Skip to main content

Variation in crustal structure along the Kyushu-Palau Ridge at 15–21°N on the Philippine Sea plate based on seismic refraction profiles


We acquired coincident wide-angle and multi-channel seismic reflection data along four profiles perpendicular to the Kyushu-Palau Ridge (KPR) between 15°N and 20°N on the Philippine Sea plate. The crustal thickness beneath the KPR, which is a remnant arc created in the Late Eocene, varies along the strike from 8 to approximately 20 km and is always thicker than the adjacent oceanic crust of the West Philippine Basin to the west and the Parece Vela Basin to the east. The thickest crust among the four profiles, which is primarily due to a thickening of the lower crust, is found where the KPR adjoins Oki-no-Tori-Shima Island. There is no clear evidence of the thick (>5 km) middle crustal layer with a P-wave velocity of 6.0–6.5 km/s that has been inferred beneath the conjugate rifted counterpart of the Izu-Ogasawara(Bonin)-Mariana Island-arc. Our results suggest that the crust of the KPR at 15–21°N represents a less mature island arc crust relative to that further north along the ridge where a mid-crustal layer of 6 km/s has been reported.


  • Fujie, G., J. Kasahara, T. Sato, and K. Mochizuki, Traveltime and raypath computation: A new method in a heterogeneous medium, J. Soc. Expl. Geophys. Jpn., 53, 1–11, 2000.

    Google Scholar 

  • Kodaira, S., T. Sato, N. Takahashi, S. Miura, and Y. Kaneda, Structural variation from mature to juvenile arc crust along the Izu Bonin arc, Eos Trans. AGU, 87(52), Fall Meet. Suppl., Abstract, V41B–1711, 2006.

    Google Scholar 

  • Korenaga, J., W. S. Holbrook, G. M. Kent, P. B. Kelemen, R. S. Detrick, H.-C. Larsen, J. R. Hopper, and T. Dahl-Jensen, Crustal structure of the southeast Greenland margin from joint refraction and reflection seismic tomography, J. Geophys. Res., 105, 21591–21614, 10.1029/2000JB900188, 2000.

    Article  Google Scholar 

  • Kubota, R., E. Nishiyama, K. Murase, and J. Kasahara, Fast computation algorithm of ray-paths and their travel times including later arrivals for a multi-layered earth model, Eos Trans. AGU, 86(52), Fall Meet. Suppl., Abstract, S41A–0966, 2005.

    Google Scholar 

  • Larsen, S. C. and C. A. Schultz, ELAS3D: 2D/3D elastic finite-difference wave propagation code, LLNL internal report, 18 p., 1995.

    Google Scholar 

  • Nishizawa, A., K. Kaneda, A. Nakanishi, N. Takahashi, and S. Kodaira, Crustal structure of the ocean-island arc transition at the mid Izu-Ogasawara (Bonin) arc margin, Earth Planets Space, 58, e33–e36, 2006.

    Article  Google Scholar 

  • Okino, Y, Ohara Y., S. Kasuga, and Y. Kato, The Philippine Sea: New survey results reveal the structure and the history of the marginal basins, Geophys. Res. Lett., 26, 2287–2290, 1999.

    Article  Google Scholar 

  • Sakai, S., T. Yamada, M. Shinohara, H. Hagiwara, T. Kanazawa, K. Obana, S. Kodaira, and Y. Kaneda, Urgent aftershock observation of the 2004 off the Kii Peninsula earthquake using ocean bottom seismometers, Earth Planets Space, 57, 363–368, 2005.

    Article  Google Scholar 

  • Shinohara, M., N. Takahashi, K. Li, K. Suyehiro, and A. Taira, Crustal structure of the northern Izu-Bonin arc and Kyushu-Palau Ridge by controlled-source seismology, Monthly Earth, 23, 67–78, 1999 (in Japanese).

    Google Scholar 

  • Suyehiro, K. et al., Continental crust, crustal underplating, and low-Q upper mantle beneath an oceanic island arc, Science, 272, 390–392, 1996.

    Article  Google Scholar 

  • Takahashi, N., S. Kodaira, S. L. Klemperer, Y. Tatsumi, Y. Kaneda, and K. Suyehiro, Crustal structure and evolution of the Mariana intra-oceanic island arc, Geology, 7, 383–394, 2007.

    Google Scholar 

  • Wessel, P. and W. H. F. Smith, New, improved version of the Generic MappingTools released, EOS Trans. AGU, 79, 579, 1998.

    Article  Google Scholar 

  • White, R. S., D. McKenzie, and R. K. O’Nions, Oceanic crustal thickness from seismic measurements and rare earth element inversions, J. Geo-phys. Res., 97, 19683–19715, 1992.

    Article  Google Scholar 

Download references

Author information

Authors and Affiliations


Corresponding author

Correspondence to Azusa Nishizawa.

Rights and permissions

Open Access  This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit

Reprints and Permissions

About this article

Cite this article

Nishizawa, A., Kaneda, K., Katagiri, Y. et al. Variation in crustal structure along the Kyushu-Palau Ridge at 15–21°N on the Philippine Sea plate based on seismic refraction profiles. Earth Planet Sp 59, e17–e20 (2007).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

Key words

  • Kyushu-Palau Ridge
  • Oki-no-Tori-Shima island
  • West Philippine Basin
  • seismic refraction
  • crustal structure