The Trembling Earth

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Tag Archives: tsunami

Sunday Reading #2

Here’s the second installment of my now weekly series in which I compile all the neat-o earthquake things I’ve relayed via Twitter over the prior week.

National Tsunami Week

From March 24-30, the U.S. National Oceanic and Atmospheric Administration (NOAA) and Federal Emergency Management Agency (FEMA) teamed up to raise awareness of tsunami hazard, assembling a huge number of resources. Get informed about the tsunami risk to your coast line, and learn what you should do–I compiled their compilations here.

Earthquake Anniversaries

There were some notable earthquake anniversaries this past week: in 1983 a hefty jolt shook Portland–the “Spring Break quake.” In 1964, the largest earthquake in North America’s modern history, the M9.2 Good Friday earthquake, shook Anchorage for several minutes, jostling loose all kinds of landslides and faults, and sent a massive tsunami racing across the Pacific.

Fluid Injection & Induced Earthquakes

A paper was published this week documenting the striking correlation between the timing/location of damaging earthquakes and the timing/location of industrial fluid injection. Oklahoma has this problem, Arkansas has this problem, and the Netherlands has this problem.
http://geology.gsapubs.org/content/early/2013/03/26/G34045.1.short
Ooops.

Turkey’s Urban Renewal/Quake Retrofitting Plan Kicks In

Earlier this year, the government of Turkey initiated an urban renewal project in Istanbul that will replace deadly apartment blocks with housing built to withstand their inevitable temblor(s).
www.invest.gov.tr
– info from Turkey’s gov’t
Earthquake Hazard for Istanbul – blog article summarizing the policy

Some are not as happy as others about this:
http://www.theatlantic.com/international/archive/2013/03/preparing-for-earthquakes-istanbul-rattles-its-apartment-dwellers/274410/

Seismic Engineering (failures)

The new eastern (Oakland) span of the San Francisco-Oakland Bay Bridge may have had a bit of a setback this week when dozens of enormous bolts used in its seismic joints failed during seismic testing. Ooops. They’ll be fixed/replaced… but the grand opening may be pushed back. :(
http://www.nydailynews.com/news/national/bay-bridge-quake-safety-bolts-fail-test-article-1.1300679

Earthquake Footage

YouTube’s “EarthquakeVideoMex” compiled a few new videos of earthquake footage, one from a M6.3 in Mexico a few years ago (with some amazing standing waves in an upper story pool):

…and one from the M6.5 that jolted Taiwan earlier this week.

Earthquakes and Cheese

In potentially the most important earthquake-related development of the week, we learned how the Parmagiano-Reggiano industry recovered from a devastating earthquake that struck almost a year ago and wrecked millions of dollars worth of cheese.
The Miracle After Italy’s ‘Parmesan Quake’ – WorldCrunch news

See you next week! Or hopefully before then. Happy reading. Join in the fun and get these in real time @TTremblingEarth on Twitter!

National Tsunami Awareness Week – March 24-30, 2013

The Great Wave by Hokusai

This week the United States has been recognizing National Tsunami Week, an awareness campaign by NOAA, the USGS, FEMA, and a whole host of other emergency response agencies to ensure that the American public is aware of the tsunami hazard facing our coasts, and that we know what to do about it.

The bottom line is that we face threats on all fronts, although they’re greatest along the Pacific shore. Local megaquakes in the Pacific Northwest will one day wash torrents of water ashore in Washington, Oregon, and Northern California. More frequently than that (we have two examples from this decade alone), giant quakes elsewhere around the Pacific will send tsunamis racing across the ocean to flood our shorelines and swirl around our harbors. Large quakes in the Caribbean and landslides out in the Atlantic pose a tsunami threat to our Gulf and Atlantic coasts.

Fortunately we’re familiar with this risk because we’ve seen the effects of even 1-meter-high tsunamis on our coastline:

NOAA maintains several tsunami warning centers (including Pacific and West Coast/Alaska), and we’re ever striving to improve our detection capabilities as well as inform the public.

Take the opportunity to inform yourself this week, and “be Tsunami Ready!”   There are tons of resources, listed below.

