Temporal changes in state of stress in the Tokachi Oki area after the 2003 Tokachi Oki Earthquake

A stress tensor inversion was carried out in the aftershock area of the 2003 Tokachi Oki earthquake for a comparative study on the preseismic and postseismic stress state. The inversion technique was adopted from Gephart (1990) to pursue the study with earthquake focal mechanism data from National Research Institute for Earth Science and Disaster Prevention (NIED). Results of the inversion revealed significant change in stress field before and after the main shock of the 2003 event. The preseismic uniaxial compression in strike slip stress regime was changed to a transition from transpressional to a radial compression in a compressional regime. Key words: 2003 Tokachi Oki earthquake, stress tensor inversion. 1