A Look Back at Ten Years of Geotripping: Geotripper Emerges From the Apocalypse...

This week is my commemoration of ten years of geoblogging. I've been digging through the archives for some of my favorite posts of the last decade, and we've reached 2011. We had a series of epic trips that year, one with my students across the Pacific Northwest and northern Rocky Mountains, and the other a personal journey across the Basin and Range, the central Rocky Mountains and the Colorado Plateau. They resulted in not one, but two blog series, A Convergence of Wonders, and Vagabonding Across the 39th Parallel. I would recommend the first if you want to know what adventures await if you attend a Modesto Junior College geology field studies course, and the second if you want to know what happens when you just up and leave on a two-week trip without a plan, and just a vague goal (Rocky Mountain National Park). Those of you who know me will understand how hard that can be, starting out a day not completely certain where one will end up that night.

But as fun as those series were for me to write, I picked three individual posts from 2011 as my favorites. One was utilitarian, one was about the adventure of being a geologist (or geology fan), and the third, my response to yet another irresponsible prediction about a giant earthquake or apocalypse or some other world-ending thing that got the web and cable news all excited. Of course the predicted date came and went with no unusual activity as they always do. Frankly, I sort of lost it. That blogpost is below. The other two are coming shortly...enjoy!


From March 24, 2011: 

Welcome, survivors of the Apocalypse! Like you, I have been hiding in my underground bunker, safe from the radiation cloud and protected from the supermoon and giant earthquake that caused California to plunge into the sea. I'm waiting to see if my investment in oceanfront property on the Carrizo Plains has paid off with a nice seaside view. Did any of the southern California mountains remain as offshore islands? I was sort of hoping to have a few on the horizon. I've been rationing my Cheetos, Pringles and beef jerky. I lined my bunker with lots and lots of tin foil to protect myself from the electronic emanations of those pointy-headed "scientists" who kept poo-pooing the predictions of those who sensed the coming Apocalypse in their minds and mathematical calculations. As soon as I saw the work of the prophets on the Internet I knew it had to be true. Their prophecies were aired by the cable news networks, so I double-knew it had to be true. I didn't feel the earthquake because I built my shelter on a spring-loaded foundation. Was it really shaky? My clock broke, so I've been estimating the number of days I've been in hiding by making chalk marks on the wall; it's 2012 isn't it? The Mayan calendar came to an end and all? Have the Zombies died out yet?

Well, that's that. The supermoon weekend passed and California is still here. The full moon didn't scrape along the ground and erase cities. There were no tidal disruptions. There was no earthquake. There were no volcanic eruptions. No one melted from the radiation cloud. The prophets and predictors were wrong, yet again, wrong again for the umpteenth time. Over and over they are wrong. Hundreds of times they have been wrong. And still they find a stage on the cable news networks, the Internet, the radio...over and over. There always seems to be a crowd of uninformed and misinformed people who take them seriously, and there are uninformed and misinformed news readers who are unable to critically assess their irresponsible claims. At the same time they dismiss the statements and findings of academics who have given over their lives to the study and understanding of the earth sciences. And in the end the charlatans and fakes are never brought to account for scaring people and causing economic disruptions.

I've seen enough of "judgment journalism" in politics to know that cable news outlets are capable of shaming those who cross the line of honesty and decency. They are capable of using their media platform to upbraid and criticize officials who steal money or engage in hypocritical behaviour. Why are they not criticizing and shaming those who carelessly predicted earthquakes and radiation poisoning without regard to the consequences of being totally (and predictably) wrong? I have never seen the news readers take a self-proclaimed "psychic" to task for their hundreds of wrong predictions.

Wouldn't it be nice just once to see a camera crew waiting outside the home of one of those self-proclaimed psychics or would-be earthquake prophets and ask them over and over why they made yet another wrong claim that needlessly scared people? Just once to hear them told to their face that they are charlatans and fakes? How long will the con artists persist when they know they will be subjected to public derision when they make their spurious claims?

In the meantime, the media outlets need to learn the real facts about the possibilities of quakes and other hazards in California (and anywhere else) and make sure their audiences know the actual magnitude of the threat. The faults are here after all, and there is a lot of built-up stress. Damaging quakes will happen, and we need to all be as prepared as possible. The first thing to do is to arm yourself with knowledge. Get this knowledge from responsible government agencies like the U.S. Geological Survey, or the California Geological Survey, or academic organizations like the Southern California Earthquake Center. Then you make the appropriate preparations: keep emergency supplies of water, flashlights, radios, batteries, and first aid kits, both in your home, and in your car. Have a family plan for what to do when disaster strikes.

