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Sunday Reading

This is the inaugural post of a weekly series I promised to start that will supplement my more in depth but sporadic blogging about topical seismic events. A couple months ago I joined Twitter to broadcast some of the interesting seismic news snippets I come across daily, including lots of content that didn’t really warrant drawn out posts. As I promised then, I’m now compiling my full week of Tweeted links into a “weekend reading” sort of post, to let you catch up on all the earthquake news you missed as it flew by on Twitter. So here goes: a bunch of articles about earthquakes to read, and why to read them.

Earthquake Early Warning

The biggest U.S. quake news was the tremor that rattled L.A. a couple weeks ago and spawned renewed lamentations about the stagnant state of California’s earthquake early warning system. The New York Times had the most comprehensive story:

…but some local media outlets had their own lamentations to add:

To me the highlight of the New York Times piece was the imaginative explanation of what benefits early warning of an earthquake could provide:

“[Japan’s EEW system was able to] activate computerized programs to slow commuter trains so they did not go off their tracks, stop elevators so passengers were not stranded between floors, flash highway warning signs instructing motorists to slow down and avoid overpasses, and open doors at fire stations so they would not be stuck shut should power be lost.
The warning would go out to home computers and personal cellphones, giving surgeons a moment to withdraw scalpels, workers at Disneyland time to shut down Space Mountain, home cooks an opportunity to turn off the gas and everyone a moment to… dive under a desk.
If you are cooking, you can step away from the boiling water… it would help people psychologically, decreasing the surprise that can freeze people in confusion and fear when the ground starts moving, or lead to panicked and dangerous reactions, like running outside a building.”

I like the introduction of the intangible psychological benefits of reducing the paralyzing suddenness with which earthquakes set upon us.

Emergency Kits

A bunch of articles have just come out regarding earthquake survival kits.

Oregon Live asks where to put them (the answer is “everywhere… and make sure they’re accessible”).

The USA Today introduces us to some particularly dedicated preppers:

And the New Zealand Herald describes an effect I think most seismologists would be ecstatic to learn of: small tremors have a huge impact on emergency kit sales (up 300%), signaling that people really do treat the benign moderate jolts as reminders of real hazard.

Prediction vs. Mitigation

On a subject intimately related to the prior two, The Guardian published an article by Dave Petley, director of the Institute of Hazard, Risk, and Resilience at the University of Durham (and perhaps known more familiarly as the author of AGU’s Landslide Blog). Dave presents the elusive ideal of earthquake prediction through a simple and plainspoken set of thought exercises, which ultimately illustrate that prediction isn’t truly what we want. Mitigation, preparation, and a few moments warning should suffice… and may have to.

Tsunamis Galore

On the 2nd anniversary of the March 11, 2011 M9.0 Tohoku earthquake, the National Oceanic and Atmospheric Administration reminded us that twenty eight other tsunamis have struck various parts of the world since then.

Earthquakes Rock the Atmosphere

A widely circulated research result this past week was the discovery of significant signals from the Tohoku earthquake… recorded by satellite gravity measurements as pressure waves passed through the edge of the atmosphere. There’s a great animation of the data here:

That should do it for now. Tune in again next weekend, or Follow me on Twitter! @TTremblingEarth

Twitter and the 21st century earthquake

You thought seismic waves were fast… you should see Twitter! The social microblogging service increasingly serves as a communication conduit between emergency management agencies and individuals during crises. The USGS has begun to exploit Twitter, both to dispatch earthquake information and in turn to collect tweets that show an earthquake has occurred, potentially before the relatively sparse network of seismometers detects and reports it. A couple of years ago USGS scientists Paul Earle, Michelle Guy, and their colleagues reported their preliminary evaluation of a system that culls tweets containing the word “earthquake” from the vicinity of a known quake epicenter. The results were strikingly effective at highlighting the epicentral region of the quake, indicated by the largest jump in the frequency of “earthquake”-related tweets. Their article is publicly available and explains the benefits and drawbacks of a Twitter-based earthquake detection system. It’s well worth a read. OMG Earthquake! Can Twitter Improve Earthquake Response? The article contains perhaps my favorite sentence of any academic paper I’ve read:

The first geocoded tweet about the earthquake arrived 19 seconds after the origin time and reported omfg, earthquake.”

