Earthquake segmentation in northern Chile correlates with curved plate geometry

Mahesh N Shrivastava,Bernd Schurr,Pablo Salazar,Marcos Moreno,Juan Carlos Báez,Gabriel González,Hugo Soto

doi:10.1038/s41598-019-40282-6

Abstract

We performed an integrated analysis of the coseismic slip, afterslip and aftershock activity of the 2014 Mw 8.1 Pisagua earthquake. This earthquake seems to be spatially located between two major historical earthquakes, the 1868 Mw 8.8 earthquake in southern Peru and the 1877 Mw 8.5 earthquake in northern Chile. Continuous GPS data were used to model the coseismic slip of the mainshock and the largest aftershock (Mw 7.6). The afterslip was modeled for 273 days (end of year 2014) after the largest aftershock, revealing two patches of afterslip: a southern patch between the mainshock and the largest aftershock and a patch to the north of the mainshock. Observations from the seismic network indicate that aftershocks were concentrated near the southern patch. Conversely, the northern patch contained hardly any aftershocks, indicating a dominant aseismic slip. The Pisagua earthquake occurred within a prominent, curved section of the Andean subduction zone. This section may have acted as a barrier for the largest historical earthquakes and as an isolated segment during the Pisagua earthquake.

Highlights

Theoretical models and earthquake observations reveal that subduction earthquake ruptures often stop their lateral propagation at specific places, which are called barriers[1]
We focus on earthquake segmentation in a section of the Andean subduction zone where the shallow part (0–40 km depth) of the plate margin is characterized by a significant curved plan view extending through southern Peru and northern Chile (Fig. 1)
This area had remained unruptured since the two major historical earthquakes that occurred in southern Peru and northern Chile, the 1868 Mw 8.8 and the 1877 Mw > 8.5 (Fig. 1) earthquakes, respectively[12]

Summary

Introduction

Theoretical models and earthquake observations reveal that subduction earthquake ruptures often stop their lateral propagation at specific places, which are called barriers[1]. It has been proposed that the occurrence of barriers may be controlled by several factors, including large-scale lithological heterogeneities[8], the nonplanarity of fault surfaces[9], or fluid localization[10] In this contribution, we focus on earthquake segmentation in a section of the Andean subduction zone where the shallow part (0–40 km depth) of the plate margin is characterized by a significant curved plan view extending through southern Peru and northern Chile (Fig. 1). We focus on earthquake segmentation in a section of the Andean subduction zone where the shallow part (0–40 km depth) of the plate margin is characterized by a significant curved plan view extending through southern Peru and northern Chile (Fig. 1) In this tectonic setting, a long-standing seismic gap was partially broken on April 1st, 2014, by the Mw 8.1 Pisagua earthquake[4,11]. The conclusions obtained in this work can be applied to understanding earthquake segmentation in subduction zones with complex curvature parallel to the trench

Methods

Results

Discussion

Conclusion