A survey of volcanic deformation on Java using ALOS PALSAR interferometric time series

Of the hundreds of volcanic centers throughout the Indonesian archipelago, few are adequately monitored for pre‐eruptive activity due to socioeconomic and logistical barriers, with the result that volcanic hazards in the region are not well quantified. The advent of satellite‐borne L‐band synthetic aperture radar provides an opportunity for detection and measurement of volcanic deformation over broad regions in heavily vegetated tropical island arcs. We use data from the PALSAR instrument on the Japanese ALOS satellite to conduct a comprehensive survey of volcanic deformation on the Indonesian island of Java, over a time period of two years (2007–2008). To obtain the most complete, temporally continuous record of ground deformation, we use a temporally overlapping set of short‐time‐interval radar image pairs to produce a deformation time series. Consistent with previous results from other regions, our survey suggests that volcanoes experiencing small eruptions are typically fed by magma bodies too small and/or too shallow or deep to produce a recognizable InSAR signal. However, we identified a deformation event at Lamongan volcano which is likely linked to a magmatic intrusion at several kilometers' depth, and a second one at Slamet volcano at a shallower depth that may have been related to a subsequent eruption. This initial test of a broad application of L‐band data allowed us to better define the satellite imaging criteria required for successful observation, as well as developing a useful methodology for monitoring deformation over a wide region.