We image the rupture history of the 2007 Niigata‐ken Chuestu‐oki (Japan) earthquake by a nonlinear joint inversion of strong motion and GPS data, retrieving peak slip velocity, rupture time, rise time and slip direction. The inferred rupture model contains two asperities; a small patch near the nucleation and a larger one located 10 ÷ 15 km to the south‐west. The maximum slip ranges between 2.0 and 2.5 m and the total seismic moment is 1.6 × 10¹⁹ Nm. The inferred rupture history is characterized by rupture acceleration and directivity effects, which are stable features of the inverted models. These features as well as the source‐to‐receiver geometry are discussed to interpret the high peak ground motions observed (PGA is 1200 gals) at the Kashiwazaki‐Kariwa nuclear power plant (KKNPP), situated on the hanging‐wall of the causative fault. Despite the evident source effects, predicted PGV underestimates the observed values at KKNPP by nearly a factor of 10.