As Saint Patrick’s Day was beginning to dawn here in Los Angeles, most people in the central and western side of the city were abruptly awakened just after 6:30 a.m. by a 4.4 magnitude quake on the north side of the Santa Monica Mountains, near Woodland Hills, where I teach geology at Pierce College. It awoke my family during the 2-5 seconds of shaking, but I slept through it. I’ve been through the 1971 Sylmar quake, the 1987 Whittier quake, the 1994 Northridge quake—every major quake here since I was born in the region, so a piddling 4.4 doesn’t even rattle me. I even was lucky enough to experience a rare Eastern earthquake when I felt the Virginia quake of August, 2011, from the top floor of the Frick Wing of the American Museum of Natural History.
We immediately turned on the news and got the basic information about the quake, as the magnitude was downgraded from 4.7 to 4.4 when better data came in, and the location was moved from Westwood to Sherman Oaks, closer to the actual fault line on the north side of the Santa Monica Mountains. Most of the reporting was competent, although in the early stages, it’s largely silly stuff like “Did you feel it?” and “What did it feel like?” rather than anything accurate or scientific that would tell us something important about the quake. Sure enough, sooner or later it was bound to happen: one of the “man-on-the-street” interviewees spouted the geologists’ least favorite myth: “Oh, it was warm yesterday, so there must have been earthquake weather.” Fortunately, the news anchor was smart enough to dismiss this urban myth and move on to another interview, but if you surfed the internet, it was full of claims that “earthquake weather” must have caused this quake. (Geologists’ other pet peeve: people—especially news anchors and reporters—using the term “tidal wave” for tsunamis, which have nothing to do with tides. Fortunately, the lessons of the Dec. 26, 2004, Sumatran quake and tsunami seem to have reduced the incidences of these displays of ignorance ).
The myth of “earthquake weather” goes back all the way to Aristotle, who thought earthquakes were generated in underground caves as the air was trapped during hot, sultry days, and supposedly shook the earth when it swirled around in the cave. This myth, like most of the fanciful notions that Aristotle dreamed up about nature, persisted for over two thousand years, as the monks faithfully copied the ancient texts, and the Church came to regard Aristotle as the final authority on nature, even when he was clearly and demonstrably wrong. It took brave scientists like Galileo to demonstrate that the pleasing and intuitive notion that heavy objects fall faster was in fact wrong, with his famous cannonball experiment on top of the Leaning Tower of Pisa. Not until Newtonian physics and Darwinian biology come along did most of the rest of Aristotle’s false ideas about science gradually get debunked, and be replaced by scientific explanations from actual observation and experiment, not intuitive fantasies. It was not until of the 1906 San Francisco quake that it was finally proved that earthquakes are caused by movement on fault lines, not air moving in and out of caves, or the wrath of God, or any such other mythic idea.
They stories of “earthquake weather” are a classic example of false correlation. People are sensitized to all the events going on during a traumatic earthquake, and especially if the weather is hot and sultry and uncomfortable just before the quake, they make the false connection that the weather caused the quakes. According to W.J. Humphreys back in 1918, “earthquake weather” is a psychological manifestation. Humphreys argued that “the general state of irritation and sensitiveness developed in us during the hot, calm, perhaps sultry weather given this name, inclines us to sharper observation of earthquake disturbances and accentuates the impression they make on our senses, so that we retain more vivid memories of such quakes while possibly over-looking entirely the occurrences on other more soothing days”.
The “earthquake weather” myth also demonstrates confirmation bias: we remember when one or two quakes happened during “earthquake weather”, but fail to notice the weather during most the quakes we feel. But the data on earthquakes have been analyzed hundreds of times, and there is absolutely no correlation between any weather phenomenon and the occurrence of quakes. Earthquakes happen around the clock every few minutes somewhere, and in active areas like California, we get many small quakes in a day, and large ones every few years or so somewhere in the state. But we never feel most of these quakes, so we never notice them. Yet one minor quake happens after a hot day, and BOOM! People are blathering on and on about “earthquake weather.” But if you think back to the last few major quakes in the Los Angeles area, none happened during hot weather spells. The Jan. 17, 1994, Northridge quake happened at 4:30 in the morning on a cool winter day, as did the February 9, 1971, Sylmar quake at about 6:00 in the morning, also in winter. The Oct. 1, 1987 Whittier quake was another that hit early in the morning (7: 42 a.m.). In fact, I can’t think of any recent major quake in this part of the world that struck during a hot autumn day. If one wanted to make a false correlation with weather, our biggest local quakes seem to occur in the early morning during the winter, the exact opposite of the conventional scenario. But of course, that is silly too: earthquakes happen around the clock, year in and year out, during every season and every kind of weather conditions, so there is no pattern whatsoever. If you buy into the idea that earthquakes happen in the early morning, you run into another problem. As explained by Snopes.com:
While there have been some memorable quakes that fit the dawn timeframe (e.g. the 1994 Northridge quake, a 45-second 6.7 shaker at 4:31 a.m. on 17 January 1994 and the (estimated) 7.9 that took apart San Francisco at 5:12 a.m. on 18 April 1906), there have been many others that haven’t. The 10 March 1933 6.4 magnitude Long Beach quake hit at 5:55 p.m., and the 18 May 1940 Imperial Valley 6.9 quake struck at 8:37 p.m. And the 17 October 1989 Loma Prieta 7.1 shaker happened at 5:04 p.m., wiping out parts of the Nimitz freeway just as commuters were driving home from work.
Even more revealing is the fact that in different cultures, there are completely different kinds of “earthquake weather”, so that just about ANY weather pattern is thought to cause earthquakes somewhere on earth!
If you think about it, there is no physical basis to believe in “earthquake weather” for one simple reason: the changes of atmospheric temperature over the course of days to hours doesn’t penetrate more than a few feet underground, while the faults that cause earthquakes are many miles underground, and cannot feel the changes of temperature under any imaginable circumstances. As humans, we are overly impressed by, and sensitive to weather and to the atmosphere, and think of its power extending everywhere. We fail to realize that underground is an entirely different world, much bigger and more thermally stable that the rapid changes in the gases of the atmosphere. To better grasp the concept, just think of all the burrowing animals in the desert that can escape killer heat with burrows just a foot or two beneath the surface, and you can better intuit why “earthquake weather” makes absolutely no sense.
However, the research continues. A couple of claims have been made that huge hurricanes and tropical cyclones can increase the frequency of aftershocks on a quake, but these have not yet been corroborated on a more rigorous basis—and there is no known mechanism that something as strong as even a hurricane could still penetrate the ground deep enough to trigger fault movement. So the scientific community hasn’t stopped looking at the possibilities—but one or two preliminary studies with a possible correlation isn’t enough to overcome the huge body of evidence showing that there is no connection between the vast majority of quakes and any weather condition.
For now, however, the myth of “earthquake weather” belong with other urban myths, such as the idea that there are alligators in the New York sewer system. Don’t believe everything you read and hear—especially when it seems to be a popular legend!