By the way, it is ok to have Pringles and Cheetos in your emergency supplies...but put some healthy stuff in there too. There is junk food and there is junk news. Too much of either can be harmful to your health.

The BIG ONE is COMING! Well, yeah, but...

The San Andreas fault in the San Francisco Bay area. The two reservoirs are Crystal Springs and San Andreas, which gave California's most important fault its name. Photo by Geotripper.

It seems like there has been a bit of shaking going on in California over the last few weeks. There was the 6.9 quake off the coast of Eureka on March 9, a 4.4 magnitude tremor in the San Fernando Valley on the 17th, and now the 5.1 magnitude quake in La Habra. It's enough to make people paranoid about quakes in general, and the BIG ONE in particular. Are these precursors to the BIG ONE? Are they relieving some of the stress that will prevent the BIG ONE from being so bad? We love to talk about the BIG ONE, and if the media outlets have their way, we will worry and fret about it, enough so as to tune in to their stations for more scary updates (to keep those ratings afloat). I've rarely been impressed by media coverage of earthquakes, and this week has been no exception. I've heard through tweets that some media outlets trumpeted official statements warning of bigger quakes to come in 24 hours while conveniently forgetting to mention the "5% chance of" statement that preceded the word "bigger".

Of course, in some ways it's worse. We're not waiting for the BIG ONE in California. We are waiting for the BIG ONES. The San Andreas fault gets lots of attention, but there are numerous active fault zones in California, and the San Andreas itself behaves like four independent fault systems. There was the devastating earthquake near San Francisco in 1906 that garners much attention, but there was an equally large quake near Fort Tejon in Southern California in 1857, and the Salton Sea region was shaken around 350 years ago. These different segments of the San Andreas seem to move every century or so. A huge quake shook the eastern Sierra Nevada in 1872, killing a tenth of the population in the Owens Valley (28 people). Each of these quakes were in the range of magnitude 7.7-7.9, although some estimates range as high as magnitude 8. Add to this list the 1952 Tehachapi quake (7.3-7.6), the Landers quake of 1992 (7.3-7.5), the Hector quake of 1999 (7.1), the El Mayor quake of 2010 (7.2, just over the border in Baja), and the Cascadia Subduction Zone quake of 1700 that no doubt affected the northernmost part of the state. It was very likely a magnitude 9 event.

I should mention that I successfully predicted these quakes. We discussed earthquakes and the "art" of earthquake prediction in my classes two weeks ago. We pointed out that psychics predict earthquakes all the time, and that they are never wrong (how wrong can you be when you say "I see a major city being devastated by an earthquake this year" without specifying a day or location?). To prove the point, I predicted that a quake would happen in northern California within a few days, and that another would happen in the south state as well. I make this prediction every semester, and I am rarely wrong. All such predictions are crap, of course, and do no one any good.

No one can predict earthquakes, and anyone who says they can is lying or is deluded. But we can predict where they will happen, and we can determine the probability that they will take place within a certain time frame, usually 30 years. This is the nature of the maps that I am posting here from the U.S. Geological Survey, the Southern California Earthquake Center, and the California Geological Survey. Such maps are a most useful tool for educating the public about where the greatest seismic risks are located in the state (note how distressingly close they are to the most populated parts). There is a lot more to the tectonic framework of our state than just the San Andreas fault!

It is interesting to me that since these probability maps came out in 2007, we've already had a 6.9 quake in northern California, and if you count just over the border, we've had our predicted magnitude 7 quake in 2010. It is important to note that neither of these events had any particular effect on the stress levels that have built up on faults like the San Andreas, Hayward and San Jacinto. They are still just as likely to shake in the next 25 years or so. What do we take from this? The quakes are coming, and we need to be prepared for them (start here: http://www.data.scec.org/earthquake/preparedness.html). Everyone who lives in California should have emergency supplies of water and food. Even if you live outside the high risk parts of the state, you will still be affected, as the energy grid will be damaged and emergency services we take for granted will be headed into the areas where damage is the worst.

