JDR Vol.18 No.7 pp. 730-739
doi: 10.20965/jdr.2023.p0730


Analysis of Orientation Changes of S-Net Accelerometers due to Earthquake Motions

Yadab P. Dhakal ORCID Icon and Takashi Kunugi ORCID Icon

National Research Institute for Earth Science and Disaster Resilience (NIED)
3-1 Tennodai, Tsukuba, Ibaraki 305-0032, Japan

Corresponding author

April 20, 2023
August 16, 2023
October 1, 2023
S-net, ocean-bottom seismographs, strong motions, rotation of sensors, earthquake early warning

S-net is a large-scale seafloor observation network for earthquakes and tsunamis around the Japan Trench, consisting of 150 observatories equipped with seismometers and pressure gauges. The sensors have been set up inside cylindrical pressure vessels, which have been buried in the shallow-water regions (water depth <1,500 m), while the vessels have been laid freely on the seafloor in the deeper-water regions. Previous studies showed that the cylindrical pressure vessels rotate during strong shakings due to poor coupling with the seabed sediments, thus making it difficult to retrieve the actual ground motions. We investigated the static changes in the orientations of S-net accelerometers due to shakings from 1,878 earthquakes of Mj greater than 4 that occurred around the network, and found that rotations as large values as 16° were observed during the 2022, Mj 7.4, off-Fukushima Prefecture earthquake. We estimated the threshold acceleration levels after which the sensors are likely to rotate at all S-net stations separately and found that the threshold values lie mostly between 5 and 50 cm/s2. Finally, we discussed the observed peak accelerations and velocities at the S-net stations with those recorded on land, where high-quality records were obtained, during the 2022, Mj 7.4 earthquake, which was also the largest magnitude earthquake to occur in the region after the network commenced operation. The results presented herein complement several previous studies and form the basis for more comprehensive future investigations.