Their supplemental material makes for an entertaining read, listing 360 seconds of tweets containing “earthquake” that followed the 2009 M4.3 Morgan Hill quake in the Bay Area. Electronic Supplement to Earle et al., 2010 While thoroughly exploring the caveats of twitter quake detection such as the general lack of true shaking records, including the fact that shaking intensity is unreported or unreliable, the authors demonstrate the powerful comparison of Twitter response times to the average reporting delays of even our fastest instrumental networks. Whereas tweets are published with a lag time of ~5 seconds, official USGS earthquake solutions are only made available minutes after an earthquake. Commonly in disasters, small data transmissions via mobile devices offer the only functional way to disseminate information, since power and telephone lines may be disrupted and data-heavy voice calls may overwhelm cell networks. Many people on both coasts may have a familiar experience in mind following moderate earthquakes: even with light shaking and no damage, the excitement stirred up by a temblor results in an overloaded cell network incapable of supporting your phone calls. It can be hours before phone calls go through.

Click to access www2010.pdf

Musings on seismology and earthquake hazard

A seismogram of the M6.8 “Nisqually” earthquake that struck central Washington state in 2001.

Phew, I’ve been a neglectful blogger… probably to the benefit of my dissertation research. I’ve got a few interesting posts in the pipeline, so I think I’ll take what time I can to finish them, then set them up so they’re nice and distributed for you to read.

In the meantime, you should all check out two cool blogs maintained by earthquake aficionado Arne Christensen, in which he compiles media and eyewitness accounts from two of the U.S.’s most notable contemporary earthquakes: Loma Prieta and Nisqually.

Arne recently asked me a few pressing questions he had about seismology and seismic risk on the U.S. west coast. The questions were very provocative and very relevant, so I crafted some responses that were as informative as I could make them without stepping on anyone’s toes. They’re good distillations of my thoughts on earthquakes, and I’ll vouch for my own synopsis of current earthquake research (although I advise anyone seeking formal advice to seek more direct sources, like the USGS, the Pacific Northwest Seismic Network, and contributing researchers). Caveats and citations aside, I think you should all go have a read of my “interview” for my personal take on modern seismic hazard “hot topics,” then you should peruse the wealth of accounts Arne has collected of recent significant quakes.

Part 1: Living with Earthquakes on the West Coast

Part 2: Seismology Issues and Changes in the State of the Art

I welcome any discussion of the points I made, and any corrections by more credible seismologists than myself.

Earthquake Alert App for Mexico City residents

Después de dos temblores grandes sentido en la Ciudad de México, el gobierno ha publicado una “app” que les alerta a los residentes del Distrito Federal cuando están grabado los señales sísmicas de un temblor grande. Porque muchos de los temblores sentido en el Distrito Federal se originan en la costa, hay mucho tiempo (algunos 30-60 segundos) para protegerse en la ciudad antes de tiembla. La aplicación está disponible solo para usuarios de los teléfonos BlackBerry, pero es gratis. Hay más información y la app está disponible del gobierno aqui:

Okay so I tried. Parece que muchas personas ven este sitio desde México a causa de estas noticias, así traté de usar mi español rudimentario para anunciarlas.

For those of you north of the border,

After two big earthquakes that shook Mexico City–a M7.4 on April 20 and a M6.0 on April 2–the Mexican government has released a very timely app that alerts residents of the capitol city to impending shaking. It’s based on the same system that provided warning to the congresspeople in the 20 April quake. The app is available only for BlackBerries right now, but the developers are open to other platforms provided the necessary speed for dissemination. The app can be downloaded for free from the Mexican government at the link above.

Here are detailed new releases:

This comes closely on the heels of a similar release in New Zealand that alerts residents to the magnitude and location of a quake immediately after it happens, but both countries lag well behind Japan, where the widespread adoption of mobile early-warning technology predated the Tohoku earthquake.

California Earthquake Early Warning interview

Cara Santa Maria's vlog on the Huffington Post this morning covers Earthquake Early Warning in CA

If all that demonstration of Earthquake Early Warning in my last post got you all excited, you’re in luck. This morning the science videocast “Talk Nerdy to Me,” produced by Cara Santa Rosa for the Huffington Post, contains a an interview with prominent CalTech seismologist Dr. Thomas Heaton, who discusses California’s developing early warning system. The video is well produced, with archival footage and great editing. It discusses the basics of an early warning system, why it would be valuable and how it would be practical, and sort of discusses why it’s still in the works–and not yet implemented as in other countries–for CA.

Have a watch!

Earthquake Early Warning Systems: Preparing for The Big One [Huffington Post]

Mexico City Earthquake Early Warning–it works!

USGS Shakemap based on instrumentally recorded shaking intensity and site conditions. Note the pockets of stronger shaking (green) in sedimentary basins well north of the epicenter.

Want to see what happens when you can know an earthquake is coming? Mexico has footage that’s got you covered.

Update 6 April 2012: They also have an app that alerts you to earthquakes before they hit… in Mexico City. (También tiene una App que se alerta de sismos antes de tiembla!)

