VISCOELASTIC LITHOSPHERE DEFORMATION MODEL BASED ON FAULT STRENGTH PARAMETERS TO SIMULATE STRAIN ACCUMULATION AROUND THE NORTHERN GREAT SUMATRAN FAULT

• Main Author: Ain Bening, Maulidia
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/67340
• Institution: Institut Teknologi Bandung

The Great Sumatran Fault is a 1900-km strike-slip fault and divided into northern, central, and southern parts. Each part has its fault strength, deformation pattern, and seismic history. Based on its seismic activity, The Great Sumatran Fault has generated many large earthquakes along the fault. These earthquakes occur when the strain accumulated is suddenly released along the fault. Therefore, modeling the accumulated strain on the lithospheric deformation is one way to understand the seismicity pattern in the northern Sumatran Fault. The strain accumulation model was carried out based on the fault strength in the northern Sumatra Fault, especially the North Aceh, Central Aceh, South Aceh, North Tripa, South Tripa and Renun segment, according to the average slip rate observed. The lithosphere deformation of the northern Sumatra Fault is modeled using the finite-element method by applying elastic materials in the upper crust and viscoelastic materials in the lower crust and upper mantle. Based on the viscoelastic lithosphere deformation model, locking and creeping events appear to affect the deformation where the locking percentage is 75%, in accordance with the average slip rate of 15-16 mm/year in the Sumatra Fault. However, the subduction and forward arc sliver movement need to be considered to model the lithosphere deformation. Adding the effect of fore-arc sliver movement can shorten the strain accumulation process by up to 2.7x shorter. From these models, we obtained the friction coefficient for each segment, e.g., North Aceh is 0.06, Central and South Aceh is 0.07, North Tripa is 0.08, South Tripa is 0.13, and Renun is 0.21. The model with different friction in each segment is in accordance with the seismicity pattern in the northern Sumatra Fault. Still, the effect of stress transfer due to earthquake subduction, especially in the North Tripa and South Tripa areas, needs to be considered. Furthermore, a small difference in friction strength (0.01) in the Aceh Utara-Aceh Tengah and Aceh Selatan-Tripa Utara segment can also explain the earthquake that occurred at the boundary between these segments.