Cite this article as:
Y. Dhakal and T. Kunugi, “Analysis of Orientation Changes of S-Net Accelerometers due to Earthquake Motions,” J. Disaster Res., Vol.18 No.7, pp. 730-739, 2023.
Data files:
  1. [1] T. Kanazawa, K. Uehira, M. Mochizuki, T. Shinbo, H. Fujimoto, S. Noguchi, T. Kunugi, K. Shiomi, S. Aoi, T. Matsumoto, S. Sekiguchi, and Y. Okada, “S-net project, cabled observation network for earthquakes and tsunamis,” SubOptic 2016, Paper ID WE2B–3, 2016.
  2. [2] S. Aoi, Y. Asano, T. Kunugi, T. Kimura, K. Uehira, N. Takahashi, H. Ueda, K. Shiomi, T. Matsumoto, and H. Fujiwara, “MOWLAS: NIED observation network for earthquake, tsunami and volcano,” Earth Planets Space, Vol.72, Article No.126, 2020.
  3. [3] K. Tamaribuchi, F. Hirose, A. Noda, Y. Iwasaki, K. Iwakiri, and H. Ueno, “Noise classification for the unified earthquake catalog using ensemble learning: The enhanced image of seismic activity along the Japan Trench by the S-net seafloor network,” Earth, Planets and Space, Vol.73, Article No.91, 2021.
  4. [4] A. Nishizawa, K. Uehira, and M. Mochizuki, “Sediment distribution beneath S-net stations derived from multi-channel seismic reflection profiles and hypocenter determination using the sediment correction,” Technical Note of the National Research Institute for Earth Science and Disaster Resilience, No.471, pp. 1-18, 2022 (in Japanese).
  5. [5] N. Hayashimoto, T. Nakamura, and M. Hoshiba, “A technique for estimating the UD-component displacement magnitude for earthquake early warnings that can be applied to various seismic networks including ocean bottom seismographs,” Q. J. Seismol., Vol.83, No.1, pp. 1-10, 2019 (in Japanese).
  6. [6] Japan Meteorological Agency, “Utilization of seafloor earthquake observation data for earthquake early warning,” 2019 (in Japanese). [Accessed April 18, 2023]
  7. [7] T. Nishikawa, T. Matsuzawa, K. Ohta, N. Uchida, T. Nishimura, and S. Ide, “The slow earthquake spectrum in the Japan Trench illuminated by the S-net seafloor observatories,” Science, Vol.365, No.6455, pp. 808-813, 2019.
  8. [8] S. Aoi, W. Suzuki, N. Y. Chikasada, T. Miyoshi, T. Arikawa, and K. Seki, “Development and utilization of real-time tsunami inundation forecast system using S-net data,” J. Disaster Res., Vol.14, No.2, pp. 212-224, 2019.
  9. [9] Y. Hua, D. Zhao, G. Toyokuni, and Y. Xu, “Tomography of the source zone of the great 2011 Tohoku earthquake,” Nature Communication, Vol.11, Article No.1163, 2020.
  10. [10] R. Takagi, N. Uchida, T. Nakayama, R. Azuma, A. Ishigami, T. Okada, T. Nakamura, and K. Shiomi, “Estimation of the orientations of the S-net cabled ocean-bottom sensors,” Seismol. Res. Lett., Vol.90, No.6, pp. 2175-2187, 2019.
  11. [11] Y. P. Dhakal, T. Kunugi, W. Suzuki, T. Kimura, N. Morikawa, and S. Aoi, “Strong motions on land and ocean bottom: Comparison of horizontal PGA, PGV, and 5% damped acceleration response spectra in northeast Japan and the Japan trench area,” Bull. Seismol. Soc. Am., Vol.111, No.6, pp. 3237-3260, 2021.
  12. [12] Y. P. Dhakal and T. Kunugi, “An evaluation of strong-motion parameters at the S-net ocean-bottom seismograph sites near the Kanto basin for earthquake early warning,” Frontiers in Earth Science, Vol.9, Article No.699439, 2021.
  13. [13] Y. P. Dhakal and T. Kunugi, “Preliminary analysis of nonlinear site response at the S-net seafloor sites during three Mw 7 class earthquakes,” Front. Earth Sci., Vol.11, Article No.1180289, 2023.
  14. [14] Y. Okada, K. Kasahara, S. Hori, K. Obara, S. Sekiguchi, H. Fujiwara, and A. Yamamoto, “Recent progress of seismic observation networks in Japan – Hi-net, F-net, K-NET and KiK-net –,” Earth, Planets and Space, Vol.56, pp. 15-28, 2004.
  15. [15] NIED, “NIED S-net,” National Research Institute for Earth Science and Disaster Resilience, 2019.
  16. [16] T. Nakamura and N. Hayashimoto, “Rotation motions of cabled ocean-bottom seismic stations during the 2011 Tohoku earthquake and their effects on magnitude estimation for early warnings,” Geophys. J. Int., Vol.216, No.2, pp. 1413-1427, 2019.