On March 20, 2012 a very large earthquake rocked southern Mexico. With a magnitude of 7.4 and a moderate depth of 20km this quake was widely felt, and resulted in damage and casualties near its epicenter in Oaxaca. But Oaxaca wasn’t the only place that got rocked. Mexico City, more than 200 miles north, felt the waves amplified as usual by the lakebed sediments it’s situated upon. The sedimentary basin upon which Mexico City lies is the seismological bane of the city, trapping and amplifying seismic waves like a swimming pool. This unfortunate setting has devastated the city in the past, but is at least widely recognized as a liability. Because the effects of distant earthquakes are amplified in the Distrito Federal, it’s actually an ideal candidate for an early warning system that relies on the time it takes damaging seismic waves to reach a sensitive area once they’ve already been detected. Along with Japan, Mexico is one of the few countries in the world with a functioning early warning system, and last week’s large quake exercised it.

Once large-amplitude shaking is detected among the nation’s seismometers, a signal is transmitted immediately to activate alarms in the capitol city that warn residents shaking may be imminent. Damaging seismic waves travel at a little over 7,000 mph, so at 200 miles from the epicenter, Mexico City would have upwards of a minute and a half of warning before they hit. Of course the seismometers couldn’t detect the seismic waves immediately as they’re initiated, and it would take even more precious seconds before they could reliably identify the quake as a dangerous magnitude, but once they did the alarm was sent.

Footage of a Mexican Senate hearing captured the whole event. A shrill alarm starts going off at the beginning of the video, and the man speaking is interrupted by concerned colleagues who immediately and orderly evacuate the room. The alarm shuts off 50 seconds into the video. Although mild shaking may have begun at this point, capturing the attention of a couple of senators by swinging ceiling fixtures, substantial shaking doesn’t begin until just after the 1:05 mark. From there it clearly continues, noisily rocking light and audio apparati suspended from the ceiling. The electricity flickers on and off a couple times, and the rest of the recording is just the earthquake dying down.

This video is a beautiful demonstration of an earthquake early warning system in action, complete with the successful evacuation of a crowded room. If only we all had the fortune of Mexico City to be hundreds of miles from the earthquakes that plague us.

Bonus video: an extremely fortunate camera crew was set up along the Paseo de la Reforma in Mexico City shooting HD video of a tall statue before the earthquake started. They realize shortly into this video that the ground is swaying, and they capture it all as the towering statue starts oscillating heavily and noisily.

Earthquake early warning in action

No country would have been better prepared for such a massive earthquake than Japan. Straddling the boundaries between four converging tectonic plates, Japan is one of the most earthquake prone nations in the world, and is probably the most earthquake savvy. They have world-class networks of monitoring instruments including seismometers, tide gauges, and GPS locating stations; they routinely practice for massive quakes, which they are often visited by; and they have something Californians at this point still only dream of: an earthquake early warning system.

Screenshot of Japan's earthquake early warning system in action during the Tohoku quake. The upper panel shows a projected shaking intensity level at the computer's location, the middle panel shows a countdown until shaking begins, and the lower panel shows the current calculation of the earthquake's size.

The idea behind it is simple: the electromagnetic waves needed to transmit a warning travel effectively instantaneously, while seismic waves travel at “only” a few kilometers per second, delaying their arrival to distant locations. It’s exactly like lightning and thunder–the flash is nearly instantaneous for everyone, but the immediate cracking thunder up close differs from the delayed rolling rumble heard from far away, which is why we count the time between the flash and the bang to judge how far away a strike was (~five seconds per mile, in case anyone needed a reminder). The analogy isn’t entirely complete. Earthquakes aren’t the product of some abrupt electromagnetic signal like thunder is produced by lightning. In effect what early warning systems do is take the loud, close thunderclap and warn people tens of miles away that they’ll hear a rumble soon.

For people close to the epicenter of an earthquake, the time between detection of the quake and the onset of shaking where they are is minimal, so early warning is of little use. People farther away, however, have potentially tens of seconds’ warning that the seismic waves are on their way. Unfortunately for the utility of the system, the intensity of shaking dies off with distance, so it’s the people closest to the epicenter who need the most warning. Too bad… for most quakes. The system is at its most ideal for a massive quake like the 9.0 last month, which took nearly three minutes to produce and ended up rupturing hundreds of kilometers along the coast, effectively stretching the epicenter–or at least the source of seismic waves–so that cities that weren’t near the epicenter still ended up being close to a part of the fault that ruptured. In that case, the 30 second warning for the onset of shaking helpfully prepared people for the intensifying shaking after 3 minutes of rupture propagation.

