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IntroductIon Geographically the Kelud Volcano is located at 7 o 56'S and 112 o 18'E. The volcano lies within two regencies, i.e. Blitar and Kediri, in East Java (Figure 1). The summit elevation of this stratovolcano is 1731 m asl. and a large lake occupies the summit crater. Historical eruption of the Kelud Volcano was recorded firstly in the year of 1000. The big erup

We report methods, based on geophysical observations and geological surveys, for the prediction of eruptions and the evaluation of the activity of 4 volcanoes in Indonesia. These are Semeru, Guntur, Kelud and Sinabung volcanoes. Minor increases in tilt were detected by borehole tiltmeters prior to eruptions at the Semeru volcano depending on the seismic amplitude of explosion earthquakes. The results show the possibility of prediction of the type and magnitude of eruption and the effectiveness of observation with a high signalto-noise ratio. The establishment of background data is important for evaluating volcanic activity in longterm prediction. Typical distributions of volcanic and local tectonic earthquakes were obtained around the Guntur volcano, where geodetic monitoring by continuous GPS observation is valuable. The cumulative volume of eruptive products is valuable for evaluating the potential for future eruption. The eruptive rate of the Kelud volcano is ca 2×106m3/y (dense rock equivalent), but the volume of the 2007 eruption was only 2×107m3, suggesting a still high potential for eruption. Based on geological surveys and dating, an eruption scenario is proposed for the activity of Mt. Sinabung, where phreatic eruptions occurred in 2010 after a historically long dormancy.

Before its 2010 eruption, Sinabung Volcano was a Btype volcano, in its Indonesian classification. A series of explosions featuring 1-5 km high phreatic-ash columns occurred from August 27, 2010 untill September 7, 2010. SO2 flux measured during the eruptions showed sizeable gas emission and the youngest volcanic product has age of 1200 years BP obtained from 14C dating. At the end of August 2010, four continuous seismic stations were established around the volcano, and 6 additional stations were deployed in October 2010. Deformation monitoring was conducted temporarily till in February 2011, four continuous GPS stations were installed. All were set up through collaboration between Indonesian and Japanese academic and government institutions. Hypocenter calculations using data of 4 seismic stations fromSeptember to October 2010 showed two concentrations for shallow volcanic earthquakes (VTB) 0.5-2 km beneath the crater and for deep volcanic earthquakes (VTA) 2.5-14 km beneath the crater. These epicenters defined a northeast-southwest lineament, near an elongated sinistral fault zone between Sinabung and Sibayak volcanoes. Earthquake sources went deeper northeastward. Results using the data of 10 stations from November 2010 to February 2011 showed that earthquakes were concentrated at depths of 4-6 km beneath Lake Lau Kawar. Tilt and Electro-optic Distance Measurement (EDM) measurements from August to September 2010 showed no significant changes We inferred that since the last explosion in 7 September 2010, stabilization process both in pressure and energy were low.

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