Quakes and fakes
By Donald Prothero, Occidental College
As many of us watch the horrors of the nonstop news coverage from Japan, a lot of misinformation seems to be sweeping through the media and the blogosphere. Since I'm a geologist trained in seismology, and also the author of the new book Catastrophes: Earthquakes, Tsunamis, Tornadoes, and other Earth-Shattering Disasters (Johns Hopkins University Press), I've been asked to write up a brief summary of the fact and myths about the earthquake.
First, the basics. The March 11, 2011, Sendai quake, which occurred at 2:46 in the afternoon local time, lasted almost 5 minutes in terms of total shaking. Its epicenter (38.322°N 142.369°E) was about 130 km (81 mi) east of the Oshika Peninsula, near Sendai, on the main island of Honshu. Its moment magnitude (Mw, a modification of the Richter scale used for largest earthquakes) was reported at 8.9 9.0, making it the largest in Japanese history (which has had at least 6 other quakes greater than Mw 8.0 since 1896, and millions of smaller quakes), and the fifth largest quake in world history since the invention of the seismograph. (The largest is the Mw 9.5 Chile quake in 1960, followed by the Mw 9.2 quake in 1964 in Alaska, the Mw 9.1 quake in Sumatra that caused the great Indian Ocean tsunami, and a Mw 9.0 in Russia in 1952; the quake in Chile last year was a Mw 9.8 8.8, just slightly smaller). Some sources place the magnitude of the Sendai quake at Mw 9.0 or 9.1, which would tie it for fourth largest in history.
Like all earthquakes in Japan and most of the countries on the west Pacific rim of the "Ring of Fire," it was produced in a subduction zone, where one tectonic plate (the Pacific plate) is sliding down beneath another plate (the Eurasian plate). The plates are not sliding smoothly, but grinding past one another at an oblique angle, so a lot of friction and stress builds up over a long time until it is released in huge earthquakes. The rupture zone is reported to be about 480 km (300 mi) long undersea, and 200 km (120 mi) wide, and the overlying plate is reported to have uplifted as much as 10 m (30 ft) once the stress was released (similar to what happened in Alaska in 1964) (see here for some interesting plots). The shaking was so extreme that the upward force on the people and objects was about 0.3 times the acceleration of gravity. Since the initial event, there were over 600 Mw 6.0 aftershocks in the first 24 hours, and thousands of smaller ones, and the area is still feeling them more than 48 hours later.
Tsunami. Ever since consciousness-raising of the 2004 Sumatran disaster, people have gradually stopped mislabeling seismic sea waves as "tidal waves" (since tides are not involved in these waves, which are generated by earthquakes, volcanoes, or landslides). Now they refer to them by their proper name "tsunami," which means "harbor wave" in Japan, a country that has experienced many of them over the past centuries. As we saw in the Indian Ocean in 2004 and again in Sendai, a tsunami is a wave with very long wavelength generated by a sudden displacement of water in the ocean (earthquake, volcanic eruption, giant submarine landslide). On the open ocean, it is a barely perceptible swell that most boats don't notice. When it reaches shallow water and the wave base intersects the bottom, however, it turns into a huge wall of water that sweeps a long way inland, then withdraws dramatically (exposing the intertidal and subtidal zone), then may come back with even longer waves every few minutes. The reports of the Sendai tsunamis are that the waves crested at 10 m (33 ft), and washed 10 km (6 mi) inland. If you saw footage of the area on TV, they often showed these huge waves carrying boats, cars, airplanes and other debris far inland or sweeping them out to sea, and advancing across the flat farmland around Sendai in an unstoppable wall of water. Thanks to the excellent earthquake-resistant construction of most buildings in Japan, relatively few people were killed by building collapse. Instead, far more victims (the count is still unknown) were killed by the tsunami.
Prediction. After any major earthquake, there are always people asking why geologists didn't predict the quake. Actually, this quake had been predicted as long overdue, since it was in a "seismic gap," a part of a known fault zone that has fewer than the expected number of quakes and is thought to be building up stress for a big one. But what most people want is a short-term warning that allows them to evacuate and seek shelter. The Japanese have hundreds of seismographs in place, so they were able to issue warnings about a minute before the quake, although that would not have made much difference to people who were too close to the quake to find protection in less than a minute. That's about as good as we can expect in terms of a short-term warning. Seismologists have been seeking the "holy grail" of short-term earthquake prediction for decades, but without much luck. After some spectacular successes and failures in the 1970s with the dilatancy model, most seismologists now realize that earthquakes have many different causes and behaviors. Some appear to have precursors, while others have none whatsoever. Thus, geologists have become more and more cautious over the decades that we will ever be able to predict most earthquakes except over the very long term. If you hear some psychic or astrologer say otherwise, it's a fake. As Charles Richter himself said, "Only fools, charlatans, and liars predict earthquakes."
