Tomography of the source zone of the great 2011 Tohoku earthquake

• Published in: Nature communications Vol. 11; no. 1; p. 1163
• Main Authors: Hua, Yuanyuan, Zhao, Dapeng, Toyokuni, Genti, Xu, Yixian
• Format: Journal Article
• Language: English
• Published: England Nature Publishing Group 03.03.2020; Nature Publishing Group UK; Nature Portfolio
• Subjects: Earthquakes; Free surfaces; Ocean floor; Radiation; Rigidity; Rupture; Seismic activity; Seismographs; Slip; Tomography; Velocity
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-020-14745-8

The mechanism and rupture process of the giant 2011 Tohoku-oki earthquake (Mw 9.0) are still poorly understood due to lack of permanent near-field observations. Using seismic arrival times recorded by dense seismograph networks on land and at ocean floor, we determine a detailed seismic tomography model of the megathrust zone beneath the Tohoku forearc. Our results show that the coseismic slip of the 2011 Tohoku-oki earthquake initiated at a boundary between a down-dip high-velocity anomaly and an up-dip low-velocity anomaly. The slow anomaly at shallow depths near the Japan trench may reflect low-rigidity materials that are close to the free surface, resulting in large slip and weak high-frequency radiation. Our new tomographic model can account for not only large slip near the trench but also weak high-frequency radiation from the shallow rupture areas.