Looks like a long strand of primer cord going off. Primer cord is a rope of encapsulated TNT used in blast dynamics. The detonation travels at 1200 feet per second in a linear fashion down the cord. I have seen many comparisons of the Sumatra quake to mega-tonnage atomic bombs. Many people have the idea that it is a single pop. Looks more like many pops along the fault line that takes time to release. Good animation John.

glen