"Lusi is tectonics in action," Miller said.
Not everyone agrees the eruption had natural causes, though.
"I am 99 percent certain this was caused by drilling activity," said Richard Davies, a petroleum geologist at Durham University in England who did not take part in this study. "The explanation is remarkably simple and not an uncommon problem.(Andrea Th1) (Charles C2)"
When a borehole is drilled, mud is used, Davies explained. Drilling mud has several purposes, one of which is to provide enough pressure in the hole to prevent fluid that occurs naturally in the rock from coming into the well and climbing to the surface.
The problem was, there was not enough mud in the hole in the early hours of May 28, 2006, "so underground fluid rushed into the hole, which led to a blowout, and the birth of the Lusi mud volcano," Davies asserted.
Davies questioned why earlier, larger earthquakes did not trigger Lusi before 2006.
"Our response to that is that the bigger earthquakes - meaning the 2004 magnitude-9.2 and 2005 magnitude-8.6 Sumatra earthquakes - were much more distant, about 2,000 kilometers [1,200 miles] away," Miller said. The seismic waves that reached Lusi were, therefore, much weaker. They were also a kind of wave that would interact with the curved rock layer at Lusi in ways that simulations revealed would prevent seismic energy from penetrating deep enough to reach the mud layer.