for the organization of energy in seismic coda into discrete time-independent frequency bands. One process involves the resonance of energy in low velocity horizons and the other requires the interaction of time offset wavefields produced by subevents within multiple-event mine explosions (ripple-fired quarry blasts). We examined data collected by high frequency seismometers in Kazakhstan, USSR, and observed regular time-independent spectral modulations in coda resulting from events strongly suspected to be Soviet quarry blasts, but not in the coda from single event calibration explosions detonated at similar ranges. We conclude these modulations are a source effect and due to ripple-firing. This modulation is independent of the source-receiver azimuth and we infer that the spatial array of subshots in each event must be small. We demonstrate that simple linear superposition theory can be used to reproduce effectively the spectral modulation observed in real quarry blasts. On the basis of these observations we attempt to discriminate between the two types of events using a spectral pattern-based algorithm that seeks time-independent features. We consider the detrimental effect that resonant energy in low velocity horizons can have on the successful application of our algorithm.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1989.tb02019.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Resolution of prominent crustal scatterers near the Noress small-aperture array (1994)
    Oxford, UK : Blackwell Publishing Ltd
    Geophysical journal international 119 (1994), S. 0 
    Details
    ISSN: 1365-246X
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Geosciences
    Notes: Our goal is to identify prominent scatterers near seismic arrays so that the secondary phases they generate can be anticipated and recognized as being of local, not teleseismic, origin. Toward this end we have developed a technique to scan seismic coda recorded by arrays for phases generated locally by scattering of teleseismic energy from large topographical and crustal heterogeneities. In this paper we test the technique by using the NORESS small-aperture array in southern Norway to image free surface secondary Rg sources excited by incoming teleseismic P waves. In essence, our technique suppresses the teleseismic energy and migrates the residual array records to image-coherent local sources.To assess the azimuthal and radial resolution that the NORESS array provides we have analysed point-source synthetics. A preliminary analysis of recorded data provides an initial view of the scatterers in the vicinity of NORESS and identifies limitations of imaging using the full coda of individual events. Single events can be used to image scatterers but more robust images, with higher azimuthal resolution, can be obtained by using a broadly distributed suite of events. Radial resolution of scatterers can be enhanced by deconvolution.A composite image generated by simultaneously considering a suite of 31 deconvolved teleseisms indicates that two secondary Rg sources are present at, or near, the free surface near NORESS. One, 27km to the south-west of the array, appears to be related to dramatic topographic relief at the south-west edge of Lake Mjosa. Another, roughly 10km to the east of the array is judged by a bootstrap-resampling analysis to be only marginally significant. This apparent source does not coincide with obvious topography and is likely buried. Although the time delay that separates the scattered and ‘parent’ phases depends somewhat on the angle of approach of the incoming waves, in general these secondary sources are contributing wave trains to the seismic coda that begin ∼ 4 and 11s, respectively, after the primary onset.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-246X.1994.tb00916.x
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Axi-symmetric Earth models and inner-core anisotropy (1988)
    [s.l.] : Nature Publishing Group
    Nature 333 (1988), S. 228-232 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Seismic waves passing through the middle of the Earth travel slightly faster in a N – S direction than in an E – W direction. A comparison of travel times for different P-wave phases shows that most of this anomaly is within the inner core, and that uniform anisotropy of the inner core ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/333228a0
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  • 4
    Electronic Resource
    Electronic Resource
    Seismic anisotropy in the mantle beneath an oceanic spreading centre (1993)
    [s.l.] : Nature Publishing Group
    Nature 366 (1993), S. 675-677 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Three earthquakes of magnitude greater than 6 were recorded during a 4-week deployment of ocean-bottom seismographs (OBSs) at the Mid-Atlantic Ridge (MAR; 34° S) in Spring 1990. The OBS array consisted of six instruments, three spaced ~25 km apart of the western flank of the ridge and three ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/366675a0
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  • 5
    Electronic Resource
    Electronic Resource
    Is the ocean floor a fractal? (1995)
    Springer
    Mathematical geology 27 (1995), S. 421-462 
    Details
    ISSN: 1573-8868
    Keywords: self-similarity ; self-affinity ; variogram-criterion ; inheritance of scaling properties ; geostatistics ; bathymetric data
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Mathematics
    Notes: Abstract The topographic structure of the ocean bottom is investigated at different scales of resolution to answer the question: Can the seafloor be described as a fractal process? Methods from geostatistics, the theory of regionalized variables, are used to analyze the spatial structure of the ocean floor at different scales of resolution. The key to the analysis is the variogram criterion: Self-similarity of a stochastic process implies self-similarity of its variogram. The criterion is derived and proved here: it also is valid for special cases of self-affinity (in a sense adequate for topography). It has been proposed that seafloor topography can be simulated as a fractal (an object of Hausdorff dimension strictly larger than its topological dimension), having scaling properties (self-similarity or self-affinity). The objective of this study is to compare the implications of these concepts with observations of the seafloor. The analyses are based on SEABEAM bathymetric data from the East Pacific Rise at 13°N/104°W and at 9°N/104°W and use tracks that run both across the ridge crest and along the ridge flank. In the geostatistical evaluation, the data are considered as a stochastic process. The spatial continuity of this process is described by variograms that are calculated for different scales and directions. Applications of the variogram criterion to scale-dependent variogram models yields the following results: Although the seafloor may be a fractal in the sense of the definition involving the Hausdorff dimension, it is not self-similar, nor self-affine (in the given sense). Mathematical models of scale-dependent spatial structures are presented, and their relationship to geologic processes such as ridge evolution, crust formation, and sedimentation is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02084611
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  • 6
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    Multipurpose acoustic networks in the integrated Arctic Ocean observing system (2015)
    Arctic Institute of North America
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © Arctic Institute of North America, 2015. This article is posted here by permission of Arctic Institute of North America for personal use, not for redistribution. The definitive version was published in Arctic 68, supple.1 (2015): 11-27, doi:10.14430/arctic4449.
