EULERIAN MODELLING OF VOLCANIC ASH TRANSPORTATION ON GALUNGGUNG ERUPTION 1982

• Main Author: Aria Santoso, Michael
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/40512
• Institution: Institut Teknologi Bandung

The Galunggung Volcano is one of the active volcanoes in Tasikmalaya, West Java, Indonesia. Before the last eruption occurred in the year of 1982-1983, the volcano had erupted in the year of 1822, 1894, and 1918. The Galunggung eruption in 1982 lasted for nine months long with the first eruption occurred at dawn of April 5th 1982 until the last at 8th of January 1983. The largest eruption happened at the 17th – 18th of May 1982 and 13th of July 1982 with its eruption column height reaching as far as 30-35 km tall. The eruptions have become a menace as British Airways jumbo jet with 240 people on board encountered an ash cloud that stalled all four of its engines. Magma composition of Galunggung kept evolving throughout the time of the explosion from April to January beginning with an andesitic magma and later evolved to basaltic magma. In order to reconstruct the event of Galunggung eruption, a volcanic ash transport simulator called FALL3D is used to generate ash isopach map. This isopach map would depict how the ashes are distributed and also provide the ash thickness amount fallout on to the surrounding region. The input parameters for the simulator are coordinates of the area that would be modeled, meteorological data (wind data), Eruption Source Parameter (ESP), TGSD (Total Grain Size Distribution), settling velocity, aggregation factor, and diffusion coefficient. The TGSD references from many of the investigated volcanoes around the world are used because the incompleteness of Galunggung eruption TGSD data. The meteorological is taken from ERA-Interim reanalysis, which is a global reanalysis of earth’s atmospheric condition and can be accessible through the ERA-Interim website. The ESP must also be determined. Some ESP parameters are the eruption duration, eruption mass column height, and MFR (Mass Flow Rate) of the erupted materials. The duration of the eruption and the column height is adapted from the record book of Galunggung 1982-1983 eruption. The result of the simulation is displayed as contours of ash thickness in the vicinity of the volcano with the ash density of 500 kg/m3 for dry uncompacted ash. The integration of various kind of data is proved to be useful for reconstructing volcanic ash distribution of the Galunggung eruption in 1982. The need of hazard mitigation as well as damage estimation of volcanic ash fallout are necessary if Galunggung volcano erupt in the future.