Tsunami Damage in Newport Beach?

11 03 2011

Got your attention!  No damage to report here.

It seems like every year we all learn a little more about tsunami’s and what they can do to low lying beach areas.

Inspiration Point, Corona del Mar, 8:45 am, 3/11/11

So, always in the pursuit of learning, I thought I’d stop by my local tsunami-watching area after the 8.9 earthquake in Japan today — Inspiration Point in Corona del Mar (Newport Beach, California).  I was there when the first surge hit the beach (or so it seemed).  I obviously wasn’t the only one there.   There had to be at least 100 fellow gawkers.  We had the all-girl (30 somethings) running club, the homeless guy with the guitar, all sorts of tourists, dogs, and construction workers.

So, what happened?

If you read my posting on tsunami physics, you know the answer.

Over a few minutes, you could see the water advance up the beach a foot or so (vertically).  The tide was supposed to be at its lowest point, so the rise would not be expected.  The second photo shows the high tide markings from overnight.  The water advanced to about 8 to 10 feet (horizontally) from that high mark.  So, yes we all got to see a tsunami, but none of the rest of the crowd seemed to notice.  I guess they all need to check out TrestlesSurfCrowd.com next time an earthquake happens.

Tide/tsunami levels at Corona del Mar

So, the real show wasn’t the tsunami.  It was the tsunami watchers.  We had the typical silicone-enhanced coffee-sippers, the retired engineers waiting for their next cruise ship, the construction workers stopping by on the way to Home Depot, the spoiled 2-year-olds tugging on their mother’s sweaters while the mothers gab away on their iPhones, and the rest of us faceless people watchers.

I left after the first surge, having seen what I came for.  The rest will probably be waiting out there through lunch waiting for the Hawaii Five-O grinder to take out the houses on the cliff.

Can’t wait til the next earthquake.  Fascinating stuff, huh?





Tsunami Physics and Trestles

28 02 2010

Waves On The Way To Trestles

With the tragic 8.8 earthquake in Chile generating a tsunami that traveled across the Pacific, the question arises again — “Just what is a tsunami (Japanese for ‘harbor wave’)?”  We add “How will it affect Trestles?”

The news cams and looky-loo’s run down to the beach looking for a Mav size set to wash away all the local fish taco stands, but are sorely disappointed when they find out the tsunami passed by without even a splash.  That’s because while tsunamis are waves from a physics standpoint, they don’t behave like the waves most people are used to seeing in news photos and movies like Big Wednesday.

Ocean waves range in velocity, wavelength and frequency from wind chop to twice-a-day tides.  Tsunamis fit in the ocean wave spectrum somewhere between surf beat and tides.   So, they behave more like a big surge.

Ordinary wind-driven waves, like the ones breaking yesterday at Snapper Rocks, range from about 5 to 15 seconds in period between waves.  Surf beat varies greatly, but it is the more correct term for what surfers call “sets.”  When I was a kid, the old pro’s on the beach would say that every 9th wave was a big one.  That was a wild guess.  Surf beat frequency and period actually depend on a lot of variables, like wave height, velocity, and frequency, not to mention the shape of the ocean bottom (bathymetry) across which they travel.   With that said, surf beat is a multiple of wave periods.  For example, every ninth 10-second wave would mean the surf beat is 90 seconds.  Tides average about 12 hours between peaks.   Tsunamis are somewhere in between.

Tsunami Wave Geometry

This diagram, borrowed from EnchantedLearning.com, shows the difference in wavelength and velocity between deep water travel and shallow water travel for tsunamis.  It is obvious that tsunamis are greatly affected by bathymetry and ocean depth.

For more on tsunami physics, here is a great link.  I especially like the video on one of the pages on this site that shows how the 1960 Chile earthquake tsunami traveled across the Pacific.  It shows graphically why tsunami effects are so difficult to predict.  That’s why it is better to be safe than sorry when responding to tsunami alerts.

http://www.geophys.washington.edu/tsunami/general/physics/physics.html

In Southern California, nobody was really able to absolutely detect the tsunami as it passed, because it was mid-tide when it was predicted to occur.   But, if it had shown up a few hours earlier, at spring (seasonal high) tide, the story may have been a little more tragic for some low lying areas like Capistrano Beach or even Newport Beach.

As for Trestles, it was a Victory at Sea day, so a little more tsunami confusion would have just blended into the background.  The train tracks are still there.