The Ramu-Markham Fault Zone, which follows the northern edge of the Markham Valley, is the active plate boundary between the South Bismarck Plate and tectonostratigraphic terranes within the New Guinea Highlands Deforming Zone. The Ramu-Markham Fault Zone has generated large thrust earthquakes (e.g. 6 April 1999 MW 6.4, 16 km North of Lae, near Hobu, and 22 November 2007 MW 6.8, 110 km North of Lae). Geological evidence suggests that major earthquakes in pre-historic times have occurred in the Lae area, and that there is the potential for another large earthquake to occur anytime within the next 100 years (in).