17:30 〜 17:45
[S13-4-05] Rupture evolution during the Mw 8.3 2015 Illapel Chile earthquake in relation to swarms
A source model for the Mw 8.3 2015 Illapel Chile earthquake is constructed by using a broad frequency range of teleseismic P-waveforms recorded at globally distributed stations. A spatiotemporal slip distribution is obtained with the kinematic waveform inversion method taking into account the uncertainty of Green's function, and an evolution of high-frequency (HF: 0.3–2.0 Hz) radiation sources is tracked with the hybrid backprojection method, which resolves locations of the HF sources by stacking cross-correlation functions of the observed waveforms and theoretically calculated Green's functions.
The source model, in a gross sense, shows apparently slow, unilateral rupture propagation at < 2 km/s along the strike direction with the maximum slip about 10 m at around 70 km northwest of the epicenter, but in detail, the model involves two independent rupture episodes, both propagating up-dip and northward direction at variable rupture velocities (2–3 km/s) along the rupturing paths. The two rupture episodes are separated by the HF bursts occurred along the deeper (around 35 km depth) parts of the fault, which possibly triggers and accelerates the secondary rupture episode.
Secondary rupture evolves in a way to avoid the interplate swarms observed in 1997–1998 locating at the northern and the northeastern edges of the rupture area, and terminates without the intense HF radiation around the boundary between the source area and the swarm region. Less excitations of HF waves at rupture termination suggests the gradual deceleration of rupture, since HF waves are radiated when a rupture front abruptly accelerates or decelerates. The HF-deficient rupture termination may correspond to the frictional property or stress state around the boundary between the source area and the swarm region, which gradually transitions from the state governing megathrust rupture to that carrying the swarms driven by the aseismic slip.
The source model, in a gross sense, shows apparently slow, unilateral rupture propagation at < 2 km/s along the strike direction with the maximum slip about 10 m at around 70 km northwest of the epicenter, but in detail, the model involves two independent rupture episodes, both propagating up-dip and northward direction at variable rupture velocities (2–3 km/s) along the rupturing paths. The two rupture episodes are separated by the HF bursts occurred along the deeper (around 35 km depth) parts of the fault, which possibly triggers and accelerates the secondary rupture episode.
Secondary rupture evolves in a way to avoid the interplate swarms observed in 1997–1998 locating at the northern and the northeastern edges of the rupture area, and terminates without the intense HF radiation around the boundary between the source area and the swarm region. Less excitations of HF waves at rupture termination suggests the gradual deceleration of rupture, since HF waves are radiated when a rupture front abruptly accelerates or decelerates. The HF-deficient rupture termination may correspond to the frictional property or stress state around the boundary between the source area and the swarm region, which gradually transitions from the state governing megathrust rupture to that carrying the swarms driven by the aseismic slip.