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  • Mid-Atlantic Ridge  (1)
  • Ocean wave  (1)
  • John Wiley & Sons  (2)
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  • 1
    Publication Date: 2022-05-25
    Description: Author Posting. © American Geophysical Union, 2016. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Solid Earth 121 (2016): 3161–3176, doi:10.1002/2016JB012928.
    Description: Near-bottom magnetic field measurements made by the submersible Nautile during the 1992 Kanaut Expedition define the cross-sectional geometry of magnetic polarity reversal boundaries and the vertical variation of crustal magnetization in lower oceanic crust exposed along the Kane Transform Fault (TF) at the northern boundary of the Kane Megamullion (KMM). The KMM exposes lower crust and upper mantle rocks on a low-angle normal fault that was active between 3.3 Ma and 2.1 Ma. The geometry of the polarity boundaries is estimated from an inversion of the submarine magnetic data for crustal magnetization. In general, the polarity boundaries dip away from the ridge axis along the Kane TF scarp, with a west dipping angle of ~45° in the shallow (〈1 km) crust and 〈20° in the deeper crust. The existence of the magnetic polarity boundaries (e.g., C2r.2r/C2An.1n, ~2.581 Ma) indicates that the lower crustal gabbros and upper mantle serpentinized peridotites are able to record a coherent magnetic signal. Our results support the conclusion of Williams (2007) that the lower crust cools through the Curie temperature of magnetite to become magnetic, with the polarity boundaries representing both frozen isotherms and isochrons. We also test the effects of the rotation of this isotherm structure and/or footwall rotation and find that the magnetic polarity boundary geometry is not sensitive to these directional changes.
    Description: 2016-11-12
    Keywords: Kane Megamullion ; Vertical magnetic profile ; Magnetic polarity reversal ; Mid-Atlantic Ridge
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2017. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 122 (2017): 9518–9529, doi:10.1002/2017JC013310.
    Description: Microseisms generated by the super typhoon Megi (13–24 October 2010) were detected on both land-based and island-based seismic stations. We applied temporal frequency spectrum analysis to investigate the temporal evolution of the microseisms. When Megi was over the deep basins of the Philippine Sea, only weak microseisms with short-period double frequency (SPDF, ∼0.20–0.40 Hz) were observed. However, after Megi traveled into the shallower waters of the South China Sea, microseisms with both long-period double frequency (LPDF, ∼0.12–0.20 Hz) and SPDF were recorded. The excitation source regions of the microseisms were analyzed using seismic waveform records and synthetic modeling in frequency domain. Results reveal that part of the LPDF microseisms were excited in coastal source regions, while the intensity of both LPDF and SPDF microseisms correlated well with the distance from seismic stations to the typhoon center. Synthetic computations of equivalent surface pressure and corresponding microseisms show that the wave-to-wave interaction induced by coastal reflection has primary effects on microseismic frequency band of ∼0.10–0.20 Hz. The coastal generation of the dispersive LPDF microseisms is also supported by the observation of ocean swells induced by Megi through the images of C-band ENVISAT-ASAR satellite during its migration process. Two source regions of the microseisms during the life span of Megi are finally distinguished: One was mainly located in the left-rear quadrant of the typhoon center that generated both LPDF and SPDF microseisms at shallow seas, while the other one was near the coasts that generated mostly LPDF microseisms.
    Description: National Natural Science Foundation of China Grant Numbers: 41104027, 91628301, U1606401, 41676044; Natural Science Foundation of Zhejiang Province Grant Number: LZ14D060001; Opening Fund of SKLGED Grant Number: SKLGED2013-1-7-E; Chinese Academy of Sciences Grant Numbers: Y4SL021001, Y6YB011001, QYZDY-SSW-DQC005
    Description: 2018-06-07
    Keywords: Microseisms ; Typhoon ; Ocean wave ; Source region ; Generation mechanism
    Repository Name: Woods Hole Open Access Server
    Type: Article
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