Presentation Information
[U15-P03]Multi-wavelength LC-InSAR detection of coseismic and off-fault surface deformation during the 2019 Ridgecrest earthquake sequence
*Kento Adachi1, Masashi Omata1, Jun Sugimoto1 (1.PASCO Corporation)
Keywords:
LC-InSAR,Coseismic surface deformation,Off-fault deformation,ALOS-2,Sentinel-1,Ridgecrest earthquake sequence
This study investigates the coseismic surface deformation associated with the 2019 Ridgecrest earthquake sequence by integrating multi-wavelength SAR observations and field surveys. The sequence consisted of an Mw 6.4 foreshock and an Mw 7.1 mainshock that activated a conjugate fault system with NE-SW left-lateral and NW-SE right-lateral ruptures. To capture the resulting deformation patterns, "low coherence interferometric SAR" (LC-InSAR) images were generated from ALOS-2 (L-band) and Sentinel-1 (C-band) SAR data by combining differential interferograms and coherence maps. Phase-discontinuity areas were extracted by identifying zones where low-coherence patches coincide with discontinuous interferometric fringes. Both ALOS-2 and Sentinel-1 successfully delineated deformation zones consistent with the geometry of the conjugate fault system. However, clear differences emerged due to their distinct wavelength characteristics. ALOS-2, with its longer wavelength, provided sharper and more linear expressions of major rupture traces, enabling detailed identification of principal fault strands. In contrast, Sentinel-1 captured broader areas of low coherence and revealed subtle distributed deformation extending away from the main fault, offering complementary insights into off-fault deformation processes. These results highlight the wavelength-dependent sensitivity of SAR sensors to varying scales of ground deformation.
To validate the remotely sensed findings, field investigations were conducted at 51 sites along the identified deformation zones. The survey confirmed up to 1 m of right-lateral displacement along the main fault associated with the Mw 7.1 event. Importantly, several centimeter-scale openings and left-lateral fractures were also identified along distributed fault traces that had not been reported in previous studies but were clearly detected as phase-discontinuity areas in the LC-InSAR results. Rose-diagram analyses of fracture orientations further demonstrated consistency between observed fracture patterns and the deformation directions inferred from SAR analysis. These results provide strong evidence for the effectiveness of LC-InSAR in detecting both principal ruptures and distributed faulting.
This study was conducted as part of the contract research in FY2020 and FY2023, sponsored by the Secretariat of Nuclear Regulation Authority, Japan.
To validate the remotely sensed findings, field investigations were conducted at 51 sites along the identified deformation zones. The survey confirmed up to 1 m of right-lateral displacement along the main fault associated with the Mw 7.1 event. Importantly, several centimeter-scale openings and left-lateral fractures were also identified along distributed fault traces that had not been reported in previous studies but were clearly detected as phase-discontinuity areas in the LC-InSAR results. Rose-diagram analyses of fracture orientations further demonstrated consistency between observed fracture patterns and the deformation directions inferred from SAR analysis. These results provide strong evidence for the effectiveness of LC-InSAR in detecting both principal ruptures and distributed faulting.
This study was conducted as part of the contract research in FY2020 and FY2023, sponsored by the Secretariat of Nuclear Regulation Authority, Japan.