[HDS08-10] Determination of Appropriate Source Models for Tsunami Forecasting: Application to Large Earthquakes in Central Sumatra, Indonesia
Keywords:Tsunami forecast, Tsunami numerical simulation, Central Sumatra
An advanced method to determine appropriate source models that can explain the tsunami heights along coastal areas is needed for tsunami warning purposes. In this study, fault parameters were estimated from the W-phase inversion and fault length and width were calculated from suitable scaling relations between those and magnitude for the 2007 and 2010 earthquakes. Tsunami numerical simulations were conducted using various slip amounts or corresponding rigidities. The best slip amount or corresponding rigidity was selected by comparing the measured and computed tsunami heights.
The 2007 great Bengkulu earthquake (Mw 8.4) was a typical interplate earthquake that occurred at the subducted plate interface. The measured tsunami heights along the coast of Sumatra Island were well explained by the computed tsunami from the source model estimated by our method using the rigidity of 3.0 × 1010 Nm-2 (7.59-m slip amount). This rigidity is consistent with the depth dependent rigidity curve estimated by Tanioka et al. (2017) at an estimated depth of 30 km (Figure). The 2010 Mentawai tsunami earthquake (Mw 7.8) occurred at the plate interface near the trench. The measured tsunami heights along the coast of Mentawai Islands were also explained well by the computed tsunami from the source model estimated using the method with a rigidity of 1.5 × 1010 Nm-2 (8.17 m slip amount). This rigidity is slightly larger than the depth dependent rigidity curve estimated by Tanioka et al. (2017) at an estimated depth of 17 km (Figure). These results indicate that the rigidity differences along the plate interface as suggested by Bilek and Lay (1999) have a considerable impact on tsunami height estimation as also suggested by Tanioka et al. (2017). These results also suggested that a blue dashed line in Figure should be used for the rigidity estimate along the plate interface off Sumatra in Indonesia. Therefore, appropriate slip amounts of source models for tsunami forecast in this region can be estimated rapidly using the results of W-phase inversion and this depth dependent rigidity (a blue line in Figure).
Bilek, S. L. & Lay, T. (1999). Rigidity variations with depth along interplate megathrust faults in subduction zones. Nature, 400, 443–446.
Tanioka, Y., Miranda, G. J. A., Gusman, A. R. & Fujii, Y. (2017). Method to Determine Appropriate Source Models of Large Earthquakes Including Tsunami Earthquakes for Tsunami Early Warning in Central America. Pure and Applied Geophysics, 174, 3237–3248.