Seismic remote monitoring of stress field

We demonstrate that a real-time based moment tensor analysis using broadband seismic waveforms provides us with the information about the spatio-temporal change of stress field. Such a capability is crucial when monitoring the volcanic activity during the eruption if it causes seismic swarm. We estimated the moment tensors of earthquakes occurring during the swarm activity before the eruption of Usu volcano in March 2000 as well as those during the swarm activity of Miyakejima volcano starting in June 2000. In both cases, we detected the stress change due to the movement of magma reservoir.