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The myth of “earthquake weather”

by Donald Prothero, Mar 19 2014
Shaking intensity map of the March 17, 2014, Sherman Oaks quake

Shaking intensity map of the March 17, 2014, Sherman Oaks quake

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

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!

16 Responses to “The myth of “earthquake weather””

  1. John H says:

    Donald – are you seriously suggesting that having been through a handful of earthquakes over several decades has somehow taught you to ignore them in your sleep? I know the quake-weary pose is part of being a native of Shakytown, but that seems very implausible.

    • I’m a heavy sleeper, so I’ve slept through a lot of small quakes. And I’ve lived through so many in the Magnitude 4 and 5 range that I hardly notice them…

      • John H says:

        I’ve heard the same from many colleagues that live in the area. It makes me think of a Chuck Jones cartoon hero, snoring away while his bed vibrates down the stairs and out into the world. Let’s hope the family does their part when the next significant one hits!

  2. David Lintner says:

    An excellent article.

  3. Rod says:

    The devastating earthquake in Lisbon in 1755 can be thought of as the birth of modern seismology.
    While many thought that they were subject to the wrath of god, a handful realised that the causes were natural and could be understood, if not predicted.

    • That is true, but no one knew anything about faults in 1755 or for another century. Geologists then suspected faults were the cause of quakes, but the 1906 San Francisco quake clinched it. See my discussion in my book “Catastrophes!”

  4. Lynne says:

    Loved the article! I had never heard of “earthquake weather”, thanks for writing about it. Now I know how to respond if I hear anyone blame an earthquake on the weather. Thanks also for addressing the issue of the time of day when earthquakes occur (that one I had wondered about).

  5. tmac57 says:

    But wait! Isn’t it true that during hot weather people are more likely to order shakes? Just sayin’

  6. Greg Laden says:

    OK, but ….

    When I lived and worked in the Northeast, I learned, from geologists with whom I worked,that there may be more frequent earthquakes during certain times of year during certain years because of snow conditions.

    The idea was this: Our small shallow earthquakes, which would happen a few times a year over a large area, small and infrequent enough that people could go decades without noticing one (I lived there for years, experienced three), can be triggered by thermal effects in this region where parent rock is not covered by much and the amount of snow from year to year varies a great deal. So, every now and then you get a few earthquakes in the spring.

    This was not definitive at the time, if I recall correctly. Since you’ve just covered earthquakes, did you come across any research on this?

    As a skeptical skeptic I like to be careful that we are not burring a small insignificant fact under a mountain of evidence contrary to a larger irrelevant falsehood!

    • Sorry, Greg–I’ve never heard of it, nor can I find any reference to it. It still sounds like an urban myth. Even the shallowest faults are still too deep to feel the weather at the surface.

  7. WScott says:

    I haven’t finished Catastrophes yet, but am enjoying it so far!

    One related topic I was disappointed you didn’t address is the claimed link between fracking and earthquakes. As I understand the consensus among geologists: the risk of fracking itself causing noticeable quakes is pretty minimal, tho you might get some magnitude 1-2s. However, deep well waste fluid disposal (which some people confuse with fracking) can and has been tied to significant earthquakes, such as the Mag 4 & 5 quakes Denver experienced in the 1960s from well injection at the Rocky Mountain Arsenal.

    So I’d be curious to hear your thoughts on the matter, as well as any good studies on the subject. The risk may be wildly overstated by some fracking opponents, but it’s not zero; so I think it’s important to have good information out there to address people’s concerns.

    • I didn’t include fracking in the book because there is not a clear-cut consensus on it, like there is on evolution, climate change, homeopathy, vaccination, AIDS, etc. Yes, those injections in the RMA are in every geology textbook, and well known–but not much has been done on that topic, either way. Fracking itself is complex. If it’s done right (tightly sealed well, careful analysis of geological hazards) there SHOULDN’T be any problems. But too many major disasters show that it’s often not done right, or even if it is, there are things they don’t account for that end up being environmental hazards.
      In my book, I raise the larger point: cheap oil is gone, and any kind of oil will be running out in a generation or less–and tracking doesn’t help, because natural gas is not what’s scarce.

      • WScott says:

        Fair enough. Your statement (paraphrased) that “fracking shouldn’t be a problem if done right, but…” summarizes most of what I’ve read, but I was hoping maybe you knew about some reasarch I hadn’t seen yet! Thanks.

      • WScott says:

        Oh, and I assumed you (Don) had heard of the RMA quakes – the link was for the benefit of other readers!

  8. WScott says:

    While we’re talking about earthquakes I have a slight nitpick with something in Catastrophes. You mention the Italian case where six scientists and one government official were convicted of involuntary manslaughter for “not predicting” the 2009 L’Aquila quake, which you called “the ultimate absurdity.” While that’s the way the case was mostly covered in the media, the actual facts of the case are a little more nuanced and much more interesting. The defendants were not convicted of failing to predict the quake, but rather of giving false reassurance to the public.

    The scientists in question served on an expert committee that advised Italy’s Civil Protection Agency (their FEMA) on natural disasters. On March 31, 2009, they met in L’Aquila to address a series of minor tremors the region had been experiencing. The meeting was not open to the public. But at a press conference immediately afterwards, a CPA official named De Barnardinis (not a scientist) told the media there was no danger, and that frequent small quakes actually *reduced* the risk of a major quake. “The scientific community tells me there is no danger, because there is an ongoing discharge of energy. The situation looks favorable.” His recommendation to the public was to have a nice glass of wine. I swear I’m not making that up.

    A week later, a 6.3 quake hit the area, killing 308 people, injuring 1600, and leaving 65,000 people homeless. Testimony showed that many people had stopped taking precautions after De Barnardinis’ reassurances, and thus were trapped indoors when their unreinforced-masonry homes collapsed.

    As I stated, De Barnardinis was not a scientist; but standing next to him at the press conference was the committee chair (Barberi), a volcanologist. Barberi made no attempt to correct/clarify De Barnardinis’ claim. Nor did any committee member issue any statement, then or later, saying De Barnardinis’ statement did not reflect their opinions, the committee’s findings, or scientific consensus. After the quake, the scientists claimed they had only agreed that frequent minor quakes does not indicate an *increased* risk of a major quake, but never claimed it reduced the risk. The minutes of the meeting seem to back up the scientists’ position…but those minutes weren’t released until after the quake, so an element of he-said-she-said remains.

    The final smoking gun: the head of Italy’s Civil Protection Agency happened to be under an unrelated investigation, and was caught on a wiretap before the meeting saying he was going to send the committee to L’Aquila “as a media move” to reassure the public. “[T]hey will say it is better to have a hundred shocks at 4 Richter than silence, because a hundred shocks release energy, so that there will never be the big one.” So it’s pretty clear De Barnardinis’ talking points had been scripted in advance of anything the committee might have actually said.

    So the case was more accurately about a failure of science *communication* than about science’s inability to predict quakes. IMO the evidence supports the conclusion that De Barnardinis and the CPA deliberately gave false reassurances to the public that were not based on good science. The court concluded the scientists were also culpable, because they never attempted to contradict/clarify De Barnardinis’ statements. Personally, I think that’s still a bit of a stretch, but I’m not a lawyer, let alone an Italian lawyer. Either way, the case is more complicated than the way it’s typically been portrayed.