TEPHRA ANALYSIS OF 2010 BROMO ERUPTION AND APPLICATION FOR VOLCANIC ASH HAZARD ASSESSMENT

• Main Author: Qurrata'aini, 'Aisyah
• Format: Final Project
• Language: Indonesia
• Subjects: Geologi, hidrologi & meteorologi
• Online Access: https://digilib.itb.ac.id/gdl/view/71658
• Institution: Institut Teknologi Bandung

As one of East Java's tourist attractions and farming centers, Tengger Complex encountered danger from Bromo’s eruption, which still shows the volcanic activities. To learn more about the threat of eruption, the writer decided to do research that aims to know the mechanism of the eruption along with deterministic and probabilistic modeling of ash fall using TephraProb. This research focused on the largest eruption in the last 50 years, the 2010 eruption. This study used event tree analysis, tephrastratigraphy, physical analysis of tephra such as material properties analysis, ash composition, petrography of bomb, and the morphology of ash, along with deterministic and probabilistic modeling of eruption. Event tree analysis showed that ash fall is the hazard with the highest probability. From tephrastratigraphy and physical examination, it is known that there are four phases of the eruption. The first phase is the vent opening phase which consists of phreatomagmatic eruption; the second phase consists of strombolian eruption; the third phase consists of ash eruption; and the final phase consists of ash and phreatomagmatic eruption. Then, deterministic modeling of the 2010 eruption was carried out, which showed differences in the impact of ash fall from each eruption phase. Based on the modeling carried out, in phase 1, the ash fall is spread as far as ~30 km to the east, ~ 70 km to the southeast in phase 2, ~30 km to the east in phase 3, and ~25 km to the east in phase 4. Finally, a probabilistic analysis was conducted using wind data from 2010-2022 to determine the probability of danger due to ash falls. Based on probabilistic modeling results, modeling throughout the year and in April-August shows that the ash fall will be inclined to the west-southwest. Meanwhile, in September-March, ash fall will lean towards the east. From the probabilistic modeling carried out, it can be seen that the Putus and Wonokitri areas, which are in the east and west of Bromo, have a hazard risk due to ash fall with an accumulation of up to 300 kg/m2. The existing KRB Map cannot convey the collection of ash fall, so other media are needed to inform the risk of danger, especially for tourists and the community around Bromo.