    Description: The dramatic reduction of sea ice in the Arctic Ocean will increase human activities in the coming years. This activity will be driven by increased demand for energy and the marine resources of an Arctic Ocean accessible to ships. Oil and gas exploration, fisheries, mineral extraction, marine transportation, research and development, tourism, and search and rescue will increase the pressure on the vulnerable Arctic environment. Technologies that allow synoptic in situ observations year-round are needed to monitor and forecast changes in the Arctic atmosphere-ice-ocean system at daily, seasonal, annual, and decadal scales. These data can inform and enable both sustainable development and enforcement of international Arctic agreements and treaties, while protecting this critical environment. In this paper, we discuss multipurpose acoustic networks, including subsea cable components, in the Arctic. These networks provide communication, power, underwater and under-ice navigation, passive monitoring of ambient sound (ice, seismic, biologic, and anthropogenic), and acoustic remote sensing (tomography and thermometry), supporting and complementing data collection from platforms, moorings, and vehicles. We support the development and implementation of regional to basin-wide acoustic networks as an integral component of a multidisciplinary in situ Arctic Ocean observatory.
    Keywords: Arctic observing systems ; Arctic acoustics ; Acoustic tomography ; Cabled networks ; Passive acoustics ; Active acoustics
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 7
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    Ocean Seismic Network Pilot Experiment (2005)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2003. It is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 4 (2003): 1092, doi:10.1029/2002GC000485.
    Description: The primary goal of the Ocean Seismic Network Pilot Experiment (OSNPE) was to learn how to make high quality broadband seismic measurements on the ocean bottom in preparation for a permanent ocean seismic network. The experiment also had implications for the development of a capability for temporary (e.g., 1 year duration) seismic experiments on the ocean floor. Equipment for installing, operating and monitoring borehole observatories in the deep sea was also tested including a lead-in package, a logging probe, a wire line packer and a control vehicle. The control vehicle was used in three modes during the experiment: for observation of seafloor features and equipment, for equipment launch and recovery, and for power supply and telemetry between ocean bottom units and the ship. The OSNPE which was completed in June 1998 acquired almost four months of continuous data and it demonstrated clearly that a combination of shallow buried and borehole broadband sensors could provide comparable quality data to broadband seismic installations on islands and continents. Burial in soft mud appears to be adequate at frequencies below the microseism peak. Although the borehole sensor was subject to installation noise at low frequencies (0.6 to 50 mHz), analysis of the OSNPE data provides new insights into our understanding of ocean bottom ambient noise. The OSNPE results clearly demonstrate the importance of sediment borne shear modes in ocean bottom ambient noise behavior. Ambient noise drops significantly at high frequencies for a sensor placed just at the sediment basalt interface. At frequencies above the microseism peak, there are two reasons that ocean bottom stations have been generally regarded as noisier than island or land stations: ocean bottom stations are closer to the noise source (the surface gravity waves) and most ocean bottom stations to date have been installed on low rigidity sediments where they are subject to the effects of shear wave resonances. When sensors are placed in boreholes in basement the performance of ocean bottom seismic stations approaches that of continental and island stations. A broadband borehole seismic station should be included in any real-time ocean bottom observatory.
    Description: This work was sponsored by the National Science Foundation (NSF Grant Numbers: OCE-9522114, OCE-9523541 and OCE-9819439) with additional support from Incorporated Research Institutions for Seismology (IRIS), Joint Oceanographic Institutions, Inc. (JOI Contract No: 12-94), Scripps Institution of Oceanography, a Mellon Grant from Woods Hole Oceanographic Institution, and the Earthquake Research Institute at the University of Tokyo (Visiting Professorship for RAS).
    Keywords: Ocean Seismic Network Pilot Experiment (OSNPE) ; Seismology ; Instruments and techniques ; Body wave propagation ; Surface waves and free oscillations
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: 2963663 bytes
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  • 8
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    Asymmetric shallow mantle structure beneath the Hawaiian Swell—evidence from Rayleigh waves recorded by the PLUME network (2011)
    John Wiley & Sons
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2011. This article is posted here by permission of John Wiley & Sons for personal use, not for redistribution. The definitive version was published in Geophysical Journal International 187 (2011): 1725–1742, doi:10.1111/j.1365-246X.2011.05238.x.
