The View of Japan's 8.9 Earthquake from Modesto, California

First off, I am sorry for the quality of the photographs. We have a seismometer, yes, but it is a simple teaching model, and the computer program is something like 15 years old (and has never been updated), so the system barely works at all. But it was working well enough to record the shaking of the ground in Modesto, California for several hours after the 8.9 magnitude earthquake in Sendai, Japan. The quake, if the 8.9 magnitude estimate remains unchanged, is the 5th largest ever recorded (I'm hearing that it might be upgraded to 9.0 or 9.1). It has killed hundreds and unleashed a horrific tsunami that has spread across the Pacific Ocean basin, causing damage even in Crescent City and Santa Cruz, California. The simple pendulum-based seismometer records ground motions in my geology laboratory on the campus of Modesto Junior College.

The first photo (above) shows the onset of the waves from the quake. Earthquakes produce a series of different waves which move in different ways, and at different velocities. The first waves arrived in Modesto at 9:58 PM local time, about 12 minutes after the quake began shaking about 80 miles offshore of Sendai, Japan (that is if the computer clock is right, not a safe assumption actually). These are Primary Waves, compressional waves that are analogous to sound waves. Obviously they travel faster than the other waves. They are an example of body waves, those which travel through the earth, not just on the surface. The second set of waves that would have arrived were Secondary Waves, a slower set of body waves that are generated by shearing motions. The closest analogy I can think of is a whipping motion, like that of shaking a stretched "slinky" up and down (this is the demonstration I use in classes). The record on the seismograph doesn't allow me to pinpoint the S-wave arrival.

A third group of waves arrive several minutes later. These are surface waves, and as their name suggests, they don't pass through the earth, they travel at the surface. One type of surface wave is analogous to ripples on a pond after a pebble has been tossed in. The surface of the water rises and falls, but fish in the water do not bob up and down. They are unaffected by the passage of the ripples. A second form of surface wave shakes side to side rather than up and down. Surface waves have a lot to do with the damage caused by earthquakes, given the way that energy is concentrated at the surface, and the distortions of the ground caused by the waves. Surface waves continued to be recorded at Modesto Junior College for hours after the quake (as well as reflecting and refracting body waves). In the picture above, 26 minutes had elapsed, and the monitor was off the scale for minutes at a time.

The seismometer is automatically set to record a two hour time period after being tripped, and at the end of two hours, the waves were still immense (above). They probably continued for three or four hours. It's important to realize that the earthquake didn't last this long. From what I've read, the shaking went on for around three minutes at Sendai, Japan (and that was more than enough to cause terrible damage). If the peal of a bell is an earthquake, the waves being recorded at Modesto are the reverberations of the bell. They waves travel back and forth around the planet for many, many hours. The refraction and reflection of these many waves provide seismologists with a picture of the Earth's interior.

A note about the magnitude scale: it is open-ended scale that originally measured the size of the biggest wave to determine if a quake was big, medium or small. It is not a 1-10 scale as is often stated in the media, although rocks can only store enough seismic energy to produce about a magnitude 9.5 event. A giant asteroid impact could produce a much larger event, well beyond a ten. The media often report that a rise of one magnitude represents a quake that is 10 times larger, but this is not exactly accurate. For smaller quakes, the increase of 10 times represents a 10-fold increase in the size of the waves. The waves of quakes at around magnitude 6.5 don't get higher, though, so the magnitude scale loses meaning.

Quakes obviously get bigger, though. The total energy of a quake increases by a factor of just over 30 times per magnitude number. Thus, a magnitude 7.0 like the one that devastated Haiti last year was 1/30th the size of a magnitude 8 quake, and roughly 1/1,000th the size of the Sendai quake. The horrible death toll of the Haiti quake (despite the smaller energy release) was the result of many other factors, such as the shallow nature of the quake, and the location of the focus directly underneath an urban area. The Sendai quake was 80 miles offshore of Japan.

I am almost always disapointed in the commentary of news readers on the cable networks. A few minutes of education would make a world of difference during fast moving events like the Sendai quake. Wikipedia has a reasonably good description of how magnitude is measured. And by the way, I am not the world's greatest authority on seismology, and I am open to correction if I got some of this wrong! That's what the comments section is for...

