Our speaker today was Dr. Bruce Jaffee from UCSC. He spoke about near shore hydrodynamics with an emphasis on catastrophic events. He began by asking us about the highest Tsunami event which was in Alaska in 1958. The most deadly tsunami was in Indonesia where over 220,000 people were killed. Oldest tsunami ever happened 60 million years ago and helped to wipe out the dinosaurs.
He began studying tsunamis in 1990. He told us if there is a tsunami go up and inland. They wreak havoc in harbors particularly. There are 4 stages to a tsunami: generation, transoceanic vs local propagation and runup. Most are generated by earthquakes, but also underwater volcanoes, asteroids and any even that displaces water can cause. Convergent boundaries are what creates large tsunamis. They can move very fast if the water is deep. For water10 meters deep they would be 20 mph. If the ocean depth is deeper the waves gets higher and faster up to the speed of a jet liner. As the wave moves the peaks get closer and higher. Wave length of the wind waves are set by the weight scale of what is uplifted. Depending on the topography the wave can take different forms.
Dr. Jaffe showed us many interesting videos and shots of tsunamis occurring around the world including Samoa, Japan, Papua New Guinea, Sumatra, Alaska and even Crescent City. He ended up talking about tsunami risk in Santa Cruz which could come Alaska and Chile as well as other sources across the Pacific. Luckily our chances are quite low due to the type of faults the San Andreas and San Gregorio are. How much time do we have to escape? Generally time to prepare unless it’s the one in Monterey county which could be as soon as 5-15 minutes.