Kinematic study of Iquique 2014 Mw 8.1 earthquake: Understanding the segmentation of the seismogenic zone

• Published in: Earth and planetary science letters Vol. 503; pp. 131 - 143
• Main Authors: Jara, Jorge, Sánchez-Reyes, Hugo, Socquet, Anne, Cotton, Fabrice, Virieux, Jean, Maksymowicz, Andrei, Díaz-Mojica, John, Walpersdorf, Andrea, Ruiz, Javier, Cotte, Nathalie, Norabuena, Edmundo
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-12-2018
• Subjects: high-rate GPS; kinematic inversion; megathrust earthquakes; strong Motion; subduction segmentation; subduction segmentation; high-rate GPS; strong Motion; megathrust earthquakes; kinematic inversion
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2018.09.025

We study the rupture processes of Iquique earthquake Mw 8.1 (2014/04/01) and its largest aftershock Mw 7.7 (2014/04/03) that ruptured the North Chile subduction zone. High-rate Global Positioning System (GPS) recordings and strong motion data are used to reconstruct the evolution of the slip amplitude, rise time and rupture time of both earthquakes. A two-step inversion scheme is assumed, by first building prior models for both earthquakes from the inversion of the estimated static displacements and then, kinematic inversions in the frequency domain are carried out taken into account this prior information. The preferred model for the mainshock exhibits a seismic moment of 1.73 × 1021 Nm (Mw 8.1) and maximum slip of ∼9 m, while the aftershock model has a seismic moment of 3.88 × 1020 (Mw 7.7) and a maximum slip of ∼3 m. For both earthquakes, the final slip distributions show two asperities (a shallow one and a deep one) separated by an area with significant slip deficit. This suggests a segmentation along-dip which might be related to a change of the dipping angle of the subducting slab inferred from gravimetric data. Along-strike, the areas where the seismic ruptures stopped seem to be well correlated with geological features observed from geophysical information (high-resolution bathymetry, gravimetry and coupling maps) that are representative of the long-term segmentation of the subduction margin. Considering the spatially limited portions that were broken by these two earthquakes, our results support the idea that the seismic gap is not filled yet.
•Causes of along-strike and -dip segmentations are revealed by Iquique earthquake.•This study shows that the Northern Chile seismic gap is not fully filled yet.•A multigrid two-step kinematic study is performed to avoid possible local minima.•Kinematic models are constrained by prior models built from static inversions.