Do these kinds of disasters make you rethink the idea of living in California? You could move to Kansas and put up with tornadoes. You could go to Nebraska and enjoy the Polar Vortex. You could go to Louisiana or Florida and deal with oil spills and hurricanes. You could move to Oregon or Washington and deal with volcanic eruptions. There really is no place that is free of natural disasters, and the processes that cause them may sometimes have the benefit of producing beautiful scenery and interesting geological outcrops. I'll pick California every time.

Earthquake Swarm in Southern California

An earthquake swarm is shaking up part of Southern California along the San Jacinto fault near the town of Anza. According to the U.S. Geological Survey, three moderate quakes occurred in quick succession at about 9:56 AM, with magnitudes 4.7, 4.7 and 4.6. Many dozens of smaller aftershocks have followed, most in the range of magnitude 1 or 2.

The San Jacinto fault is a major structure in Southern California, an active right lateral strike slip fault that trends parallel to the San Andreas. It has produced damaging quakes in the past, most notably in 1899 and 1918 which caused serious damage in Hemet and San Jacinto. At least 10 historic quakes have exceeded magnitude 6.

The quakes today are not nearly as large (a magnitude 5 quake has only 1/30 the energy of a magnitude 6 event), but all earthquake swarms on active fault systems should be noted carefully. Most of the time nothing else happens, but on occasion these swarms may presage a larger event. If you live in the region, it is a good time to evaluate your earthquake preparedness, storing water, flashlights, food, batteries, first aid kit, and radio, and having a family emergency plan.

For more information on earthquake hazards in California refer to this site from the USGS: http://earthquake.usgs.gov/prepare/ . For a look at the historical record of large earthquakes in Southern California, check here: http://www.data.scec.org/significant/index.html . For an interactive map that provides the latest data on earthquakes in California (and other parts of the world), check here: http://earthquake.usgs.gov/earthquakes/map/. If you felt any of the earthquakes and want to report your experience, check out Did You Feel It?.

Update:
As is often the case, the preliminary data is a bit uncertain, and the latest official count is one magnitude 4.7 quake, which as of 1:30 PM has been followed by over 200 aftershocks.

Source: http://www.consrv.ca.gov/cgs/rghm/psha/Pages/index.aspx

Just Gotta Love Days Like This...Earthquakes, Earthquakes, Earthquakes

I just love days like this...The Great California ShakeOut has people thinking about earthquakes all over the state of California, with upwards of 8 million people practicing and preparing for a major seismic event in the state. I just happen to be introducing the topic of earthquakes in my physical geology classes today. I just finished blogging about the myths of earthquakes in California. Then...two earthquakes just happen to shake the Bay Area! The events, registering magnitude 4.0 and 3.8, were felt across the region, but probably caused little damage. They took place on or near the Hayward fault, which is one of the major active fault zones in the state. It is capable of generating events in the magnitude 7 range.

The quakes today did a great job of making people aware of the seismic hazards of living in the state (and really...just HOW did the ShakeOut people arrange for actual earthquakes???). Few people were hurt, but everyone is talking about them.

There is a more ominous note in the quakes today. The Hayward fault is one of the most dangerous fault zones in California at this time, partly for the size of the quakes that it can produce, but even more for the level of urbanization along the trace of the fault. A magnitude 7 quake has the potential to kill and injure tens of thousands, and to cause untold billions of dollars of damage. The U.S. Geological Survey calculates a 31% chance of a 6.7+ magnitude quake along the Hayward within the next 30 years (and only a 21% chance along the San Andreas within the same time period).

Foreshocks may often precede a major earthquake, and there is a slight chance (maybe 5%) that today's events are precursor quakes. They are reminders that to live in California is to live in earthquake country, and that it is critical to be prepared. All Californians, and especially those in the urban centers of the Bay Area, Los Angeles, and the Inland Empire should always have spare water, food and first aid supplies handy, both at home and in their cars. Find out what the hazards are in your particular area. Have a family plan for when you are separated following a major event. Check out the Great ShakeOut website for more information.

Stay safe!

Giant California Earthquakes and the Radiation Cloud; California Falls into the Sea: Geotripper Emerges from the Apocalypse...

