Observing lava dome roughness on synthetic aperture radar (SAR) data: Case study at Mt. Sinabung and Merapi — Indonesia

Detecting ground surface changes at active volcanoes is crucial for better hazard mitigation. Ground based measurements are commonly used to detect surface changes especially on the flanks near to the summit. However, the selection of observation points is limited by field conditions such as rough terrain and topographical barrier. The few number of observation points may lead to miss-interpretation when the displacements related to magma ascent occurred beneath unobserved flanks. This classical problem is common for dormant volcanoes. Overcoming the problem, we used the Synthetic Aperture Radar (SAR) data to observe surface roughness changes at the summit of active volcanoes. This paper discussed the potential capability of the SAR backscattering intensity to observe ground surface changes in view point of surface roughness around the summit. We presented two study cases at Mt. Sinabung in North Sumatra and Mt. Merapi in Central Java - Indonesia. Mt. Merapi was selected for comparison following published references. Mt. Sinabung is currently active since the first phreatic eruption has been occurred in August 2010. Time series of lava dome roughness on SAR (drSAR) method were used to detect ground surface changes prior to the eruption. Based on this method, the ground surface at the summit of Mt. Sinabung changed from 5121 to 6584 m². The temporal pattern slightly agreed to the ground surface changes at summit of Mt. Merapi prior to the 2010 eruptions. Observing ground surface changes related to surface roughness at the summit might be used as new tools for observing volcanic activity.