Tsunami Awareness Week from the National Tsunami Hazard Mitigation Program:
http://nthmp.tsunami.gov/taw/tsunami-awareness-week.html

What to do to protect yourself:
http://www.tsunamiready.noaa.gov/

Tons of tsunami resources from California
http://www.calema.ca.gov/NewsandMedia/Pages/Current%20News%20and%20Events/National%20Tsunami%20Preparedness%20Week.aspx

USGS report on “Community Exposure to Tsunami Hazards” [pdf document]
http://pubs.usgs.gov/sir/2012/5222/sir2012-5222.pdf

NOAA’s Center for Tsunami Research has a ton of cool models and animations (their YouTube channel is chock full, at YouTube.com/noaapmel) that represent the best measurements and calculations from actual tsunami events that have happened. One recently released model shows the best estimate of what happened during the Good Friday earthquake of 1964 in Alaska. The tsunami from that quake ravaged the U.S. coastline in Alaska, Hawaii, Washington, Oregon, and California and caused fatalities. Get informed! These things happen.

First-hand documentaries from the Tohoku quake and tsunami

Several eye-witnesses of the March 11 M9.0 in Japan have posted chilling first-hand footage of their experiences. The following two videos document the entire disaster, from the shaking until deep into the tsunami.

First, here’s the harrowing video taken by a professional storm chaser who happened to be in Otsuchi, Japan doing volunteer work for Save Japan Dolphins when the earthquake roared along the coast. He struggles to keep his balance at the tail end of the earthquake, then they hop in their car and spend eight precious minutes fleeing to high ground with the rest of the alarmed population. These guys are clearly professionals; they have incredible composure. As they navigate their way through town you hear radio correspondence with a second car behind them full of other dolphin activists, the Sea Shepherds. While the tsunami roils its way into the bay from the open ocean, the water level creeps up and floods the seaside industrial buildings. As usual with footage of the tsunami, it keeps on coming, getting higher and higher against all belief.

This next video is unprecedented: a high-def dashboard camera in a bus records the entire event, most of it from in/on the tsunami! It was recently recovered, and we get to witness its journey. It would be marvelous if someone who knows Japanese could do a little translation of this report. Watch this; the following text is a spoiler.

It’s incredible to watch as the bus helplessly bobs with mounds of urban flotsam, but the literally immersive perspective reveals fascinating gradients in the velocity and height of the tsunami’s flow as it rages through city streets. The bus seems for a while fortunately stuck in an eddy behind a huge concrete building… until it gets entrained in a rapid flow and slammed up against something, at which point debris pierces the windshield, water rushes in, and the camera dies.

There’s at least one more street-level recording of the tsunami pouring into town. Once again what begins high and dry ends up so far below water it defies imagination.

Japanese videos of the Tohoku earthquake and tsunami

So many videos of the March 11 M9.0 Tohoku earthquake and ensuing tsunami exist that collecting and disseminating them is a daunting task. In my three earlier posts on the subject I referred you to a variety of perspectives of both events (the quake and the tsunami). Since then plenty more clips have emerged, and continue to. I’ll make an attempt to guide you to a few of the more spectacular or interesting ones; the rest can be found through potentially endless browsing among the chain of “related videos” on YouTube.

The earthquake

The following surveillance video is one of the few that I’ve found recorded from a well-mounted stationary camera, removing the shakiness of handheld cameras that makes it difficult to discern real ground motion. As the camera remains strongly braced against the ceiling/wall, we can much more clearly see the motion of the contents of this building as it sways in the quake. The footage is from a 5th floor office in Koto Ward, Tokyo. Note the duration of shaking–over two minutes!–and pay attention to changes in the direction of shaking. The two most remarkable aspects of this footage are the variability in direction and intensity of shaking. The shaking we observe doesn’t reflect true ground motion, but rather the building’s response to that force from below. The building twists and wobbles as it’s shaken from beneath, perhaps adding to the fluctuating intensity of the shaking. The large source area of the earthquake (a huge patch of the subduction interface that ruptured) also contributes to the fluctuations in shaking as waves from early in the earthquake bounce around beneath the city and interfere with incoming waves from the later parts of the rupture. Shaking intensifies as it proceeds, likely representing both the interference of old and new waves and the gradual approach of the earthquake wave source southward as the rupture propagated down the coast, closer to this building.

The next clip was filmed outside and only coincidentally captured the quake, unlike most of the others in which people had enough time to run and grab their cameras.

