Diversity of the 2014 Iquique’s foreshocks and aftershocks: clues about the complex rupture process of a Mw 8.1 earthquake
We study the foreshocks and aftershocks of the 1 April 2014 Iquique earthquake of Mw 8.1. Most of these events were recorded by a large digital seismic network that included the Northern Chile permanent network and up to 26 temporary broadband digital stations. We relocated and computed moment tensors for 151 events of magnitude Mw ≥ 4.5. Most of the foreshocks and aftershocks of the Iquique earthquake are distributed to the southwest of the rupture zone. These events are located in a band of about 50 km from the trench, an area where few earthquakes occur elsewhere in Chile. Another important group of aftershocks is located above the plate interface, similar to those observed during the foreshock sequence. The depths of these events were constrained by regional moment tensor (RMT) solutions obtained using the records of the dense broad band network. The majority of the foreshocks and aftershocks were associated to the interplate contact, with dip and strike angles in good agreement with the characteristics of horst and graben structures (>2000 m offset) typical of the oceanic Nazca Plate at the trench and in the outer rise region. We propose that the spatial distribution of foreshocks and aftershocks, and its seismological characteristics were strongly controlled by the rheological and tectonics conditions of the extreme erosive margin of Northern Chile.
KeywordsEarthquake Chile Nazca Plate Moment tensor Erosive margin
We thank the support of the Chilean National Science Foundation project FONDECYT No. 11130230 and Programa Riesgo Sísmico (AIN, Universidad de Chile). A.M was supported by project FONDECYT 3150160. We thank Centro Sismológico Nacional (www.sismologia.cl) and IPOC consortium for making raw data available to us.
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