We combined two types of research methods in this study. The research methods used in this study are the SAR products and Landsat 8 Operational Land Imager (OLI)
Varieties of strategies were used to achieve the study’s goals.
The two types of SAR images were collected in HH and VV polarizations, ALOS-2 and sentinel 1A, covering the study area. The ALOS-2 sensor, in ascending and descending orbits, has a radar incidence angle of 47.2◦ with HH polarization and pixel spacing of 20 m in range and 25 m in azimuth. The visual scene's range and azimuth are approximately 350 km by 350 km. The ascent and descent angles are 91◦ and 170◦, respectively. The ALOS-2 has a longer wavelength of 23.6 cm (L band) and is less affected by SAR signal temporal decorrelation. We collected SAR images before and after the Sarpol Zahab earthquake to obtain the surface deformation field.
The observed timing of the SAR images closest to the 2017 Sarpol Zahab earthquake was used in the DInSAR deformation field to avoid the detrimental effect of the co-seismic signal on the recovered co-seismic DInSAR deformation field. The detailed information and ground coverage of the employed SAR pairs are in Table 1.1. Sentinel-1A data was collected in ascending and descending orbits using Interferometric Wide (IW) mode, with a radar incidence angle of 39.2◦ and VV polarization, with heading angles of 167◦. The image scene covers approximately 170 km and 250 km, with a pixel spacing of 25 m and 5m in range and azimuth, respectively. This image has a wavelength of 5.6 cm (C band). The Digital Elevation Model Mission v.4 (SRTM-4 DEM) removed the topographic phase component from the original interferogram (Ferretti, 2007). Presented pertinent data parameters in (Table 1.1) and (Figure 1.1b).
The Landsat 8 OLI data has 11 bands 8 of the bands (OLI 1, 2, 3, 4, 5, 6, 7, 9) have a spatial resolution of 30 m, and TIRS 10 and TIRS 11 have a spatial resolution of 100 m. The panchromatic band 8 has a spatial resolution of 15 m. This image covers the Sarpol Zahab region and reflects the summer season to minimize cloud cover, with Path 168 ROW 36 and an acquisition date of 2020-09-011. Only bands 2, 3, 4, 5, 6, 7, and 8 are used in this study (Table 1.2). In addition, the digital terrain model of the Shuttle Radar Topography Mission (SRTM) with a resolution of 90 meters is used. We also utilized the geologic map with 1/200 000 and 1/50 000 scales for the National Iranian Oil Company ((Ashayeri et al., 2020)), which included the study area map.
Table 1.1: The dataset of 2017 for the Sarpol Zahab earthquake
Table1.2: The dataset of Landsat OLI 8 bands
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