Yeah, Ara, I think someone I work with, Leonardo Seeber, wrote a paper with John Armbruster on an earthquake a decade ago in India that killed about 10,000 people...the offset of, I think 65 million year old lavas (Deccan), was the same as offset of the surface...so, new fault. But, this is more likely away from plate boundaries....and even away from boundaries a lot of quakes are on existing faults.....there is a difference between knowing there was no fault before, like in India, and just not knowing about an existing fault before the earthquake. And, who knows what is going on at 10 or 20 km depth...perhaps the Indian earthquake started at depth on a fault but took a shortcut near the surface....(or the fault was older than 65 million years and was buried...).
Chris