Advanced interferometric synthetic aperture radar (InSAR) time series analysis using interferograms of multiple‐orbit tracks: A case study on Miyake‐jima

InSAR time series analysis is an effective tool for detecting spatially and temporally complicated volcanic deformation. To obtain details of such deformation, we developed an advanced InSAR time series analysis using interferograms of multiple‐orbit tracks. Considering only right‐ (or only left‐) looking SAR observations, incidence directions for different orbit tracks are mostly included in a common plane. Therefore, slant‐range changes in their interferograms can be expressed by two components in the plane. This approach estimates the time series of their components from interferograms of multiple‐orbit tracks by the least squares analysis, and higher accuracy is obtained if many interferograms of different orbit tracks are available. Additionally, this analysis can combine interferograms for different incidence angles. In a case study on Miyake‐jima, we obtained a deformation time series corresponding to GPS observations from PALSAR interferograms of six orbit tracks. The obtained accuracy was better than that with the SBAS approach, demonstrating its effectiveness. Furthermore, it is expected that higher accuracy would be obtained if SAR observations were carried out more frequently in all orbit tracks. The deformation obtained in the case study indicates uplift along the west coast and subsidence with contraction around the caldera. The speed of the uplift was almost constant, but the subsidence around the caldera decelerated from 2009. A flat deformation source was estimated near sea level under the caldera, implying that deceleration of subsidence was related to interaction between volcanic thermal activity and the aquifer.