Slip Model of the 2015 Mw 8.3 Illapel (Chile) Earthquake Using Sentinel 1a Data

Abstract eng:
The Mw 8.3 earthquake that occurred on September 16th 2015 west of Illapel, Chile, ruptured a ~200 km section of the plate boundary between 29°S and 33°S. SAR data acquired by the Sentinel 1A satellite was used to obtain the interferogram of the earthquake, and from it, the component of the displacement field of the surface in the line of sight of the satellite. Based on this interferogram, the corresponding coseismic slip distribution for the earthquake was determined based on different plausible finite fault geometries. The model that best fits the data gathered is one whose rupture surface is consistent with the Slab 1.0 model, with a constant strike angle of 4° and variable dip angle ranging from 2.7° near the trench to 24.3° down dip. Using this geometry the maximum slip obtained is 7.52 m and the corresponding seismic moment is 3.78·1021 equivalent to a moment magnitude Mw 8.3. The interferogram processed is also used to analyze specific site effects, such as deformations found in areas of affected mining tailing dams. A comparison between this earthquake rupture model and the inversion models of two previous earthquakes, the Mw 8.2 Pisagua (Chile, 2014) and the Mw 8.8 Maule (Chile, 2010) is done to study different earthquake characteristics, and provide a suite of methodologically consistent and spatially detailed characterizations of the fault rupture mechanisms and the permanent superficial effects of megathrust events along the Chilean coastline. These results are a key input for the generation of synthetic seismic records that combine deterministic and stochastic methods for representation of low- and high-frequency components of ground motions, respectively, and will hence enable us to characterize the seismic demand for both flexible and rigid structures in earthquake-affected areas, and thereby investigate the direct damage and losses that may be expected during future events.

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