No abstract

The islands of Sumatra and Sinabung are located southwest of the Sundaland Continent which is a convergence route between the Indian-Australian Plate that infiltrates to the west of the Eurasian/Sundaland Plate. The increase in activity of Mount Sinabung was preceded by large earthquakes to the west and south while the eruption of Mount Sinabung produced pyroclastics. The purpose of this study is to find out the analysis of coulomb stress from the Sumatra Island earthquake to the pyroclastic flow of Sinabung as data on volcanic disasters. This study used the coulomb stress method with coulomb 3.3. The earthquake data analyzed was Mw, depth, and focal mechanism. The results of the analysis in the form of the direction of the spread of stress and the value of increased coulomb stress in Sinabung in 2014-2016. Sinabung's positive stress coulomb value in 2014 was 0.113 bar with a positive coulomb stress spread angle of 90o against sinabung pyroclastic flow. Sinabung's positive stress coulomb value in 2015 was 0.235 bar with a positive coulomb stress spread angle of 90o against sinabung pyroclastic flow. Sinabung's positive stress coulomb value in 2016 was 0.118 bar with a positive coulomb stress spread angle of 90o against sinabung pyroclastic flow. Coulomb stress analysis affects the direction of prioclastic flow by as far as 180o although it is not the same as the results in the field. This is because the peak of Sinabung has landslides in the southeast-south, thus opening a pyroclastic flow road to the southeast-south.

Sinabung is a small stratovolcano located in northern Sumatra about 50 km northwest of the Toba caldera. On August 27, 2010, it was confirmed that Sinabung experienced a phreatic eruption for the first time in history. Initially the eruption formed a lava dome that fell out on January 10, 2014 forming pyroclastic density currents. An increase in pore fluid pressure in the crust supports Coulomb Failure Friction. Positive coulomb stress values ​​are thought to trigger Sinabung activity. The research uses a combination of Monte Carlo simulation to predict the next earthquake parameters and coulomb stress analysis to determine the direction and value of stress . The Monte Carlo simulation produces earthquake parameter prediction, longitude 98o latitude 3.175o depth 104.5 meters, Mw 6.0, strike 28.125 o, slip 42o, dip 44.17o. Coulomb Stress analysis of the combined 2001-2021 earthquake data produces an average coulomb value of 0.24 bar, 0.14 bar shear, 0.25 bar normal and the direction of the stress vector to the southwest of Mount Sinabung. The results of the combined coulomb stress analysis and Monte Carlo simulation predict the direction of pyroclastic flows to the northeast, east, and southeast of Mount Sinabung, in accordance with the direction that is inversely proportional to positive stress so that the area needs to receive early warning of volcanic eruption natural disasters in 2022.

Research on SST and chlorophyll-a content using GEE Cloud technology in Sibolga Waters has been carried out since February-December 2019. The analysis was carried out using the MODIS AQUA-L3SMI satellite. The SST results showed that it spread evenly from the coast of Sibolga to the sea, which was 28-33 0C and did not fluctuate, while the content of chlorophyll-a spread evenly, from February-April with a value of 0,1-1 mg/m3 varied, namely from June-August, and fluctuations namely in October-December 2019 with an amount of 0,5-2 mg/m3. SST spreads evenly, varies, and fluctuates around the outskirts of Sibolga coastal waters to the middle of Sibolga Waters, which is unsuitable for demersal fish species. Meanwhile, the chlorophyll-a content spreads evenly, varies, and fluctuates. The high content of chlorophyll-a in all waters and the high SST will make a certain type of fish that can live, namely carnivorous fish species. Image data can be used to map SST distribution patterns and chlorophyll-a content in Sibolga Waters.

The TSS research using GEE Cloud Technology in Belawan Waters was carried out from January to May 2021. The analysis was carried out using the Sentinel-2 Satellite. TSS results obtained that the amount is 0,011010879-53,74369064 mg/liter. The content of TSS is spread evenly around the outskirts of Belawan Waters to the Middle of Belawan Waters and has passed the quality standard limit according to the Minister of Environment of Republic Indonesia that means the Harbour area is polluted and improper for drinking water as well as for fish cultivation.