Topographic changes at Volcán de Colima Observed by Double Differential InSAR using TanDEM-X
Kubanek, Julia; Westerhaus, Malte; Heck, Bernhard

Although being one of the most important parameters of volcanic activity and the intensity of volcanic eruptions, the estimation of magma ascent rates is one of the main challenges in volcano research. Regarding dome building volcanoes, the ascent of volcanic material becomes apparent in a changing summit. During an eruption, the volcano dome changes, material is rearranged and new material ascends which hence affects the local topography. In the present study, we show a new approach to observe topographic changes at dome building volcanoes which can further be used as a basis to calculate magma ascent rates. We therefore employ data of the innovative TanDEM-X mission. Due to the fact that two satellites fly in a close formation, we get two images of the Earth surface at the same time acquired from slightly different positions. This facilitates to generate digital elevation models (DEMs) of the area of investigation using SAR interferometry (InSAR). A time series analysis of these DEMs enables to assess large topographic changes in the summit areas of volcanoes and hence to estimate volume changes caused by volcanic activity. We show a time series analysis of Volcán de Colima, Mexico. While being a dome building volcano, phases of quiescence interchange with phases of dome growth and dome destructions. In the end of June 2011, a small explosion at the crater wall signaled the end of the current magma intrusion. We can see the related topographic change by comparing DEMs taken before and after the explosion. As the material change due to the explosion is rather small, the present study allows analyzing the accuracy of the TanDEM-X based DEMs. It can further be seen as a feasibility study for applying TanDEM-X data in volcano research.