To test large scale socially embedded systems, this paper proposes a multiagent-based participatory design that consists of two steps; 1) participatory simulation, where scenario-guided agents and human-controlled avatars coexist in a shared virtual space and jointly perform simulations, and the extension of the participatory simulation into the 2) augmented experiment, where an experiment is performed in real space by human subjects enhanced by a large scale multiagent simulation. The augmented experiment, proposed in this paper, consist of 1) various sensors to collect the real world activities of human subjects and project them into the virtual space, 2) multiagent simulations to simulate human activities in the virtual space, and 3) communication channels to inform simulation status to human subjects in the real space. To create agent and interaction models incrementally from the participatory design process, we propose the participatory design loop that uses deductive machine learning technologies. Indoor and outdoor augmented experiments have been actually conducted in the city of Kyoto. Both experiments were intended to test new disaster evacuation systems based on mobile phones.