9:15 AM - 9:30 AM
[SCG56-26] Seismic imaging of the source zone of the 2011 Tohoku-oki earthquake
Keywords:The great Tohoku-oki earthquake, seismic tomography, Earthquake mechanism
Our results reveal a close relationship between structural heterogeneities in and around the megathrust zone and rupture processes of the 2011 Tohoku-oki earthquake (Liu and Zhao, 2018). Its mainshock nucleated in an off-Miyagi area with high seismic velocity, low seismic attenuation and strong seismic coupling, indicating a large asperity (or a cluster of asperities) in the Tohoku megathrust zone. Strong coseismic high-frequency radiations also occurred in high-velocity patches, whereas large afterslips took plate in low-velocity areas, which may reflect changes in fault friction and lithological variations. These results indicate that structural anomalies in and around the Tohoku megathrust originate from both the upper Okhotsk plate and the lower Pacific plate, which controlled the generation and rupture processes of the 2011 Tohoku-oki earthquake. This huge earthquake was caused by collision of harder rocks in both the upper and lower plates.
This work sheds new light on the causal mechanism of megathrust earthquakes. It also suggests that the location of a future great earthquake may be pinpointed by investigating the detailed structure of the megathrust zone.
In this presentation, we will also show our new results obtained by adding the data recorded by the S-net that has been installed in the eastern Japan forearc region under the Pacific Ocean.
Bassett, D., D. Sandwell, Y. Fialko, A. Watts (2016) Upper-plate controls on co-seismic slip in the 2011 magnitude 9.0 Tohoku-oki earthquake. Nature 531, 92-96.
Liu, X., D. Zhao (2018) Upper and lower plate controls on the great 2011 Tohoku-oki earthquake. Science Advances 4, eaat4396.
Zhao, D., Z. Huang, N. Umino, A. Hasegawa, H. Kanamori (2011) Structural heterogeneity in the megathrust zone and mechanism of the 2011 Tohoku-oki earthquake (Mw 9.0). Geophys. Res. Lett. 38, L17308.
Zhao, D., O.P. Mishra, R. Sanda (2002) Influence of fluids and magma on earthquakes: seismological evidence. Phys. Earth Planet. Inter. 132, 249-267.