Welcome, survivors of the Apocalypse! Like you, I have been hiding in my underground bunker, safe from the radiation cloud and protected from the supermoon and giant earthquake that caused California to plunge into the sea. I'm waiting to see if my investment in oceanfront property on the Carrizo Plains has paid off with a nice seaside view. Did any of the southern California mountains remain as offshore islands? I was sort of hoping to have a few on the horizon. I've been rationing my cheetos, pringles and beef jerky. I lined my bunker with lots and lots of tin foil to protect myself from the electronic emanations of those pointy-headed "scientists" who kept poo-pooing the predictions of those who sensed the coming Apocalypse in their minds and mathematical calculations. As soon as I saw the work of the prophets on the Internet I knew it had to be true. Their prophecies were aired by the cable news networks, so I double-knew it had to be true. I didn't feel the earthquake because I built my shelter on a spring-loaded foundation. Was it really shaky? My clock broke, so I've been estimating the number of days I've been in hiding by making chalk marks on the wall; it's 2012 isn't it? The Mayan calendar came to an end and all? Have the Zombies died out yet?

Well, that's that. The supermoon weekend passed and California is still here. The full moon didn't scrape along the ground and erase cities. There were no tidal disruptions. There was no earthquake. There were no volcanic eruptions. No one melted from the radiation cloud. The prophets and predictors were wrong, yet again, wrong again for the umpteenth time. Over and over they are wrong. Hundreds of times they have been wrong. And still they find a stage on the cable news networks, the Internet, the radio...over and over. There always seems to be a crowd of uninformed and misinformed people who take them seriously, and there are uninformed and misinformed news readers who are unable to critically assess their irresponsible claims. At the same time they dismiss the statements and findings of academics who have given over their lives to the study and understanding of the earth sciences. And in the end the charlatans and fakes are never brought to account for scaring people and causing economic disruptions.

I've seen enough of "judgment journalism" in politics to know that cable news outlets are capable of shaming those who cross the line of honesty and decency. They are capable of using their media platform to upbraid and criticize officials who steal money or engage in hypocritical behaviour. Why are they not criticizing and shaming those who carelessly predicted earthquakes and radiation poisoning without regard to the consequences of being totally (and predictably) wrong? I have never seen the news readers take a self-proclaimed "psychic" to task for their hundreds of wrong predictions.

Wouldn't it be nice just once to see a camera crew waiting outside the home of one of those self-proclaimed psychics or would-be earthquake prophets and ask them over and over why they made yet another wrong claim that needlessly scared people? Just once to hear them told to their face that they are charlatans and fakes? How long will the con artists persist when they know they will be subjected to public derision when they make their spurious claims?

In the meantime, the media outlets need to learn the real facts about the possibilities of quakes and other hazards in California (and anywhere else) and make sure their audiences know the actual magnitude of the threat. The faults are here after all, and there is a lot of built-up stress. Damaging quakes will happen, and we need to all be as prepared as possible. The first thing to do is to arm yourself with knowledge. Get this knowledge from responsible government agencies like the U.S. Geological Survey, or the California Geological Survey, or academic organizations like the Southern California Earthquake Center. Then you make the appropriate preparations: keep emergency supplies of water, flashlights, radios, batteries, and first aid kits, both in your home, and in your car. Have a family plan for what to do when disaster strikes.

By the way, it is ok to have pringles and cheetos in your emergency supplies...but put some healthy stuff in there too. There is junk food and there is junk news. Too much of either can be harmful to your health.

Predicting Earthquakes in California? I can do that too! I'll do it right now...

By golly, there is going to be an earthquake in California tomorrow! I'm going to go out on a limb and predict it. In fact, I will state unequivocally that there will be several earthquakes in California, some in the north state, and some in the south state. And I will be correct in my predictions. So, that should net me a few stories on the cable news networks, and a flood of tweets across the Internet by worried people who don't really believe it, but it could be true, you know....

What's my secret? There is no secret. California has earthquakes every day. We had 368 of them in the last week alone (368 quakes in a week is NOT unusual...sometimes there are more, sometimes there are less, but always there are hundreds). Check out the map below:

This blog was prompted by another flurry of requests from students and readers about someone somewhere predicting that we would have a big quake in California tomorrow; I won't provide links. They scare people needlessly, and it is irresponsible.