Are we seeing more big quakes than normal? This is another question buzzing over the Internet and the media. With our short attention spans, it sure seems like the events in Japan, Haiti, New Zealand and Chile add up to a lot more than average. However, if you do the statistics carefully, the quakes of this past few years are about normal for a given period of time. In any given year, we average about three huge quakes worldwide that are bigger than Mw 6.0 or greater, and thousands of smaller ones; earthquakes are happening every second somewhere around the world. And if we look over enough decades, we see that this current crop of big events is not even the biggest in the past 50 years. The 1960s, with the biggest earthquake on record (1960 Chile) and the second biggest (1964 Alaska), had far more giant quakes than we have had in the past decade.
The myth probably arises because we have short memory spans, and most of us were not even born then, let alone adults paying attention the news in 1960 or 1964. In addition, we now have worldwide instant media coverage of a big quake, especially those in countries like Japan where there are cameras everywhere. By contrast, there was almost no film coverage of the 1960 disaster in southern Chile, and only a few films were made of the 1964 Alaska quake. Most people learned of those quakes by the newspaper days later, and saw little or no film footage on TV.
The "supermoon" theory. The media are buzzing with the predictions of an astrologer who claims that this quake was caused by the unusual perigee (closest point of its orbit) of the moon (the "supermoon") on March 19, when it will be closer than it has been in 18 years. But this, like all of astrology, is pure garbage. As Hank Campbell, Steve Shimmrich, Phil Plait and others have pointed out in their blogs, the "supermoon" idea is ridiculous. The Sendai quake happened on March 11, a week too early, when the moon was nowhere near perigee. Likewise, it is absurd to link the moon's perigee to last month's quake in New Zealand. That time framework is ridiculously broad, so that ANY event occurring anywhere near the "supermoon" of March 19 could be claimed to be related. In fact the moon reaches perigee every 29.5 days, and none of the other perigees over the past few decades can be statistically associated with earthquakes, either, or any of the many "supermoons" of the past 30 years. Finally, the physics of the situation rules the "supermoon" prediction impossible. The distance is only 15 km closer for an object over 360,000 km away, so the difference between the gravitational attraction on March 19 and any other perigee of the moon is minuscule. It will make higher and lower tides than a normal full moon, but it has no effect whatsoever on something more massive like the earth's crust.
All this attempt to stir up a media frenzy and put out crazy notions about supermoons affecting earthquakes, volcanoes, and weather is pure bunk (see Phil Plait's links on the topic. Those who do so are trying to get free media attention, since the media these days can't tell what is news and what is garbage. They are relying on our usual psychological blind spots of "confirmation bias" (remember the hits, forget the misses) and "correlation does not equal causation" to get people to buy into their crazy ideas and garner attention. And when, after March 19, nothing really happens, no one will go back to these astrologers and demand an explanation for their failures.
And of course, nothing brings out the "end of the world" crazies like a big earthquake. As always, this kind of talk is purely in the realm of religion and supernaturalism, not science.
63 Comments
Mike Elzinga · 12 March 2011
And for sheer stupidity, it’s hard to top AiG’s “explanation.”
Stanton · 12 March 2011
explainhandwave natural disasters as being one of the prices for original sin.burk · 12 March 2011
"the quake in Chile last year was a Mw 9.8, just slightly smaller"
I think you meant to type "8.8".
Good read - thanks!
Eamon Knight · 12 March 2011
It's fairly bog-standard fundamentalist theology that Adam's sin in some way knocked all of creation a-kilter; thus we have not only human evil and sickness, but also natural disaster. I believe the proof-text is Romans 18:20&ff.
Coturnix · 12 March 2011
Link to Steve Shimmrich actually goes to the excellent post by Callan Bentley.
Donald Prothero · 12 March 2011
Matt G · 12 March 2011
For every natural disaster that occurs, there are a billion religious nuts who try to ascribe some theological importance to the event. Plate tectonics, people! Mindless religious rationalizations trivialize the anguish and the deaths of the victims.
DavidK · 12 March 2011
I heard on the evening abc news of 3/12/11 that the earth's orbit was slightly affected by the quake. Nonsense. The earth's rotation around it's axis was slightly changed, but that has happened before and will again. The earth going around the sun was in no way impacted by this/these quakes. Unfortunate that the news can't get their science correct.
DavidK · 12 March 2011
FYI. Here's a handy website where you can track earthquakes worldwide. You can zoom in to any particular area (not real close however) and also get details about the quake/s. If you zoom in on the area of Japan you'll see an incredible number of quakes/shocks that have taken place.
http://earthquake.usgs.gov/earthquakes/recenteqsww/index.php?old=world.html
Ichthyic · 12 March 2011
thanks for the review, Donald.