Postscript: Silver Fox at Looking for Detachment has a list of the geoblogosphere's response to the Japan earthquake here.

Update: Both the USGS and Japanese geologists have upgraded the magnitude of the quake to 9.0, making it the 4th largest ever recorded.

8.9 Earthquake in Japan

We are learning more about a massive quake in Japan, with an estimated magnitude of 8.9 offshore of Sendai, Honshu. A major tsunami has been generated and the cable news shows are showing aerial shots of an extraordinary wave spreading across agricultural fields, overwhelming roads and villages. From the maps, it appears that the quake was generated in the subduction zone on the Pacific side. There is a good chance that a tsunami could be spreading through the Pacific, but I have not heard any confirmation. I would only say that if the authorities issue a warning, take it seriously and get to a safe place.

The most stunning aspect so far has been the aerial perspective of the tsunami spreading across the landscape. The 2004 tsunami in Indonesia was documented better than any previous event, but I don't recall seeing any aerial shots like this. Tsunamis are not really waves, they are surges of water that rush inland at speeds sometimes approaching 100 mph. The surge picks up debris and uses it as a battering ram. It is terrifying to see.

The TV commentators are starting to get up to speed, but for the best information from seismologists, check out the U.S. Geological Survey here. They have links to the current tsunami conditions in the Pacific basin.

My night class watched the 7.2 quake on Tuesday on our teaching seismograph, and I assume it was a foreshock to this event. Ironically, the subject of the day in my physical geology class was the types of damage caused by quakes. We mentioned tsunamis...

I pray for those in the path of the devastation.

UPDATE #1: A tsunami watch has been issued for the Hawaiian Islands. If a wave has been generated, it will arrive about 3 am Hawaii time.

UPDATE #2: The tsunami watch has been upgraded to a tsunami warning in Hawaii. Please take it seriously. The waves, if any, will reach the coast of California and Oregon around 7-7:30 am local time. At that distance, I don't expect much, but things can change overnight.

UPDATE #3: If 8.9 magnitude becomes official, this is the 5th largest quake in the world since 1900. Chile 1960, 9.5; Alaska 1964, 9.2; Sumatra 2004, 9.1; Kamchatka, Russia, 1952, 9.0. I finally hear an MSNBC commentator get the energy numbers right: the difference in energy between this and the Haiti quake at 7.0 is closer to 1,000 times, not 100 times. The equivalent of 1,000 Haiti quakes just hit offshore of Japan.

UPDATE #4: A tsunami watch has been announced for the coast of California. Take it seriously if you live in coastal areas. If it comes, it will arrive around 7:30-7:45 am in the morning. Listen for official warnings and obey them! Don't do the California thing and wander down to the beach to look for it.

UPDATE #5: The Pacific Coast is now under a tsunami warning, with expected wave heights of 3 feet or so, arriving around 8 in the morning depending on location. Take it seriously; if you are on the beach, you could easily be swept away by such waves. Follow official warnings; emergency personnel know what they are doing!

UPDATE #6: Some damage is now being reported in California as surges of water hit Crescent City and other coastal towns. Damage is "significant", not major, mostly along the lines of boats being jostled and ripped from moorings. I'm hearing of waves 5-6 feet high along parts of the California coast, and of 8 foot waves in Hawaii. 11 people were killed at Crescent City in 1964 from a tsunami of 12 feet, in part because they didn't realize the waves come in groups, and the first wave is not necessarily the largest. It is a cautionary tale for all the people rushing out to the beach to "see the tsunami". It might not be a good idea to become, literally, part of the story. Stay out of coastal areas until an "all clear" signal is given.

UPDATE #7: Silver Fox at Looking for Detachment has a list of the geoblogosphere's response to the Japan earthquake here.

UPDATE #8: Both the USGS and Japanese geologists have upgraded the magnitude of the quake to 9.0, making it the 4th largest ever recorded.

Momma, I want to be a Paleomagnetologist when I grow up!