Anyone can predict quakes. But no one can predict large quakes with any kind of accuracy that will save lives. We can make long-term evaluations about the chances that a particular fault will rupture within a period of decades. But we can't predict big quakes a few days in advance. Anyone who says so is plain flat-out wrong. They will keep predicting quakes one after another, and one of these days, one of their hundreds of predictions will come true, and they will cash in.

I have a funny sense of deja vu, like we've been here before...

From my post of April 13, 2010:
8.4 Quake in California? Don't believe everything that Tweets...

No.

I should stop there, but I will say that no one can predict quakes in any useful way.

California's biggest quakes will be in the range of 7.8-8.0, quite a few times smaller than an 8.4. The stresses are there for a large quake to happen, but a magnitude 8 quake is given only a 4% chance of occurring sometime in the next 30 years.

Please don't believe everything that tweets....

But do prepare for quakes in California. They CAN happen any time, but NO ONE can predict them.

From my post of April 15, 2010:

8.4 Quake in California? Not so fast there, Twitterers...

If you have not read XKCD comics, you have been missing out on a great treat, especially if you are the scientific nerdy type of personality. On the heels of the Sierra El Mayor earthquake in Baja California, the comic above made the rounds, revealing a great truth: we are a wired, interconnected society (surprise!). Of course, there are the disadvantages as well.

So, to explain Tuesday's brief post: the XKCD comic above came true in a fashion...except there was no earthquake. I was checking my e-mails during a short break in my night class, and I had several people asking if the tweets they had received from friends were true, was the state of California declaring that an 8.4 magnitude quake would be hitting within the next 48 hours? Then I saw a few phones open up in class, and someone asked me directly about the Tweet on their phone. Clearly a rumor was spreading with the speed of electromagnetic energy and texting fingers. A hoax? An idiot crying 'fire' in a theatre? Undoubtedly. I posted my brief message explaining why the Tweet wasn't true, and had more than 2,000 hits in the space of 90 minutes. By the midnight, the 20th ranking query on Google was '8.4 magnitude earthquake in California'.

A lot of damage is done when rumors like this spread. No one can predict earthquakes, and a false prediction like this (or from 'psychics') can unnecessarily frighten people, and lead to a situation that will be perceived as crying 'Wolf'. People will stop paying attention to real warnings by qualified seismologists and vulcanologists.

We cannot predict earthquakes in such a way as to know the day, the week, or the month. We can use the history and prehistoric behaviour of fault zones to determine the possibility of a large quake within a time frame of decades. If you want a scientifically grounded prediction about earthquakes in California, check out the diagram below, from the Uniform California Earthquake Rupture Forecast (UCERF). The message to take away? Ignore the tweets, and pay attention to your personal emergency preparations. Quakes will happen.

Update #1: A nice explanation of why we can't predict big quakes can be found here.

I Didn't Feel Like Teaching Today...

...but it was the kind of day that demands teaching.

My first day back with classes after the magnitude 9.0 quake and tsunami in Sendai, Japan, and the perfect teachable moment. Only it doesn't feel like a teachable moment. I just felt sorrow. So much is going on, and the situation seems to change hour to hour. First it was a magnitude 9.0 earthquake. Those don't happen very often, and that would be enough by itself to toss out the lesson plan of the day and discuss earthquakes and magnitude. But then there was the horrific tsunami that changed everything. 80 miles is a pretty good distance to be from a magnitude 9 quake, and it looks like the structures along Japan's coast weathered the shaking pretty well. But the tsunami raged through and erased towns, wiping them out of existence. Without the tsunami, the quake would have been a footnote. With the tsunami this event became the ultimate human tragedy. Thousands dead, hundreds of thousands homeless. It's hard to even speak of it, much less try and understand the pain and suffering that is taking place across the sea.

But then a new threat; the nuclear power stations began failing one after another in a story that is still unfolding. A human-induced tragedy superimposed over a nature event. We've concentrated radioactive substances in order to produce a form of energy, and the engineers have always told us that it can be made safe. Despite Three-Mile Island, despite Chernobyl, despite the other 30 'incidents' in the past 50 years. We've 'learned' from each of the accidents, it is said. They can't happen elsewhere. We have back up systems. We can't give up nuclear energy they say, because it is the bridge to a renewable energy future. Otherwise we'll have to burn more coal, and coal contributes to global warming. In all of the chattering among the talking heads on cable news this weekend, I have heard nothing of the threat of terrorism at nuclear power plants, nor have I heard anyone talk about where the highly radioactive waste is going to go. We've been avoiding the second problem for 50 years now. Will these questions start emerging, or will they disappear once the meltdown is complete, or once they stop the meltdown from occurring.

