Skip to main content


We’d like to understand how you use our websites in order to improve them. Register your interest.

Splay fault and megathrust earthquake slip in the Nankai Trough


We consider whether splay fault slip may be a factor influencing the behavior of megathrust earthquakes in the Nankai Trough. Consideration of tsunami inversion results from other studies indicates that slip on one or more splay faults may be particularly important for the segment of the Nankai Trough offshore western Shikoku. These results suggest that during at least two megathrust earthquakes substantial slip may have occurred on one or more splay faults which cut the island arc crust over 100 km landward of the trench axis. In contrast to smaller subsidiary thrusts in the semi-consolidated and unconsolidated sediments very near the trough axis, the crustal faults considered here could accumulate and release considerable tectonic stress. Through a simple finite element calculation we demonstrate that slip on such faults can release some of the shear stress on the megathrust accumulated through plate subduction, and therefore may have some influence on the behavior of megathrust earthquakes.


  1. Aida, I., Numerical experiments of historical tsunamis generated off the coast of the Tokaido district, Bull. Earthq. Res. Inst., 56, 715–730, 1981 (in Japanese).

  2. Ando, M., Source mechanisms and tectonic significance of historical earthquakes along the Nankai Trough, Japan, Tectonophys., 27, 119–140, 1975.

  3. Clarke, S. H. and G. A. Carver, Late Holocene Tectonics andpaleoseismicity, southern Cascadia subduction zone, Science, 255, 188–192, 1992.

  4. Cummins, P. R. and Y. Kaneda, Possible splay fault slip during the 1946 Nankai earthquake, Geophys. Res. Lett., 27, 2725–2728, 2000.

  5. Hyndman, R. D., K. Wang, and M. Yamano, Thermal constraints on the seismogenic portion of the southwestern Japan subduction thrust, J. Geophys. Res., 100, 15,373–15,392, 1995.

  6. Kagami, H., K. Shiono, and A. Taira, Plate subduction and formation of the accretionary complex in the Nankai Trough, Kagaku, 53, 429–438, 1983 (in Japanese).

  7. Kanamori, H., Tectonic implications of the 1944 Tonankai and 1946 Nankaido earthquakes, Phys. Earth Planet. Inter., 5, 129–139, 1972.

  8. Kodaira, S., N. Takahashi, J. Park, K. Mochizuki, M. Shinohara, and S. Kimura, The western Nankai Trough seismogenic zone: Result from wide-angle ocean-bottom seismographic survey, J. Geophys. Res., 105, 5887–5905, 2000.

  9. McCaffrey, R., On the role of the upper plate in great subduction zone earthquakes, J. Geophys. Res., 98, 11,953–11,966, 1993.

  10. Okada, Y., Internal deformation due to shear and tensile faults in a half-space, Bull. Seismol. Soc. Am., 82, 1018–1040, 1992.

  11. Plafker, G., Alaskan earthquake of 1964 and Chilean earthquake of 1960: implications for arc tectonics, J. Geophys. Res., 77, 901–923, 1972.

  12. Sagiya, T. and W. Thatcher, Coseismic slip resolution along a plate boundary megathrust: The Nankai Trough, southwest Japan, J. Geophys. Res., 104, 1111–1129, 1999.

  13. Savage, J. C., A dislocation model of strain accumulation and release at a subduction zone, J. Geophys. Res., 88, 4984–4996, 1983.

  14. Seno, T., Syntheses of the regional stress fields of the Japanese islands, The Island Arc, 8, 66–79, 1999.

  15. Stein, R. S. and G. C. P. King, Seismic potential revealed by surface folding: 1983 Coalinga, California, earthquake, Science, 224, 869–872, 1984.

  16. Sugiyama, Y., Neotectonics of Southwest Japan due to the right-oblique subduction of the Philippine Sea plate, Geofis. Int., 33, 53–76, 1994.

  17. Tanioka, Y. and K. Satake, Coseismic slip distribution of the 1946 Nankai earthquake and aseismic slips caused by the earthquake, Earth Planets Space, 53, this issue, 235–241, 2001.

  18. Wang, K. and J. He, Mechanics of low-stress forearcs: Nankai and Cascadia, J. Geophys. Res., 104, 15,191–15,205, 1999.

  19. Wang, K., R. D. Hyndman, and M. Yamano, Thermal regime of the southwest Japan subduction zone: effects of age history of the subducting plate, Tectonophys., 248, 53–69, 1995.

  20. Zienkiewicz, O. C. and R. L. Taylor, in The Finite Element Method, 648 pp., McGraw-Hill, London, 1997.

Download references

Author information



Corresponding author

Correspondence to Phil R. Cummins.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Cummins, P.R., Hori, T. & Kaneda, Y. Splay fault and megathrust earthquake slip in the Nankai Trough. Earth Planet Sp 53, 243–248 (2001).

Download citation


  • Plate Boundary
  • Fault Slip
  • Accretionary Prism
  • Nankai Trough
  • Trench Axis