How many of you woke up one day and told yourself "when I grow up, I want to be a paleomagnetologist"? It's a question I ask my classes as we start to talk about continental drift and plate tectonics, and it's usually good for a chuckle (sometimes even two), and not once has anyone raised their hand in an affirmative response. It's a relatively obscure field in geophysics, and although most geologists know what paleomagnetologists do, most of the rest of us do not. What follows in the class is a rather extended discussion about Earth's magnetic field and the behaviour of compasses. We're trying to get to a comprehension level to where we can talk about one of the more stunning discoveries ever made in the field of the geological sciences, a line of reasoning and research that provided unexpected evidence for continental "drift" and plate tectonics. It had to do with the Earth's magnetic field.

Every child has probably played with magnets, dragging them through the soil picking up iron filings, or playing with the Wooly Willy face drawing toy. Later on, some kids encounter the use of compasses by orienteering while hiking with the scouts or other outdoor groups. For many it stops there, but the exploration of the mysteries of magnetism throughout history is quite an interesting affair, and I was unaware of much of the story. So it was that when I was given a review copy and asked to comment on a new book by Gillian Turner, North Pole, South Pole, I was intrigued, and agreed to check it out. In short, I found the book to be well-written, well-illustrated, and quite interesting. I actually read two books in the last few weeks, and on the face of it they couldn't be more different, but I noticed an interesting parallel. Besides Turner's book, I read an online version of "The Last Ringbearer" by Kirill Yeskov, a Russian paleontologist (!), a re-telling of the "Lord of the Rings" saga from the point of view of the residents of Mordor. It was a fascinating thought exercise that explores the idea that winners get to write the history, and that Mordor's "evilness" was more a construct of the elve's and men's prejudices than of reality.

I recognized the need for a different point of view of history as I read Turner's book. By concentrating on the study of magnetism throughout history, she provides a whole new perspective of the sequence of events that led to the discoveries of "apparent" polar wandering and paleomagnetic reversals, two of the most important lines of evidence that support plate tectonics theory. Unlike Alfred Wegener, who seemed hell-bent on proving his drift hypothesis, the magnetism people were just following the evidence, trying to understand how the Earth's magnetic field worked, and how it had changed throughout time. When they stumbled onto one of the most critical pieces of evidence for the movement of continents (and ocean floors), it was a happy accident, but they were quick to recognize the importance of their findings, even if others outside the field were not. For instance, the polar wander curves for different continents, an unambiguous record of independent continental movements, were worked out in the 1950's, a full decade before the acceptance of plate tectonic theory by most geologists.

I'm not suggesting that the paleomagnetologist's contributions to the debate over continental drift have been ignored, it's just that their methods and findings can be a bit harder to explain or appreciate. That is the value of Gillian Turner's book. She has provided a concise and interesting history of the study of magnetism, and a fascinating new perspective of one of the most important geological discoveries of the twentieth century, plate tectonics. It's well worth a look!

Turner, Gilliam, 2010, North Pole, South Pole: The Epic Quest to Solve the Great Mystery of Earth's Magnetism, The Experiment Publishing, New York, 272 pages.

My Favorite Geologic Picture: Oh, so many to choose from...(Accretionary Wedge #32)

The Accretionary Wedge for early March is sponsored by Ann's Musings on Geology and Other Things, and we are asked for our favorite geological picture. What a hard choice!

Long before I had a digital camera, I used a particular slide from a trip in the 1980s to introduce my students to the idea of the fascination of geology. It was taken next to one of the most famous photography spots in our national park system, but it is not a picture of the iconic feature. It's the trail leading to it. Delicate Arch of the "Real" Jurassic Park lies just around the corner, and a crowd is often found there, especially at sunset. But I see fewer people stop and consider this scene....

I got into geology in part because of the wonderful journey of imagination that it is; a geologist is a world traveler, and a time traveler. The trail in this picture is formed on a natural break in the rock. Why is the break there?

