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Two parallel trench-normal fault planes within the Pacific slab associated with the 1994 and 2000 Kurile earthquakes as revealed by simultaneous relocation of their main shocks and aftershocks
Earth, Planets and Space volume 59, pages e25–e28 (2007)
Abstract
The 1994 Hokkaido-Toho-Oki (Mw 8.3) and the 2000 Nemuro-Hanto-Oki (Mw 6.8) earthquakes have been regarded as great/large intraslab events within the subducted Pacific plate along the southern Kurile trench. Determining which nodal planes of their mechanism solutions are actual fault planes and whether or not the 2000 event occurred on the southwestern extension of the 1994 fault plane have been problematic. In order to clarify these points, we examine the relative location of their main-shock and aftershock distributions accurately by simultaneous relocation of their hypocenters using the Modified Joint Hypocenter Determination (MJHD) method. The result clearly shows that the two earthquakes occurred on trench-normal shallow-dipping fault planes within the Pacific slab, apart from and parallel to each other. Therefore, the 2000 earthquake was not a rupture on the deeper extension of the 1994 fault plane, but one on another fault plane. A large intraslab earthquake (Mw 7.8; depth, about 100 km) occurred to the northwest of the 1994 event in 1978, and two trench-normal fracture zones exist outside the trench to the southeast of the 1994 and 2000 events. Therefore, these three intraslab great/large earthquakes are considered to have been ruptures along pre-existing trench-normal weak zones within the subducted Pacific plate.
References
Enescu, B., J. Mori, and S. Ohmi, Double-difference relocations of the 2004 off the Kii peninsula earthquakes, Earth Planets Space, 57, 357–362, 2005.
Hilde, T. W. C., N. Isezaki, and J. M. Wageman, Mesozoic sea-floor spreading in the north Pacific, in The Geophysics of the Pacific Ocean Basin and its Margins, Geophys. Monogr. Ser. 19, edited by G. H. Sutton, M. H. Manghnani, and R. Moberly, pp. 205–226, AGU, Washington, D. C., 1976.
Hurukawa, N., Quick aftershock relocation of the 1994 Shikotan earthquake and its fault planes, Geophys. Res. Lett., 22, 3159–3162, 1995.
Hurukawa, N. and M. Imoto, Subducting oceanic crusts of the Philippine Sea and Pacific plates and weak-zone-normal compression in the Kanto district, Japan, Geophys. J. Int., 109, 639–652, 1992.
International Seismological Centre, On-line Bulletin, http://www.isc.ac.uk/Bull, Internatl. Seis. Cent., Thatcham, United Kingdom, 2005.
Kanamori, H., Faulting of the great Kanto earthquake of 1923 as revealed by seismological data, Bull. Earthq. Res. Inst., 49, 13–18, 1971.
Kasahara, M. and T. Sasatani, Source characteristics of the Kunashiri strait earthquake of December 6, 1978 as deduced from strain seismograms, Phys. Earth Planet. Inter., 37, 124–134, 1985.
Katsumata, K., M. Ichiyanagi, M. Miwa, M. Kasahara, and H. Miyamachi, Aftershock distribution of the October 4, 1994 Mw8.3 Kurile islands earthquake determined by a local seismic network in Hokkaido, Japan, Geophys. Res. Lett., 22, 1321–1324, 1995.
Kennett, B. L. N., E. R. Engdahl, and R. Buland, Constraints on seismic velocities in the Earth from traveltimes, Geophys. J. Int., 122, 108–124, 1995.
Kikuchi, M. and H. Kanamori, The Shikotan earthquake of October 4, 1994: Lithospheric earthquake, Geophys. Res. Lett., 22, 1025–1028, 1995.
Miyoshi, T. and K. Ishibashi, A tectonic interpretation of NW-SE strike-slip faulting during the 2004 off the Kii peninsula earthquake, Japan: Probable tear of the Philippine Sea plate, Earth Planets Space, 57, 1115–1120, 2005.
Seno, T., T. Sakurai, and S. Stein, Can the Okhotsk plate be discriminated from the North American plate?, J. Geophys. Res., 101, 11305–11315, 1996.
Takahashi, H. and K. Hirata, The 2000 Nemuro-Hanto-Oki earthquake, off eastern Hokkaido, Japan, and the high intraslab seismic activity in the southwestern Kuril Trench, J. Geophys. Res., 108(B4), 2178, doi:10.1029/2002JB001813, 2003.
Tanioka, Y., L. Ruff, and K. Satake, The great Kurile earthquake of October 4, 1994 tore the slab, Geophys. Res. Lett., 22, 1661–1664, 1995.
Tsuji, H., Y. Hatanaka, T. Sagiya, and M. Hashimoto, Coseismic crustal deformation from the 1994 Hokkaido-Toho-Oki earthquake monitored by a nationwide continuous GPS array in Japan, Geophys. Res. Lett., 22, 1669–1672, 1995.
Utsu, T., Large earthquakes near Hokkaido and the expectancy of the occurrence of a large earthquake off Nemuro, Rep. Coord. Comm. Earthq. Predict., 7, 7–13, 1972 (in Japanese).
Wessel, P. and W. H. F. Smith, Free software helps map and display data, Eos Trans. AGU, 72,441, 445–446, 1991.
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Harada, T., Ishibashi, K. Two parallel trench-normal fault planes within the Pacific slab associated with the 1994 and 2000 Kurile earthquakes as revealed by simultaneous relocation of their main shocks and aftershocks. Earth Planet Sp 59, e25–e28 (2007). https://doi.org/10.1186/BF03352025
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DOI: https://doi.org/10.1186/BF03352025