← Back to Sessions

Repeating Earthquakes Cluster at the Edge of the Afterslip in the Aftermath of the 16 April 2016 M7.8 Pedernales Earthquake in Ecuador

Session: Subduction Processes Along Latin America Subduction Zones I

Type: Oral

Date: 4/19/2021

Presentation Time: 10:00 AM Pacific

Description: 

The South American subduction zone is host to a variety of interacting seismic and aseismic processes. Among them are repeating earthquakes, earthquakes that repeatedly break a single, time-invariant fault patch. Repeating asperities are thought to be loaded by aseismic slip, 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.

Presenting Author: Caroline Chalumeau

Student Presenter: Yes

Authors