Using PS-InSAR Technique to Monitor Surface Deformation over Datun Volcanoes in Taiwan

Datun Volcanoes consisting of 29 volcanoes forms the largest volcano group in Taiwan. Although there was no eruption occurring for a long period, the recent ground monitoring reveals that Datun Volcanoes may be still active. As Datun Volcanoes are very close to Taipei City, serious damages would occur if the volcanoes erupted. Therefore it is critical to continuously monitor the behavior of the volcanoes. Normally this task is performed from various aspects, such as observation of emission of gas, detection of hot spots, etc. Among which, ground surface deformation is a key feature as it can be interpreted in terms of magma movement beneath the ground. Hence we proposed to monitor surface deformation over Datun volcanoes in this study. Based on the observation, a warning message could be delivered as a precursor to eruption once unusual deformation was derived. Synthetic aperture radar interferometry (InSAR) is one of the methods broadly applied to monitor surface deformation. Moreover, considering the volcano area was covered with forest, the Persistent Scatterer (PS-) InSAR technique and the Stanford Method for Persistent Scatterers (StaMPS) software was applied. In order to understand the long-term deformation, three types of SAR imagery, including 8 ERS-2 (1995/12-2000/05), 28 ASAR (2003/04-2008/06) and 6 PALSAR (2007/01-2010/03) images, were applied to perform the monitoring. As a result, the displacement velocity in line-of-sight (LOS) direction occurring in the three time periods was shown. For further volcanic analysis with the ground displacement solved using SAR image data, local GPS observations and ground leveling surveying data were employed to verify the PS-InSAR results. The trend of the PS-InSAR results generally agreed with the leveling and GPS data. The implementation of PS-InSAR analysis using multiple SAR data in StaMPS software has been demonstrated achievable, and the long-term surface deformation occurring over the Datun Volcanoes was shown and assessed. Based on the observation, an interpretation of the deformation and possible trigger power in the volcano area can be performed. Supplementary information in the test area (a) and resultant displacement velocity (in LOS direction) maps generated using ERS-2 (b), ASAR (c) and PALSAR (d) image data