What mechanical coupling reveals about seismic potential: A case study in the Chilean Atacama Gap

Valeria Becerra-Carreño, Jorge G. Crempien, Marcos Moreno, & Roberto Benavente

Submitted August 30, 2026, SCEC Contribution #15232, 2026 SCEC Annual Meeting Poster #TBD

Plate interface locking distributions are essential for estimating the potential size of future subduction zone earthquakes. However, they do not directly reveal the stress state, namely mechanical coupling, along the seismogenic zone, which is crucial for assessing seismic hazards and understanding the physical processes driving the subduction seismic cycle. Here, we propose a method to estimate stress rates from GNSS-derived displacements and apply it to the North-Central Chile seismic gap, a region with high seismic potential where the last major megathrust earthquakes occurred in 1819 and 1922. Using a Bayesian framework incorporating the Akaike Bayesian Information Criterion (ABIC) for model selection, our method rigorously accounts for uncertainties, enabling robust statistical analysis. From the geodetic data, we infer a model with three high shear stress-rate asperities, which are spatially delineated by background microseismicity. This provides evidence of a mechanical link between stress build-up and deeper seismogenic zone seismicity. We estimate that each asperity could individually generate an ~M8.0 earthquake, whereas a full simultaneous rupture could produce an ~M8.5 event. Furthermore, forearc gravity anomalies and oceanic ridges appear to modulate the stress-rate distribution, suggesting a structural control on interseismic stress accumulation. Our study offers key insights into spatial variations in stress state along the megathrust, significantly improving the identification of seismic asperities and providing a framework for future rupture scenario modeling.

Key Words
Interseismic coupling, Stress rate estimation, Bayesian inversion, GNSS geodesy, Subduction megathrust

Citation
Becerra-Carreño, V., Crempien, J. G., Moreno, M., & Benavente, R. (2026, 08). What mechanical coupling reveals about seismic potential: A case study in the Chilean Atacama Gap. Poster Presentation at 2026 SCEC Annual Meeting.

Related Projects & Working Groups
Tectonic Geodesy