San Diego's Tsunami Escape Routes

Hey Matt:

I had a dream that we had a giant earthquake and the entire coast was under tsunami warning. I had to drive to Point Loma and rescue my dog. We lived on Sunset Cliffs across the street from the ocean. I picked up my dog and started driving up Hill Street, with water lapping at my wheels. So, my question is this: is the top of Hill Street high enough away from a tsunami? And just what is the elevation from sea level to the top of Hill Street, anyway? Just want to be sure I have an exit strategy.

— MR, via email

Hill Street’s a pretty good exit strategy. It’s about 350 feet above sea level where it meets Catalina, way higher than any tsunami wave that has hit or is likely to hit San Diego’s coast. Tsunami waves are different from ordinary wind-/weather-generated waves. Both are large balls of energy that pass through water, pushing the water upward as they approach shallower sea bottom. But tsunamis are generated by massive events such as huge coastal landslides, underwater volcanic activity, and earthquakes, especially those caused by subduction activity, one tectonic plate sliding over another. The Pacific “ring of fire” has all these risks, and we’re part of that ring. Far out at sea, tsunami swells are pretty much invisible, unlike wind waves.

Tsunamis are also a series of upwellings that might have a few minutes or an hour or more between the peak of each wave. They don’t break like wind waves but arrive on land like a huge wall of water, then spread inland. Tsunami waves can travel at hundreds of miles an hour. Risk from tsunamis is not only the smash of each wave into buildings and the like, but also from the strong raking power of the wave as it recedes.

So what’s the deal with you and your pup? Well, after the devastating south Asia tsunamis of 2004, the U.S. decided they were napping on the job and needed to reevaluate the Pacific coast’s risk. In 2009, state geologic agencies drew a line down the coast connecting points at 30-foot elevations and looked at geology and history to make a realistic assessment of human risk. About 350,000 coastal Californians could be affected by a tsunami, though none of the potential waves were predicted to be anywhere near 30 feet high at their peaks. The most vulnerable area on our coast is beleaguered Crescent City, so far north of us that, given a few more feet, it would be Oregon’s problem. Though other Pacific Rim countries have experienced tsunami swells of hundreds of feet, California is predicted to suffer, at worst (in Crescent City), waves in the low 20s. If the tsunami precursor is from the north, wave height will diminish as it heads south.

The old risk-assessment map predicted that Coronado could be completely inundated in a tsunami event. The post-2009 map shows that the worst-case scenario would have the city hit by 15- to 18-foot water walls — bad enough, I guess, considering how far inland the water would spill. Our biggest risk is from high-energy geologic activity in Alaska and the eastern Aleutians, though quakes as far away as Chile can affect us.

Hey Matt:

For the last while, I’ve been noticing a phenomenon regarding television commercials. They’re cutting each other off in record numbers. As an example, a car commercial will be cut right off by a drug store commercial and so on and so on. It happens instantaneously. Doesn’t matter which station or the time of day. Even saw this happen between a news station (being cut off) and the following upcoming scheduled program. Don’t they have technical resources in place to keep this from happening? I mentioned this to a friend the other day and she was amazed because she’s observed it too and wondered what the heck is going on. Any ideas?

— Observant Senior Citizen, Sent from my iPad

As usual, plenty of ideas. As usual, it’s human error. As automated as so much of radio and TV are these days, there’s still a human bean in midsystem available to screw something up. When TV shows are sent out to affiliates, complete with national commercials in them, there are spaces in the programs that are available to be filled by local advertisers. At the affiliate station, it’s a human’s job to insert the local commercials into the program stream flawlessly. Get the timing wrong and the local commercial can step on the feet of the preceding commercial. And even at the program’s origin, some semi-techie can mistime the insertion of a national commercial’s beginning with the same result. I don’t know why there should be such a spate of timing problems recently. But, anyway, good observing, Senior Citizen.