Abstract
We used a global positioning system (GPS), levelling, and Sentinel-1 data to evaluate the stability of the Darbandikhan dam in northeast Iraq after the 2017 Mw 7.3 Sarpol-e Zahab earthquake. GPS and levelling datasets collected in March and November 2017 were used to compute the co-seismic surface displacements of the dam. Sentinel-1 synthetic aperture radar (SAR) images collected between October 2014 and March 2018 were employed to recover the displacement time series of the dam. The large-magnitude displacement gradient on the dam crest hindered the estimation of the co-seismic displacement using this medium-resolution SAR data. However, Sentinel-1 images are sufficient to examine the stability of the dam displacement before and after the earthquake. The results show that the dam was stable between October 2014 and November 2017, but after the earthquake, Sentinel-1 data shows a continuous subsidence of the dam crest between November 2017 and March 2018. To the best knowledge of the authors, this study is the first that utilises InSAR to investigate the behaviour of a dam after a large earthquake.
Highlights
The 12 November 2017 Sarpol-e Zahab earthquake was one of the largest earthquakes occurring in the Iran–Zagros zone since 1900 [1]
We investigated the impact of the Mw 7.3 Sarpol-e Zahab earthquake on the deformation of the Darbandikhan dam in northeast (NE) Iraq
We discussed the limitations of using interferometric SAR (InSAR) techniques for monitoring sloping surfaces, and the spatial and temporal resolution required to recover large-gradient displacements
Summary
The 12 November 2017 Sarpol-e Zahab earthquake was one of the largest earthquakes occurring in the Iran–Zagros zone since 1900 [1]. About 396 lives were lost, and 7000 people were injured on both sides of Iraq–Iran border [2], with the majority of fatalities occurring in the Iranian city of Sarpol-e Zahab, whereas Darbandikhan was the most impacted city in Iraq. According to the map of the shaking intensity from the United States (US) Geological Survey (USGS) (Figure 1b), the dam lies within the region of 8 MMI (modified Mercalli intensity) for the 2017 event. Following this earthquake, the dam operators immediately lowered the water level in the reservoir because of concern about the dam’s safety. This region exhibited 53 aftershocks with Mw > 4
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