Low Coseismic Shear Stress on the Tohoku-Oki Megathrust Determined from Laboratory Experiments
Large coseismic slip was thought to be unlikely to occur on the shallow portions of plate-boundary thrusts, butthe 11 March 2011 Tohoku-Oki earthquake [moment magnitude (Mw) = 9.0] produced huge displacements of ~50 meters near the Japan Trench with a resultant devastating tsunami. To investigate the mechanisms of thevery large fault movements, we conducted high-velocity (1.3 meters per second) friction experiments onsamples retrieved from the plate-boundary thrust associated with the earthquake. The results show a smallstress drop with very low peak and steady-state shear stress. The very low shear stress can be attributed tothe abundance of weak clay (smectite) and thermal pressurization effects, which can facilitate fault slip. This behavior provides an explanation for the huge shallow slip that occurred during the earthquake.
Center for Coastal and Ocean Mapping
Journal or Conference Title
342, Number 6163
American Association for the Advancement of Science (AAAS)
Digital Object Identifier (DOI)
K. Ujiie et al., "Low Coseismic shear stress on the Tohoku-Oki Megathrust determined from laboratory experiments," Science, vol. 342, no. 6163, pp. 1211–1214, Dec. 2013.