HR: 0800h
AN: G51B-0813    [Abstracts]
TI: Crustal Deformation Around the Atotsugawa Fault System, Northern Central Japan, Based on GPS Measurements
AU: * Ohzono, M
EM: ohzono@eps.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
AU: Hirahara, K
EM: hirahara@eps.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
AU: Hoso, Y
EM: hoso@rcep.dpri.kyoto-u.ac.jp
AF: Disaster Prevention Research Institute, Kyoto University, Gokasyo, Uji, Uji, 611-0011 Japan
AU: Wada, Y
EM: yasuo@rcer.dpri.kyoto-u.ac.jp
AF: Kamitakara Observatory, Disaster Prevention Research Institute, Kyoto University, Hongo, Kamitakara-cho, Takayama, 506-1317 Japan
AU: Sagiya, T
EM: sagiya@eps.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
AU: Ando, M
EM: ando@seis.nagoya-u.ac.jp
AF: Graduate School of Environmental Studies, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602 Japan
AB: The Atotsugawa fault system consists of three active faults the Atotsugawa fault, Mozumi-Sukenobu fault, and the Ushikubi fault. These faults are located in the Niigata Kobe Tectonic Line (NKTZ), which was identified as a 50-200 km wide NE-SW trending zone with a large (> 0.1 ppm/yr) strain rates by the continuous GPS observation (Sagiya et al., 2000). In order to investigate details about strain accumulation around the Atotsugawa fault system, we installed two sense linear arrays (east and west) of continuous GPS sites since 1997. By the end of 2004, the 17 sites have been established within 30km from the Atotsugawa fault. Accordingly, we can cover the monitoring more precisely between the GEONET sites located intervals of about 25 km. We analyzed daily carrier phase data of 22 continuous GPS data from 1998 to 2004 to obtain daily precise coordinates. Then we calculate velocity of each site with a linear regression. Obtain velocity field exhibits E-W shortening of about 10 mm/yr across the Atotsugawa fault. For the eastern profile, the velocity gradually changes according to the distance from the fault trace, indicating the fault is located at the seismogernic depth range (0-15 km). On the other hand, the southern part of the western profile shows a block-wise motion, which may be interpreted as a result of creeping on the fault. Such a lateral heterogeneity along the fault is actually in the opposite sense to the idea considered so far. The overall deformation pattern can be reproduced by assuming a colliding two elastic blocks of 15 km width at a rate of 14 mm/yr at far field. One interesting feature is that if we plot the velocity pattern referring to a station just on the fault trace, the far field velocity pattern are anti symmetric, that is, the southern fault has a larger fault normal motion. More advanced modeling including lateral heterogeneity of the fault, contribution from other surrounding faults and fault creeping, is necessary for successful interpretation of observed data and tectonic loading of the Atotsugawa fault system.
DE: 1209 Tectonic deformation (6924)
DE: 1240 Satellite geodesy: results (6929, 7215, 7230, 7240)
DE: 8004 Dynamics and mechanics of faulting (8118)
SC: Geodesy [G]
MN: Fall Meeting 2005