In Jurassic time 180 and 140 million years ago, tidal flats and coastal sand dunes spread across this part of Utah. The surfaces of the dunes were pathways for all kinds of creatures, from insects to giant lumbering dinosaurs. The walked and crawled on these sands, and later the surfaces were preserved by subsequent layers of windblown sand. The surface later hardened a bit more than the others, and millions of years later, erosion exposed the old sands. A fracture developed along the surface, and the trail-builders of a few decades ago found it a great deal easier to just remove the overlying rock than to carve a new flat surface at great expense. And so it is that during our brief sojourn on the planet, we walk on the same surface, and perceive the significance of that fact. We use our minds to explore strange alien worlds, and yet these are the worlds that existed before ours and which became the raw materials for our own.
Again, practically everyone walks up to Delicate Arch, but there is another arch just a few steps off the trail that provides a stunning view the distant La Sal Mountains, the laccolithic cores of 25 million year old volcanoes. This picture, taken just a few yards from the one above, contains the four elements of ancient human thought: water, earth, fire and sky (the water is in the sky and in the creek below). The essence of earth science...

Thanks to Ann for sponsoring the Wedge!

UPDATE 8/19/11: Do you need geology-themed photos and images for teaching or research purposes? I have hundreds of geologic images posted at Geotripper Images. Check it out!

"I'm a Geologist": Why That's Important

The following words are not mine, but I wish I had said them. Allen Glazner is a professor at the University of North Carolina-Chapel Hill, and a former classmate at Pomona College (in another century). He has written a number of excellent books on the geology of California, including a beautiful book on Yosemite National Park (with Greg Stock). Geology is not about rock collecting, it's about the sustainability of living on planet Earth. This is part of a column from NewsObserver.com. Please give the whole editorial a look.

"If I were to ask average people where gasoline comes from, most wouldn't really know. They might have a mental image, from a children's book, of a black pool of oil underground with a pipe sticking into it, but this is far from the truth. Many think drinking water comes "from the faucet," with little idea of what the source is. The average American home has more than 400 pounds of copper in it. Where does that come from? Even the sources of the sand and gravel vital to construction are a mystery to most people.

Well over 90 percent of the power used in the U.S. comes from fossil fuels and nuclear energy. Thank a geologist - we're the ones who find oil, natural gas, coal and uranium. Even if you think that these energy sources are loathsome, we're stuck with them for some years to come. Geothermal energy? That's an easy one - thank a geologist.

We all take clean, fresh water for granted. Thank a geologist - we find that fresh water and monitor its quality and inventory. Many "green power" devices, such as high-capacity batteries, LEDs and superstrong magnets, depend upon rare, obscure elements such as dysprosium, neodymium and indium. Thank a geologist - we're the ones who know how those elements are cycled in the Earth and where to find them.

The prices of many of these metals, including all that copper in your house, have doubled or tripled in recent years, and the price of oil has quadrupled in the past decade. Business people would benefit from learning a little geology so that they could understand this better.

Geologists are the go-to people for natural hazards. We monitor earthquakes and map faults so that buildings and bridges can be sited as safely as possible. We advise on where to put roads and houses to avoid landslides, and where to put tunnels for roads, pipelines and other infrastructure. We monitor volcanoes for risks to the local populace and aviation. We map areas susceptible to flooding. When the gasoline storage tank at the corner gas station starts to leak, we figure out where that underground gasoline plume is going and how to fix the problem."

Read more: http://www.newsobserver.com/2011/03/05/1029942/geology-can-you-dig-it.html#ixzz1FmXtLCUD . Thanks to Lockwood and Anne Jefferson for the tip.

A Great Opportunity: CalPaleo, May 14 at Sierra College

This came across my desk this week. It looks like a great opportunity to learn about California's unique paleo-past!

"Sierra College and Sierra College Natural History Museum are pleased to host the 2011 meeting of CalPaleo on Saturday May 14 – only two and a half months from now. PaleoResource Consultants – a company providing paleontological mitigation services -- is co-sponsoring the meeting.

Don't miss this great opportunity to present your own research and learn about the latest research of others. CalPaleo meetings have typically emphasized the research of students from California colleges and universities, with a sprinkle of research papers by professors and other researchers. The cohesive factor that makes us CalPaleo is that we are California Paleontologists -- either we live here and do research here, we live here and do research elsewhere, or we live elsewhere and do research here. Regardless, we are all California Paleontologists. CalPaleo meetings bring us all together in a way that GSA, BSA, AAPG, AASP, or even SVP meetings cannot.

