Can we observe North Andean Sliver motion using long InSAR time-series analysis?

Description

In Northern Andes, oblique subduction of the Nazca plate below the South America Plate induces a northward motion of the North Andean Sliver, at a rate of ~10 mm/yr with respect to Stable South America. In Ecuador in particular, the associated strain is mainly accomodated along the large Chingual-Cosanga-Puna-Pallatanga (CCPP) fault system, which hosted several 7+ magnitude earthquakes in the historical period. Recent studies using block-modeling of GNSS data raise important questions about the partitioning and the localization of the deformation both inside and at the limits of the North-Andean sliver. Therefore, time-series analysis of InSAR data, allowing a large spatial resolution, would complement the existing geodetic dataset of observation of low-rate crustal motions in this region. Taking advantage of 7 to 8 years of Sentinel-1 archive, we compute long time-series of InSAR data for the whole Interandean region of Ecuador (~100 by 400 km), using the NSBAS processing chain. Because processing of InSAR data in this ecuatorial region raises several challenges, such as low-coherence due to vegetation, ionospheric and troposheric noise, and fading signals,we develop strategies to mitigate the noise terms. By using an optimized interferogram network, improvedweighting during multilooking, and a temporal decomposition of the time-series, we produce the first InSAR velocity maps of the Ecuadorian Cordilleras. We then compare these results to the existing block-model derived from GNSS horizontal data in order to evaluate the possibility of characterizing the motion of North Andean Sliver with an increased spatial resolution.

Abstract

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