In an earlier post I highlighted an amateur video showing the warning system in action. Thanks to the similarly excited Dr. Matthew d’Alessio at Cal State Northridge, I can guide you to an excerpt from one of Japan’s TV networks as the alert for the 9.0 quake preempts coverage of parliamentary proceedings:

The video gives an eerie perspective of the event unfolding: the quake is detected and reported long before shaking reaches Parliament, and the staff at the news studio have only just begun to realize the gravity of the event as the shaking intensifies. Only once the shaking has died down does attention shift to the dire tsunami warning.

The mere seconds of warning afforded by earthquake detection apparently pale in comparison to the minutes we have for tornadoes, days we have for hurricanes, and weeks we have for flood events, but they do allow you to drop crucial tasks and focus on the calamity at hand before it gets the best of you, a function automated systems are even better at!

The technology behind this is impressive, and by no means beyond the grasp of the U.S., but the development of a useful system requires a major budget, and the U.S. is busy… prioritizing. But that’s a subject for many a different blog.

In Japan, the software that runs these systems is developed by scientists and private companies, and has a variety of manifestations.

I’ll leave you to marvel at the system in action in a few different cases. As more information is processed from the ever-increasing number of seismometers detecting the earthquake, the epicenter and magnitude are revised, altering the estimates of arrival time and shaking level at the site, in a format unfortunately reminiscent of a painful scene in a certain NBC mini-series…

Here’s a little wall-mounted device that tells you all you need to know–don’t mind that this guy fakes the quake (maybe a test?):

Here’s a family taking appropriate action in an earlier, much milder quake:

The revision of magnitude calculations is common–in most cases it happens well after the earthquake, as data comes in from seismic stations around the world that help constrain just how much energy was released. It’s especially common after the so-called great earthquakes, which produce such large waves for so long that they drown out their own signals on seismograms, making them especially difficult to analyze. In any earthquake, however, realtime assessment of the magnitude is a dicey game. That’s not to say it produces inaccurate results from the data–there just isn’t enough data when only a few seismometers have been shaken yet! As more sensors detect the earthquake, a more robust magnitude and location can be determined. It’s more or less the same reason you have to watch replays from multiple angles to truly disagree with sports referees.

More unique perspectives of the 8.9 quake

As expected, videos continue to surface from people all over Japan documenting the shaking, rattling, and swaying of everything. Below I have collected some of the more interesting sights.

I recommend visiting Highly Allocthonous where Chris Rowan has summarized the which, what, where, and how of this massive quake. He’s also put together some nice little diagrams illustrating the more technical concepts.

The whole country of Japan shook for a very long time on Friday afternoon (their time). Beaches, farms, rural villages, forests, mountains, trains, and high-rise office or apartment buildings rattled for around two minutes while the plate boundary deep beneath them unzipped.

In Tokyo, the towering steel high-rises swayed with the low frequency waves passing through–a humbling sight from any perspective:

People’s responses to the shaking varied. This man has an understandably difficult time comprehending the emotional response of his neighbors. He’s alarmed at how much worse than the 7.2 foreshock two days prior this earthquake turns out to be. He runs outside into a cacophony of rattling structures:

This awesome video demonstrates Japan’s earthquake early warning system in effect. When the first seismometers in the country pick up the high-amplitude waves from this quake and determine its epicenter, an electronic signal is broadcast instantaneously, far in advance of the much slower seismic waves. This person has at least 30 seconds warning before the brunt of the shaking arrives. The shaking also gets worse and worse as it goes on–something many people would not be prepared for and anyone would find quite alarming.

In addition to informing people through the software shown in the previous video, the early warning system stops trains around the country to prevent derailment at high speeds. These folks are on one of the stopped trains when the waves start passing:

Here are some other videos I’ve stumbled across:

Other than the cameraman, these folks very aptly demonstrate the appropriate earthquake protection procedure while their apartment shakes heavily. On the other hand these fellows don’t seem to realize the import of the situation, although they appear to be only “gently” rocking in the upper stories of a building, like these office workers whose video doesn’t capture much apparent motion, but whose dialogue reveals the eerie sensation they’re witnessing.
In this video the quake rocks a 6th-floor bookstore.
Here we see the quake rocking a snowy temple, one that no doubt has experienced hundreds of these before. Watch the trees shake!
A shocked man sits helplessly in his car as the city trembles and the power goes out.
A transit station shakes noisily for a long time while commuters crouch to avoid being knocked off their feet.

In these videos it is indeed clear that despite extensive training drills, people are often overcome by the surprise and novelty of such a huge quake. In most cases, running outside is not a good strategy–imagine windows and cornices crashing down from the building you were in, or tiles sliding off the roof. Doorways are only safe to the extent that you can get yourself within a shear wall–your real security depends on the strength of the wall. Heavy, compact furniture is most often your best bet. Don’t let curiosity and surprise get the best of you!

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