Mapping secondary surface deformation related to the 2018 Sulawesi earthquake via synthetic aperture radar offset tracking

Synthetic aperture radar (SAR) multiple kernel offset tracking provide efficient measurements of large and complex surface deformations, which is approximately three times more accurate than traditional offset tracking approaches. This method allows measurement of precise two-dimensional (2D) surface deformations from a pair of interferometers through azimuth and slope offset measurements, resulting in precise three-dimensional (3D) surface deformations from ascending and descending interferometer pairs. It is very important to measure precise 3D deformations because 3D deformation measurements are allowed to improve understanding of geological events such as earthquakes, volcanic eruptions, and glacier movements. The 2018 Sulawesi earthquake is M 7.5, which occurred on September 28, 2018. Because of fault movement, the surface deformation of about -3.5, 3.7 and -2.5 m in the east, north and upper direction occurred, respectively. In addition, there also were reports of secondary surface deformation such as landslides, liquefaction and land subsidence. Secondary surface deformation extremely increased the damage caused by the earthquake. However, the measuring surface deformation was only focused on the fault movements. In this study, we proposed a deformation field related to the Sulawesi earthquake by integrating multiple kernel-based offset tracking measurements in ascending and descending interferometer pairs of space-based SAR sensors. Especially we focus on secondary surface deformation. For that, we utilized two ALOS-2 PALSAR-2.