The words "earthquake" and "ozone" are two terms you don't often find used in the same sentence. Like "congress" and "effective", or "health food" and "delicious." And yet, MSNBC recently published a news item whose title did just that: "Is ozone gas an earthquake precursor?"
As it turns out, when rocks such as basalt and granite are crushed, they produce substantial quantities of O3 – ozone gas. According to researchers at the University of Virginia, the amount of ozone released varied between 100ppb and 10ppm. To put that into perspective, the low end of this range is comparable to a very smoggy day in Los Angeles (1). The high end is 100x worse.
So I guess now we’ve got yet another reason to hate earthquakes: they split houses, swallow cars, and pollute the air. Although, perhaps if a quake destroyed enough cars this would offset the amount of ozone released. But I digress. The real question here is, “Can elevated ozone concentrations predict earthquakes?” Well according to researcher Catherine Dukes, no, not really: “It’s just a way to warn that the Earth is moving and something — an earthquake, or a landslide or something else — might follow.”
I suspect that any rock crushing action which produces ozone is also detectable via seismograph (although I’m just guessing). So perhaps this discovery isn’t so useful.
But crushed rocks producing ozone? This is still a rather strange phenomenon. Scientists are not yet certain of the precise mechanism at work here, but suspect that differences in electric charge between rock surfaces are the most likely cause. As you may know, lightning strikes are another natural means of ozone formation, particularly in the upper atmosphere where ozone is more beneficial (2). While the strike itself does not directly form ozone, it breaks apart O2 into atomic oxygen, which may then recombine as O3 (3). Lightning also yields nitrogen oxides (also a popular automotive pollutant) which, in the presence of sunlight, react with other chemicals to form ozone (4). So the theory here is that differences in electric charge between the crushed rocks are producing small electrostatic arcs (miniature lightning strikes) which lead to the formation of ozone.