Dense GPS Array observations across the Atotsugawa fault, central Japan

[1] A cross-fault GPS array is established to reveal the crustal motion around the Atotsugawa fault located in a large strain rate zone, in central Japan. The array has 7 sites along a baseline of 30 km. Four-year observations delineate a characteristic rate field; the eastward and the westward motions of 5 mm/yr at the sites 25 km apart from the fault gradually decrease and the directions of the motion change towards the ENE-WSW fault strike, as approaching the fault. These observations are explained by a simple model; two 15-km thick elastic blocks are obliquely colliding along the Atotsugawa fault with a rate of 20 mm/yr in an EW direction. However, in the zone sandwiched by the Atotsugawa and the Ushikubi faults, the rates are small and the rate vectors have the fault-normal components, suggesting that the collision boundary forms a zone with lower elasticity or inelastic property.