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Insights Into the Kinematic Rupture of the 2015 M w 8.3 Illapel, Chile, Earthquake From Joint Analysis of Geodetic, Seismological, Tsunami, and Superconductive Gravimeter Observations

2018; Wiley; Volume: 123; Issue: 11 Linguagem: Inglês

10.1029/2018jb016065

2169-9356

Chengli Liu, Chao An, Bin Shan, Xiong Xiong, Xiaohong Chen,

High-pressure geophysics and materials

Abstract We investigated the spatiotemporal slip distribution of the 2015 Illapel earthquake ( M w = 8.3) by joint analyses of geodetic, seismological, tsunami, and superconductive gravimeter observations. The coseismic rupture directly overlaps the interseismic coupling zone determined by onshore geodetic measurements. The main slip asperity is located north of the hypocenter with a peak slip of ~9.2 m, and the rupture spans ~200 km along strike and ~150 km along dip with an average rupture speed of ~2.0 km/s. Most aftershocks reveal a clear complementary distribution with the coseismic rupture; that is, aftershock clusters are located at the border of unbroken barriers and regions of sudden transition from high to low rupture area. The calculated Coulomb failure stress changes indicate that 80% of the aftershocks were triggered by the main event. The low‐frequency radiation corresponds to the large coseismic rupture at the shallow portion of the megathrust, while the high‐frequency radiation is associated with the edge of large slip asperity or an isolated patch at a deeper position. The large coseismic slip region correlates well with the high Vp/Vs ratio of the subduction interface, which implies that the Illapel earthquake might nucleate at a relatively weak patch within a strong coupled zone. Furthermore, we argue that the coseismic slip did reach to the trench from tsunami simulations, and historical earthquakes analyses indicate a complex strain accumulation and release in central Chile.