Abstract
After the twenty-first century, the Global Navigation Satellite System-Acoustic ranging (GNSS-A) technique detected geodetic events such as co- and postseismic effects following the 2011 Tohoku-oki earthquake and slip-deficit rate distributions along the Nankai Trough subduction zone. Although these are extremely important discoveries in geodesy and seismology, more accurate observation that can capture temporal and spatial changes are required for future earthquake disaster prevention. In order to upgrade the accuracy of the GNSS-A technique, it is necessary to understand disturbances in undersea sound speed structures, which are major error sources. In particular, detailed temporal and spatial variations are difficult to observe accurately, and their effect was not sufficiently extracted in previous studies. In the present paper, we reconstruct an inversion scheme for extracting the effect from GNSS-A data and experimentally apply this scheme to the seafloor sites around the Kuroshio. The extracted gradient effects are believed to represent not only a broad sound speed structure but also a more detailed structure generated in the unsteady disturbance. The accuracy of the seafloor positioning was also improved by this new method. The obtained results demonstrate the feasibility of using the GNSS-A technique to detect a seafloor crustal deformation for oceanography research.
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References
Altamimi Z, Collilieux X, Legrand J, Garayt B, Boucher C (2007) ITRF2005: a new release of the International Terrestrial Reference Frame based on time series of station positions and Earth Orientation Parameters. Geophys J Int 112:B09401. https://doi.org/10.1029/2007JB004949
Asada A, Yabiki T (2001) Centimeter-level positioning on the seafloor. Proc Jpn Acad B 77:7–12. https://doi.org/10.2183/plab.77.7
Colombo OL (1998) Long range kinematic GPS. In: Kleusberg A, Teunissen P (eds) GPS for Geodesy, 2nd edn. Springer, New York
Colombo OL, Sutter AW, Evans AG (2004) Evaluation of precise, kinematic GPS point positioning, Proceedings of ION GNSS-2004, Long Beach, California, September
DeMets C, Gordon RG, Argus DF (2010) Geologically current plate motions. Geophys J Int 181:1–80. https://doi.org/10.1111/j.1365-246X.2009.04491.x
Fujita M, Ishikawa T, Mochizuki M, Sato M, Toyama S, Katayama M, Kawai K, Matsumoto Y, Yabuki T, Asada A, Colombo OL (2006) GPS/acoustic seafloor geodetic observation: method of data analysis and its application. Earth Planet Space 58:265–275. https://doi.org/10.1186/BF03351923
Ikuta R, Tadokoro K, Ando M, Okuda T, Sugimoto S, Takatani K, Yada K, Besana GM (2008) A new GPS-acoustic method for measuring ocean floor crustal deformation: application to the Nankai Trough. J Geophys Res 113:B02401. https://doi.org/10.1029/2006JB004875
Kido M, Osada Y, Fujimoto H (2008) Temporal variation of sound speed in ocean: a comparison between GPS/acoustic and in situ measurements. Earth Planets Space 60:229–234. https://doi.org/10.1186/BF03352785
Kido M, Osada Y, Fujimoto H, Hino R, Ito Y (2011) Trench-normal variation in observed seafloor displacements associated with the 2011 Tohoku-oki earthquake. Geophys Res Lett 38:L24303. https://doi.org/10.1029/2011GL050057
Matsumoto Y, Fujita M, Ishikawa T (2008) Development of multi-epoch method for determining seafloor station position (in Japanese, Abstract in English). Rep Hydro Ocean Res 26:16–22
Miyazawa Y, Zhang R, Guo X, Tamura H, Ambe D, Lee JS, Okuno A, Yoshinari H, Setou T, Komatsu K (2009) Water mass variability in the western north Pacific detected in a 15-year eddy resolving ocean reanalysis. J Oceanogr 65:737–756. https://doi.org/10.1008/s10872-009-0063-3
