Fig. 2.

Different subevents during the mainshock are indicated by different contours, and the background colour shows the relative amounts of energy released at each location (warmer colours indicating more energy release). The cyan contour shows the area ruptured during subevent 1 which occurs within the first 40 seconds, and covers an area around the epicentre (red star with black outline). The two white contours show areas associated with the main part (dashed curve) and later bilateral rupture (solid curve) of subevent 2. The solid magenta and yellow contours are the ruptures that propagate updip during subevents 3 and 5, respectively. The dashed magenta and yellow contours are subevents 4 and 6, respectively, that behave nearly as a point source. The aseis-mic patch imaged using the coherency function is located between the white outline of the subevent 2 and magenta outline of subevent 3, and clearly shows up as a gap between northern and central parts of imaged high-frequency rupture region. The yellow dots are aftershocks between March 11 and 17 as given by the JMA catalogue. The black and red curves show the coastline and the trench location, respectively. The range of colours used in this plot is shown on the bottom right corner.