The Iquique earthquake sequence of April 2014: Bayesian modeling accounting for prediction uncertainty

Abstract

The subduction zone in northern Chile is a well‐identified seismic gap that last ruptured in 1877. On 1 April 2014, this region was struck by a large earthquake following a two week long series of foreshocks. This study combines a wide range of observations, including geodetic, tsunami, and seismic data, to produce a reliable kinematic slip model of the Mw=8.1 main shock and a static slip model of the Mw=7.7 aftershock. We use a novel Bayesian modeling approach that accounts for uncertainty in the Green's functions, both static and dynamic, while avoiding nonphysical regularization. The results reveal a sharp slip zone, more compact than previously thought, located downdip of the foreshock sequence and updip of high‐frequency sources inferred by back‐projection analysis. Both the main shock and the Mw=7.7 aftershock did not rupture to the trench and left most of the seismic gap unbroken, leaving the possibility of a future large earthquake in the region.

Slip distribution of the 2014 Mw = 8.1 Pisagua, northern Chile, earthquake sequence estimated from coseismic fore‐arc surface cracks

“…In addition to evaluating the goodness-of-fit of our crack-based coseismic slip estimates to the constraining data, we compare the slip distributions to estimates made from GPS, interferometric synthetic aperture radar, strong motion, teleseismic, and tsunami data Duputel et Figure 2b). That is, the crack-based slip estimate is as similar to previously published slip distributions estimated from geodetic, seismic, and/or tsunami data as most of these estimates are to each other.…”

“…al., 2015;Gusman et al, 2015;Hayes et al, 2014;Liu et al, 2015;Schurr et al, 2014;Yagi et al, 2014]. For the main shock, the crack-based 2 m slip contour shows spatial overlap that from with other estimates, while the peak slip is located around 70.9°W, 5°S, northwest of that derived from other data sets(Figure 2a).…”

“…For the main shock, the crack-based 2 m slip contour shows spatial overlap that from with other estimates, while the peak slip is located around 70.9°W, 5°S, northwest of that derived from other data sets(Figure 2a). Estimation of subduction interface slip from crack orientations is affected by the same geographical bias as that from geodetic data sets: we have no offshore observations directly overlying the region of greatest subduction zone slip (Figure S3).To formally compare the spatial correlation of the crack-based main shock slip distribution with estimates made from other data sets (specifically,An et al [2014],Duputel et al [2015],Hayes et al [2014],and Schurr et al [2014]), we first interpolate the published slip maps onto our subduction zone geometry and then calculate the correlation coefficient among the slip magnitudes. Estimation of subduction interface slip from crack orientations is affected by the same geographical bias as that from geodetic data sets: we have no offshore observations directly overlying the region of greatest subduction zone slip (Figure S3).To formally compare the spatial correlation of the crack-based main shock slip distribution with estimates made from other data sets (specifically,An et al [2014],Duputel et al [2015],Hayes et al [2014],and Schurr et al [2014]), we first interpolate the published slip maps onto our subduction zone geometry and then calculate the correlation coefficient among the slip magnitudes.…”

Foreshock Patterns Preceding Great Earthquakes in the Subduction Zone of Chile

“…More recently, the rupture process of the 1 April 2014 Iquique great earthquake (M w 8.1) and its possible initiation by the intense foreshock activity was examined by several authors, including Brodsky and Lay (2014), Yagi et al (2014), Lay et al (2014), Ruiz et al (2014), Schurr et al (2014), Kato and Nakagawa (2014), Bedford et al (2015), Meng et al (2015), Duputel et al (2015).…”

Calibrating coseismic coastal land-level changes during the 2014 Iquique (Mw=8.2) earthquake (northern Chile) with leveling, GPS and intertidal biota

“…Given that no major earthquakes had affected this region since 1877, it had long been considered as one of the most mature seismic gaps in South America, capable of generating a M w >8.8–9 earthquake. The 2014 Iquique earthquake filled only a fraction of this seismic gap, leaving a ~300-km-long unruptured segment capable of producing an M w ~8.5 event [23–25] located between Iquique and Mejillones. A rapid assessment of the rupture length along coasts affected by such megathrust earthquakes is important, not only for estimating damages to local infrastructure and loss of economic resources, but also to estimate the extent of plate-boundary slip and evaluate the probability for future earthquakes occurring on neighboring segments.…”