Sulawesi Tsunami on Sep. 28, 2018  


 

We have simulated the tsunami generated from the Sulawesi earthquake (0.178°S, 119.840°E, depth=10.0 km, M = 7.5 at 10:02:43 UTC according to USGS) on Septmber 28, 2018 (Fig. 1). The assumed tsunami source is located within the aftershock area (Fig. 1). The fault length and width are 100 km × 10 km. The focal mechanism is strike:350º, dip:67º, slip:-17º from the USGS's W-phase moment tensor solution. The top depth of the fault was assumed to 0 km. The average slip on the fault is 4.5 m. The seismic moment is 2.25 x 10**20 Nm (Mw = 7.5) assuming the rigidity of 5 x 10**10 N/m**2. As the initial condition for tsunami, static deformation of the seafloor is calculated for a rectangular fault model [Okada, 1985] using the source model. To calculate tsunami propagation, the non-linear shallow-water equations were numerically solved by using a finite-difference method [Satake, 1995]. The used bathymetry data is a 12 arc-second grid data resampled from GEBCO_2014 for the near-field computation. We show the simulated tsunami waveforms with the maximum tsunami height (Fig. 2). We also show the tsunami propagation in the animation (Fig. 3).


 

Fig.1 Tsunami Source Model

Fig.1 Tsunami Source Model
 The red lines indicate uplift with the contour interval of 0.05 m, while the blue dotted lines indicate subsidence with the contour interval of 0.1 m. Aftershocks and foreshocks determined by USGS are shown by red and purple circles, respectively. The focal mechanism determined by USGS is also shown.


 

Fig.2 Maximum Height of Tsunami

Fig.2 Maximum Height of Simulated Tsunami and Tsunami Waveforms
 Solid lines in purple indicate the calculated tsunami waveforms with the effect of horizontal deformation by Tanioka and Satake (1996).


Fig.3 Tsunami propagation

Fig.3 Tsunami Propagation (Click to start animation)
The red color means that the water surface is higher than normal sea level, while the blue means lower.


 

by Yushiro Fujii (IISEE, BRI) and Kenji Satake (ERI, Univ. of Tokyo)
 
 
References
Okada, Y. (1985), Surface Deformation Due to Shear and Tensile Faults in a Half-Space, Bull. Seismol. Soc. Am., 75, 1135-1154.
Satake, K. (1995), Linear and Nonlinear Computations of the 1992 Nicaragua Earthquake Tsunami, Pure and Appl. Geophys., 144, 455-470.
Tanioka, Y. and K. Satake (1996), Tsunami generation by horizontal displacement of ocean bottom, Geophys. Res. Lett., 23, 8, 861-864.


Last Updated on 2018/10/4