introduction

the 1964 Alaska tsunami

three phases of tsunami evolution:
• generation
• propagation
• runup

the model and grids

references

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During the generation phase, a sea floor disturbance due to an earthquake reshapes the sea surface into a tsunami. We assume that this sea surface displacement is the same as the ocean bottom displacement, due to incompressibility of the ocean. Prof. Miho Aoki from the University of Alaska Fairbanks Art Department created an animation that shows how the tsunami wave is generated by a subduction zone earthquake.

We use output of a submarine seismic source model as an initial condition for ocean surface displacement that then propagates away from the source. The amplitude of this initial disturbance is one of the major factors that affect the resulting runup amplitudes along the shoreline. Here we use an algorithm developed by Okada (1985) to calculate the distribution of coseismic uplift and subsidence resulting from the motion of the buried fault. The fault parameters that are required to compute the deformation of the ocean bottom are location of the epicenter, area of the fault, dip, rake, strike, and amount of slip on the fault.

This plot shows a source function for the 1964 event. Squares represent unit subfaults, and numbers represent slip in meters on each subfault. We used this fault dislocation model developed by Johnson and others (1996) that has eight subfaults representing the Kodiak asperity, and nine subfaults in the Prince William Sound asperity. We used the equations of Okada (1985) to calculate the distribution of coseismic uplift and subsidence resulting from the given slip distribution. Then, the derived surface deformation was used as the initial condition for tsunami propagation.