Rupture details of the 28 March 2005 Sumatra Mw 8.6 earthquake imaged with teleseismic P waves -: art. no. L24303

We image the rupture of the 28 March 2005 Sumatra Mw 8.6 earthquake by back-projecting teleseismic P waves recorded by the Global Seismic Network and the Japanese Hi-net to their source. The back-projected energy suggests that the rupture started slowly, had a total duration of about 120 s, and propagated at 2.9 to 3.3 km/s from the hypocenter in two different directions: first toward the north for similar to 100 km and then, after a similar to 40 s delay, toward the southeast for similar to 200 km. Our images are consistent with a rupture area of similar to 40,000 km 2, the locations of the first day of aftershocks, and the Harvard CMT Mw of 8.6, which implies an average slip of similar to 6 m. The earthquake is similar in its location, size, and geometry to a Mw similar to 8.5 event in 1861. Our estimated average slip is consistent with a partially coupled subduction interface, GPS forearc velocities, and the similar to 59 mm/yr convergence rate if the 2005 earthquake released elastic strain that accumulated over many hundreds of years rather than just since the last 1861 event.