Scotia Sea Tsunami on Nov. 17, 2013

We have simulated the tsunami generated from the Scotia Sea earthquake (60.296°S, 46.362°W, depth=10.0km , M = 7.8 at 09:04:55 UTC according to USGS) on November 17, 2013 (Fig. 1). The assumed tsunami source is located within the aftershock area during one day after the mainshock (Fig. 2). The fault length and width are 250 km × 20 km. The focal mechanism is strike:99º, dip:50º, slip:-1º 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 3 m. The seismic moment is 6.0 x 10**20 Nm (Mw = 7.8) assuming the regidity of 4 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 30 arc-second grid data from GEBCO. 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 Tide gauge data from UNESCO/IOC's web site and compared the simulated tsunami waveforms and the observed ones (Fig. 3). We can see the tsunami propagation in the Scotia Sea (Fig. 4).

Fig.1 Epicenter and Tide GaugesFocal mechanism is from USGS's W-phase moment tensor solution.

Fig.2 Tsunami Source ModelThe red lines indicate uplift with the contour interval of 0.01 m, while the blue dotted lines indicate subsidence with the contour interval of 0.01 m. Aftershocks (determined by USGS) during one day after the mainshock are also shown by red circles.

Fig.3 Maximum Height of Simulated Tsunami and Tsunami WaveformsSolid lines in red and blue indicate the observed tsunami waveforms and synthtic ones, respectively.

Fig.4 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)

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 2013/11/20