Here a couple of young American tourists witnesses the quake in a Tokyo park. The rustling trees and alarmed birds provide a glimpse of quakes sans humans, while the warning siren adds an eerie gravity to the situation.

The tsunami

All of the videos of the tsunami I have seen are powerful, terrifying, and staggering to watch. Here are a few Japanese videos of it pouring into coastal harbors on the northeast coast, filmed from shore-front office buildings.

The most astounding part of these videos is how quickly the surge in sea level overtakes the seawalls and surges inland. It happens so quickly and easily it seems almost calm, belying the utter violence of torrents of water pouring into the city streets.

The tsunami easily overtakes the seawall in Shiogama, and the warning siren adds a chillingly stoic urgency to the unfolding disaster. “This is really happening” is the message I get.

Another video from just down the pier in Shiogama, where passenger ferries wait at a floating boarding platform. This video is filled with markers to indicate how high the water rises–watch especially the loading ramps and the bottom of the 2nd or 3rd floor balcony the videographer is standing on.

[Updated 4/18/11 10:35am]: Here’s a 3rd video of the tsunami overtopping a seawall, this time in Kesennuma port. The utter devastation wrought by the tsunami surge is plain to see here: it destroys absolutely everything in its path–everything you think it might wipe out from the beginning of the video… it does. This is how you end up with those scenes of utterly razed coastal towns. I can’t imagine this cameraman wasn’t utterly fearing for his life.

Below is yet another unbelievable video of the tsunami swelling into Kesennuma. This one is chock full of massive ships being swept through town, and like the other ones it shows the sea continue to flood inland to an astonishing depth.

This next video is a long one (~10 minutes), but well worth watching to see the full beginning of the tsunami unfold. There are fascinating eddies, currents, and surges to watch interact; you see how easily boats can get tossed around; and believe me, it doesn’t get truly intense until the end, even after you thought the worst was past. It’s like the first quake video above: don’t be fooled by the duration or waning intensity of the disaster at hand. In both cases it just gets worse and worse.

Finally two much shorter clips of the wave crashing ashore. The first I haven’t been able to find the raw clip of, but the news excerpt will suffice. The perspective is from the ground in what appears to be a similar area to–if not the very same–the region filmed so famously from the helicopter as the flaming black goo surged ashore. The clip of interest is short, and it’s merely of the wave cresting and crashing, but it is a formidable sight to see with its towering height:

Here watch the incredible volume of water surging forth as it’s launched over a breakwater and then speeds rapidly ashore:

The last video I want to share today serves as an incredible illustration of the age-old wisdom that a deep drawback of the sea forebodes a devastating surge back inward. Don’t go collect fish when you see the ocean get sucked out! Throughout this video there are various items for scale that give a staggering perspective on just how low the sea has dropped in advance of the inward surge of the tsunami:

I have hardly referred you to a fraction of the videos out there, so if you’re in awe of these there are plenty more to be found by clicking through the related videos on YouTube. As you watch these videos that bring you closer to the scene and evoke some vicarious experience of the terror, do consider the plight of those millions displaced; there are links to major aid organizations in the right-hand panel.

Footage of the March 11 tsunami around the Pacific

Plenty of news organizations have been collecting the extensive footage of last week’s tsunami generated by the M8.9 earthquake in Japan, so following along with them is a great way to keep up with the utterly humbling images from the interface between humanity and this planet’s powerful nature.

In particular the BBC has compilations of video from Japan, CNN has a scary view, and the L.A. Times has some footage from the California coast.

A good place to start is with the BBC’s superb explanatory video describing how tsunamis form. Despite the ocean-wide impact of Friday’s tsunami ($50 million in damage along even the CA coast alone), the risk that the U.S. faces from a locally-generated tsunami varies depending on where you live. In particular, although the entire west coast is a tectonic plate boundary, only the northern portion of it is a subduction zone, capable of producing the huge displacements of the seafloor that spawn tsunamis. An L.A. Times article begins to explain that SoCal’s earthquakes don’t pose a tsunami threat.

Here are a couple of humbling tsunami videos from Japan that I haven’t seen widely circulated on the major English news networks. In each of these the incessant and ever-increasing influx of water is almost unbearable to watch and gives a clear sense of the power behind this natural phenomenon.

