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The Merapi-Project Interdisciplinary monitoring of a high-risk volcano as a basis for an early warning system

Jochen Zschau1, R. Sukhyar2, M. A. Purbawinata3, B.-G. Lühr1, M. Westerhaus1
1
GeoForschungsZentrum Potsdam,Telegrafenberg E424, D-14473 Potsdam, Germany.
Tel. : +49-331-288-1200, Fax: +49-331-288-1204,
E-mail: zschau@gfz-potsdam.de.
2Volcanological Survey of Indonesia, Bandung, Indonesia
3Volcanological Technology Research Centre, Yogyakarta, Indonesia

Abstract:
Merapi volcano in Central Java is one of the most active volcanoes in the world. Located at the subduction zone between the Eurasian and the Indo-Australian Plate, Merapi shows andesitic character, which is currently demonstrated by active dome formation, accompanying dome-avalanches and pyroclastic flows up to distances of 2 to 8 km. This type of volcanism exhibits a high degree of explosivity. Even small volcanic events are a permanent danger to life within the densely populated area at the flanks of the volcano. A large eruption like in 1006 would immediately endanger more than one million of inhabitants in the region around Yogyakarta, about 35 km from the summit. Due to these reasons Merapi has been classified as a high-risk volcano and included into the list of 15 Decade Volcanoes by IAVCEI.

In co-operation with the Volcanological Survey of Indonesia and other institutions in Indonesia and Germany, the GeoForschungsZentrum initiated an interdisciplinary monitoring program in 1994, supplementing a number of ongoing national and international activities on this volcano. The so-called MERAPI project (Mechanism Evaluation, Risk Assessment, Prediction Improvement) is supposed to contribute to the development of prediction and warning strategies on different time scales, including intermediate and short-term prediction of volcanic events as well as early warning at different stages of the volcano's activity. Investigation of the internal structure of the edifice, of magmatism and of the explosive history of the volcano form the basis for a better understanding of the complex processes prior to an eruption and, thus, for the improvement of hazard assessment as well as for improved warning capabilities.

Special emphasis has been put on continuously monitoring the most important activity indicators of the volcano such as seismicity, deformation and gas emanation. Directional microphones are expected to facilitate a discrimination between shallow volcanic earthquakes and rock avalanches, which would be of basic importance for an automatically working early warning system. All the data is transmitted by radio to the office of the Volcanological Technology Research Centre (BPPTK) in Yogyakarta. Following the last catastrophic eruption in November 1994 (66 fatalities), the BPPTK has considerably improved the infrastructure for information and protection of the inhabitants. It is planned to install a central online data bank at BPPTK that incorporates any volcanological data including the results from all national and international groups working at Merapi.