14:45 〜 15:00
[SCG61-05] Geofluid mapping in the Atotsugawa fault-Takayama area, Central Japan, based on simultaneous analysis of seismic velocities and electrical conductivity
キーワード：跡津川、地殻流体、地震波速度、電気伝導度
Geofluids, such as aqueous fluid and magma, play crucial roles in driving Earth's dynamics and evolution, especially in subduction zones. They influence various geological processes, including mantle convection, plate motion, crustal deformation, seismicity, and magmatism-metamorphism-volcanism, which contribute to crustal growth. Despite their significance, identifying the distribution of geofluids remains challenging. Various observational methods, such as seismic tomography and magnetotelluric (MT) inversion, have been employed to understand geofluid distribution within the Earth's interior, based on observed P- and S-wave velocities (Vp and Vs) and electrical conductivity (σ). However, neither seismic velocity nor electrical conductivity alone is sufficient to constrain geofluid distribution. In this study, we use a recently developed Bayesian inversion method capable of simultaneously analyzing Vp, Vs, and σ (Iwamori et al., 2021; Kuwatani et al., 2023) for quantitative mapping.
The Atotsugawa fault-Takayama area is one of the most tectonically active regions in Central Japan, encompassing several active faults such as the Ushikubi fault, the Atotsugawa fault, and the Takayama-Oppara fault zone, located northwest of the active Ontake volcano. Seismic and MT studies suggest that aseismic shear zones in the fluid-rich lower crust may accumulate stress in the region (e.g., Nakajima et al., 2010; Usui et al., 2021). To identify the types of geofluids (aqueous fluid, basaltic magma, andesitic magma) and quantitatively map their distributions, we employ the aforementioned Bayesian inversion method, which simultaneously analyzes the seismic velocity structure (Nakajima et al., 2010) and electrical conductivity structure (Usui et al., 2021). Preliminary results of geofluid mapping will be presented to discuss the distribution, origin, and roles of geofluids in connection with geodynamic processes in the study area.
The Atotsugawa fault-Takayama area is one of the most tectonically active regions in Central Japan, encompassing several active faults such as the Ushikubi fault, the Atotsugawa fault, and the Takayama-Oppara fault zone, located northwest of the active Ontake volcano. Seismic and MT studies suggest that aseismic shear zones in the fluid-rich lower crust may accumulate stress in the region (e.g., Nakajima et al., 2010; Usui et al., 2021). To identify the types of geofluids (aqueous fluid, basaltic magma, andesitic magma) and quantitatively map their distributions, we employ the aforementioned Bayesian inversion method, which simultaneously analyzes the seismic velocity structure (Nakajima et al., 2010) and electrical conductivity structure (Usui et al., 2021). Preliminary results of geofluid mapping will be presented to discuss the distribution, origin, and roles of geofluids in connection with geodynamic processes in the study area.