Measurement of precise three-dimensional volcanic deformations via TerraSAR-X synthetic aperture radar interferometry

Multiple-aperture SAR interferometry (MAI) is an advanced technique that is used to retrieve actual surface motions by complementing missing components of InSAR measurements. Despite the wide use of the MAI method in the geosciences, X-band SAR has rarely been applied in MAI-based studies due to the relatively shorter decorrelation periods involved. Thus, we need to evaluate the MAI measurements from X-band SAR for the use in the geosciences. In this paper, an assessment of the MAI performance for TerraSAR-X system was carried out at the test site, Kīlauea Volcano, Hawaii, focusing on the Kamoamoa fissure eruption episode that occurred on March 6–10, 2011. The root-mean-square (RMS) errors of single MAI interferograms were 3.26 ± 1.32 cm and 2.95 ± 0.77 cm for descending and ascending datasets, respectively. Multi-stacked MAI interferograms showed reduced error levels of 1.77 and 2.04 cm for descending and ascending datasets, respectively. In addition, empirical uncertainty models of the MAI measurements were generated with respect to the interferometric coherence of single- and multi-stacked MAI measurements, and these regression models enabled us to confirm the difference between the theoretical and practical accuracies of the MAI measurements. Moreover, the MAI-based 3D model based on high accuracy 3D maps showed some possibilities of new findings and interpretations of the geologic sources.