8:45 AM - 9:00 AM
[J09-4-02] Estimation of coupling ratio on subducting plate interface and block boundary in southwest Japan using MCMC method
In southwest Japan, the Philippine sea plate is subducting under the overriding plate, such as Amurian plate. The last interplate earthquakes occurred along the Nankai trough at 1944 and 1946. The recurrence interval is guessed around 90-200 years from historical earthquake. Although, it already passed over 70 years, the event did not occur yet. So, it is important to evaluate earthquake potentials for preparing huge damage due to large earthquake in near future.
In last decade, seafloor geodetic observation revealed detailed interplate coupling distribution in expected source region of Nankai trough earthquake (e.g., Yokota et al., 2016). In this study, we try to make the new block motion model based on 24 seafloor geodetic observation along the Nankai trough and 609 inland GNSS sites in southwest Japan.
Crustal block motion model
We developed crustal block motion model, including elastic plate coupling and crustal block relative motion [Kimura et al., 2017 (JpGU-AGU Joint Meeting 2017)]. At first, we make several crustal block rigid motion models, based on geological information, such as surface trace of active fault. In typically, these block motion models are too fine, because geodetic data does not have resolution for fine model based on geological information. We try to select the optimal crustal block motion model using Akaike's information criteria. After this model selection, we set the more detail of configuration, such as plate interface. In this study, we employ the algorithm for optimized number of subfaults along plate interface [Kimura et al., 2016 (126th Meeting of the Geodetic Society of Japan)].
We will present the result and discussion for crustal block motions and the interplate coupling distributions in southwest Japan. Especially we focus on the defference in derived interplate coupling distribution along the Nankai trough due to the effect of coupling along Median Tectonic Line and Izu Micro Plate motion.