In this 2nd announcement of the 2011 CalPaleo meeting, we provide an update on the CalPaleo 2011 website, fieldtrip plans, registration fees, local lodging, and the first Call for Papers (both oral and poster). With the next/3rd announcement, we hope that you will be able to download an attractive, colorful Call for Papers to give to all your friends. In the meantime, please forward this simple and rather plain 2nd announcement to everyone that you think needs to know about the 2011 CalPaleo meeting and encourage them to be here. You may even want to offer to let them ride along with you!

You will love the Rocklin area, located in the foothills of the Sierra just 20 minutes east of Sacramento right off I-80. Unlike much of California, we have trees, lakes, and permanent streams! In other words, our environment is much more like the late Tertiary. Plan ahead. You may just want to spend an extra day or two here in the Pliocene!

CalPaleo.org Website – It’s up; it’s working. It’s just still under construction. CalPaleo.org that is. Check it out and give us feedback on what needs to be added to make it more “user friendly”. Thanks to Kristin McCallister who has been doing most of the work. Kristin is a former Sierra College student, a recent graduate from University of Nevada at Reno, and now employed with PaleoResource Consultants in Auburn.

Fieldtrip Plans – On Sunday, following the CalPaleo presentations on Saturday, Dick Hilton will be leading an informal fieldtrip from Sierra College up to Donner Pass. Some of us are calling it – “From the Pliocene, back to the Pleistocene”. During this trip we will examine outcrops that have in the past produced Jurassic invertebrates, Eocene wood and leaves, and Miocene leaves. Plus we will see classic Sierra Nevada geology, Mesozoic low-grade metamorphics, Cretaceous granites with xenoliths, Paleozoic roof pendants, Tertiary auriferous gravels and volcaniclastic sediments, and Quaternary alluvial deposits. Both the Tertiary and Quaternary deposits have produced vertebrates elsewhere, but not so far in the outcrops we plan to examine.

Registration Fees – After considerable gnashing of teeth, the CalPaleo 2011 Organizing Committee has decided that, in order to pay for both a continental breakfast and lunch, we will need to charge a nominal $20.00 registration fee. There will be an extra charge of $25.00 for the Sunday fieldtrip, including lunch, bus transportation, and a copy of the fieldtrip guidebook.

Housing Ideas – In the next/3rd announcement, we will provide a list of motels available near the Sierra College campus. There are both inexpensive and four-star hotels within walking distance of the campus.

Call for Papers -- Abstract deadline is Friday 01 April. April Fool! Actually the deadline is Saturday 02 April. Expect another reminder in late March, but why not put the date on your calendar now? Follow the Boy Scout motto -- “Be Prepared”. Help us capture the diversity of paleontological research underway in California. Remember that not all fossils have bones and teeth! Be present to ensure that your area of expertise is represented -- be it ichnofossils, microfossils, invertebrates, plants, fish, birds, other dinosaurs, or those lovable, warm, fuzzy guys!

Save the Date! -- As we stated in the 1st announcement, what's most important right now is that you Save the Date! Saturday 14 May 2011. We hope to see you at CalPaleo in 2011 at Sierra College in Rocklin.

CalPaleo 2011 Organizing Committee

The Other California: Why worry about Yellowstone? We've got our own "Supervolcanoes" to worry about

First off, let's get something straight. As far as geologists are concerned, there are no "supervolcanoes". There are stratovolcanoes, plug domes, cinder cones, and shields, but no "supervolcanoes". What the tv documentaries call a "supervolcano" wouldn't technically be a volcano at all, since it is a giant hole in the ground, not a mountainous feature produced by lava flows.

The volcanic features referred to as "supervolcanoes" are actually calderas, large, generally round depressions in the crust that form when huge eruptions of hot ash empty out magma chambers. The destablilized crust collapses inward to fill the void. Calderas form in a number of circumstances, and are not always catastrophic events. On the Big Island of Hawaii, for instance, the calderas on the summit of the vast shield volcanoes are just a few miles across, and are stable enough that the Hawaii Volcano Observatory is perched on the edge of one. On the other hand, the formation of some calderas is a catastrophe of almost unimaginable proportions. The eruption that produced the caldera at Crater Lake involved the extrusion of something like 25 cubic miles of ash, and turned the 11,000-12,000 foot high mountain into a gaping crater 4,000 feet deep, with a crater rim elevation of only 8,000 feet or so. The eruption was around 7,000 years ago, and human witnesses related stories of the eruption that have survived as myths into the present day. A similar-sized eruption in 1815 at Tambora in Indonesia caused food shortages in the northern hemisphere by blocking sunlight. Snow fell during the summer months, disrupting agriculture.

