5:15 PM - 7:15 PM
[SVC34-P03] Spatial stress change around fluid supply source detected from clastic dikes in the Miocene Tanabe Group
Keywords:clastic dike, fluid supply source, stress, McTigue model, mud diapir
Dike orientation has been used to estimate regional stress as an indicator for tectonics. A periphery of the fluid supply source, such as a magma chamber and mud diapir, is suitable for estimating stress because of a greater number of dike intrusions. However, stress changes locally due to a fluid supply source-accompanied radial compression, and the effects of regional and local stresses need to be distinguished. McTigue (1987) introduced the stress field model around the spherical cavity in the simi-infinite elastic body. Based on the model, this study proposed a new stress field model by summing homogeneous regional stress and verified it by comparing the model with the actual spatial stress variation.
This study measured the orientation of the conglomerate-bearing mudstone dikes associated with mud diapirs in the Miocene Tanabe Group, southwestern Japan. The stress inversion method was performed using the mixed Bingham distribution method (Yamaji & Sato, 2011) for each sub-area of tens to hundreds of meters. The general trend of E–W σ3 axes suggests regional E–W tension stress. σ3 axes are relatively dispersed in the southern part of the study area. The density of dike intrusion increases from north to south. These suggest that slurry originated from the source in the south. Stress regime changes spatially, as normal faulting, σ1-plunging southward, and strike-slip faulting from south to north. This pattern corresponds to the stress field suggested by McTigue (1987).
The parameters of the newly proposed model were estimated inversely for stresses detected in this study, and regional stress was well constrained as E–W tension normal faulting stress. It is consistent with stress in another area of the Tanabe Group (Abe & Sato, 2025).
The new stress field model also contributes to predicting the influence zone of volcanic activity and is helpful for disaster prevention and geological disposal of radioactive wastes.
<Acknowledgement> This study was carried out as a part of supporting program titled "Program to support research and investigation on important basic technologies related to radioactive waste (2024 FY)" under the contract with Ministry of Economy, Trade and Industry (METI).
<Reference> Abe & Sato, 2025, Isl. Arc, in press. McTigue, 1987, J. Geophys. Res., 92, 12931–12940; Yamaji & Sato, 2011, J. Struct. Geol., 33, 1148–1157.
This study measured the orientation of the conglomerate-bearing mudstone dikes associated with mud diapirs in the Miocene Tanabe Group, southwestern Japan. The stress inversion method was performed using the mixed Bingham distribution method (Yamaji & Sato, 2011) for each sub-area of tens to hundreds of meters. The general trend of E–W σ3 axes suggests regional E–W tension stress. σ3 axes are relatively dispersed in the southern part of the study area. The density of dike intrusion increases from north to south. These suggest that slurry originated from the source in the south. Stress regime changes spatially, as normal faulting, σ1-plunging southward, and strike-slip faulting from south to north. This pattern corresponds to the stress field suggested by McTigue (1987).
The parameters of the newly proposed model were estimated inversely for stresses detected in this study, and regional stress was well constrained as E–W tension normal faulting stress. It is consistent with stress in another area of the Tanabe Group (Abe & Sato, 2025).
The new stress field model also contributes to predicting the influence zone of volcanic activity and is helpful for disaster prevention and geological disposal of radioactive wastes.
<Acknowledgement> This study was carried out as a part of supporting program titled "Program to support research and investigation on important basic technologies related to radioactive waste (2024 FY)" under the contract with Ministry of Economy, Trade and Industry (METI).
<Reference> Abe & Sato, 2025, Isl. Arc, in press. McTigue, 1987, J. Geophys. Res., 92, 12931–12940; Yamaji & Sato, 2011, J. Struct. Geol., 33, 1148–1157.