EGU21-2918, updated on 03 Mar 2021
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Repeating earthquakes follow afterslip gradient in the aftermath of the 16th April 2016 M7.8 Pedernales earthquake in Ecuador

Caroline Chalumeau1 and the Pedernales research team*
Caroline Chalumeau and the Pedernales research team
  • 1Université Côte d'Azur, Géoazur, Biot, France (
  • *A full list of authors appears at the end of the abstract

Repeating earthquakes are earthquakes that repeatedly break a single, time-invariant fault patch. They are generally associated with aseismic slip, which is thought to load asperities, leading to repeated rupture. Repeating earthquakes are therefore useful tools to study aseismic slip and fault mechanics, with possible applications to earthquake triggering, loading rates and earthquake forecasting.

In this study, we analyze one year of aftershocks following the 16th April 2016 Mw 7.8 Pedernales earthquake in Ecuador to find repeating families, using data recorded by permanent and temporary seismological stations. In our area, seismicity during both the inter-seismic and post-seismic periods has been previously linked to aseismic slip. We calculate waveform cross-correlation coefficients (CC) on all available catalogue events, which we use to sort events into preliminary families, using a minimum CC of 0.95. These events were then stacked and used to perform template-matching on the continuous data. In total, 376 earthquakes were classified into 62 families of 4 to 15 earthquakes, including 8 from the one-year period before the mainshock. We later relocated these earthquakes using a double-difference method, which confirmed that most of them did have overlapping sources.

Repeating earthquakes seem to concentrate largely around the areas of largest afterslip release, where afterslip gradient is the highest. We also find an increase in the recurrence time of repeating events with time after the mainshock, over the first year of the postseismic period, which highlights a possible timeframe for the afterslip’s deceleration. Our results suggest that while most repeating aftershocks are linked to afterslip release, the afterslip gradient may play a bigger role in determining their location than previously thought.

Pedernales research team:

Caroline Chalumeau (1), Hans Agurto-Detzel (1), Louis De Barros (1), Philippe Charvis (1), Audrey Galve (1), Andreas Rietbrock (2), Alexandra Alvarado (3), Stephen Hernandez (3), Susan Beck (4), Yvonne Font (1), Mariah C. Hoskins (5), Sergio Leon-Rios (2), Anne Meltzer (5), Colton Lynner (6), Frederique Rolandone (7), Jean-Mathieu Nocquet (1), Marc Regnier (1), Mario Ruiz (3), Lillian Soto-Cordero (5), Sandro Vaca (3), Monica Segovia (3)

How to cite: Chalumeau, C. and the Pedernales research team: Repeating earthquakes follow afterslip gradient in the aftermath of the 16th April 2016 M7.8 Pedernales earthquake in Ecuador, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-2918,, 2021.

Corresponding presentation materials formerly uploaded have been withdrawn.