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A preliminary fault model of the 2003 July 26, M6.4 northern Miyagi earthquake, northeastern Japan, estimated from joint inversion of GPS, leveling, and InSAR data
Earth, Planets and Space volume 55, pages 751–757 (2003)
Abstract
A shallow M6.4 earthquake with a M5.6 foreshock and the M5.5 largest aftershock occurred in northern Miyagi Prefecture, northeastern Japan on July 26, 2003. The coseismic displacement was observed not only by GEONET (continuous GPS) but also by campaign GPS, leveling, and InSAR. We have plenty of displacement data by multiple geodetic measurements, which is unusually abundant as the M6-class earthquakes. The leveling route in the epicentral area was surveyed on the day just before the earthquake by chance, and that it was resurveyed just after the earthquake. RADARSAT SAR interferograms provide high resolution of surface displacements which reach 240 mm. We construct coseismic rectangular fault model by inversion of the multiple geodetic data. The number of observation points used in the inversion are 23, 17, 49 and 1601 for continuous GPS, campaign GPS, leveling, and InSAR, respectively. We found that two thrust-type fault segments whose strike differs by 50° were necessary to reproduce the observed deformation. Seismic moment for both segments is 1.8 × 1018 Nm (Mw 6.1), assuming rigidity of 30 GPa. Because rake angle of two segments is different by only 15°, azimuth of slip vectors is significantly different between two faults. Two segments having different orientation can explain the apparent disagreement of focal mechanisms estimated from initial phase of P wave and CMT waveform inversion.
References
Active Fault Research Group, Active Faults in Japan: sheet maps and inventories (Revised edition), 437 pp., University of Tokyo Press, Tokyo, 1991 (in Japanese).
Goldstein, R. M. and C. L. Werner, Radar interferogram filtering for geophysical applications, Geophys. Res. Let., 25, 4035–4038, 1998.
Massonnet, D., K. L. Rossi, C. Carmona, F. Adragna, G. Peltzer, K. Fiegl, and T. Rabaute, The displacement field of the Landers earthquake mapped by radar interferometry, Nature, 364, 138–142, 1993.
Matsu’ura, M. and Y. Hasegawa, A maximum likelihood approach to nonlinear inversion under constraints, Phys. Earth Planet. Inter., 47, 179–187, 1987.
Nishimura, T., S. Fujiwara, M. Murakami, M. Tobita, H. Nakagawa, T. Sagiya, and T. Tada, The M6.1 earthquake triggered by volcanic inflation of Iwate volcano, northern Japan, observed by satellite radar interferometry, Geophys. Res. Let., 28, 635–638, 2001.
Nishimura, T., T. Sagiya, and S. Miura, Crustal deformation around the Nagamachi-Rifu fault zone and its vicinity (central Tohoku), northeastern Japan, observed by continuous GPS measurements, Zisin, 2004a (in press) (in Japanese with English abstract).
Nishimura, T., T. Hirasawa, S. Miyazaki, T. Sagiya, T. Tada, S. Miura, and K. Tanaka, Temporal change of interplate coupling in northeastern Japan during 1995–2002 estimated from continuous GPS observations, Geophys. J. Int., 2004b (in press).
Okada, Y., Internal deformation due to shear and tensile faults in a halfspace, Bull. Seismol. Soc. Am., 82, 1018–1040, 1992.
Okada, T., N. Umino, and A. Hasegawa, Rupture process of the July 2003 northern Miyagi earthquake sequence, NE Japan, estimated from double-difference hypocenter locations, Earth Planets Space, 55, this issue, 741–750, 2003.
Sagiya, T., Crustal movements as earthquake precursors—Leveling anomaly before the 1944 Tonankai Earthquake revisited—, Bull. Geogra. Surv. Inst., 44, 23–36, 1998.
Sagiya, T., S. Miyazaki, and T. Tada, Continuous GPS array and present-day crustal deformation of Japan, PAGEOPH, 157, 2303–2322, 2000.
Sato, H., Some precursors prior to recent great earthquakes along the Nankai Trough, J. Phys. Earth, 25, S115–S121, 1977.
Savage, J. C., Displacement field for an edge dislocation in a layered halfspace, J. Geophys. Res., 103, 2439–2446, 1998.
Yarai, H., T. Ozawa, T. Nishimura, and T. Imakiire, Crustal deformation associated with the northern Miyagi earthquake detected by RADARSAT and ENVISAT SAR interferometry, Earth Planets Space, 2003 (submitted).
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Nishimura, T., Imakiire, T., Yarai, H. et al. A preliminary fault model of the 2003 July 26, M6.4 northern Miyagi earthquake, northeastern Japan, estimated from joint inversion of GPS, leveling, and InSAR data. Earth Planet Sp 55, 751–757 (2003). https://doi.org/10.1186/BF03352484
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DOI: https://doi.org/10.1186/BF03352484