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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Pure and applied geophysics 151 (1998), S. 463-475 
    ISSN: 1420-9136
    Keywords: Key words: Anisotropy, mantle flow, subduction zones, shear-wave splitting.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract —We have obtained constraints on the strength and orientation of anisotropy in the mantle beneath the Tonga, southern Kuril, Japan, and Izu-Bonin subduction zones using shear-wave splitting in S phases from local earthquakes and in teleseismic core phases such as SKS. The observed splitting in all four subduction zones is consistent with a model in which the lower transition zone (520–660 km) and lower mantle are isotropic, and in which significant anisotropy occurs in the back-arc upper mantle. The upper transition zone (410–520 km) beneath the southern Kurils appears to contain weak anisotropy. The observed fast directions indicate that the geometry of back-arc strain in the upper mantle varies systematically across the western Pacific rim. Beneath Izu-Bonin and Tonga, fast directions are aligned with the azimuth of subducting Pacific plate motion and are parallel or sub-parallel to overriding plate extension. However, fast directions beneath the Japan Sea, western Honshu, and Sakhalin Island are highly oblique to subducting plate motion and parallel to present or past overriding plate shearing. Models of back-arc mantle flow that are driven by viscous coupling to local plate motions can reproduce the splitting observed in Tonga and Izu-Bonin, but further three-dimensional flow modeling is required to ascertain whether viscous plate coupling can explain the splitting observed in the southern Kurils and Japan. The fast directions in the southern Kurils and Japan may require strain in the back-arc mantle that is driven by regional or global patterns of mantle flow.
    Type of Medium: Electronic Resource
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  • 2
    Publication Date: 2012-08-01
    Description: A detailed record of earthquake frequency and distribution is essential to understanding regional tectonic strain and seismic hazard, particularly in regions of low, but significant, seismicity levels. Comprehensive analyses of seismicity within Arizona have not been previously possible due to a lack of seismic stations in many regions, contributing to the perception that earthquakes within Arizona are rare and generally limited to the north-central and northwestern portions of the state. The EarthScope USArray Transportable Array (TA) was deployed within Arizona from April 2006 to March 2009 and provided the opportunity to examine seismicity on a statewide scale. In this study, we developed a streamlined workflow for producing a comprehensive earthquake catalog using TA data. We combined our new catalog with historical earthquake catalogs from several sources to produce the first comprehensive historical earthquake catalog for the state of Arizona. The TA-derived catalog is complete to local magnitude ( M L )~1.2, contains crustal events as small as M L  0.0, and includes events located within several previously unidentified areas of seismic activity in Arizona. We also identified 16 earthquake clusters, many of which have swarmlike behavior. These earthquake clusters account for 42% of the events identified during the study period, and they occur in all physiographic, geophysical, and tectonic settings. We suggest that swarms and clusters, such as those documented in this study, may represent an important mechanism for small-scale tectonic strain release within intraplate regions with otherwise apparently low seismicity levels. Online Material: Figures comparing earthquake depth to physiographic province, elevation, crustal thickness, and heat flow; data tables including earthquake catalogs and velocity models; and an introductory User's Guide to the Antelope Environmental Data Collection Software suite.
    Print ISSN: 0037-1106
    Electronic ISSN: 1943-3573
    Topics: Geosciences , Physics
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  • 3
    Publication Date: 2022-11-14
    Description: The Joint Task Force, Science Monitoring And Reliable Telecommunications (SMART) Subsea Cables is working to integrate environmental sensors (temperature, pressure, seismic acceleration) into submarine telecommunications cables. This will support climate and ocean observation, sea-level monitoring, observations of Earth structure, tsunami and earthquake early warning, and disaster risk reduction. Recent advances include regional SMART pilot systems that are the initial steps to trans-ocean and global implementation. Building on the OceanObs’19 conference and community white paper (https://doi.org/10.3389/ fmars.2019.00424), this paper presents an overview of the initiative and a description of ongoing projects including: InSea wet demonstration project off Sicily; Vanuatu and New Caledonia; Indonesia; CAM-2 ring system connecting the Portuguese mainland, Azores, and Madeira; New Zealand; and Antarctica. In addition to the diverse scientific and societal benefits, the telecommunications industry’s mission of societal connectivity will also benefit because environmental awareness improves both individual cable system integrity and the resilience of the overall global communications network. Keywords: telecommunication cables, SMART sensors, seafloor sensing, earthquake early warning, tsunami detection
    Language: English
    Type: info:eu-repo/semantics/article
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  • 4
    Publication Date: 2022-02-18
    Description: The Joint Task Force, Science Monitoring And Reliable Telecommunications (JTF SMART) Subsea Cables, is working to integrate environmental sensors for ocean bottom temperature, pressure, and seismic acceleration into submarine telecommunications cables. The purpose of SMART Cables is to support climate and ocean observation, sea level monitoring, observations of Earth structure, and tsunami and earthquake early warning and disaster risk reduction, including hazard quantification. Recent advances include regional SMART pilot systems that are the first steps to trans-ocean and global implementation. Examples of pilots include: InSEA wet demonstration project off Sicily at the European Multidisciplinary Seafloor and water column Observatory Western Ionian Facility; New Caledonia and Vanuatu; French Polynesia Natitua South system connecting Tahiti to Tubaui to the south; Indonesia starting with short pilot systems working toward systems for the Sumatra-Java megathrust zone; and the CAM-2 ring system connecting Lisbon, Azores, and Madeira. This paper describes observing system simulations for these and other regions. Funding reflects a blend of government, development bank, philanthropic foundation, and commercial contributions. In addition to notable scientific and societal benefits, the telecommunications enterprise’s mission of global connectivity will benefit directly, as environmental awareness improves both the integrity of individual cable systems as well as the resilience of the overall global communications network. SMART cables support the outcomes of a predicted, safe, and transparent ocean as envisioned by the UN Decade of Ocean Science for Sustainable Development and the Blue Economy. As a continuation of the OceanObs’19 conference and community white paper (Howe et al., 2019, doi: 10.3389/fmars.2019.00424), an overview of the SMART programme and a description of the status of ongoing projects are given.
    Type: info:eu-repo/semantics/article
    Format: application/pdf
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