The March 11, 2011 Tohoku‐oki earthquake and cascading failure of the plate interface

Abstract

A continuous back‐projection analysis using data recorded in North America between March 9, 2011 and April 7, 2011 is applied to the Mw 9.0 2011 Tohoku‐oki earthquake and the foreshocks and aftershocks of this event. As with the Mw 8.8 2010 Maule, Chile earthquake, back‐projection results of the mainshock show variations in rupture behavior when data filtered to different frequency ranges are used. In particular, there is a relationship between the frequency of data used and the position along the dip direction of the energy release, with the highest‐frequency result imaging energy at the down‐dip edge of the rupture and progressively lower frequencies showing a continuous shift updip. In addition, these results show that late in the rupture (∼200 seconds after the hypocentral time), energy at all frequencies is imaged very close to the trench at about 37°N, which, with the energy imaged near and updip of the epicenter, may have acted as a tsunami source. Comparing the mainshock rupture area to the area that ruptured during M ≥ 6 foreshocks and aftershocks between March 9th and April 7th shows that total failure of the plate interface nearly doubled compared to the mainshock alone. Building upon the idea that the mainshock occurred through interactions between multiple segments, the results imply that the total failure area of the interface may represent the area that can rupture during a single event as a series of in‐phase interface segments.