Rupture imaging of the 2011 Tohoku Earthquake. (a) Spatial and temporal (color bar shows the rupture time) distribution of three high-frequency energy sources during the whole rupture time of at least 143 s (given in Fig. 2(b)). First, the earthquake ruptured towards the northeast and then northwest of the epicenter. After a time delay, the rupture started from the epicenter again and extended towards the southwest with a distinct variation of the rupture direction at the latitude of 37°. (b) The relationship between released energy and rupture time. The dashed blue line indicates the ending time of the earthquake (143 s). There are three energy-radiation peaks at 23, 77, and 111 s. (c) The rupture time-distance relationship during the rupture process. First, the earthquake ruptured towards the northeast and then northwest of the epicenter at a slow rate of 0.92~1.10 km/s. The rupture front did not appear on the southwestern branch until 74 s. Then the earthquake ruptured towards the southwest for 150 km at an average rate of 2.78~4.70 km/s from about 74 s to 100 s. Finally, the earthquake ruptured to the southeast for a length of about 110 km on the third fault segment at an average rate of 1.51~1.62 km/s.