9.5 is enormously bad. Perhaps they’re going with quakes for which there are actual seismograph readings available. What you said about Everest rings a bell, not sure how long ago that was. The New Madrid quake (the biggest one) rerouted the Mississippi by a few miles, and that takes some doing.
New Madrid also created Realfoot Lake which I think is 20 miles long when a big chunk of earth dropped some 20 feet. I guess it was a Graben Fault.