HR: 1340h
AN: V33A-0671    [Abstracts]
TI: Online Classification of Dome Processes at Merapi Volcano, Indonesia, Using Doppler Radar Monitoring
AU: * Voege, M
EM: voege@dkrz.de
AF: Institute of Geophysics, University of Hamburg, Bundesstr. 55, Hamburg, 20146 Germany
AU: Hort, M
EM: hort@dkrz.de
AF: Institute of Geophysics, University of Hamburg, Bundesstr. 55, Hamburg, 20146 Germany
AU: Ratdomopurbo, A
EM: mvopgm@yogya.wasantara.net.id
AF: Volcanological Technology Research Centre, Jalan Cendana 15, Yogyakarta, 55166 Indonesia
AB: Merapi volcano is one of the most active dome building volcanoes in the world. Especially dome collapses generating block and ash flows or pyroclasic flows present a large thread to the highly populated areas south and west of the volcano. Therefore a continuous observation of dynamic processes at the dome is very important for hazard mitigation reasons. We installed two frequency modulated Doppler radar systems (10 and 24GHz) on the flanks of Merapi, each at a distance of approx. 4.5km from the dome, allowing a quasi-visual observation of dome activity independent of weather conditions. These measurements provide velocity distributions of all material moving inside the radar beam. Because of the frequency modulation this can be done for several distance intervals. At Merapi's dome we basically observe material breaking of the dome as well as rain. The signals of these two processes can easily be discriminated. Analysing the shape of the velocity distributions we can identify two different processes that cause material to break off the dome: rocks sliding/tumbling due to gravitation and explosive outbursts caused by degassing. In order to provide a useful tool for hazard mitigation we developed algorithms to automatically detect and classify the different types of events. For each event characteristic features are calculated in order to reduce the dimensionality of the classification task. Then the classification is performed in a two step process using artificial neural networks. These algorithms are integrated into the monitoring system, so that the user can easily create daily statistics of dynamic dome processes. We present results of 3 years of continuous measurements showing the variability of the activity. A comparison with seismic observations by the Merapi Volcano Observatory (MVO) clearly shows that our system is able to characterise the state of activity of Merapi's dome. Because we are able to also locate the activity along the beam, we can also record rain at the dome. In terms of assessing the activity of the dome this is very important as we can now explore the relation between dome activity and rain.
DE: 8419 Volcano monitoring (7280)
DE: 8485 Remote sensing of volcanoes
DE: 8488 Volcanic hazards and risks
DE: 8494 Instruments and techniques
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005