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Do Earthquakes Spread Like Wildfire?
sciencehabit writes "A simple model of forest fires could help explain the distribution of the sizes of earthquakes and their aftershocks, a theoretical physicist says. In the so-called Drössel-Schwabl model, trees sprout at random on a square grid like a vast checkerboard. Once the forest gets dense enough, lightning sets a random tree on fire, and fire spreads instantaneously among trees that occupy adjacent squares. The conflagration continues until there are no more neighbors to jump to. Then, the process starts all over again. In the team's model, the 'forest' is the plane of a fault cutting through Earth's crust, divided into a 10,000-by-10,000 grid. Sprouting trees correspond to the buildup of stress along the fault; burning areas, to the part of the fault that moves during a quake."
do a car analogy instead?
Very well.
In the so-called DrÃssel-Schwabl-rossdee model, Ford Pintos sprout at random on a square grid like a vast checkerboard. Once the traffic jam gets dense enough, a minor collision sets a random Pinto on fire, and fire spreads instantaneously among Pintos that occupy adjacent squares. The conflagration continues until there are no more neighbors to jump to. Then, the process starts all over again.
(Yes, I'm aware that Pintos weren't in reality the blazing firetraps I'm using them as here. Artistic license ftw!)
http://xkcd.com/793/
It's been known for a while that the distribution of forest fire and earthquake severities exhibits "scale invariant" properties, and it is thought that both are due to some sort of self-organized criticality phenomenon.
However, the problem with SOC is that a lot of things that are called "scale free" aren't, in fact, and they just *look* that way because it's easy to make things look linear on a log-log plot. Will consult some graduate class notes and respond to this comment with citations to back this up.
But, in general, my point is that it's not new or revolutionary to find structural similarities between earthquakes and forest fires, and it's not surprising that a model could be built from the same principles. But that doesn't mean at all that this model explains the mechanisms behind earthquakes.
The wildfire model appears to ignore some parameters encountered in wildfires: air temperature, insolation, wind speed and patterns in 3D, terrain, relative humidity, moisture in the plants, winds created by the fire, litter, and some interactions between the local winds and those created by the fire, to name a few. Perhaps there are analogs in the model.
It would have been more accurate to title this: "Do Earthquakes Spread as a Wildfire Model Predicts Wildfires Spread?"
Never the less, it's ingenious.
Nate