  17. [17] NIED, “NIED K-NET, KiK-net,” National Research Institute for Earth Science and Disaster Resilience, 2019.
  18. [18] H. Si and S. Midorikawa, “New attenuation relations for peak ground acceleration and velocity considering effects of fault type and site condition,” J. Struct. Constr. Eng., Vol.64, No.523, pp. 63-70, 1999 (in Japanese).
  19. [19] H. Si and S. Midorikawa, “New attenuation relations for peak ground acceleration and velocity considering effects of fault type and site condition,” Proc. of the 12th World Conf. on Earthquake Engineering., Paper ID 0532, 2000.
  20. [20] F. Hirose, “Plate configuration.” [Accessed May 10, 2022]
  21. [21] NIED, “Provisional source rupture process of the 2022 off Fukushima Prefecture earthquake,” 2022 (in Japanese). [Accessed March 1, 2023]
  22. [22] Z. J. Spica, K. Nishida, T. Akuhara, F. Pétrélis, M. Shinohara, and T. Yamada, “Marine sediment characterized by ocean-bottom fiber-optic seismology,” Geophys. Res. Lett., Vol.47, No.16, Article No.e2020GL088360, 2020.
  23. [23] L. Yamaya, K. Mochizuki, T. Akuhara, and K. Nishida, “Sedimentary structure derived from multi-mode ambient noise tomography with dense OBS network at the Japan Trench,” J. Geophys. Res.: Solid Earth, Vol.126, No.6, Article No.e2021JB021789, 2021.
  24. [24] A. H. Farazi, Y. Ito, E. S. M. Garcia, A. M. Lontsi, F. J. Sánchez-Sesma, A. Jaramillo, S. Ohyanagi, R. Hino, and M. Shinohara, “Shear wave velocity structure at the Fukushima forearc region based on H/V analysis of ambient noise recordings by ocean bottom seismometers,” Geophys. J. Int., Vol.233, No.3, pp. 1801-1820, 2023.
  25. [25] L. Viens, M. Perton, Z. J. Spica, K. Nishida, T. Yamada, and M. Shinohara, “Understanding surface wave modal content for high-resolution imaging of submarine sediments with distributed acoustic sensing,” Geophys. J. Int., Vol.232, No.3, pp. 1668-1683, 2023.
  26. [26] F. Nagashima, Y. P. Dhakal, H. Kawase, and K. Nakano, “Underground structure identification at S-net seafloor sites using horizontal-to-vertical spectral ratio of earthquake acceleration records,” DPRI Annual Meeting, Paper ID B310, 2023 (in Japanese). [Accessed April 5, 2023]
  27. [27] T. Kanno, A. Narita, N. Morikawa, H. Fujiwara, and Y. Fukushima, “A new attenuation relation for strong ground motion in Japan based on recorded data,” Bull. Seism. Soc. Am., Vol.96, No.3, pp. 879-897, 2006.
  28. [28] Y. P. Dhakal, N. Takai, and T. Sasatani, “Empirical analysis of path effects on prediction equations of pseudo-velocity response spectra in northern Japan,” Earthquake Eng. Struct. Dyn., Vol.39, No.4, pp. 443-461, 2010.
  29. [29] N. Morikawa and H. Fujiwara, “A new ground motion prediction equation for Japan applicable up to M9 mega-earthquake,” J. Disaster Res., Vol.8, No.5, pp. 878-888, 2013.
  30. [30] T. Furumura and B. L. N Kennett, “Subduction zone guided waves and the heterogeneity structure of the subducted plate: Intensity anomalies in northern Japan,” J. Geophys. Res., Vol.110, No.B10, 2005.
  31. [31] T. Tonegawa, R. Takagi, K. Sawazaki, and K. Shiomi, “Short-term and long-term variations in seismic velocity at shallow depths of the overriding plate west of the Japan Trench,” J. Geophys. Res., Vol.128, No.1, Article No.e2022JB025262, 2023.
  32. [32] Y. P. Dhakal, T. Kunugi, H. Yamanaka, A. Wakai, S. Aoi, and A. Nishizawa, “Estimation of source, path, and site factors of S waves recorded at the S-net sites in the Japan Trench area using the spectral inversion technique,” Earth, Planets and Space, Vol.75, Article No.1, 2023.
  33. [33] K. Sawazaki and T. Nakamura, ““N”-shaped Y/X coda spectral ratio observed for in-line-type OBS networks; S-net and ETMC: Interpretation based on natural vibration of pressure vessel,” Earth, Planets and Space, Vol.72, Article No.130, 2020.
  34. [34] P. Wessel and W. H. F. Smith, “New, improved version of generic mapping tools released,” Eos, Trans. American Geophysical Union, Vol.79, No.47, p. 579, 1998.

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