Tuesday, May 04, 2004

Gutenberg, Richter, Omori, Mallet, Mercalli, Love, Lamb, Rayleigh, Jeffreys, & Benioff:

Argh. NBC's show "10.5" has done a lot of damage! To science, that is. What a bunch of hooey. I put this one firmly in a category with "The Core" and "Armageddon." Just watching the little toy train collapse into an opening crevice made me cringe, and I lost interest.

Here's my (short) list of serious scientific problems and outright inaccuracies in NBC's 10.5:

  • First off, the title: 10.5 refers to the magnitude of the supposed earthquake. Earthquake magnitudes are on a logarithmic scale, so a 10.5 is ten times bigger than a magnitude 9.5, which happens to be the largest recorded earthquake. Logically enough, earthquake magnitudes also depend on the size of the fault surface that ruptures - the larger the surface that lets go, the more energy is released. The 9.5 that occurred on May 22 1960 in Chile was from a fault surface over 1,000 km long with about 200,000 km^2 of total fault rupture area. A 10.5 earthquake, releasing ten times the energy, would need between 1,250,000 and 2 million km^2 of fault area. Since most faults in California reach only a few tens of km into the earth, this would mean that the fault would have to be about, oh, say 10,000 to 60,000 km long. Umm, I don't think so. Earthquakes this big are impossible.
  • Sealing the fault with nuclear bombs? Oh please. Let's just compare energies for a moment. On December 10 I noted that a magnitude 4.5 earthquake releases about 100 kt of energy. A 10.5 earthquake would release about 100 Gt of energy. Yes folks, 100 GIGAtons. You would have to lock the fault against that kind of energy. A totally back of the envelope estimate, I know, but say we tried to equal that energy with our biggest bomb, the B53, which can get up to a 9 Mt yield. We'd need 11,000 bombs. Oh wait, we only have 50 of them. ...let's throw in the next biggest as well, the B83, with yields up to 1.2 Mt. Even counting all the energy from the B53's, we would still need 83,000 B83's, and we only have 650 of those. You see where I am going with this. It wouldn't matter if the Russians, the British, the French, the Chinese, the Indians, the Pakistanis, the Israelis, the South Africans and the North Koreans gave us their entire stockpiles. We couldn't bounce enough rubble, even if this kind of technique would work.

Of course, that kind of analysis is rubbish, given the first point. But it clearly points out that NBC does not understand logarithms, and also that the earthquake magnitude scale is pretty useless when you get that big.

So what is the biggest earthquake possible? My guess is that a fault area two to three times the size of the 1960 Chile event is possible. In terms of magnitude, that translates to about 9.8 to 9.9.

I don't want to think about what would happen if one of these events were to arrive - NBC didn't get the specifics right about the phenomena. There would be no large gaping (mawing!) crevices, no California dropping off into the ocean, but they did get things right about many structures collapsing (but not the Golden Gate or Space Needle), and about rushing water. Probably the worst part about an event like this would be the tsunami. More about coastal tsunamis in another post.

I toss a concessionary bone to seismologists here: I have ignored the issue that there are different kinds of magnitude, and have simply used body wave magnitude, M(w).

I was happy to notice an article in EOS' GeoFIZZ column (login required) today by Los Alamos' Andrew Newman which also went through this exercise. Newman points out that a 10.5 would be ten thousand times as big as the 1994 Northridge quake. Newman also answered the question "When will California drop off into the ocean?" His answer: "During sweeps week."

Of course, there are plenty of people out there picking on movies and TV series like these. Here are two of those sites: http://www.nitpickers.com/ and http://www.moviemistakes.com/.

I'm amazed people have this much time on their hands.

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