Alaska Earthquake and Tsunami: 50 years on

Steve's picture

March 27, 2014 marks the 50-th anniversary of the Great Alaska Earthquake and Tsunami.  Although perhaps not an occasion for cake and ice cream, it certainly is an occasion for thought regarding both historical and future earthquake disasters. Who can say, 50 years from now we might be reminiscing about the Great Cascadia Earthquake and Tsunami of 2015.    

Scientifically, the 1964 magnitude 9.2 quake was a landmark.  Analysis of both seismograms and geodetic movements conclusively proved for the first time that massive ruptures around the Pacific Rim are “thrust type”.  Prior to this, legitimate debate flowed as to whether all Pacific Rim quakes were “strike slip type”, like those on California’s San Andreas Fault.

Moreover, extensive measurements of the tectonic deformation of the 1964 event first quantitatively linked the pattern of coseismic uplift and subsidence with the pattern, size, and timing of subsequent sea waves.  

On the other hand, the quake “muddied the tsunami water”, so to speak, because the majority of wave damage in interior Alaska resulted from shaking-induced landslides and slumps, not large-scale tectonic uplift offshore.  It took a long time for scientists to sort out these complications.

Still, after 50 years, the Alaska tsunami holds the record for wave-related property damage on the United States west coast. Part of the reason for this was the radiation pattern of the quake. Tsunami aren’t emitted equally strongly in all directions you know. The biggest waves run out perpendicular to the long direction, or strike direction, of the fault.  If you are in this ‘Flashlight Beam’, as I call it, you get lit up with tsunami. In 1964, the U.S. west coast found itself in the beam.

I made this movie to overview the Alaska tsunami and related issues. (Can you see the Flashlight Beam bearing down the coast?) The movie also broaches that forever over-your-shoulder question,  “where next”.

I don‘t know, maybe a little cake and ice cream really would be in order.

Here’s looking at you ’64.

Steven N. Ward   Santa Cruz

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