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TitleLarge fault slip peaking at trench in the 2011 Tohoku-oki earthquake
AuthorSun, T; Wang, K; Fujiwara, T; Kodaira, S; He, J
SourceNature Communications vol. 8, (2017), 14044, 2017.,
Alt SeriesEarth Sciences Sector, Contribution Series 20160230
Mediapaper; on-line; digital
File formatpdf
AreaTohoku-oki; Japan
Lat/Long WENS 141.0000 144.0000 40.0000 36.0000
Subjectsgeophysics; tectonics; faults, slip; earthquake magnitudes; earthquake mechanisms; earthquakes; earthquake risk; earthquake studies; subduction zones; subduction; bathymetry
IllustrationsLandsat images; graphs; cross-sections, structural; seismic reflection profiles
ProgramWestern Canada Geohazards Project, Public Safety Geoscience
AbstractDuring the 2011 magnitude 9 Tohoku-oki earthquake, very large slip occurred on the shallowest part of the subduction megathrust. Quantitative information on the shallow slip is of critical importance to distinguishing between different rupture mechanics and understanding the generation of the ensuing devastating tsunami. However, the magnitude and distribution of the shallow slip are essentially unknown due primarily to the lack of near-trench constraints, as demonstrated by a compilation of 45 rupture models derived from a large range of data sets. To quantify the shallow slip, here we model high-resolution bathymetry differences before and after the earthquake across the trench axis. The slip is determined to be about 62 m over the most near-trench 40 km of the fault with a gentle increase toward the trench. This slip distribution indicates that dramatic net weakening or strengthening of the shallow fault did not occur during the Tohoku-oki earthquake.
Summary(Plain Language Summary, not published)
It is known that the devastating tsunami caused by the 2011 M=9 Tohoku-oki earthquake is due to the slip of the shallowest part of the megathrust, but the magnitude and distribution of the shallow slip are very poorly known because of the lack of near-field observations. In this work, we use the most near-field observations - bathymetry differences before and after the earthquake at the trench to determine the shallow slip. Our modeling indicates fault slip exceeding 60 m and peaking at the trench, and the rate of the slip increase towards the trench is very small. The results have important implications to rupture mechanics and tsunami generation, not only for Japan Trench but also for other subduction zones such as Cascadia.