Special Issue: Slip and Flow Processes in and below the Seismogenic Region (2)
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Seismicity of the northern part of the Itoigawa-Shizuoka Tectonic Line
Earth, Planets and Space volume 56, pages 1279–1283 (2004)
Abstract
The relationship between recent seismicity and the active fault system was investigated using the precise hypocentral distribution by taking into consideration the heterogeneity of the velocity structure around the northern part of the Itoigawa-Shizuoka Tectonic Line (ISTL), the western boundary of the northern Fossa Magna basin. Since a velocity structure suitable for the ISTL is necessary for precise hypocentral determination, deep seismic reflection and refraction profiling were undertaken in 2002 across the northern part of the ISTL and a reliable velocity model was obtained. The hypocenters were located using the station corrections derived from the velocity model. The obtained hypocenters were found to be distributed in a straight line in an almost north-tosouth direction. The hypocenters, whose lower limit was approximately 15 km, were distributed around a vertical plane. The focal mechanism solutions were primarily strike-slip and the direction of their P-axis was NW-SE to WNW-ESE. The fault planes expected from these mechanisms are consistent with the distribution of the hypocenters. However, they are not consistent with the thrust fault planes of previous large earthquakes, which were inferred from the near-surface feature of the active fault system. This suggests that the recent seismicity cannot be attributed to aftershocks of the previous large earthquakes and is not induced by the movement of the active thrust fault.
References
Hirata, N. and M. Matsu’ura, Maximum-likelihood estimation of hypocenter with origin time eliminated using nonlinear inversion technique, Phys. Earth Planet. Inter., 47, 50–61, 1987.
Imai, T., T. Iwasaki, T. Takeda, T. Kawanaka and H. Sato, Detailed upper crustal structure across the Itoigawa-Shizuoka Tectonic Line from the 2002 seismic expedition, Proceedings of the 2nd International Symposium on Slip and Flow Process in and below the Seismogenic Region, 2004.
Okumura, K., K. Shimokawa, H. Yamazaki and E. Tsukuda, Recent surface faulting events along the middle section of the Itoigawa-Shizuoka Tectonic Line—trenching survey of the Gofukuji Fault near Matsumoto, central Japan—, Zisin, 46, 425–438, 1994 (in Japanese with English abstract).
Sagiya, T., T. Nishimura, Y. Iio and T. Tada, Crustal deformation around the northern and central Itoigawa-Shizuoka Tectonic Line, Earth Planets Space, 54, 1059–1063, 2002.
Sato, H., T. Iwasaki, S. Kawasaki, Y. Ikeda, N. Matsuta, T. Takeda, N. Hirata and T. Kawanaka, Formation and shortening deformation of a backarc rift basin revealed by deep seismic profiling across the Itoigawa- Shizuoka Tectonic Line active fault system, Central Japan, Tectonophysics, 2004 (in press).
Takeda, T., H. Sato, T. Iwasaki, N. Matsuta, S. Sakai, T. Iidaka and A. Kato, Crustal structure in the northern Fossa Magna region, central Japan, from refraction/wide-angle reflection data, Earth Planets Space, 56, this issue, 1295–1301, 2004.
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Sakai, S. Seismicity of the northern part of the Itoigawa-Shizuoka Tectonic Line. Earth Planet Sp 56, 1279–1283 (2004). https://doi.org/10.1186/BF03353351
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DOI: https://doi.org/10.1186/BF03353351