Kinematic rupture features of the 2016 Amatrice M_W6.2 Italy earthquake inverted from the near-fault strong ground motions

The 2016 M_W6.2 Amatrice Italy earthquake， with moderate magnitude but very shallow rupture region after the damaged 2009 L'Aquila earthquake in the central seismogenic region， caused near-fault ground motions exceeding 0.85g and 40 cm/ s. In this study， the rupture process and the generation mechanism of strong ground motions of its mainshock were investigated through waveform inversions of strong-motion data in the frequency range of 0.2–2.0 Hz through empirical Green’s functions （EGFs）. The results reveal that， two large slip regions were identified during the mainshock: the primary one with a maximum slip of approximately 1.5 m was centered ～ 4 km northwest of the hypocenter， which was shallower than the hypocenter， and the secondary one was centered ～ 5 km southeast of the hypocenter. Outside these regions， the slip was rather small and restricted to rather shallow parts of the fault. A relatively large rupture velocity of 3.0 km/s was identified. The robustness and reliability of the source model was examined by conducting additional inversion analyses with various combinations of EGF events and near-fault stations. Furthermore， near-fault strong motions which were not adopted in the inversion calculations were synthesized relied on the preferred source model. Comparison results illustrated that the synthetic waveforms captured the timing of the main phases of observed waveforms， illustrating the validity of the principal spatiotemporal characteristics of the source model. Our large slip regions are also generally visible in the models proposed by other researchers based on different datasets and focusing on lower frequency ranges （lower than 0.5 Hz in general）. In particular， the identified two large slip regions in our model are consistent with the models along the horizontal directions apart from the depth， which may indicate that the near-fault strong ground motions in different frequency range are dependent to the depth of large slip regions.