We develop a new method of probabilistic estimate for a large earthquake originated from an active fault, incorporating stress transfer from an adjacent earthquake. We applied the method to the Kego fault that is an active fault just beneath the city of Fukuoka. The earthquake probability for the next 30 years on the Kego fault is now raised to about 7% due to stress transferred from the March 20, 2005 Fukuoka-ken-seiho-oki, Japan, earthquake.