Energy constrained nature and unattended deployment of sensors motivates the need of special techniques for designing reliable wireless sensor networks. Recently many approaches are considering mobile sensor nodes to deal with this problem. But making all the sensors mobile involves more signaling overhead for network maintenance. It is energy efficient to move the base station which has no power limitations. Also, there are many real life applications in which event based approach is more appropriate. In this paper, we propose an adaptive scheme for a mobile base station that moves according to the occurrence of events. We propose two optimization schemes: moving the BS towards the event centroid and moving the BS towards distance based weighted centroid. Simulation results show that moving the base station adaptively significantly prolongs the network lifetime.