Solomon Tsunami on April 1, 2007

We have simulated the tsunami generated from the earthquake of Solomon Islands (8.453°S, 156.957°E, Mw = 8.0 at 20:39:56 UTC according to USGS) on April 1, 2007. The computed tsunami travel times assuming the point source (epicenter) are shown in Fig. 1.

The assumed tsunami source area corresponds to the low activity area of aftershocks during one day after the mainshock (Fig. 2). The fault size is 230 km × 100 km. Top depth of the fault is 1 km. Average slip on fault is 3 m. The seismic moment is 2.1 x 10**21 Nm (Mw = 8.1) assuming the regidity of 3 x 10**10 N/m**2. The focal mechanism is strike = 300º, dip angle = 14º and slip angle = 82.5º from the source model of Y. Yagi.

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' grid interval resampled from General Bathymetric Chart of the Oceans (GEBCO) 1' grid data. To calculate tsunami propagation, the linear shallow-water, or long-wave, equations were numerically solved by finite-difference method [Satake, 1995].

Fig.1 Tsunami Travel TimesThick contours indicate tsunami travel times in hour.

Fig.2 Tsunami Source ModelThe red contours indicate uplift, while the blue contours indicate subsidence with the contour interval of 0.1 m.

Aftershocks (determined by USGS) during one day after the mainshock are also shown by red circles.

Fig.3 Maximum Height of Computed Tsunami and Simulated Tsunami Waveforms

Fig.4 Tsunami Propagation (Click to start GIF 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 (GSJ, AIST)

ReferencesOkada, 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 2007/4/3