Friday, March 11, 2011

Tsunami Update

Here's a report from Rico's dad at Scripps:

Not to worry. It's arrival coincided with low tide in San Diego (about 10 minutes ago if NOAA got it right) so would be hard to notice. The only serious tsunami damage ever in California occurred from a Chilean and an Alaskan quake, both in the last century, and was limited to one coastal city (Crescent City) near the Oregon border. There is a unique bathymetry here which allows the excitation of oscillatory shelf waves which are shore parallel and are pumped by the tsunami (a classical induced harmonic motion). Southern California, fortunately, does not resonate so we just see a slow rise and fall that is difficult to detect because it is so gradual. Our wave buoys, which measure vertical accelerations, cannot detect the tsunami waves in deep water (order 15 minute periods -- so accelerations are two orders of magnitude less than wind waves). However, we have one pressure sensor left from the old days on the end of Scripps Pier and we have developed special software to filter out tides and wind waves and can record tsunamis as small as a couple of inches. I was very impressed by NOAA's tsunami model. They make a prediction for our gage and for the previous tsunami they hit the arrival time within a few minutes and the height was right on.

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