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Abstract:
At the northern Chilean subduction zone, the IPOC network has been monitoring seismicity since 2006. For the observation time until 2021 a recent catalog has been published holding more than 182,000 events. We have performed a complete template matching run on the continuous seismic data using this catalog, enabling us to identify a large amount of repeating earthquake families. Many identified family members were not in the original catalog, but solely identified by the template matching. High data quality and long observation time allow analyzing these sequences in detail.Using a relative relocation approach based on wave phase based cross correlation refined s-p travel time differences, we are able to compute highly precise relative locations for these events. Paired with very recently obtained stress drop information, we are able to distinguish between true repeaters and similar events. This distinction is important, especially when the families are utilized as creep proxies and are being compared to the plate convergence rate or plate coupling.The repeaters in the vicinity of the Mw8.1 2014 Iquique earthquake show different characteristic behavior reflecting signatures corresponding to pre-, inter-, and post-seismic phase of a megathrust event. We observe clear precursor patterns, burst reactions and unresponsive families simultaneously. Their cumulative slip and characteristic decay rates correspond well with the slip and after slip patterns reported for the Iquique event.Interestingly, repeating series are also found in deeper parts of the subduction channel, where the classical repeating earthquake theory loses validity.
