Jin cannot spot any apparent mechanism for the room, perhaps there are pressure plates in the floor, but he would have to enter the room to disable those, risking certain death.
An extensive search of the foyer-area where Jin stands finds little, until he begins running his hands across every surface. As he does so, a stone slides back, beginning a ticking sound. The tempo of the sounds speed up, and then abruptly stops as the room explodes in violence.
Apparently you've found a timed trigger, giving you a few moments to safely cross the room and into that alcove.