    Description: We present models of the 3-D shear velocity structure of the lithosphere and asthenosphere beneath the Hawaiian hotspot and surrounding region. The models are derived from long-period Rayleigh-wave phase velocities that were obtained from the analysis of seismic recordings collected during two year-long deployments for the Hawaiian Plume-Lithosphere Undersea Mantle Experiment. For this experiment, broad-band seismic sensors were deployed at nearly 70 seafloor sites as well as 10 sites on the Hawaiian Islands. Our seismic images result from a two-step inversion of path-averaged dispersion curves using the two-station method. The images reveal an asymmetry in shear velocity structure with respect to the island chain, most notably in the lower lithosphere at depths of 60 km and greater, and in the asthenosphere. An elongated, 100-km-wide and 300-km-long low-velocity anomaly reaches to depths of at least 140 km. At depths of 60 km and shallower, the lowest velocities are found near the northern end of the island of Hawaii. No major velocity anomalies are found to the south or southeast of Hawaii, at any depth. The low-velocity anomaly in the asthenosphere is consistent with an excess temperature of 200–250 °C and partial melt at the level of a few percent by volume, if we assume that compositional variations as a result of melt extraction play a minor role. We also image small-scale low-velocity anomalies within the lithosphere that may be associated with the volcanic fields surrounding the Hawaiian Islands.
    Description: This research was financed by the National Science Foundation under grants OCE-00-02470 and OCE-00-02819. Markee was partly sponsored by a SIO graduate student fellowship.
    Keywords: Mantle processes ; Surface waves and free oscillations ; Seismic tomography ; Oceanic hotspots and intraplate volcanism ; Pacific Ocean
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 9
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    Facilitating open exchange of data and information (2015)
    Details
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2014. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Earth Science Informatics 8 (2015): 721-739, doi:10.1007/s12145-014-0202-2.
    Description: By broad consensus, Open Data presents great value. However, beyond that simple statement, there are a number of complex, and sometimes contentious, issues that the science community must address. In this review, we examine the current state of the core issues of Open Data with the unique perspective and use cases of the ocean science community: interoperability; discovery and access; quality and fitness for purpose; and sustainability. The topics of Governance and Data Publication are also examined in detail. Each of the areas covered are, by themselves, complex and the approaches to the issues under consideration are often at odds with each other. Any comprehensive policy on Open Data will require compromises that are best resolved by broad community input. In the final section of the review, we provide recommendations that serve as a starting point for these discussions.
    Description: The authors acknowledge the support of the National Science Foundation through Grant Award No. OCE-1143683.
    Description: 2016-01-07
    Keywords: Open Data ; Interoperability ; Governance ; Data publication
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
    Format: application/pdf
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  • 10
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    Progress report on the development of the seafloor borehole array seismic system (phase II) : July 14, 1992 to January 31, 1996 (2016)
    Woods Hole Oceanographic Institution
    Details
    Publication Date: 2022-05-25
    Description: The Seafloor Borehole Array Seismic System (SEABASS) was originally developed to record autonomously on the seafloor the signals received on a four-sonde three-component borehole geophone array in the VLF band (2-50Hz)(Stephen eta!., 1994). The system is designed to use the wireline re-entry capability (Spiess, 1993; Spiess eta!., 1992) to install and retrieve the seafloor instrumentation (Figures 1 and 2). Following the successful demonstration of this technology on the LFASE (Low Frequency Acoustic-Seismic Experiment) project in September 1989, it was decided to extend the capability to broadband (1000sec-5Hz) borehole seismometers which could be used for permanent seafloor seismic observatories in the Ocean Seismic Network (Orcutt and Stephen, 1993; Purdy and Dziewonski, 1988; Purdy and Orcutt, 1995; Stephen, 1995; Sutton and Barstow, 1990; Sutton eta!., 1988; Sutton eta!., 1965). The Broadband Borehole Seismic System (B3S2) is the prototype system for permanent broadband borehole seismic observatories on the seafloor. It has three major components: i) a broadband borehole seismometer, the Teledyne 54000, modified for seafloor operations by Scripps-IGPP; ii) the re-entry system provided by Scripps-MPL; and iii) the seafloor recording system developed by WHO I. Because of the similarity of the seafloor recording system to SEABASS we have named this new system SEABASS-ll. This report discusses the development of SEABASS-Il at WHOI in the period from July 14, 1992 to January 31, 1996. The motivation for the project and a work statement are contained in WHOI proposals 7016 and 7016.1. This report is a collection of documentation prepared while the work was being carried out. Some of the issues discussed in early memos were subsequently changed. Modifications and further testing of SEABASS-ll, as well as final system integration tests with the borehole andreentry systems (both of which are also still being modified and tested) have still to be carried out in preparation for the OSN Pilot Experiment Cruise in Spring 1997. This is a preliminary report only and presents work in progress. It will be useful to the engineering team as a historical reference of the sequence of events in the development of SEABASS-ll but it should not be considered as a technical manual for the instrumentation.
    Keywords: Seismology ; Borehole gravimetry ; Ocean bottom ; Oceanographic instruments
    Repository Name: Woods Hole Open Access Server
    Type: Working Paper
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