So the lesson plan for the day is tossed. We talk about the earthquake, the tsunami, the nuclear power plants. Questions, one after another. Some I can answer, some I cannot.

Can we have a magnitude 9 quake in California? Yes and no. The legendary San Andreas fault can produce events in the range of magnitude 8, about 1/30th of the size of the Sendai earthquake. Many other faults in California have produced dozens of quakes in the range of magnitude 6.5-7.5, and some have been very damaging. Magnitude 9? Not exactly. The Cascadia subduction zone lies off the coast of Northern California, and extends across Oregon and Washington. That system produced a magnitude 9 quake in 1700. Studies show such a quake takes place every few hundred years. Such a quake would have devastating consequences in NorCal and the Pacific Northwest.

Are the nuclear power plants going to have a full meltdown? I have no idea. I'm not an expert, and I don't know that the experts even know.

Will we be hit by a dangerous radioactive cloud? I don't think so, the experts say it will dissipate in the atmosphere and fall into the ocean before it gets here. I'm more worried about the people who live in the vicinity of the power plants. If the worst case scenario happens, the land they have lived on all their lives could be declared uninhabitable. Where will they go?

I'm glad the meltdown didn't happen here. How many of you know where your energy comes from? California has two operating nuclear power plants, both on the coast, both near fault systems. Another mothballed power plant sits unused just 80 miles from us, with all the fuel rods on site. The engineers for the plants say they're ready for whatever happens (I bite my tongue to avoid getting political).

Can a tsunami hit us in the Central Valley the way it did in Japan? No, not likely, but we have a different problem: the Sacramento Delta. The three dozen or so islands in the Delta are 'protected' by century-old levees that are prone to failure from causes as simple as excessive muskrat burrowing. The islands have sunk over the last century, and most are now below sea level. A moderate quake on nearby faults could cause widespread failure and flood the islands with seawater. If it were just lost farmlands, we could deal with it. But the intake pumps for the California Water Project are in the midst of the islands and the inundation could cut off the water supply for 20 million people for months, if not years.

What will the "Big One" do to us? It depends which "Big One" you are talking about. A repeat of the 1906 earthquake in San Francisco? Or the 1857 Fort Tejon earthquake? Or the 1872 Lone Pine quake Or another? All of them were close to magnitude 8, and if they happened again, the results would be profound. And there are dozens of other active fault zones in California. But here in the Central Valley? Harder to say. The 1906 quake was certainly felt in the region, but didn't do much damage in our town. Cities and towns on the west side of the valley will have some serious problems with shaking and liquefaction, but we are on relatively stable sediments.

Where's the best place to live? Kansas or Nebraska I should think. But watch out for tornadoes. Here in California, I would pick the Sierra foothills. Solid bedrock foundations and relatively far removed from the most active fault zones.

I have a question for the class: How many of you have an earthquake emergency kit ready at home (and in the car)? Two or three hands, including my own...

We are not ready...

Do you have questions? Use the comments section to ask and I will answer if I can, or find an answer somewhere.

The San Andreas Fault in Southern California: What does a Wake-Up Call Sound Like?

Those who live, or have lived, in Southern California may have wondered once or twice why there are 11,000 foot high mountains situated adjacent to valley at close to sea level (San Gorgonio Peak looms above Banning in the picture above). The reasons invariable point to the multitude of active faults that slice through the crust in the south state.

This might sound like another post where the Easter day Cucaph El Mayor Quake or some other event is used as a reminder that my SoCal friends live in earthquake country, and it is something like that, but not entirely. Science doesn't actually work the way media portrays it, where there is a sudden insight, and suddenly there is the solution to the problem, and everything is suddenly understood. The movie that comes to mind is 1995's "Outbreak", where they catch the damn monkey, and twenty minutes later they are injecting the sick people with a serum from said monkey that cures the pandemic disease. No, science is not like that at all. Scientific discovery and insight is incremental.