The ultimate in a caldera eruption, though, is one that forms over a rhyolite magma chamber. Rhyolite is a silica-rich magma that can be highly explosive. It is also pasty (highly viscous), and the magma chambers can grow to massive proportions, sometimes tens of miles across. Rhyolite magma underlies Yellowstone National Park, and eruptions produced 185 cubic miles of ash 640,000 years ago, 67 cubic miles of ash 1.3 million years ago, and a simply unimaginable 585 cubic miles of ash 2.1 million years ago. An eruption of that size in the present day would be a civilization killer by way of a more or less instant ice age and massive disruptions of agriculture worldwide.

Everyone (at least everyone on cable tv channels) seems worried that the Yellowstone "supervolcano" is going to explode and kill us all. But if you live in California, you have other volcanic catastrophes to worry about. But that's not what I'm writing about today. I want to talk about a giant caldera that is part of California's past.

Rhyolite and granite are the same rock, at least as far as composition is concerned. The difference between them is crystal size; granite has visible crystals of quartz, feldspar and mica, while the crystals in rhyolite are too small to see. The difference arises from the place where the rock cooled. Granite cools slowly over many years deep in the crust, while rhyolite cools in a matter of hours or days following an eruption at the earth's surface. The Sierra Nevada is justly famous for the extensive exposures of granitic rock that form the sharp pointed alpine peaks and deep glacial valleys. The range is essentially a 400 mile-long tilted block of the speckled rock. What intrigues me is that while all that granite was intruding into the crust 100 million or so years ago (actually from about 140 to 85 million years), there must have been quite a collection of volcanoes and volcanic features on the surface above, features that would have been removed long ago by erosion. Except in a few spots...

The Minarets are probably the most beautiful and spectacular mountain ridge in the state that is not protected in the boundaries of a national park or monument (It is however protected as a National Forest Wilderness Area). The peaks are familiar to travelers headed to Devils Postpile National Monument, as they pass a pullout called Minarets Vista as they cross the crest of the Sierra Nevada. Far fewer actually walk among the pinnacles and towers in the depths of the wilderness.
The rocks of the Minarets are clearly different than your "average" Sierra. Granitic rock doesn't usually have the dark tones that are characteristic of the Minarets and is not usually as "spiky" (is that a geology word?). A closer inspection of the rock reveals that they are metamorphic, that is, baked and pressurized. Usually such rocks are older than the surrounding granite, but research reveals that this is not the case here. The metamorphic rocks are roughly the same age as some of the surrounding granitic rocks. The rocks include ash flow tuffs and large chunks of various kinds of volcanic rocks. Chunks, as in pieces as much as a mile wide. Big pieces of rock that collapsed into an evacuated magma chamber. The rocks of the Minarets are the remains of giant caldera, as seen from inside the crust of the earth.

So...Yellowstone National Park is a really neat place to see an active caldera, and if the cable news channels are right, it will probably kill us all by erupting, I dunno, maybe in 2012, but what a cool idea to be able to explore a caldera from the inside out! And it has the added virtue of being absolutely extinct, so it won't destroy us and our society in a cataclysmic explosion (just 15 miles to the east, the news isn't so good; more on that later).

As noted before, the Minarets are easily seen from a distance at places like Minaret Vista, and a somewhat less visited view can be had from the Sierra Vista Scenic Byway on the west slope of the Sierra Nevada. The only good way to see the rocks themselves is to hike in. I did some hiking there in my pre-geology days, and would love to return!

R. S. Fiske and O. T. Tobisch, 1994, Middle Cretaceous ash-flow tuff and caldera-collapse deposit in the Minarets Caldera, east-central Sierra Nevada, California: GSA Bulletin; v. 106; no. 5; p. 582-593 (abstract here)