Slow slip events precursory to the 2014 Iquique Earthquake, revisited with long-base tilt and GPS records

SUMMARY The M= 8.1, 1 April 2014 Iquique earthquake, which broke part of the northern Chile seismic gap, was preceded by a strong foreshock sequence starting early January 2014. reported analysis continuous records nearby GPS stations from Integrated Plate Observatory Chile, North array lead to contradictory results concerning existence and location slow slip events (SSEs) on interplate contact. Resolving this controversy is an important issue, as although many SSEs are in subduction zones, only few were found be precursory large earthquakes. Here we show that long base tiltmeter installed near Iquique, when corrected for coseismic steps, long-term drift, tidal signals oceanic atmospheric loading, significant residual signals. These can modelled with four located close Iquique. Their signature already some stations, but their source then characterized very low resolution time space, leading contradicting models. With tilt records, rule out previously proposed models single SSE closer main shock. Combining greatly improves alone, one could locate sources 100–180 km south–southeast shock epicentre, moment magnitudes between 5.8 6.2, at edge aftershock asperities. moderate thus did not directly trigger shock, contributed aftershock. Only sensitivity tiltmeter, added allowed us describe unprecedented accuracy process cascade cross-triggered, short-term aseismic earthquakes This three months activation appears final acceleration burst weaker, longer term started mid-2013, reported, release history quantify. From methodological point view, our study takes advantage interesting complementarity measurements, due different dependence distance strain, turns efficient resolving strain sources, even both instruments each other. It finally demonstrates removal sequences small or undetected steps high record signal order retrieve purely signal, presently impossible task noise.