Frictional Properties of Shallow Early Afterslip of the 2016 Pedernales Earthquake Spatially Coincident With Slow Slip Events Along the Ecuador Subduction Zone
Abstract
The Ecuador subduction zone exhibits a diverse range of seismic and aseismic slip behavior. Intriguingly, peak early afterslip of the 2016 Mw 7.8 Pedernales earthquake was localized on two patches in the shallow portion of the megathrust, which shows little correspondence to the spatial pattern of mainshock-induced Coulomb stress changes [Tsang et al., 2019; Rolandone et al., 2018]. Here, we investigate the frictional properties of these patches. We perform a grid-search to estimate frictional parameters that explain the temporal evolution of early afterslip in these shallow patches, using the kinematic afterslip models of Tsang et al. [2019], and assuming an analytical solution of the rate-strengthening friction law derived by Perfettini and Avouac [2004]. Our first results suggest very different ranges of frictional parameters compared to those found by studies that performed similar analyses of afterslip following other earthquakes - in particular, we find substantially smaller values of the frictional parameter (aσ), and larger velocity jumps (V+/Vpl). The frictional models also allow us to extrapolate the pattern of afterslip to future time periods where we currently lack geodetic observations. Finally, it turns out that along this subduction zone shallow afterslip patches spatially overlap areas of previously reported and inferred slow slip events. Afterslip and slow slip events are often considered to be governed by different frictional regimes. We discuss our results in this context, as well as the implications on the pattern and diversity of aseismic slip behavior on the megathrust.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.T43H0424T
- Keywords:
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- 1242 Seismic cycle related deformations;
- GEODESY AND GRAVITY;
- 7223 Earthquake interaction;
- forecasting;
- and prediction;
- SEISMOLOGY;
- 8118 Dynamics and mechanics of faulting;
- TECTONOPHYSICS;
- 8163 Rheology and friction of fault zones;
- TECTONOPHYSICS