I was reminded of that as I thumbed through my newly arrived edition of GSA Geology and caught this article about some of the latest research on the paleoseismic history of the San Andreas fault in Southern California (author's page with full article link is here). The team has spent a decade or more documenting paleo-earthquakes on the San Andreas fault going back 3,000 years at a site near the mountain village of Wrightwood, which sits right on the fault. What they have documented is ominous: 29 major quakes in two distinct periods covering 3,000 years (major quakes defined as magnitude 6.8-7.9 with at least several meters of surface offset). That's an average recurrence interval of only a century or so. Only two of these quakes are historic, an 1812 event and the 1857 Fort Tejon quake.

At issue is whether major earthquakes on the San Andreas system are periodic or whether they cluster, with several events in a few decades followed by a long period of quiescence. Finding paleo-earthquakes is not the easiest task, which helps explain why this is a decades-long project. Most of the work is accomplished by digging deep trenches across the fault in places where sediments are most likely to reveal past ground disturbances. The illustration below, from an earlier paper by the same group shows how a fossil earthquake looks in a trench wall. The lower layers are offset, but the upper layers are not. If one can find the age of the oldest undisrupted layer, the timing of the quake can be resolved by radiometric dating of carbonized wood or snail shells.

Fossil earthquake from Scharer et al., 2007

So, each couple of months reveals more and more information until there is enough to start to draw some conclusions. The judgement in this month's report is that the quakes are more periodic in nature than clustered. But the last line of the abstract is the most ominous, and made me sit up: it's been 153 years since the last major earthquake on the San Andreas fault, and out of a record of 29 major quakes, only 4 times has there been a time gap that long. In their words, this is "highlighting the current hazard posed by this fault". What that means is that the fault is severely overdue for a major ground-rupturing quake.

What does a wake-up call look like? It looks like three magnitude 7+ quakes in isolated corners of California and Baja California (1992 Landers, 1998 Hector and 2010 Cucapah El Mayor) that killed few, but would have been catastrophes if they had occurred closer to major urban centers. A repeat of the 1857 event would devastate Palmdale and San Bernardino. Damage would be widespread throughout the Los Angeles basin. What do you do with a wake-up call? Do you go back to sleep? How many of you, after the Easter quake, decided to put together an emergency supply kit, one for the house, and one for your car? How many of you did it? Tens of millions of people are sitting in the path of the oncoming quake, and few are really prepared.

One of the great many factors that led to the horrific catastrophe in Haiti last January (and I hope you are remembering them and sending donations) was the lack of previous earthquakes in the collective memory of the population. They had never experienced a serious earthquake, and therefore did not expect, or prepare for one. In California, we don't have that excuse. We know they are coming. We have up-to-date architectural standards that will save many thousands of lives, but even with those standards, a death toll in the thousands, even the tens of thousands is possible. Think seriously about the coming quakes and make the preparations, not just for the quake but for the aftermath, when emergency services will not be available in many areas.

8.4 Quake in California? Not so fast there, Twitterers...

If you have not read XKCD comics, you have been missing out on a great treat, especially if you are the scientific nerdy type of personality. On the heels of the Sierra El Mayor earthquake in Baja California, the comic above made the rounds, revealing a great truth: we are a wired, interconnected society (surprise!). Of course, there are the disadvantages as well.

So, to explain Tuesday's brief post: the XKCD comic above came true in a fashion...except there was no earthquake. I was checking my e-mails during a short break in my night class, and I had several people asking if the tweets they had received from friends were true, was the state of California declaring that an 8.4 magnitude quake would be hitting within the next 48 hours? Then I saw a few phones open up in class, and someone asked me directly about the Tweet on their phone. Clearly a rumor was spreading with the speed of electromagnetic energy and texting fingers. A hoax? An idiot crying 'fire' in a theatre? Undoubtedly. I posted my brief message explaining why the Tweet wasn't true, and had more than 2,000 hits in the space of 90 minutes. By the midnight, the 20th ranking query on Google was '8.4 magnitude earthquake in California'.

A lot of damage is done when rumors like this spread. No one can predict earthquakes, and a false prediction like this (or from 'psychics') can unnecessarily frighten people, and lead to a situation that will be perceived as crying 'Wolf'. People will stop paying attention to real warnings by qualified seismologists and vulcanologists.