Always a pleasure.
mplavcan · 12 March 2011
William Young · 12 March 2011
It amazes me that there are still people who believe that there is a supernatural reason for earthquake and other natural disasters ie: floods, tsunamis, hurricanes, tornadoes, volcanoes etc.
BDeller · 13 March 2011
Can any one answer this question. On March 5th Kilauea eruptive intensity increased. 2 new eruption sites occurred along a rift zone. On going eruptions increased in intensity and flow. After the quake on March 10th. all the erupting stopped, Kaputt. Obviously Hawaii is in the mid Pacific plate. Could these event be connected or it this coincidence?
Here is a link to the eruption page at the USGS
http://volcanoes.usgs.gov/hvo/activity/kilaueastatus.php
Straightpoint · 13 March 2011
God, if he exists, is a bastard- easy observation without all the mind bending illogical gymnastics. Now lets get back to understanding the science, and helping people in need. We can do that because we are caring humans; we don't need a God variable to justify it.
Now, getting back to my aid work.
John Kwok · 13 March 2011
Great post Don. Thanks for writing it.
Matt G · 13 March 2011
Claude · 13 March 2011
And once again the fundamentalist evangelical atheists are blaming God, who they don't believe in, for all the evil in the world.
It's just an earthquake, okay? It's a fleeting temporal event with no effect on eternal souls.
The real question is how to help the survivors and get the infrastructure moving again so they can make a quick recovery.
Peter Henderson · 13 March 2011
Paul Burnett · 13 March 2011
Thanatos · 13 March 2011
Paul Burnett · 13 March 2011
Thanatos · 13 March 2011
Matt Young · 13 March 2011
TomS · 13 March 2011
harold · 13 March 2011
RobLL · 13 March 2011
Tsunami, harbor wave, is not an entirely satisfactory term either. Especially with the international warning graphic, also from Japan, which shows a gigantic storm wave. While earthquake caused waves can be focused and heightened in a harbor, they can likewise be lessened. And much of Japan devastrated by this Tsunami were in fact in open coastland, and not harbors.
Oh well, language is always ambiguous, and often inexact. The metaphor of a Tsunami as temporarily raising sealevel in a succession of waves lasting up to several hours does have some tidal aspects to it, as opposed to a series of storm waves. It is its own thing, and does vary greatly from place to place.
Ichthyic · 13 March 2011
And once again the fundamentalist evangelical atheists are blaming God, who they don’t believe in, for all the evil in the world. It’s just an earthquake, okay? It’s a fleeting temporal event with no effect on eternal souls. The real question is how to help the survivors and get the infrastructure moving again so they can make a quick recovery.
"I'll take: Out of Left Field for a thousand, Alex."
stevaroni · 13 March 2011
Bobsie · 13 March 2011
Michael Roberts · 13 March 2011
I get it .
Tsunamis are the result of Adam's scrumping.
Others were not punished like that for my scrumping
Mike Elzinga · 13 March 2011
I am guessing that there are no subduction zones that are above water level anywhere on the planet.
Presumably those places on the planet where one plate slips beneath another would have the upper plate pushing down on the subducting plate creating a low spot at the boundary where oceans will fill in. The upper plate would be mostly above water and populated.
Might that also be because the continents are generally less dense and hence float on top of the subducting material as they move across it?
So tsunamis are generally the result of the top plate edge popping upward as a result of slip-stick motion at the boundary.
Are there any records of tsunamis that have resulted from a sudden downward acceleration of a subducting plate as it breaks?
There are, however, places on the planet surface where we see spreading (e.g., Iceland and the Rift Valley in Africa); and even where these are under water, they don’t generally cause any kind of vertical thrust that would lead to a tsunami.
Can any geologists here clarify this?
Michael Roberts · 13 March 2011
Paul Burnett · 13 March 2011
DavidK · 13 March 2011
Brian · 13 March 2011
The author says "However, if you do the statistics carefully, the quakes of this past few years are about normal for a given period of time."
Whereas this guy says:
'Gary Gibson, a Melbourne University seismology research fellow, said the world averages one magnitude-8 quake a year, but the rate was inconsistent.
''There is no question that the last two years have been very active, and well above average,'' Mr Gibson said.'
http://www.theage.com.au/world/another-huge-quake-likely-20110313-1bt14.html
I tend to agree with you. Even research fellows from Melb. Uni can be victim to confirmation bias. Or perhaps it's journalistic misquoting?
harold · 13 March 2011
Brian -
The two statements are contradictory only if we assume that "normal" and "average" are synonymous.
Let's say I flip a fair coin five times, and every result in a series of five is a head.
I could say "those results are perfectly normal and don't have any long term significance"; which is true.
You could say "the proportion of heads is well above average for a single series of five flips", and that, too, would be true.
Whether recent earthquake activity has been above average for some given period of time is probably dependent on which earthquakes we count and which arbitrary amount of time we work with.
