Physical properties controlling earthquake ruptures: Two study cases along the South American subduction zone

Seismic velocity models were compared with coseismic slip distributions for two megathrust earthquakes that occurred along the South American subduction zone. By analyzing the distribution of Vp/Vs ratios, we found that seismic anomalies with values higher or lower than the average coincide with the boundaries of the earthquake ruptures. In contrast, the regions characterized by intermediate Vp/Vs values may represent a mechanical ?sweet spot? where the physical properties create favorable conditions for sustained rupture propagation. Our methodology, which combines the Vp/Vs distribution and the analysis of coseismic slip models, could reveal the rupture-prone regions and the likely magnitude of potential earthquakes, providing relevant information for seismic hazard assessment.