Shaking It Off

I've generally been avoiding the coverage of the earthquake in Japan, because as an Angeleno who's lived through a large earthquake only a few miles from my house, the orders of magnitude from that tremor to 8.9 is terrifying.

Still, I've started to see references to a USGS report estimating deaths and damage in a California quake:

A magnitude 7.8 quake in California — Japan’s quake was 30 times more powerful — would kill at least 2,000 people and cause $200 billion in damage, a United States Geological Survey estimates.

The Week via Tumblr (Note that even The Week's Tumblr writer misstated its own article, calling it "a United States Geological Survey", instead of "a United States Geological Survey study.")

The USGS report in question is "The ShakeOut Scenario," which was a detailed model of the effects of a large earthquake in Southern California. It was prepared as part of a push to better prepare Southern California for the occurrence and aftermath a large quake, and the results were used in planning, regulations, and in modeling large-scale drills as part of The Great Southern California ShakeOut, which has grown to become The Great California Shakeout. This year, the project will include Oregon and British Columbia, and eight states in the central U.S.

This 2008 study was to create a very detailed model of a very particular hypothetical earthquake. This quake would be large (7.8 moment-magnitude) and focused on the San Andreas Fault. This is a relatively likely scenario, which is why it was chosen, but it isn't the only kind of earthquake that could hit Southern California.

So what does the study say? Here's the executive study on deaths:

Because of strong life-safety building codes over the years, the ShakeOut Scenario estimates only approximately 1,800 deaths, of which about half occur because of the fires following the earthquake. There will also be about 750 people with very severe injuries who will require rapid, advanced medical care to survive. Approximately 50,000 people will have injuries that need emergency room care. The final mortality could increase if hospitals cannot function because of damage or if the transportation disruptions prevent people getting to emergency rooms.

Because the quake was modeled to be far from the coast, the tsunami possibility was negligible, but fires figure heavily in the aftermath of the ShakeOut scenario. It's likely that fires will start either in areas close to brush, or in clusters of wood-framed housing, which will allow them to spread rapidly. There's also a likelihood of water supplies being disrupted, which could make fighting fires harder. For the dollar value, here's the table adding it up, with values in billions of 2008 dollars:

Building Damage: $32.7
Related Content Damage: $10.6
High-Rise Building Damage: $2.2
Related Content Damage: $0.7
Fire Damage: $40.0
Related Content Damage: $25.0
Highway Damage: $0.4
Pipeline (water, sewer, gas) Damage: $1.1
Sub-total Property Damage: $112.7

Business Interruption: $96.2

Relocation Costs: $0.1
Traffic Delay Costs: $4.3
Sub-total Additional Costs: $4.4

Total: $213.3

The scenario measures "economic losses" which includes damage and the loss of stock, as well as the amount of loss caused by having to shut down for a period of time. And note that, again, fires after the quake result in more than half of the modeled cost of damages.

There's other interesting things in the report, including the fact that because the fault is located in San Bernadino county, the damage and loss of life will be focused there, not in Los Angeles or Orange County. There's also the modeling of steel-structure high-rises collapsing, which was done a bit off-the-cuff because nothing similar had occurred. (Did any high-rises collapse in Japan due to shaking? All I can find when I search for it is 9/11 conspiracy theorists.)

So that's what the numbers mean.

Looking Up?

Incidentally, while obviously it's useful to prepare for the Big One around LA, it's probably not going to get as big as Japan.

"What's especially important in the U.S. is we expect an even larger earthquake on our own Cascadia Subduction Zone," said Heaton, specifying that related hazards are located in Northern California, Oregon, Washington and British Colombia - not along the San Andreas fault that runs through inland Southern and Central California.

"We don't believe we could have an 8.9 here," Heaton said.

"If you want the Big One, you'll have to go to Portland," remarked Lucy Jones, chief scientist for the USGS Multi-Hazards Demonstration Project for Southern California.

Graves explained that known faults in Southern and Central California simply don't have long structures like the Subduction Zone that caused the Japan quake.

"We just don't have these types of structures in Southern California. "I wouldn't say it's impossible, but certainly it would be unprecedented," he said.

"Caltech Scientists Eagerly Await Lessons from Monster Quake," San Gabriel Valley News.

Earthquakes in the Northwest won't be a surprise to those familiar with another geological catastrophes, but 9.0 is still pretty huge to consider for that areas, and a quake that large would affect a wide range, as it has in Japan.