Hello concerned folks. It would probably be impossible for the same part of the subduction zone to fail again before many decades, and probably would not fail again as a M9 for more than a century. So, there is essentially zero chance that we will have a repeat of the Dec 26 05 quake this year. And, there is not another fault that can cause a M9+ earthquake at those latitudes. The Great Sumatra Fault is a right-lateral strike-slip fault like the San Andreas fault, and it could probably be capable of a M8 quake...but such a quake would be mostly onshore and would not cause the submarine vertical motions that could cause a large tsunami. On the other hand, it could set off submarine landslides that could cause local tsunamis. There is no particular reason to think that this fault would fail this month, or next, but I can't rule this out. I have not read the scientific literature on this area in detail...but recall that there may be some tendancy for the Great Sumatra Fault to fail within a couple of years of a subduction earthquake...but someone needs to check me there....and I just called someone who has read more of the literature and she had not heard this.

On the other hand, I would not rule out a M9 earthquake south of the equator...rupturing south of the part that broke in March 2005.That area failed in the early and mid 1800s in 2 Great quakes (M>8), but not a M9+. I am reasonably sure that no credible research could state that it is likely that this part of the subduction zone will fail in the next month or 2. I made some possibly slightly irresponsible posts here after the March quake about the odds of the part south of the equator failing...while I was guessing, I still think my guesses were educated and have no reason to change them...only to update them
However, all interested should look at the link, which is to Kerry Sieh, who before the Dec 26 quake distributed 1000s of educational leaflets (I heard) warning people what to do if there was an large earthquake...warning them of tsunamis. However, his work has been south of the equator. He is the U.S. expert on that area (there may be Indonesian experts, or some from other countries).

There is also reason to be concerned in the next years or decades about the plate boundary north of the Dec 26 rupture...but again, I am not aware of any research suggesting such a quake is imminent...and no one can credibly predict such a quake within a short (1 month) time frame. However, the subduction failure of such a large (1500 km) lenth of the subduction zone probably advanced the time of a large earthquake on either side by years....but...if it advanced the time of the quake by 5 years, we don't know whether it would have occurred in 100 years and now there are still 95 years, or whether it is likely much sooner.

I said that no one can predict such an earthquake with credibility in a 1 month time frame...but to be fair, Shan on this page did come very close to accurately predicting the March 2005 M8.7...in a time frame of about a week (he missed on location be several hundred km, but these are big ruptures). On the other hand, he followed this interesting prediction with 3 more for Great earthquakes and all of those failed.

I am a research geologist at one of the campuses of the University of California, working on active faults of California, but am not a seismologist. I am concerned that people whose first language is not English might mis-read this post: I read it over carefully.
Chris

• Kerry Sieh Sumatra