Nagai T, Tandon A, Yamazaki H, Doubell MJ, Gallager S (2012) Direct observations of microscale turbulence and thermohaline structure in the Kuroshio Front. J Geophys Res 117:C08013. https://doi.org/10.1029/2011JC007228
Obara K, Kato A (2016) Connecting slow earthquakes to huge earthquakes. Science 353:253–257. https://doi.org/10.1126/science.aaf1512
Sato M, Ishikawa T, Ujihara N, Yoshida S, Fujita M, Mochizuki M, Asada A (2011) Displacement above the hypocenter of the 2011 Tohoku-oki earthquake. Science 332:1395. https://doi.org/10.1126/science.1207401
Sato M, Fujita M, Matsumoto Y, Saito H, Ishikawa T, Asakura T (2013) Improvement of GPS/acoustic seafloor positioning precision through controlling the ship’s track line. J Geod 87:825–842. https://doi.org/10.1007/s00190-013-0649-9
Spiess FN (1985) Suboceanic geodetic measurements. IEEE Trans Geosci Remote Sens GE-23(4):502–510
Tadokoro K, Ikuta R, Watanabe T, Ando M, Okuda T, Nagai S, Yasuda K, Sakata T (2012) Interseismic seafloor crustal deformation immediately above the source region of anticipated megathrust earthquake along the Nankai Trough, Japan. Geophys Res Lett 39:L10306. https://doi.org/10.1029/2012GL051696
Tomita F, Kido M, Osada Y, Hino R, Ohta Y, Iinuma T (2015) First measurement of the displacement rate of the Pacific Plate near the Japan Trench after the 2011 Tohoku-Oki earthquake using GPS/acoustic technique. Geophys Res Lett 42:8391–8397. https://doi.org/10.1002/2015GL065746
Tomita F, Kido M, Ohta Y, Iinuma T, Hino R (2017) Along-trench variation in seafloor displacements after the 2011 Tohoku earthquake. Sci Adv 3:e1700113. https://doi.org/10.1126/sciadv.1700113
Watanabe S, Sato M, Fujita M, Ishikawa T, Yokota Y, Ujihara N, Asada A (2014) Evidence of viscoelastic deformation following the 2011 Tohoku-oki earthquake revealed from seafloor geodetic observation. Geophys Res Lett 41:5789–5796. https://doi.org/10.1002/2014GL061134
Yasuda K, Tadokoro K, Taniguchi S, Kimura H, Matsuhiro K (2017) Interplate locking condition derived from seafloor geodetic observation in the shallowest subduction segment at the Central Nankai Trough, Japan. Geophys Res Lett 44:3572–3579. https://doi.org/10.1002/2017GL072918
Yokota Y, Ishikawa T, Watanabe S, Tashiro T, Asada A (2016) Seafloor geodetic constraints on interplate coupling of the Nankai Trough megathrust zone. Nature 534:374–377. https://doi.org/10.1038/nature17632
Yokota Y, Ishikawa T, Watanabe S (2018) Original data of seafloor crustal deformation along the subduction zones around Japanese Islands. PANGAEA. https://doi.org/10.1594/PANGAEA.885139
Acknowledgements
The authors would like to thank O. L. Colombo of the NASA Goddard Space Flight Center for providing us with the Interferometric Translocation (IT) kinematic GNSS software and the Geospatial Information Authority of Japan (GSI) for providing us with the high-rate GNSS data for the kinematic GNSS analysis and the daily coordinates of the sites on the GSI’s website. JCOPE2 data was provided by JAMSTEC’s JCOPE website. We thank R. Zhang for speaking about and providing advice regarding the JCOPE2 data. We also thank the editor and two anonymous reviewers for their comments, which improved this article. Many among the staff of the JHOD, including the crews of the S/V Takuyo, S/V Shoyo, S/V Meiyo and S/V Kaiyo, have supported our observations and data processing.
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Yokota, Y., Ishikawa, T. & Watanabe, Si. Gradient field of undersea sound speed structure extracted from the GNSS-A oceanography. Mar Geophys Res 40, 493–504 (2019). https://doi.org/10.1007/s11001-018-9362-7
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DOI: https://doi.org/10.1007/s11001-018-9362-7