D35 Interferograms over Azores including SAR acquisitions provided annually with first delivered at M12 – TOUL

The Mw 6.1 1998 Pico-Faial earthquake was one of the largest instrumental events occurred in the Azores (North Atlantic) in recent years. It generated a significant permanent deformation that was measured by the GPS network on Faial Island. The lack of systematic GPS observations over neighbouring Pico Island led us to attempt INSAR.

We selected images from the ERS archives with the DESCW software of European Space Agency (ESA).Ten interferograms, span a maximum interval of more than 6 years, were derived from the seventeen ERS SAR images acquired from two different tracks (track 52 and 281). All these images correspond to descending orbits and were acquired at day-time (12:36 local time). We used the two-pass approach implemented by the Diapason software developed at CNES (Centre National d’Etudes Spatiales). The contribution of topography was removed using a Digital Elevation Model (DEM) provided by the Instituto Geográfico do Exército, with a 20-m horizontal resolution and average height accuracy better than 5 m.

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Chart of useful interferometric pairs composed of ERS SAR images over Pico and Faial islands, Azores. The ERS orbit numbers are shown above the bar whose length represents the temporal separation of the images that form the interferogram. The altitude of ambiguity (Ha) of each pair is given on the right side of the bar. The scale on the top corresponds to the year and the bottom scale to the number of days since January of 1992.

Dec95-Oct98

Dec95-Oct98

Dec95-Sep98

Nov95-Sep98

Interferograms analyzed on Pico Island (A = pair 22585-17942; B = pair 3413-17942; C = pair 23315-18171; D = pair 3642-18171).