9:45 AM - 10:00 AM
[SSS09-19] Japan Integrated Velocity Structure Model Version 2
Keywords:velocity structure, nation-wide model
After revising the Japan Integrated Velocity Structure Model Version 1 (Koketsu et al., 2012) so that it conforms to the global geodetic system (Japanese Geodetic Datum 2000), the following modifications were sequentially made to this revised edition.
(1) In the western half of Version 1, the basement structure of southwestern Japan was too complicated, so it was returned to that of Version 0.
(2) The structure of the accretionary prism along the Nankai Trough was modified to match the relationship between P-wave velocity and depth given by Baba (2005a) (Figure: 1.0 and 1.7 km/s of VS correspond to 2.4 and 3.2 km/s of VP).
(3) A narrow band of accretionary prism was also added along the Japan Trench and Sagami Trough based on the distribution map by Baba (2005b).
Long-period ground motion simulations for the 2004 sequence of earthquakes off the Kii Peninsula were performed using the Version 2 model after the above three modifications. For the foreshock of this sequence, Watanabe et al. (2014) conducted a simulation using the Version 1 model. In their result, the duration of long-period ground motion in the Tokyo lowland can be reproduced, but there is a problem with the amplitude. The simulation for the mainshock with the Version 2 model improves the amplitude problem considerably, and slight overestimation can also be solved by introducing sea water into the model. However, there remains an underestimation limited to the southern part of the Boso Peninsula.
Next, we performed a long-period ground motion simulation for the 2011 Tohoku earthquake. The results of the simulation by Kawabe et al. (2013) using the Version 1 model and the source model of Kawabe and Kamae (2013) show slight underestimations in the Tohoku to Kanto region, and slight overestimations in the Kinki region. These problems are generally improved in our simulation with the Version 2 model. However, since the improvement extends to the entire region, it is possible that not only the modifications of the velocity structure model but also the adjustment of the source model of Kawabe and Kamae (2013) to fit in the third layer of the oceanic crust has an effect.
Acknowledgment: This study was supported by Grant-in-Aid for Scientific Research (A) No. 19H00807 from the Japan Society for the Promotion of Science.
(1) In the western half of Version 1, the basement structure of southwestern Japan was too complicated, so it was returned to that of Version 0.
(2) The structure of the accretionary prism along the Nankai Trough was modified to match the relationship between P-wave velocity and depth given by Baba (2005a) (Figure: 1.0 and 1.7 km/s of VS correspond to 2.4 and 3.2 km/s of VP).
(3) A narrow band of accretionary prism was also added along the Japan Trench and Sagami Trough based on the distribution map by Baba (2005b).
Long-period ground motion simulations for the 2004 sequence of earthquakes off the Kii Peninsula were performed using the Version 2 model after the above three modifications. For the foreshock of this sequence, Watanabe et al. (2014) conducted a simulation using the Version 1 model. In their result, the duration of long-period ground motion in the Tokyo lowland can be reproduced, but there is a problem with the amplitude. The simulation for the mainshock with the Version 2 model improves the amplitude problem considerably, and slight overestimation can also be solved by introducing sea water into the model. However, there remains an underestimation limited to the southern part of the Boso Peninsula.
Next, we performed a long-period ground motion simulation for the 2011 Tohoku earthquake. The results of the simulation by Kawabe et al. (2013) using the Version 1 model and the source model of Kawabe and Kamae (2013) show slight underestimations in the Tohoku to Kanto region, and slight overestimations in the Kinki region. These problems are generally improved in our simulation with the Version 2 model. However, since the improvement extends to the entire region, it is possible that not only the modifications of the velocity structure model but also the adjustment of the source model of Kawabe and Kamae (2013) to fit in the third layer of the oceanic crust has an effect.
Acknowledgment: This study was supported by Grant-in-Aid for Scientific Research (A) No. 19H00807 from the Japan Society for the Promotion of Science.