An intriguing problem for fundamentalists is that the rate of earthquakes is NOT going up anywhere near as fast as the total human population. Yet the amount of sin should be proportional to the number of humans. Creationists, where are the missing earthquakes?
Scott F · 13 March 2011
Stuart Weinstein · 14 March 2011
Don,
There were not 600 aftershocks over 6.0 (That would be really awful). Certainly there have been dozens over 5.0. For a period of a couple of days, there was a 5.0+ earthquake on average every 12-15 minutes.
With respect to prediction, we are nowhere nears being able to generate an earthquake forecast that would be of use by emergency management services.
It always amuses me how the doomsayers come out of the woodwork every time there is a major earthquake. Between 1946 and 1964, there were 5 ocean crossing destructive tsunamis. Chile 2010 was the first Pacific ocean-crossing tsunami with destructive power since 1964. Perhaps we may entering a phase where the subduction zones rimming the Pacific have *woken up*, in which case over the next 10-15 years we may have a few more of these. Then again, maybe not.
By the way, I'm the Asst. Diretcor of the Pacific Tsunami Warning Center. If you have any questions feel free to ask.
Stuart Weinstein · 14 March 2011
Prometheus68 · 14 March 2011
David Fickett-Wilbar · 14 March 2011
Stuart Weinstein · 14 March 2011
MosesZD · 14 March 2011
MosesZD · 14 March 2011
MosesZD · 14 March 2011
MosesZD · 14 March 2011
Robert Byers · 14 March 2011
This comment has been moved to The Bathroom Wall.
Donald Prothero · 14 March 2011
Prometheus68 · 14 March 2011
Matt Young · 14 March 2011
Further responses to the Byers troll will be moved to the Bathroom Wall.
Dave Thomas · 14 March 2011
M.W. · 15 March 2011
Mostly what God does is warn us that all these catastrophes can and do happen. He even recommends what you should do when they do happen. i.e. run to safety. The bible is one ancient source that does warn about these happenings that have happened in the pasted such as the flood, or describes that this sort of thing happened and what to do in case it does, such as build a large arc. Spans and cubits might not sound scientific now but then that was their term for math. Just because terminology has progressed doesn’t make the calculations less feasible. That reality or story was given to inspire to cater for the people, and the flora and the fauna as well. It has inspired lots of generations to strive for the best way to preserve animals and flowers in times of disaster hopefully right up to the final one, if ever there were to be the final one, in that case it shouts out to me, I don’t know about you, to make sure there is something space worthy for a whole lot of people and flora and fauna, even if it were to be billions if not thousands of years from now the sooner and faster these things were explored and started the better in my view.
I don’t think building a nuclear reactor on a plate tectonic fault line was a very good idea, as a scientist or Christian I don’t think anyone would have sanctioned to that. One lesson to be learnt is that a special assembly should be made for applications to build such reactors and where they should be built. I wonder if there is any other nuclear stations built in a dangerous area. Preferably alternative methods for providing fuel should be made, such as wind turbines and solar power and hydroelectric power.
Just Bob · 15 March 2011
Matt Young · 15 March 2011
M.W. is not the Byers troll. I will let her comment stand, but I will be grateful if we keep God out of what is essentially a scientific or political discussion.
Rick Miler · 15 March 2011
The seismic influence of the moon should be calculated in a similar manner to tidal tables, not by an oversimplified apogee/perigee model. And I've never heard of anyone coming even close to doing it right.
Matt Young · 17 March 2011
colored contacts · 18 March 2011
there seems to be some lack of pre planning regarding that nuclear plant,in relation to the terrible situation that they now find themselves in. Why did they erect,such a dangerous commodity in such an an area,profit before people. Naturural catrospheas,in these areas of Japan,are well documented,it is known for earth instabality,and yet they erect a nuclear plant, some Deep investigation is required, nothing should be held back,for what could come out of all this terrible natural disaster is a monumental creation of our doing,and it boils down to profit before people. A lesson has to be learned from all this and that is you cant cut corners,for what lies ahead mostly in those circumstances is a dead end road,so clearly defined in the present situation
Mike Elzinga · 18 March 2011
mrg · 18 March 2011
I tend to waver on the nuclear power issue, but I think the pro-nuke advocates have really taken it in the shorts on this one.
Mike Elzinga · 18 March 2011
Carl Peter Klapper · 22 March 2011
Don't blame it on religion. It's politics, pure and simple. As an economist, I have seen the same media phenomenon where absolute rubbish is published as economic fact in order to garner political support and power. The charlatans predicting earthquakes are of the same order,political hustlers using both pseudo-science and pseudo-religion to lead the lost into the woods, as Jesus put it.
mrg · 22 March 2011
Opatija Apartmani · 19 April 2011
This comment has been moved to The Bathroom Wall.