Multi-scale Simulation of tsunami from Tohoku Earthquake and Diffracted Tsunami Waves in Hokkaido ZHU AIYU, Zhang Dongning Institute of Geophysics, China Earthquake Administration Yuen Dave A. University of Minnisota Song Shenyi Computer Network Information Center, China Academy of Science

Outlines  Governing equations and numerical methods  Numerical simulation  Tsunami diffraction  Generation  Propagation  Runup  Inundation

 Governing equations 2D nonlinear shallow water equations  Numerical methods Finite volume method (clawpack) bottom frictional terms

Computing Domain  longitude from 135° to 160°E  latitude from 30 ° to 45°N  DART 21401, DART 21413, DART and DART

Generation  length L=510km  width W=150km  the fault dips δ=14˚  rakes λ=81˚  strikes θ=193˚  average slip D=20m Figure 1 The tsunami source model based on USGS  The first source model

 Figure 5 Offshore DART buoys wave height records versus computed results of the F1 model Figure 5 Offshore DART buoys wave height records versus computed results of the F1 model

Figure 3 (a) Surface projection of the slip distribution superimposed on ETOPO2 ( (b) The tsunami source model based on UCSBhttp://  The second source model consists in a 190 sub-faults system (a)(b)

 Figure 6 Offshore DART buoys wave height records versus computed results of the F2 model

 finite element method,  uses the GPS data for constrain condition Figure 3 The tsunami source model of GPS  The third source model

 Figure 7 Offshore DART buoys wave height records versus computed results of the F3 model

Which is the best source model ?  The arrival times of the first wave, the results of F2 and F3 gives have a generally better agreement with the observed data, but not for case of F1 that is much slower than the observation.  The amplitude of the first wave, all of the model have there bad side and good side It is indeed difficult to distinguish which one is the best

 correlation coefficient Table 1 the correlation relation of the different models Models Buoy gauge Correlation coefficient Average correlation strength F F F The second source model is the best!

Grid is 1800×3000  Propagation Visualized by Avizo Characters: (1) The tsunami wave is split into two waves, one is towards to the northeast coast of Japan, Another wave faces to the Pacific Ocean (2) tsunami wave is that first arriving wave is negative and then the positive wave which agrees with the observed data.

Table 2 Maximum run-up values for calculated and observed values Location Coordinates (Lat,. Long.) Computational height (m) Observed height (m) Shimakita( , ) Hachinohe*( , ) or more Miyako*( , ) or more Ofunato*( , ) or more Onahama( , ) Ohoshigyoko( , ) Mera( , ) Chiba( , ) Okada( , )  runup m m the notation * means the maximum height of tsunami cannot be retrieved so far due to the troubles, and actual maximum height might be higher according to the observed data

Adaptive mesh refinement method  Inundation

Tohoku tsunami diffraction  movie

 Add the Gaussian noise to the topography Topography Topography add Gauss noise

 movies

No flooding phenomenon at Hokkaido Island ? Possible reason  The earthquake source is not exactly correct  The shallow water equations are not a perfect model for the wave motion,  The 1-mintute resolution etopo ocean bathymetry is maybe not fine enough  The Gaussian noise maybe not appropriate

Thank you

Diffraction