5:15 PM - 7:15 PM
[HDS10-P05] Variability in Tsunami Height Prediction Due to Heterogeneous Fault Slip: A Case Study in the Marmara Sea, Turkey
Keywords:Marmara Sea, Tsunami Prediction, Heterogeneous Fault Slip
Tsunami prediction is generally conducted by numerical simulations with an initial condition calculated by a fault model. Because slip heterogeneity on a fault significantly affects predicted tsunami height, considering slip heterogeneity has become common for great interplate earthquakes such as the Nankai Trough earthquake. On the other hand, it is also regarded as necessary to account for slip heterogeneity in tsunami predictions for M7-class earthquakes, such as the Noto Peninsula earthquake. However, research and efforts in this area are still in the early stages.
In this study, we focused on the Marmara Sea in Turkey, where M7-class earthquakes are highly probable, and evaluated the variability in predicted tsunamis caused by heterogeneous slip on the fault. We assumed an M6.8 earthquake that may occur on the eastern part of the Prince Islands Fault, with a fault length of 32 km, width of 18 km, strike ranging from 108° to 130°, dip of 70°, rake of 270°, average slip amount of 0.87 m, and an upper depth of 0.74 km. Furthermore, we randomly generated 100 fault models with heterogeneous slip patterns by placing multiple circular sub-events on the fault. Using these heterogeneous slip models, we conducted numerical simulations of tsunami propagation. The topographic data was gridded at 30-arcsecond intervals (GEBCO). For the tsunami calculations, we employed the open-source software JAGURS to solve the nonlinear shallow water equations.
The difference between the maximum and minimum values of the maximum tsunami height among the 100 patterns in the whole computational domain was 1.6 m with a standard deviation of 0.44 m. These values were highest in coastal areas near the epicenter. In contrast, the coefficient of variation of the maximum tsunami height (standard deviation/mean) was estimated to be 0.39, with the highest values occurring near the epicenter. This phenomenon would be related to the shoaling deformation of the tsunami.
Regarding the relationship between maximum tsunami height and the fault model, fault models where all sub-faults slipped almost uniformly tended to produce lower maximum tsunami heights. In contrast, fault models with an isolated large asperity exhibited higher maximum tsunami heights. These results suggest that the slip distribution on the fault has a significant impact on tsunami generation and propagation, providing important insights for improving the accuracy of future tsunami predictions.
In this study, we focused on the Marmara Sea in Turkey, where M7-class earthquakes are highly probable, and evaluated the variability in predicted tsunamis caused by heterogeneous slip on the fault. We assumed an M6.8 earthquake that may occur on the eastern part of the Prince Islands Fault, with a fault length of 32 km, width of 18 km, strike ranging from 108° to 130°, dip of 70°, rake of 270°, average slip amount of 0.87 m, and an upper depth of 0.74 km. Furthermore, we randomly generated 100 fault models with heterogeneous slip patterns by placing multiple circular sub-events on the fault. Using these heterogeneous slip models, we conducted numerical simulations of tsunami propagation. The topographic data was gridded at 30-arcsecond intervals (GEBCO). For the tsunami calculations, we employed the open-source software JAGURS to solve the nonlinear shallow water equations.
The difference between the maximum and minimum values of the maximum tsunami height among the 100 patterns in the whole computational domain was 1.6 m with a standard deviation of 0.44 m. These values were highest in coastal areas near the epicenter. In contrast, the coefficient of variation of the maximum tsunami height (standard deviation/mean) was estimated to be 0.39, with the highest values occurring near the epicenter. This phenomenon would be related to the shoaling deformation of the tsunami.
Regarding the relationship between maximum tsunami height and the fault model, fault models where all sub-faults slipped almost uniformly tended to produce lower maximum tsunami heights. In contrast, fault models with an isolated large asperity exhibited higher maximum tsunami heights. These results suggest that the slip distribution on the fault has a significant impact on tsunami generation and propagation, providing important insights for improving the accuracy of future tsunami predictions.