NAU Professor Dr. David Brumbaugh discusses activity along the Quaternary Lake Mary Fault. The fault extents from south of Mormon Lake to the Flagstaff City boundary. It's capable of delivering a magnitude 6 to magnitude 7 earthquake.
Bezy, J.V., 2003, A Guide to the Geology of the Flagstaff Area. Arizona Geological Survey Down-to-Earth Series DTE-14, 56 p. http://repository.azgs.az.gov/uri_gin/azgs/dlio/1540