Abstract
AbstractRepeating earthquakes repeatedly rupture the same seismic asperity and are strongly linked to aseismic slip. Here, we study the repeating aftershocks of the April 16, 2016 MW 7.8 Pedernales earthquake in Ecuador, which generated a large amount of afterslip. Using temporary and permanent stations, we correlate waveforms from a one‐year catalog of aftershocks. We sort events with a minimum correlation coefficient of 0.95 into preliminary families, which are then expanded using template‐matching to include events from April 2015 to June 2017. In total, 376 repeaters are classified into 62 families of 4–15 events. They are relocated, first using manual picks, and then using a double difference method. We find repeating earthquakes during the whole period, occurring primarily within large aftershock clusters on the edges of the areas of largest afterslip release. Their recurrence times, shortened by the mainshock, subsequently increase following an Omori‐type law, providing a timeframe for the afterslip's deceleration. Although they are linked temporally to the afterslip, repeater‐derived estimates of slip differ significantly from GPS‐based models. Combined with the fact that repeaters appear more spatially correlated with the afterslip gradient than with the afterslip maxima, we suggest that stress accumulation at the edge of the afterslip may guide repeater behavior.
Highlights
Subduction zones host the largest, most destructive earthquakes, along with a large variety of seismic and aseismic slip processes
To extract repeating earthquakes occurring during the postseismic phase of the Pedernales earthquake, we use both the permanent seismic network in place in Ecuador (Alvarado et al, 2018), and the one-year temporary deployment of land and ocean bottom seismic (OBS) stations deployed in the aftermath of the Pedernales earthquake (Agurto-Detzel et al, 2019; Meltzer et al, 2019)
We have conducted a systematic search for repeating earthquakes in 14 months of postseismic data of the MW 7.8 2016 Pedernales earthquake in Ecuador, as well as 12 months of interseismic data
Summary
Subduction zones host the largest, most destructive earthquakes, along with a large variety of seismic and aseismic slip processes Understanding these processes, and the relationships between them, is necessary to better constrain the mechanical properties of the fault and to better assess seismic hazard. H. Chen et al, 2008) and megathrust faults (Dominguez et al, 2016; Uchida et al, 2003) In all these settings, repeaters are associated with aseismic slip, be it creep, afterslip, or slow slip events (SSEs). Repeaters are associated with aseismic slip, be it creep, afterslip, or slow slip events (SSEs) The recurrence of these earthquakes suggests that a seismic asperity is being continually loaded, likely by aseismic slip, and breaking at regular intervals This makes repeaters ideal tools to probe the properties of a fault and its slip history
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