You can find the other videos here and in this overwhelming film posted on facebook.

Our plight here on the west coast of the U.S. pales in comparison to the utter destruction Japan is facing, but footage of the surge coming ashore in California and Oregon serves as an eye-opening reminder of the tsunami’s power. In this beautiful video we see the surge in sea level coursing through San Francisco Bay toward the coast of Berkeley.

In that video the incoming water has slowed and risen into an elegant series of waves, which crash ashore onto an exposed beach. The waves immediately inundate the shoreline, revealing the elevated sea level driving them. You’ll also notice sharp waves reflected from the shore, crossing the incoming waves almost perpendicularly. Great illustration of constructive and destructive interference.

The tsunami surges into San Francisco Bay on the morning of March 11. The bay bridge and hilly SF skyline are visible in the background. Photographed by Steven Winter. Thanks to http://www.geomika.com/blog/ for highlighting it.

There are many more videos of the wave entering San Francisco Bay, as well as some great time lapse views of other coastal areas, and an impressive shot of one surge barreling through Santa Cruz Harbor that clearly illustrates how so much damage was done by a relatively small wave.

Tidal gauge stations and buoys are another great way to view the effects of the wave all around the Pacific. In Japan, tide gauges are still recording rapidly oscillating water levels along the shore. These hardly compare to the water levels associated with the initial onset of the tsunami, but the Pacific ocean is still clearly in much more tumult than it was in the relaxed days before the quake.

Tidal gauging station from the central coast of Japan on March 11, recording the onset of the tsunami. The green line below is the "risidual," which is effectively the difference between the water level and the expected tide.

Check out other tidal records from Japan yourself:

http://www1.kaiho.mlit.go.jp/KANKYO/TIDE/real_time_tide/sel/index_e.htm

Thanks to friends, relatives, and colleagues alike for directing my attention to some of these amazing perspectives.

Japan quake felt over >2500km radius

One of the many remarkable features about this planet’s largest quakes (like the one that just happened in Japan) is their truly global effect. Be it the tsunami or seismic waves perceptible and imperceptible, most parts of the planet have been touched significantly by the 8.9.

Let’s start with perceptible seismic waves, i.e., ones people don’t need sensitive instruments to detect. The elastic energy released by this earthquake was enough to set the ground rippling at frequencies and amplitudes people can percieve at distances of greater than 2,500 kilometers (over 1,500 miles).

Shaking intensity as reported online by citizens of east Asia. Data points are colored by intensity and sized by city population. The USGS Did-You-Feel-It page (click image for link) contains the original data and plots of response time and attenuation with distance.

Note the felt reports in Taiwan and Beijing. This affected radius is quite comparable to the huge swaths of the globe that felt both the M8.8 Maule, Chile event last year (most of South America) and the 2004 9.1 Sumatra, Indonesia quake (most of southeast Asia and India):

Felt reports from the other M~9 earthquakes that have occurred since the advent of the USGS's Did You Feel It surveys.

Not only did the perceptible shaking stretch far around the globe in all of these cases, but sizeable elastic waves detected only by sensitive seismometers rippled through the solid crust (and bounced around deep in the mantle), observably circling the globe several times.

Seismic events larger than M~6.5 tend to be recorded globally on broadband seismometers–those that can detect a broad range of frequencies, from sharp local jolts to the long, slow undulations of large, distant quakes. I’ll have another post on seismic waves and attenuation later, for now suffice it to demonstrate the following: Below is a seismic record from northern California showing waves from the 7.2 “foreshock” in Japan on March 9.

Northern California seismic recording of a 7.2 in Japan on March 8 (9th in Japan). Read this like a book; each line represents 15 minutes of recording, so where the oscillations last >15 minutes the records overlap, making it a bit messy. Basically, the ground oscillated detectably in California from the distant quake. The amplitude of ground motion is small, and the frequency of the largest waves is 1 per ~30 seconds, meaning it takes the ground 30 seconds to oscillate one way then back the other, slower than your bedroom fan... no wonder we can't sense it without seismometers.

Compare that to the Mar 11 M8.9 in virtually the same location recorded on the same instrument:

Magnitude 8.9 earthquake in Japan recorded in northern California. The amplitude of ground motion is literally off the charts, but since the frequency is relatively low, we couldn't feel the waves passing though they certainly were.

