Interesting article.

We have yet to see a genuine megaquake.

This is defined either...
1:
by a footprint crossing more then one megathrust and relaxation of the bulk crust of at least one tectonic plate (usually 2)in a single event. The event of ~950AD in Guatemala immediately following the Mayan apocalypse(#1), appears to have been one of this type.{Coverage: Guatemala backrange, Guatemala arc, Chiapas backarc basin, Salvador backarc basin Central American backarc basin: and lurch of Cocos plate & Caribbean plate}.

2: by a death toll of one million casualties or more.{The closest so far was approximately 500,000 during the 3 province transform fault quake in central China}.

Type 1 megaquakes are no more probable now than they were then, the causative item is a cordillera range that finally becomes too high & steep to hold up against gravity vs. the megathrust.

Type 2 megaquakes are far more likely now than in the past as direct result of a large number of people in high density conurbations in earthquake zones. The Port Au Prince event of a major quake, ground zero on a 3rd world mega city was a case in point, and had a death toll (~200,000) very similar to the boxing day tsunami toll.

The fact that a megaquake is likely this century is unsurprising. The location has yet to be pinned down with any accuracy.

Have a nice day: Ag