Solomon Tsunamis on Apr. 12 and 13, 2014  


 

We have simulated the tsunamis generated from the Solomon earthquake (11.315°S 162.211°E depth=29.3km, M = 7.6 at 20:14:39 UTC according to USGS) on April 12, 2014 and the aftershok (111.451°S 162.069°E depth=35.0km , M = 7.4 at 12:36:18 UTC according to USGS) on April 13, 2014 (Fig. 1). The assumed tsunami source is located within the aftershock area (Fig. 1).
For the mainshock (M7.6), the fault length and width are 150 km × 30 km. The focal mechanism is strike:116º, dip:74º, slip:24º from the USGS's W-phase moment tensor solution. The top depth of the fault was assumed to 5 km. The average slip on the fault is 0.8 m. The seismic moment is 2.5 x 10**20 Nm (Mw = 7.5) assuming the regidity of 7 x 10**10 N/m**2.
For the aftershock (M7.4), the fault length and width are 60 km × 30 km. The focal mechanism is strike:104º, dip:44º, slip:94º from the USGS's W-phase moment tensor solution. The top depth of the fault was assumed to 10 km. The average slip on the fault is 1.2 m. The seismic moment is 1.5 x 10**20 Nm (Mw = 7.4) assuming the regidity of 7 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. The used bathymetry data is 2 arc-minute grid data resampled from the 30 arc-second grid GEBCO data. To calculate tsunami propagation, the linear shallow-water, or long-wave, equations were numerically solved by using a finite-difference method [Satake, 1995]. We have downloaded the DART data from NOAA's web site, and compared the simulated tsunami waveforms and the observed ones (Fig. 2). We can see the tsunami propagation in the Pacific ocean (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 0.05 m. Aftershocks determined by USGS are shown by red (before the event of M7.4) and purple (after the event of M7.4) circles. Focal mechanisms determined by USGS are also shown.


 

Fig.2 Maximum Height of Tsunami

Fig.2 Maximum Height of Simulated Tsunami and Tsunami Waveforms
 Mainshock (M7.6): Solid lines in red and blue indicate the observed tsunami waveforms and synthtic ones, respectively.
Aftershock (M7.4): Solid lines in green and purple indicate the observed tsunami waveforms and synthtic ones, respectively.


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.


Last Updated on 2014/4/15