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.

Sorik Marapi is an active volcanic mountain with an altitude of 2,145 meters located in Batang Gadis National Park, Sibanggor Julu Village, Mandailing Natal Regency, North Sumatra, Indonesia. Since the earthquake in Aceh on December 26, 2004, geological conditions in the western part of Sumatra Island have increased in stress. This affects the volcano in Sumatra, Mount Sorik Marapi, so it needs to be studied to find out the condition of changes in coulomb stress in Sorik Marapi. The method used in this study is a descriptive method with an analysis of the coulomb stress method. From the Aceh earthquake year of December 2004 to 2021, Mount Sorik Marapi experienced the highest average increase in coulomb stress in 2012, which was 0.171 bars. The highest average increase in shear in 2015 was 0.25 bars, and the highest average normal increase in 2018 was 0.202 bars. While at depth, Sorik Marapi mountain experienced an average change in coulomb stress highest of 0.368 bars, the average increase in the highest shear by 0.269 bars, and the average normal increase of 0.246 bars. All such increases are at a depth of 90 km below sea level. Based on the results of this study, it is stated that Mount Sorik Marapi experiences inconsistent changes in coulomb stress every year.

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.

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.