Abstract

The area of the 2014 M8.2 Iquique earthquake in northern Chile is of interest to the scientific community as evidenced by the great number of studies and data available. Different approaches have been taken to understand the complex rupture process, as well as the dynamics of the fore- and aftershock sequences. Here we present a 3D seismic tomography that combines active-offshore and passive sources, both recorded at an inland temporary seismic network. When compared to tomography models derived only with natural seismicity, this amphibious approach serves to improve the estimation of body wave velocities in the overriding plate at the marine forearc, as well as in the subducting slab. The active seismic dataset used in this study correspond to marine airgun shots from 2016 PICTURES project recorded at the temporary inland seismic network, which also registered natural seismicity that was used as an input for the tomography. We complemented these datasets with local seismicity recorded at three different networks and time periods. First arrival times of the shots were estimated using CORREL, a novel technique for automated picking of active seismicity developed by the authors, while onsets of local seismicity were estimated with the Regressive ESTimator package (REST). This work highlights the contribution of using offshore active seismic sources to better image the structure and features of the plate above the seismogenic zone, which could give insights of what controls the complex rupture processes of large earthquakes.