Understanding about Indonesia standard of volcanic activities early warning system is one important aspects for visitor coming to hike up some volcanoes in Indonesia archipelago. Vulcanological Survey Of Indonesia ( VSI ) is official reference for that matter. VSI has defined the standard based on the seismic, geochemistry, visual, deformation, and magnetic monitoring data. Hope its useful for visitor visiting volcanoes in Indonesia. There are four early warning alert levels :
>Stage / level 1 named locally “Aktif Normal” ( Normal active ) with criteria monitoring of visual, seismicity and other volcanic event do not indicate changes. The Criteria Interpretation: no eruption in foreseeable future. early warning alert Code: Green.
>Stage / level2.named locally “Waspada” ( Attention ) with criteria increasing activity of seismicity and other volcanic events, and visual changes around the crater. The Criteria Interpretation: magmatic,tectonic or hydrothermal disturbance, no eruption imminent. Early warning alert code;Yellow
>Stage / level 3 named locally “Siaga” ( Standby ) with criteria intensively increasing of seimicity with supported by other volcanic monitoring and crater based on observation data analysis, the activity will be followed by main eruption. Criteria Interpretation: If trend of increasing unrest continues, eruption possible within 2 weeks. Early warning alert code: Orange.
>Stage / level 4 named locally “Awas” (Evacuation) with criteria following the main eruption, the initial eruption begin to occur as ash and vapor. Based on observation data analysis, the activity will be followed by main eruption. Criteria interpretation: Eruption possible within 24 hours. Early warning alert code: Red.
In "Normal" (Normal Active / level 1) and "Waspada" (Attention / level 2), activity level is evaluated once a week, and daily evaluation for higher level. Information about the level of activity is sent to the local governments around the volcano as a warning for people living there.
On Merapi Volcano area, whenever “ Awas “ (Evacuation) is declared, some sirens installed around the Merapi are switch on. Local government is responsible for evacuation, in the sense that the decision to evacuate people is taken by regional authority.