Frontal wedge deformation near the source region of the 2011 Tohoku-Oki earthquake

TLDR

The study used an ocean‑bottom pressure gauge and acoustic ranging of local benchmarks to measure vertical uplift and horizontal displacement of the frontal wedge during the 2011 Tohoku‑Oki earthquake. The frontal wedge experienced a 5‑m uplift and 60‑plus‑meter horizontal shift, indicating an 80‑m coseismic slip that likely generated the tsunami that struck northeastern Japan.

Abstract

[1] We report an uplift of 5 m with a horizontal displacement of more than 60 m due to the 2011 Tohoku-Oki earthquake. The uplift was measured by an ocean-bottom pressure gauge installed before the earthquake on a frontal wedge, which formed an uplift system near the Japan Trench. Horizontal displacements of the frontal wedge were measured using local benchmark displacements obtained by acoustic ranging before and after the earthquake. The average displacements at the frontal wedge were 58 m east and 74 m east-southeast. These results strongly suggest a huge coseismic slip beneath the frontal wedge on the plate boundary. The estimated magnitude of the slip along the main fault was 80 m near the trench. Our results suggest that the horizontal and vertical deformations of the frontal wedge due to the slip generated the tremendous tsunami that struck the coastal area of northeastern Japan.