Résumé
The tsunamis related to the Mw8. 6-8.8-1906 and Mw8.2-1979 Ecuador-Colombia subduction earthquakes produced important local damages. Recent works suggested that the tsunamis were caused by significant slip of the shallow plate interface during the earthquakes. Analyzing seafloor morphology and sub-seafloor acoustic images collected in the near-trench, 1906 and 1979 earthquake rupture zones, has allowed documenting the trench-parallel, 200 km-long, segmented strike-slip Ancon fault which has developed above a zone of high coupling of the inter-plate fault. Although continuous strike-slip faults are not prone to produce large tsunamis in deep waters, ridges, scarps or troughs associated to the fault segmentation can provide tsunami sources when the fault ruptures. We found that slip along the Ancon fault segments is accompanied by tectonic deformation of the near-fault region and adjacent tectonic block involving shortening, uplift or subsidence, and massive landslides potentially triggered during the fault motion. Given that a major near-trench fault contributed to producing a giant tsunami during the Mw 9.0-2011 Tohoku-Oki subduction earthquake in Japan, the contribution of the Ancon fault rupture and its multiple mass failures to the 1906 and 1979 tsunamis is plausible. In such a scenario, this fault should be considered at risk