Study of geothermal and volcanic activity at Mount Awu, the deadliest active volcano in North Sulawesi Province, Indonesia using Optical Satellite Imagery

Abstract

The history of the north part of Sangihe Island is the motivation for using the strengths of remote sensing methods to monitor the volcano activities and geothermal potential of Awu Volcano. We used the last 50 years of satellite image data composed by Landsat 1, Landsat 4, Landsat 5, Landsat 7, ASTER, and Landsat 8 to get the multi-temporal analysis and results. This study used the single-channel algorithm to derive land surface temperature (LST). We also used the band combination and ratio to understand the relationship between the Awu Volcano's geological condition and geothermal potential. The NDVI result as a component of the LST calculation shows that the vegetation is increasing when there is no eruption event. However, the amount of vegetation decreased after the 1994 and 2004 eruptions. The LST results show the 2004 eruption gave the highest surface temperature in the last 50 years, with a number of 318.69 °K as the mean value in the caldera. The multi-temporal nature of LST explained the activity of Awu Volcano, including the increased status announced by the Center for Volcanology and Geological Hazard Mitigation (CVGHM) in 2016 and 2021. The accuracy of LST results is seen by the same pattern in the LST provided from the Landsat and ASTER data and the R2 of time and LST with the values of 0.1529 and 0.2436 in the volcano slope and caldera, respectively. The long gap between the phreatic eruption in 1994 and the previous eruption in 1964 revealed that there was a caldera lake formed in Awu Volcano, which was detected by the natural color band combination from 1972 to 1996. The geothermal potential is centralized in the volcano slope around the caldera, with a value of almost 10 °K and some areas in the slope with a value of >5 °K. The first area that contains high geothermal potential is located in the basaltic andesite, with the alteration detected by the combination of bands 7/4, 6/3, and 5/7. Mount Awu's multiple eruptions have shown that multi-source optical satellites could be used to keep an eye on volcanic activity and could also be used as a first step in figuring out geothermal potential.