Abstract
The study of crustal deformation fields caused by earthquakes is important for a better understanding of seismic hazard and growth of geological structures in tectonically active areas. In this study, we present, using interferometric measurements constructed from Sentinel-1 Terrain Observation with Progressive Scan (TOPS) data and ALOS-2 ScanSAR, coseismic deformation and source model of the Mw 7.3, 12 November 2017 earthquake that hit northwest of the Zagros Mountains in the region between Iran–Iraq border. This was one of the strongest seismic events to hit this region in the past century, and it resulted in an uplift area of about 3500 km2 between the High Zagros Fault (HZF) and Mountain Front Fault (MFF) with a maximum amount of 70 cm south of Miringe fault. A subsidence over an area of 1200 km2 with a maximum amount of 35 cm occurred near Vanisar village at the hanging wall of the HZF. Bayesian inversion of interferometric synthetic aperture radar (InSAR) observations suggests a source model at a depth between 14 and 20 km that is consistent with the existence of a decoupling horizon southwest edge of the northern portion of the Zagros Mountains near the MFF. Moreover, we present evidence for a number of coseismically induced rockslides and landslides, the majority of them which occurred along or close to pre-existing faults, causing decorrelation in differential interferograms. Exploiting the offset-tracking technique, we estimated surface motion by up to 34 and 10 m in horizontal and vertical directions, respectively, due to lateral spreading on a big coseismic-induced landslide near Mela-Kabod. Field observations also revealed several zones of en echelon fractures and crack zones developed along a pre-existing fault passing through Qasr-e Shirin City, which exhibited secondary surface slip by up to 14 cm along its strike.
Highlights
Basement-involved thrust faulting is common in fold and thrust belts and is mostly associated with irregular tectonic relief and structures [1,2]
The suture zone is located on the northeast (NE) edge of the mountain belt along the Main Zagros Reverse Fault (MZRF) and the Main Recent Fault (MRF) in the southern and northern Zagros, respectively (Figure 1)
We used six C-band Copernicus Sentinel-1A/B interferometric wide-swath Terrain Observation with Progressive Scan (TOPS) data and four L-band Japanese Aerospace Exploration Agency (JAXA) ALOS-2 ScanSAR to produce two descending and three ascending coseismic interferograms associated with the 12 November 2017, Mw 7.3 Sarpol-e Zahab Iran earthquake
Summary
Basement-involved thrust faulting is common in fold and thrust belts and is mostly associated with irregular tectonic relief and structures [1,2]. As it occurs beneath the sedimentary cover and rarely reaches the ground surface, its faulting is mainly dominated by buried dislocation accommodated by basement This makes determining the accurate geometry of the source and the relationship between the deep seismic displacement and the tectonic structure in the overlying area very challenging. The suture zone is located on the northeast (NE) edge of the mountain belt along the Main Zagros Reverse Fault (MZRF) and the Main Recent Fault (MRF) in the southern and northern Zagros, respectively (Figure 1) These major faults take up ∼10 mm/year of oblique convergence in the region [11]. We integrated observations from radar and optical remote sensing, seismology, and field mapping to investigate source parameters, coseismically triggered slope failures, and secondary faulting related to the Mw 7.3, Sarpol-e Zahab earthquake in Iran. We present the result of our field survey and provide detailed information for the characteristics of the earthquake-induced geological effects, such as landslides and secondary faulting
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