Tsunami Hazard Analysis of Future Megathrust Sumatra Earthquakes in Padang, Indonesia Using Stochastic Tsunami Simulation

Abstract

This study assesses the tsunami hazard potential in Padang, Indonesia probabilistically using a novel stochastic tsunami simulation method. The stochastic tsunami simulation is conducted by generating multiple earthquake source models for a given earthquake scenario, which are used as input to run Monte Carlo tsunami simulation. Multiple earthquake source models for three magnitude scenarios, i.e., Mw 8.5, Mw 8.75, and Mw 9.0, are generated using new scaling relationships of earthquake source parameters developed from an extensive set of 226 finite-fault models. In the stochastic tsunami simulation, the effect of incorporating and neglecting the prediction errors of earthquake source parameters is investigated. In total, 600 source models are generated to assess the uncertainty of tsunami wave characteristics and maximum tsunami wave height profiles along coastal line of Padang. The results highlight the influence of the uncertainty of the scaling relationships on tsunami simulation results and provide a greater range of tsunamigenic scenarios produced from the stochastic tsunami simulation. Additionally, the results show that for the future major earthquakes in the Sunda megathrust, the maximum tsunami wave height in Padang areas can reach 20 m and, therefore, significant damage and loss may be anticipated in this region.

Tsunami evacuation plans for future megathrust earthquakes in Padang, Indonesia, considering stochastic earthquake scenarios

“…Muhammad et al (2016) concluded that the regional earthquake source parameters calculated from the 19 past Sunda earthquakes are in good agreement with these scaling relationships; subsequently, the global models are adopted in this study. A set of 100 source models is then generated for each magnitude.…”

“…In addition, in terms of selected magnitude scenarios, three scenario magnitudes are considered: M w 8.5, M w 8.75, and M w 9.0. The magnitude M w 8.5 is used as the minimum scenario because the tsunami hazard produced from the magnitude below this level, e.g., M w 8.25 and M w 8.0, is relatively small (less than 1 m wave height in the coastal areas; see Muhammad et al, 2016). The maximum magnitude scenario (M w 9.0) is selected based on paleogeodetic, geodetic, and paleotsunami studies (Zachariasen et al, 1999;Natawidjaja et al, 2006;Sieh et al, 2008); they indicated that the accumulated slip in the Mentawai segment of the Sunda subduction zone may generate tsunamigenic earthquakes with a magnitude range from M w 8.8 to M w 9.0.…”

“…It is carried out by estimating earthquake source properties including geometry (fault length, L, and fault width, W ), slip statistics (mean slip, D a , maximum slip, D m , and Box-Cox parameter, λ), and spatial heterogeneity parameters (correlation length along strike direction, A x , correlation length along dip direction, A z , and Hurst number, H ). Those parameters are calculated using the effective dimension analysis method (Mai and Beroza, 2000), Box-Cox analysis (Goda et al, 2014), and spectral analysis (Mai and Beroza, 2002); see Muhammad et al (2016) for the details.…”

“…In the coastal areas where people can afford a relatively short evacuation time (less than 30 min), the vertical evacuation is highly desirable (Scheer et al, 2012;Wood et al, 2014). In previous investigations, the tsunami arrival time in Padang was estimated to be 20-30 min (Borrero et al, 2006;McCloskey et al, 2008;Schlurmann et al, 2010;Muhammad et al, 2016) and, therefore, effective vertical evacuation plans are needed in this region. In Padang, 23 tsunami evacuation shelters (TESs) have been planned and built in the urban areas near the coastal line.…”

“…In previous investigations, those regional earthquake characteristics have not been properly taken into account (McCloskey et al, 2008;Griffin et al, 2016). Recently, Muhammad et al (2016) have evaluated the tsunami potential in Padang by developing the stochastic tsunami simulation method, allowing us to generate numerous scenarios of stochastic tsunami hazard. However, that work was limited to evaluating the tsunami hazards offshore and near the coast only because of the gross bias of the elevation model in Padang (Griffin et al, 2015) and, therefore, was not suitable to carry out rigorous assessment of tsunami mitigation systems.…”