Detection of surface deformation caused by the 2019 Ridgecrest earthquake sequence with ALOS-2 data

We identified and interpreted surface deformation associated with the 2019 Ridgecrest earthquake sequence using L-band synthetic aperture radar (SAR) images acquired with the Advanced Land Observing Satellite-2 (ALOS-2). We produced “low coherence interferometric SAR” (LC-InSAR) images which contain differential InSAR (DInSAR) and coherence analysis information. Phase discontinuity lines that indicate surface rupture and displacements were interpreted from those LC-InSAR images. We also conducted pixel offset tracking to measure the offset between pixels of the same area in two different SAR images. By comparing these results, we found that LC-InSAR analysis is an effective method for detecting relatively small surface displacements, and pixel offset tracking is advantageous in that it can show clear boundary and slip direction of the main fault trace. We also compared our mapping of phase discontinuity lines with a previous study results that infer surface fractures with C-band SAR data from Sentinel-1 satellite. ALOS-2 images can detect surface displacements that occurred near the main fault in more detail, whereas Sentinel-1 images can detect smaller displacements that are distributed away from the main fault. Our study suggests that proper combination of LC-InSAR and pixel offset tracking depending on the scale and direction of the displacements is a key to a better understanding of the characteristics of surface deformation. Moreover, SAR data with different wavelength can help us to understand more detailed mapping of surface deformation.