Largest aftershock nucleation driven by afterslip during the 2014 Iquique sequence

Abstract

Various earthquake source models predict that aseismic slip modulates the seismic rupture process. However, observations of aseismic slip associated with earthquakes are scarce, which has left the earthquake source model controversial. Here, we characterise seismic and aseismic processes for 3 days during the 2014 Iquique earthquake sequence in northern Chile by analysing seismicity and crustal deformation time series measured by high-rate Global Positioning System (GPS). We demonstrate that the early afterslip started immediately after the M 8.1 mainshock and led to the largest M 7.6 aftershock 27 hours later, located ~120 km to the south. At the mainshock latitude, the interevent early afterslip is located downdip of the mainshock rupture, and is associated with aftershocks. These afterslip and aftershocks exhibit a rapid temporal decay. In contrast, south of the mainshock slip patch, a peak of afterslip separates the mainshock rupture from the largest aftershock, suggesting that this area acted as a barrier to the southward propagation of the mainshock rupture. Seismicity count and moment accelerate in this southern area during the interevent stage. We conclude that the largest aftershock nucleation was driven by the interevent afterslip. The mechanical connection between sequential great earthquakes can therefore be mediated by aseismic slip.

Coseismic and Early Postseismic Deformation of the 2024 Mw7.45 Noto Peninsula Earthquake

“…Itoh et al. (2023) also discovered that the distribution of aftershocks during different stages (27 hr, 2 days) overlapped with the afterslip distribution within the rupture area. They hypothesized that the early aftershocks were a result of the early afterslip following the 2014 Iquique earthquake.…”

“…However, there were still a large amount of aftershocks on F1. Recent studies proposed that afterslip and aftershock areas usually overlap with the rupture area of the mainshock (Hsu et al., 2006; Itoh et al., 2023; Milliner et al., 2020; Woessner et al., 2006; Wetzler et al., 2018). Milliner et al.…”

“…The aseismic segment may often act as a barrier and terminate seismic ruptures (Nishikawa et al., 2019; Perfettini et al., 2010). In nature, the occurrence of early aftershocks (first few hours) is often controlled by the early afterslip (Itoh et al., 2023; Jiang et al., 2021). These studies suggest that the relationship between the seismic and aseismic slip is complex.…”

Largest Aftershock Nucleation Driven by Afterslip During the 2014 Iquique Sequence

“…We made our processed GPS displacements and slip distributions available in Zenodo as Itoh et al. (2023).…”

“…We used a Fortran 90 translation of the DC3D subroutine (Okada, 1992) provided by Miyashita (2020). We made our processed GPS displacements and slip distributions available in Zenodo as Itoh et al (2023). reviews from the Editor Germán Prieto, Roland Burgmann and four anonymous reviewers to this or an earlier version manuscript, which highly improved this study.…”