aaand? Shouldn't this be in world events? You introduce no earth science discussion. Anyways, here's an article in BBC http://news.bbc.co.uk/1/hi/world/asia-pacific/4388579.stm
Well, excuse me. For once I thought there might be sufficient interest, intellect and experience out there to generate discussion from the questions implicit in the event and the information contained in the link, such as: was this directly related to the Dec 26th shock? does this validate the recent predictions in Nature of exactly this type of follow-on event? should we anticipate further events of this order of magnitude? in terms of total energy release how do the two events compare? have seismologists got a good grip on long term (century/millenia) earthquake severity/frequency? could the stress changes induce/increase volcanic activity in Sumatra? (Krakatoa?) how did the duration of the two events compare? what technical means are available to assess stress levels in surface rocks, sub-sea rocks, deep rocks? what effect does the 3-D geometry of the descending plate have on earthquake magnitude? is the concept of an epicentre outmoded and misleading? can detailed analysis of magnitude and form of shock waves allow better prediction of tsunami probability and size? if so, are P, S or surface waves likely to be more relevant? et cetera......
In answer to your question of whether the March 28th shock of 8.7 is connected to the Boxing Day quake, yes it is--here's how; The Boxing Day quake, as you'll know by now, was the result of the Indo-Australian Plate pushing eastward and subducting underneath the Burma Plate. This had the effect of heaving the Burma Plate ten metres up, which was the direct cause of the tsunami waves. Now the stresses of that 26/12 quake are being transmitted further east, along the faultline that forms the border of the Australian plate south of Indonesia. This is a slip-strike zone; earthquake stresses are transmitted laterally, and the movement is lateral as well, with the two sides of the fault shearing and slipping past each other instead of over or under, as when they come face to face (as you'll see on the geological map you provided from the USGS.) What you have at the moment is the loosening up of the entire plate boundary, with the stresses being released in a west-to-east movement. This is because the Indo-Australian plate is rotating in a clockwise fashion with respect to the Burma plate. The Pacific Plate is rotating in an anticlockwise movement with respect to the Indo-Australian Plate. This explains why the Pacific Plate is being subducted under the North Island of New Zealand, while in the South Island the movement along the Alpine Fault is lateral, slip/strike shearing motion, as is the motion of the San Andreas Fault in California. What really disturbs me about that map is that the area directly to the east of the 28th March 8.7 shock, (as you'll see by the map) has not had a major tremor since 1833. If I was living in that area, which is most likely to be hit by the next massive quake, I'd be thinking seriously about living under canvas for a while to avoid being crushed by a falling roof or wall.
