- Open Access
Deep crustal structure along the Niigata-Kobe Tectonic Zone, Japan: Its origin and segmentation
Earth, Planets and Space volume 59, pagese5–e8(2007)
A seismic tomography study has revealed a detailed three-dimensional seismic velocity structure along a highstrain-rate zone, the Niigata-Kobe Tectonic Zone (NKTZ), located in Japan. The results show that the depth extent of the low-velocity zone varies along the NKTZ. We divided the NKTZ into three regions on the basis of the velocity structure. A low-velocity anomaly observed in the lower crust beneath the southwestern part of the NKTZ is probably attributable to the fluids derived from the Philippine Sea slab, while a prominent low-velocity anomaly extending from the upper crust to the uppermost mantle in the volcanic region, the middle part of the NKTZ, may be caused by the existence of melts and a higher-temperature condition that results from magmatic activity. The northeastern part exhibits low-velocity anomalies in the upper crust and the uppermost mantle, which are probably due to the thick sediment and fluids related to the back-arc volcanism, respectively. The strength of the crust and uppermost mantle along the NKTZ may have been weakened by the concentration of the fluids, which in turn facilitates the large contraction there. The heterogeneous structures revealed in this study suggest that the origin of the high-strain-rate zone varies along the NKTZ.
Hasegawa, A. and J. Nakajima, Geophysical constraints on slab subduction and arc magmatism, in The State of the Planet: Frontiers and Challenges in Geophysics, Geophys. Monogr. Ser., vol. 150, pp. 81–94, AGU, Washington, D.C., 2004.
Hasegawa, A. and J. Nakajima, N. Umino, and S. Miura, Deep structure of the northeastern Japan arc and its implications for crustal deformation and shallow seismic activity, Tectonophysics, 403, 59–75, 2005.
Hashimoto, M. and D. D. Jackson, Plate tectonics and crustal deformation around the Japanese islands, J. Geophys. Res., 98, 16149–16166, 1993.
Hyodo, M. and K. Hirahara, A viscoelastic model of interseismic strain concentration in Niigata-Kobe Tectonic Zone of central Japan, Earth Planets Space, 55, 667–675, 2003.
Iio, Y., T. Sagiya, Y. Kobayashi, and I. Shiozaki, Water-weakened lower crust and its role in the concentrated deformation in the Japanese Islands, Earth Planet. Sci. Lett., 203, 245–253, 2002.
Iio, Y., S. Takeshi, and Y. Kobayashi, Origin of the concentrated deformation zone in the Japanese Islands and stress accumulation process of intraplate earthquakes, Earth Plants Space, 56, 831–842, 2004.
Iwamori, H., Deep subduction of H2O and deflection of volcanic chain towards backarc near triple junction due to lower temperature, Earth Planet. Sci. Lett., 181, 41–46, 2000.
Miyoshi, T. and K. Ishibashi, Geometry of the seismic Philippine Sea slab beneath the region from Ise bay to western Shikoku, southwest Japan, J. Seismol. Soc. Jpn., 57, 139–152, 2004 (in Japanese with English abstract).
Nakajima, J. and A. Hasegawa, Anomalous low-velocity zone and linear alignment of seismicity along it in the subducted Pacific slab beneath Kanto, Japan: Reactivation of subducted fracture zone?, Geophys. Res. Lett., 33, L16309, doi:10.1029/2006GL026773, 2006.
Nakajima, J., T., Matsuzawa, A. Hasegawa, D. Zhao, Three-dimensional structure of Vp, Vs and Vp/Vs beneath the northeastern Japan arc: Implications for arc magmatism and fluids, J. Geophys. Res., 106, 21843–21857, 2001.
Ogawa, Y. and Y. Honkura, Mid-crustal electrical conductors and their correlations to seismicity and deformation at Itoigawa-Shizuoka Tectonic Line, Central Japan, Earth Plants Space, 56, 1285–1291, 2004.
Sagiya, T., S. Miyazaki, and T. Tada, Continuous GPS array and present-day crustal deformation of Japan, Pageoph, 157, 2303–2322, 2000.
Sato, H., The relationship between late Cenozoic tectonic events and stress field and basin development in northeast Japan, J. Geophys. Res., 99, 22261–22274, 1994.
Shimazaki, K. and Y. Zhao, Dislocation model for strain accumulation in a plate collision zone, Earth Planets Space, 52, 1091–1094, 2000.
Ueno, H., S. Hatakeyama, T Aketagawa, J. Funasaki, N. Hamada, Improvement of hypocenter determination procedures in the Japan Meteorological Agency, Quart. J. Seism., 65, 123–134, 2002 (in Japanese).
Yamasaki, T. and T. Seno, High strain zone in central Honshu resulting from the viscosity heterogeneities in the crust and mantle, Earth Planet. Sci. Lett., 232, 13–27, 2005.
Zhao, D., A. Hasegawa, and S. Horiuchi, Tomographic imaging of P and S wave velocity structure beneath northeastern Japan, J. Geophys. Res., 97, 19909–19928, 1992a.
Zhao, D., S. Horiuchi, and A. Hasegawa, Seismic velocity structure of the crust beneath the Japan islands, Tectonophysics, 212, 289–301, 1992b.
About this article
Cite this article
Nakajima, J., Hasegawa, A. Deep crustal structure along the Niigata-Kobe Tectonic Zone, Japan: Its origin and segmentation. Earth Planet Sp 59, e5–e8 (2007) doi:10.1186/BF03352677
- Seismic tomography
- low-velocity zone
- Niigata-Kobe Tectonic Zone