The December 26, 2004 Sumatra earthquake generated tsunami in the Indian Ocean and caused more than 200,000 casualties. AIST made computer simulation of the tsunami (Figure) in the same day and the animation was posted on the website. It reproduced the observed features of the tsunami; the initial tsunami to the east (e.g., Phuket) began with receding wave while to the west (e.g., Sri Lanka) large wave suddenly reached, and the tsunami was larger in the direction perpendicular to the fault orientation. On the following day (December 27) alone, more than 60,000 accesses from all over the world were recorded.