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[SVC34-03] Monitoring long-term volcanic activities of Aso volcano with crustal deformation: correction of postseismic deformation of Kumamoto earthquake
Keywords:Crustal deformation, Kumamoto earthquake, Postseismic deformation, Aso volcano, Magma chamber
Monitoring long-term volcanic activities of Aso volcano with crustal deformation: correction of postseismic deformation of Kumamoto earthquake
Hiroshi Munekane (Geospatial Information Authority of Japan)
Keywords: Crustal deformation, Kumamoto earthquake, Postseismic deformation, Aso volcano, Magma chamber
It is important to evaluate volume changes of the magma source of Aso volcano for monitoring long-term activities of Aso volcano using crustal deformation data. However, after Kumamoto earthquake that occurred in 2016, it became difficult to evaluate volume changes since observed crustal deformation is contaminated by post-seismic deformation of the Kumamoto earthquake. Hence, in this study, I tried to develop a method to evaluate the volume changes of the magma source while accounting for the post-seismic deformation.
Post-seismic deformation consists of two parts, namely, viscoelastic deformation and afterslip. For the former, I employed the two-layer model (an elastic plate over a viscoelastic halfspace) whose parameters (thickness of the first elastic layer and viscoelasticity of the second layer) are adaptively determined with the deformation data at a specific epoch. For the latter, I employed a set of small rectangular faults over the extension of the coseismic fault planes, whose slip are adaptively determined from the deformation data at a specific epoch. Then I removed viscoelastic deformation from the observed deformation data with the above-mentioned model and then evaluated the time-evolution of the volume changes of the Aso magma source along with the afterslip using the time-dependent inversion (Segall and Matthews, 1997). In the calculation, the position of the Aso magma source is fixed to the north of Kusasenrigahama and 4km bsl following the preceding studies (e.g., Nobile et al., 2017).
The estimated volume changes suggest large inflation after the Kumamoto earthquake, which might be caused by the stress changes by the mainshock (Ozawa and Fujita, 2016). Then they general decrease with exception of short periods during 2019 and 2021 where enhanced volcanic activities were observed.
References:
Nobile, A. et al (2017) Bull. Volcanol., 79, 32, https://doi.org/doi:10.1007/s00445-017-1112-1
Ozawa T. and E. Fujita (2016) Earth Planets Space, 68,186, https://doi.org/10.1186/s40623-016-0563-5
Pollitz, F. et al. (2017) Geophys. Res. Lett., 44. 8795--8803, https://doi.org/10.1002/2017GL074783
Segall, P. and M. Matthews (1997) J Geophys. Res., 102, 22391--22409, https://doi.org/10.1029/97JB10795
Yarai, H. et al. (2016) Journal of Geospatial Information Authority of Japan, 128, 169--176.
Hiroshi Munekane (Geospatial Information Authority of Japan)
Keywords: Crustal deformation, Kumamoto earthquake, Postseismic deformation, Aso volcano, Magma chamber
It is important to evaluate volume changes of the magma source of Aso volcano for monitoring long-term activities of Aso volcano using crustal deformation data. However, after Kumamoto earthquake that occurred in 2016, it became difficult to evaluate volume changes since observed crustal deformation is contaminated by post-seismic deformation of the Kumamoto earthquake. Hence, in this study, I tried to develop a method to evaluate the volume changes of the magma source while accounting for the post-seismic deformation.
Post-seismic deformation consists of two parts, namely, viscoelastic deformation and afterslip. For the former, I employed the two-layer model (an elastic plate over a viscoelastic halfspace) whose parameters (thickness of the first elastic layer and viscoelasticity of the second layer) are adaptively determined with the deformation data at a specific epoch. For the latter, I employed a set of small rectangular faults over the extension of the coseismic fault planes, whose slip are adaptively determined from the deformation data at a specific epoch. Then I removed viscoelastic deformation from the observed deformation data with the above-mentioned model and then evaluated the time-evolution of the volume changes of the Aso magma source along with the afterslip using the time-dependent inversion (Segall and Matthews, 1997). In the calculation, the position of the Aso magma source is fixed to the north of Kusasenrigahama and 4km bsl following the preceding studies (e.g., Nobile et al., 2017).
The estimated volume changes suggest large inflation after the Kumamoto earthquake, which might be caused by the stress changes by the mainshock (Ozawa and Fujita, 2016). Then they general decrease with exception of short periods during 2019 and 2021 where enhanced volcanic activities were observed.
References:
Nobile, A. et al (2017) Bull. Volcanol., 79, 32, https://doi.org/doi:10.1007/s00445-017-1112-1
Ozawa T. and E. Fujita (2016) Earth Planets Space, 68,186, https://doi.org/10.1186/s40623-016-0563-5
Pollitz, F. et al. (2017) Geophys. Res. Lett., 44. 8795--8803, https://doi.org/10.1002/2017GL074783
Segall, P. and M. Matthews (1997) J Geophys. Res., 102, 22391--22409, https://doi.org/10.1029/97JB10795
Yarai, H. et al. (2016) Journal of Geospatial Information Authority of Japan, 128, 169--176.