Seafloor observations indicate spatial separation of coseismic and postseismic slips in the 2011 Tohoku earthquake

• Published in: Nature communications Vol. 7; no. 1; p. 13506
• Main Authors: Iinuma, Takeshi, Hino, Ryota, Uchida, Naoki, Nakamura, Wataru, Kido, Motoyuki, Osada, Yukihito, Miura, Satoshi
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 17-11-2016; Nature Publishing Group; Nature Portfolio
• Subjects: 704/2151/508; 704/2151/562; Earthquakes; Fault lines; Friction; Global positioning systems; GPS; Humanities and Social Sciences; Interfaces; multidisciplinary; R&D; Research & development; Science; Science (multidisciplinary); Viscoelasticity; Japan
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/ncomms13506

Large interplate earthquakes are often followed by postseismic slip that is considered to occur in areas surrounding the coseismic ruptures. Such spatial separation is expected from the difference in frictional and material properties in and around the faults. However, even though the 2011 Tohoku Earthquake ruptured a vast area on the plate interface, the estimation of high-resolution slip is usually difficult because of the lack of seafloor geodetic data. Here using the seafloor and terrestrial geodetic data, we investigated the postseismic slip to examine whether it was spatially separated with the coseismic slip by applying a comprehensive finite-element method model to subtract the viscoelastic components from the observed postseismic displacements. The high-resolution co- and postseismic slip distributions clarified the spatial separation, which also agreed with the activities of interplate and repeating earthquakes. These findings suggest that the conventional frictional property model is valid for the source region of gigantic earthquakes.
Postseismic slip of the 2011 Tohoku earthquake in Japan has occurred on the plate interface, but quantifying the slip has been difficult due to a lack of seafloor data. Here, the authors use seafloor and terrestrial data and show that areas of co- and postseismic slip are spatially separated.