Chile Tsunami on Apr. 3, 2014

 

We also simulated the tsunami generated from the Chile earthquake (20.518°S, 70.505°W, depth=31.8km, M = 7.6 at 02:43:14 UTC according to USGS) on April 3, 2014 (Fig. 1). The fault length and width are 80 km × 40 km. The focal mechanism is strike:357º, dip:19º, slip:94º from the USGS's W-phase moment tensor solution. The top depth of the fault was assumed to 20 km. The average slip on the fault is 1 m. The seismic moment is 2.2 x 10**20 Nm (Mw = 7.5) 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 the 30 arc-second grid data from GEBCO for coastal tide gauges. For the far-field computation we used 2 arc-minute grid data resampled from the 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 and Tide gauge data from NOAA's and UNESCO/IOC's web sites, respectively, and compared the simulated tsunami waveforms and the observed ones (Fig. 2).

 

Fig.1 Tsunami Source Model
The red lines indicate uplift with the contour interval of 0.2 m. Aftershocks determined by USGS are shown by red (before the event of M7.6) and purple (after the event of M7.6) circles. Focal mechanisms determined by USGS are also shown.

 

Fig.2 Maximum Height of Simulated Tsunami and Tsunami Waveforms
Solid lines in green and purple indicate the observed tsunami waveforms and synthtic ones, respectively.

 

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 2014/4/4