15:30 〜 16:30
[S13-P-11] Source imaging of the 2016 Kumamoto earthquake by back-projection of near-filed P wave records
The direction and the speed at which fault rupture proceeds, as is well known, controls major feature of ground motion around the causal faults. However, heterogeneous rupture process has been only partially taken into account in the current framework of strong ground motion prediction.
For more realistic and precise strong ground motion calculation, slip velocity function and rupture velocity variable on fault planes are expected to be take into consideration in the future. Actually, some attempts to incorporate such heterogeneity for ground motion prediction are under way in the world. In pursuing the goal, accumulation of information on fault rupturing process is essential to constitute a heterogeneous source model.
In this study, I applied back-projection technique to reveal the time history of seismic wave emission during the Kumamoto earthquake. Strong motion records recorded at 27 KiK-net and K-NET stations within 100km hyopocentral distance were used. Traveltime data were processed in the similar way as Takenaka and Yamamoto(2004) to obtain seismic emission image with more precision in relative location. The back-projection technique used in this study is similar to that by Kao and Shan(2004), and Ishii et al.(2005).
As a result, clear image of rupture propagation from Takano-Shirahata segment of the Hinagu fault zone to Futagawa segment of the Futagawa fault zone was obtained, where the strike and the dip of those two fault planes are different. The rupture rapidly increased its seismic wave emission while it's moving toward northeast.
However, both the accuracy and resolution of the present results still leave plenty of scope for improvement. In the future study, I am planning to scrutinize data and data processing techniques, such as traveltime data and waveform stacking methods, to get more exact and high-resolution image of the source process.
Acknowledgement: I would like to express my gratitude to NIED for providing me with KiK-net and K-NET data.
For more realistic and precise strong ground motion calculation, slip velocity function and rupture velocity variable on fault planes are expected to be take into consideration in the future. Actually, some attempts to incorporate such heterogeneity for ground motion prediction are under way in the world. In pursuing the goal, accumulation of information on fault rupturing process is essential to constitute a heterogeneous source model.
In this study, I applied back-projection technique to reveal the time history of seismic wave emission during the Kumamoto earthquake. Strong motion records recorded at 27 KiK-net and K-NET stations within 100km hyopocentral distance were used. Traveltime data were processed in the similar way as Takenaka and Yamamoto(2004) to obtain seismic emission image with more precision in relative location. The back-projection technique used in this study is similar to that by Kao and Shan(2004), and Ishii et al.(2005).
As a result, clear image of rupture propagation from Takano-Shirahata segment of the Hinagu fault zone to Futagawa segment of the Futagawa fault zone was obtained, where the strike and the dip of those two fault planes are different. The rupture rapidly increased its seismic wave emission while it's moving toward northeast.
However, both the accuracy and resolution of the present results still leave plenty of scope for improvement. In the future study, I am planning to scrutinize data and data processing techniques, such as traveltime data and waveform stacking methods, to get more exact and high-resolution image of the source process.
Acknowledgement: I would like to express my gratitude to NIED for providing me with KiK-net and K-NET data.