Inelastic deformation zone in the lower crust for the San-in Shear Zone, Southwest Japan, as observed by a dense GNSS network

We analyze Global Navigation Satellite System (GNSS) within the San-in Shear Zone (SSZ), Southwest Japan, in order to clarify the width of the inelastic deformation zone in the lower crust beneath it. We assumed multiple discrete fault dislocations distributed below the seismogenic depth in a channel to represent inelastic deformation in the lower crust. Kinematic models at 68% confidence level at three profiles indicate that deformation can be explained by a deep inelastic deformation zone with a width of 0.5-56.0 km, 0.5-79.5 km, and 0.0-58.5 km, for the Eastern, Central and Western profiles, respectively; and a relative moving rate between the two blocks sandwiching the zone of 6.2-8.0 mm/year. In Eastern Tottori, the center of the estimated inelastic zone coincides with the source region of the 1943 Tottori earthquake. In Central and Western Tottori, the channel is in agreement with the source regions of the 2000 Western and the 2016 Central Tottori earthquake. Current GNSS network provides a limited contribution to constraining the width of the deformation in the lower crust.