Dense GPS Array observations across the Atotsugawa fault, central Japan

Abstract

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.