Physical Properties in the Northern Ecuador Subduction Zone Appear to Contribute to the Occurrence of Moderate-to-Strong Earthquakes and Aftershock Propagation

Megathrust faults in subduction zones often serve as seismogenic environments for destructive earthquakes. To verify whether the material properties of subduction zones influence aftershock propagation and earthquake magnitude, we investigated the northern Ecuador subduction zone using local 8G network data to locate seismicity in July 2016 and obtained the deformation field (the maximum deformation reached about 60 cm) of the 2016 Mw 7.8 earthquake from InSAR. Additionally, we refined the locations of moderate-to-large earthquakes (Mw > 5.2) over the past 20 years via surface waveform relocation and depth-phase modeling based on the global network data. We obtained 895 earthquake events for July 2016 (with horizontal uncertainties < 0.01° and vertical uncertainties < 2 km), and the relocation uncertainties of the historical moderate-to-large events were within 4 km. Both the aftershock and the relocated historical events are found to be concentrated in regions with moderate Vp/Vs ratios (~1.78–1.82), indicating that the material properties in these areas may facilitate subduction zone aftershock propagation and the nucleation of moderate-to-large earthquakes. In contrast, regions with high or low Vp/Vs ratios may act as barriers that inhibit earthquake rupture and constrain rupture scales.