Constraining interseismic deformation in Northern Ecuador using Interferometry of Sentinel-1 and ALOS-2 Data

Abstract:

Ecuador is a seismically active country with several sources of seismicity, including the Nazca – South America megathrust in the west, the Interandean Fault System (IFS) within the Interandean valley that accommodates northward translation of the North Andean Sliver, and an active back-arc fold and thrust belt in the East, referred to as the Sub-Andean zone. The surface deformation associated with the subduction megathrust has been well constrained in prior studies, but this is not the case for the other two systems, which represent a major source of near-surface seismic hazard. The IFS runs directly under or close to several major cities including Quito, Riobamba and Ibarra (all of which have been destroyed by earthquakes in historical times), and the back-arc faults underlie areas with active mining and petroleum infrastructure. In this study, we focus on developing a better understanding of these two fault systems using spaceborne geodetic data.

We perform interferometric synthetic aperture radar (InSAR) processing of data from Sentinel-1 in the dry Interandean valley, and from ALOS-2 in the more densely vegetated Sub-Andean zone to generate maps of surface deformation. Sentinel-1 provides regular acquisition, global coverage, and a free and open data policy. ALOS-2 data was provided by JAXA through a data grant. We generate a large set of interferograms using 280 Sentinel-1 scenes and 60 ALOS-2 scenes. We then use time-series analysis to obtain rates of deformation across the faults during recent years. We expect these results to help constrain the complex partitioning of deformation in the region and contribute to a better understanding of seismic hazard in Ecuador.