A Review of Source Models of the 2015 Illapel, Chile Earthquake and Insights from Tsunami Data

Abstract

The 16 September 2015 Illapel, Chile, earthquake has been studied by many researchers from various aspects. This paper reviews studies on the source model of the earthquake and examines tsunami data. The Illapel earthquake occurred in the source region of previous earthquakes in 1943 and 1880. The earthquake source was studied by using various geophysical data, such as near-field seismograms, teleseismic waveform and backprojection, GPS and InSAR data, and tsunami waveforms. Most seismogram analyses show the duration of ~ 100 s with a peak at ~ 50 s. The spatial distribution has some variety, but they all have the largest slip varying from 5 to 16 m located at 31°S, 72°W, which is ~ 70 km NW of the epicenter. The shallow slip seems to be extended to the trench axis. A deeper slip patch closer to the epicenter is proposed. A late tsunami earthquake model with a total duration of 250 s and the third asperity south of the epicenter is also proposed, but, by tsunami backward ray tracing, we show that the tsunami data do not support this model.

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

“…The 2015 Illapel earthquake struck the northern part of the 1730 event, where two major earthquakes (1943 and 1880) occurred in the same region (Figure 1; Beck et al, 1998). The slip region of the 2015 Illapel earthquake agrees well with the possible rupture zone proposed by Kelleher (1972) and Beck et al (1998), and it is identified as a rerupture of the 1943 earthquake (Satake & Heidarzadeh, 2017). The last major earthquake occurred on 15 October 1997 at a depth of 68 km in the Punitaqui region, and located in the northeastern segment of the 1939 event ( Figure 1).…”

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“…The megathrust event ruptured an about 200 km long stretch along the Central Chilean subduction zonewhere the Nazca Plate subducts beneath the South American Plate(Ye et al, 2017). Previous larger earthquakes occured in this region in 1943 and 1880 (e.g Satake and Heidarzadeh, 2017;Ye et al, 2017)…”

“….The Chilean subduction zone is prone to large megathrust events with the Illapel event being the third tsunamigenic earthquake with a magnitude greater than 8 in Northern and Central Chile in this decade (first event was the 2010 Mw 8.8 Maule event, second was the 2014 Mw 8.1 Iquique event). The largest slip (between 5 and 16 m) is located about 70 km to the NW of the epicentre and with the shallow part of the slip seeming to extend to the trench axis(Satake and Heidarzadeh, 2017). The main shock triggered various aftershocks (1388 events in the ISC Bulletin between 33 • S to 29 • S and 73 • W to 71…”

Early Stage and Main Ruptures of the 2015 Mw8.3 Illapel, Chile, Megathrust Earthquake: Kinematic Elliptical Inversions and Dynamic Rupture Simulations

“…The kinematic rupture process of the 2015 Illapel earthquake has been studied by many groups; some use a combination of teleseismic waveform and geodetic data (i.e., Barnhart et al., 2016; Carrasco et al., 2019; Grandin et al., 2016; Klein et al., 2017; Lange et al., 2016; Meng et al., 2018; Okuwaki et al., 2016; Williamson et al., 2017; Zhang et al., 2016) and the others include tsunami information (i.e., An et al., 2017; Li et al., 2016; Satake & Heidarzadeh, 2017; Williamson et al., 2017). However, the strong motion data of the National Seismological Center and the continuous recording of 1‐s sampling of GNSS data (Baez et al., 2018; Leyton et al., 2018a) have not yet been sufficiently explored.…”