10:45 AM - 12:15 PM
[SSS07-P03] 3D S-wave velocity and anisotropy in Chuetsu area by applying surface wave analysis to dense seismometer network
Keywords:Microtremor, Zero-cross approach, Niitaga, S-wave velocity, anisotropy
The estimation of geological formations for resource exploration and CO2 geological storage in the Carbon dioxide Capture and Storage (CCS) project is strongly required. Specifically, CO2 geological storage is one potential strategy for reducing greenhouse gas emissions to the atmosphere (Metz et al., 2005). The Japanese government proposed to decrease 120-240 million tons of CO2 reduction every year, based on CO2 storage (METI, 2022). To achieve this CO2 reduction, we need to drill 240-480 boreholes around Japanese Island (METI, 2022). The conventional geophysical survey (i.e., seismic reflection survey) that is used to investigate geological formation for CO2 storage is expensive because it uses active seismic sources as well as many receivers. Thus, exploration methods with lower costs have been required (Yokota 2000). Therefore, miscellaneous microtremor analysis has been attracting attention in recent years because it does not require an artificial seismic source and is inexpensive and easy to perform (Harayama 2016).
Knowledge of the geological structure and its composition allows us to predict the earthquake intensity which is important for assessing earthquake damages related to drilling. Earthquake intensity is varied by a transmission path and local geological conditions such as P-wave and S-wave velocity structure of geological formations (Pitarka et al., 1998). In the 2016 Kumamoto earthquake, for example, the earthquake intensity was strongly related to the local geology; the intensity varied within a few hundred meters (Oshima 2016). Therefore, it is necessary to evaluate the impact of local geological conditions on seismic motions for predicting earthquake damages.
In this study, we use surface wave analysis for ambient noise to investigate S-wave velocity and anisotropy in an extensive area. The S-wave velocity structure is one of the most significant parameters in such local geological variables (Song et al., 2014). In the conventional surface wave approach, the resolution of the estimated S-wave velocity has not been enough to identify the local heterogeneity for disaster prevention as well as for resource exploration and CO2 geological storage. Thus, we applied the zero-crossing approach (e.g., Nthaba et al., 2022, Nimiya et al., 2020) to construct the higher resolution S-wave velocity model in Niigata region.
Knowledge of the geological structure and its composition allows us to predict the earthquake intensity which is important for assessing earthquake damages related to drilling. Earthquake intensity is varied by a transmission path and local geological conditions such as P-wave and S-wave velocity structure of geological formations (Pitarka et al., 1998). In the 2016 Kumamoto earthquake, for example, the earthquake intensity was strongly related to the local geology; the intensity varied within a few hundred meters (Oshima 2016). Therefore, it is necessary to evaluate the impact of local geological conditions on seismic motions for predicting earthquake damages.
In this study, we use surface wave analysis for ambient noise to investigate S-wave velocity and anisotropy in an extensive area. The S-wave velocity structure is one of the most significant parameters in such local geological variables (Song et al., 2014). In the conventional surface wave approach, the resolution of the estimated S-wave velocity has not been enough to identify the local heterogeneity for disaster prevention as well as for resource exploration and CO2 geological storage. Thus, we applied the zero-crossing approach (e.g., Nthaba et al., 2022, Nimiya et al., 2020) to construct the higher resolution S-wave velocity model in Niigata region.