3:00 PM - 4:00 PM
[J08-P-06] Deep Conductive Structure beneath the Kutcharo Caldera, Revealed by 3-D Inversion Analysis
Kutcharo caldera is the biggest caldera in Japan, which has potential to cause catastrophic eruption. We think it is very important to clarify the current subsurface state of the volcano. There are some report for the caldera structure by gravity surveys and AMT explorations (e.g. Yokoyama, 1958, J. Phys. Earth; Honda et al., 2011a, J. Fac. Sci. Hokkaido Univ.; Ichihara et al., 2009, EPS), however, no obvious structures which associate any volcanic activities has been reported. We report the result of the 3-D analysis of the resistivity structure in and around the Kutcharo caldera.
Our survey was executed by wide-band and the long-period observations during 2009 and 2010. With our survey data, we compiled the wide-band MT data from Ichihara et al. (2009, EPS) and Ichihara et al. (2013, Tectonophys.), which are the observation data around the focal area of Teshikaga Earthquake. We adopted the remote reference analyses (Gamble et al., 1978, Geophysics) to these MT data. We used the reference magnetic data of Kakioka Magnetic Observatory and the Esashi station for the long wavelength and the wide-band data, respectively.
The three dimensional analysis is executed by WSINV3DMT (Siripunvaraporn et al., 2005, PEPI; Siripunvaraporn et al., 2009, PEPI). The characteristic resistivity structures found in the result is almost consistent with the result of the 2-D analyses (Honda et al., 2011). The extraordinary low resistivity body piercing the high resistivity layer towards the Atosanupri volcano from the deep layer was remarkable in the 2-D result. By the 3-D analysis, the conductor under the Kutcharo caldera became sharp.
Acknowledgement
For this study, we have used the computer systems of the Earthquake and Volcano Information Center of the Earthquake Research Institute, the University of Tokyo. We are thankful for the magnetic data provided by the GSI and JMA.
Our survey was executed by wide-band and the long-period observations during 2009 and 2010. With our survey data, we compiled the wide-band MT data from Ichihara et al. (2009, EPS) and Ichihara et al. (2013, Tectonophys.), which are the observation data around the focal area of Teshikaga Earthquake. We adopted the remote reference analyses (Gamble et al., 1978, Geophysics) to these MT data. We used the reference magnetic data of Kakioka Magnetic Observatory and the Esashi station for the long wavelength and the wide-band data, respectively.
The three dimensional analysis is executed by WSINV3DMT (Siripunvaraporn et al., 2005, PEPI; Siripunvaraporn et al., 2009, PEPI). The characteristic resistivity structures found in the result is almost consistent with the result of the 2-D analyses (Honda et al., 2011). The extraordinary low resistivity body piercing the high resistivity layer towards the Atosanupri volcano from the deep layer was remarkable in the 2-D result. By the 3-D analysis, the conductor under the Kutcharo caldera became sharp.
Acknowledgement
For this study, we have used the computer systems of the Earthquake and Volcano Information Center of the Earthquake Research Institute, the University of Tokyo. We are thankful for the magnetic data provided by the GSI and JMA.