We cannot predict earthquakes in such a way as to know the day, the week, or the month. We can use the history and prehistoric behaviour of fault zones to determine the possibility of a large quake within a time frame of decades. If you want a scientifically grounded prediction about earthquakes in California, check out the diagram below, from the Uniform California Earthquake Rupture Forecast (UCERF). The message to take away? Ignore the tweets, and pay attention to your personal emergency preparations. Quakes will happen.

8.4 Quake in California? Don't believe everything that Tweets...

No.

I should stop there, but I will say that no one can predict quakes in any useful way.

California's biggest quakes will be in the range of 7.8-8.0, quite a few times smaller than an 8.4. The stresses are there for a large quake to happen, but a magnitude 8 quake is given only a 4% chance of occurring sometime in the next 30 years.

Please don't believe everything that tweets....

But do prepare for quakes in California. They CAN happen any time, but NO ONE can predict them.

Has it Been That Long Already? Loma Prieta Earthquake 20 Years Ago Today

It's been quite a week, this year's Earth Science Week, starting with a record-breaking storm in California, suffering cuts in the geology field studies program at our school, and the 20-year anniversary of the Loma Prieta Earthquake on October 17. I hate to be missing the GSA meeting starting this week in Portland; many members of the geoblogosphere will be there.

Andrew Alden at About.com: Geology and the Berkeley Seismological Laboratory are asking for our stories about the quake. In 1989 I was a brand-new instructor at Modesto Junior College, in my third semester. I taught classes in the old 1950's-era Science Building on our east campus, up on the second floor. I had all the modern teaching technology; there was a chalkboard, and two television monitors hung from the ceiling for showing those newfangled "videotape cassettes". The monitors also served as my decidedly low-tech seismometers. They shook noticeably during the smallest of earthquakes (most memorably during a class test on earthquakes; no one but me even noticed).

On October 17th at 5:04 PM, my physical geology laboratory had just finished and almost everyone had gone home to watch the World Series. A couple of students were helping me (it was Maureen and Sonny; funny how I remember the names of the first students I had better than the ones I had last semester). We were 100 kilometers from the epicenter, so when the seismic waves started to shake our building, the movement was a strong rolling motion instead of sharp vibrations. We looked at swaying TV monitors, and commented that it was an earthquake. It was a most scholarly discussion, actually. We realized the shaking was not stopping, and we thought we could sense the direction of the quake as well. We started to guess where it might be happening, but when the shaking reached the 40 second mark (the energy was spreading out, it lasted only 10 seconds or so near the epicenter), we realized it was a major event, and that fatalities were probably occurring (and unfortunately we were right). The deodar trees out the window were whipping back and forth as if they were in a high wind. The strangest part for me was the unconscious decision I was making as the shaking progressed. Despite having a quiet scholarly discussion, my body was moving from the front of the podium to the back, where there was a nice solid space to hide under. I would have dived under if the quake had lasted any longer.

In hindsight, I should have been a bit more aggressive about taking shelter under the desk. An analysis of our building a year or two later revealed an architectural weakness that suggested the building could collapse if the seismic waves hit it from a particular direction. A seismic retrofit a decade later included some massive shear walls in the lab I taught in.

Meanwhile, at the city library, my children were making me proud. At the time of the quake, there were huge sailing ship models on display, in some cases right on top of the book stacks. The stacks were not reinforced or braced, so there was a real potential for injuries if the quake was strong enough to knock those stacks over. I was told that most people were just standing there watching the bookstacks swaying, but my kids, my well-trained and intelligent kids were the only people in the room to take shelter under the sturdy study tables. Luckily, as I said before, we were on the fringes of the effects of the earthquake and no one was hurt.

The Loma Prieta earthquake, a magnitude 6.9 event at a depth of 11 miles, was a tragedy: 63 people died, and 3,700 were injured. The Bay Area was in chaos for days and months passed before life got back to normal. We were on the fringes, so instead of pain and suffering, we had a profound learning experience that was remembered by my students for the next decade and a half. But it has been 20 years now, and many of my students weren't born when the quake happened. Few of them have felt a quake at all. The large quakes like Loma Prieta and Northridge are ancient history, and there is less of that innate knowledge of what they should do when one hits. Few admit to having any kind of emergency kits at home, and they have no plan for what to do when the next big one hits.

Fault studies across California make it clear that more big tremors are coming, almost surely within the next decade or two. We educators must keep these past events alive in the minds of our students so they will be ready for these events when they come.