Persistent scatterer InSAR for monitoring active volcanoes: Measuring deformation at Merapi using ALOS PALSAR data

We applied Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) onto the Advanced Land Observing Satellite (ALOS) Phased Array L-band SAR (PALSAR) dataset from December 2006 to February 2011 to monitor the inter-eruption (2006 and 2010) period and the post 2010 eruption of Mount Merapi. L-band is chosen for the long wavelength to improve coherence in vegetated region. We observe periodic uplift and subsidence of less than 0.4 mm/day for the non-eruption period, and a large uplift of 1.8 mm/day immediately before the eruption. ALOS PALSAR is limited by the 46 days repeat pass, but newer L-band satellites will have the potential to monitor active volcanoes such as Merapi.