Now, check out yesterday’s:

March 11 seismic record section from northern California

At the top of the record section is the messy, high-amplitude disruption from the initial passage of the 8.9’s surface waves. Just before 12:00 UTC you can see the dense green squiggle that represents the arrival of seismic waves from a 7.1 aftershock in Japan, with the early high-frequency waves superimposed on the low frequency oscillations continuing from the 8.9.

Several large Japanese aftershocks are apparent throughout the next few hours (in the low- to mid- M6 range, represented by occasional dense, high-frequency squiggles). The record in the background continues to undulate irregularly as elastic waves reverberate through the Earth, bouncing off of the dense metal core, refracting and reflecting off of every boundary or irregularity they come to. Imagine someone jumping into an undisturbed swimming pool–or try it yourself!–and watch as the initial coherent rings of waves bounce off the walls and turn the pool surface into a sloshy, ripply mess. That’s what has happened to the planet.

At around 02:00 UTC another extended period of oscillation begins. This likely represents the (much-diminished) seismic waves from the original earthquake re-circling the globe. Hopefully someone with more seismology expertise than myself will soon put together a nifty stacked plot like this one from 2004 illustrating this repetition.

Of course, the tsunami still has the Pacific ocean sloshing about, roiling in turbulent currents where it reaches the shallow topography of coastlines.

You can see just how turbulent and dangerous this ocean-wide surge of water can be in this video from the coast of northern California, taken as the tsunami arrived. Pay attention to the speed with which the water rises and falls.

Many thanks to Aron Meltzner for doing some superb video sleuthing and pointing me to many of the tsunami clips. I may post a compilation of more footage from all around the Pacific in the near future.

Japan’s 8.9 quake and the Pacific tsunami

Everyone–scientists and public alike–has been inundated with information and media about yesterday’s gargantuan earthquake in the subduction zone off the coast of Japan. Its occurrence at midday in one of the most technologically advanced countries in the world has offered some unprecedented views of the phenomena accompanying Great earthquakes.

The tsunami generated by the Magnitude 8.9 earthquake pours ashore along the Iwanuma coast in Japan on March 11. Image courtesy http://www.nola.com

There is an innumerable multitude of videos of the quake happening, which YouTube has already begun compiling on its CitizenTube channel. No doubt this collection will grow and grow in the coming hours and days. Here are some highlights:

A grocery store rocks relentlessly as workers scramble to hold up jostling goods:

Two high-rise buildings sway threateningly toward each other while officeworkers across the street look on

There’s also a noisy video of the city shaking filmed from outside on the street:

In this immediately post-quake video you hear the eerie wail of civil defense sirens warning of the imminent tsunami:

A video I find particularly fascinating is this footage from inside a laboratory of some fancy seismic safety equipment doing what it’s supposed to: buffering the countertop equipment from the shaking of the room around it

Everyone has no doubt seen the truly horrific footage of the tsunami surging inland on the hard-hit northern coast of Japan, compiled here by the BBC.

This was the 5th largest earthquake humans have ever recorded with instruments, surpassed by a 1957 9.0 on the Kamchatka peninsula, the 2004 9.1 in Sumatra, the 1964 9.2 in Alaksa, and Chile’s 9.5 in 1960. The energy released by this earthquake was tremendous, and is still ringing the globe. People may be surprised to hear the relatively low casualty count of such a sizable temblor (tsunami aside), but this tends to be the M.O. of subduction zone megathrust quakes. Although they represent the unzipping of a vast swath of Earth’s crust, the ruptures are buried deep and emerge far offshore, meaning that despite ground shaking that lasts for hundreds of seconds, only modest accelerations are experienced on land, nothing strong enough to bring down buildings.

As is common, the New York Times has some excellent graphics illustrating what went on.

Unfortunately, I must get on with the day’s actual research, so I’ll update this post a bit later. Feel free to add links to info, images, etc. that you find. Callen Bentley at Mountain Beltway blog has a good summary post and links to blogs a-plenty covering this event. I’ll be back once today’s to-do list is all checked off!

Tsunami misconceptions

Exactly one year ago today we (some of us) sat glued to our TVs as the tsunami generated by the gargantuan 8.8 Chilean earthquake barreled into bays around the Pacific Ocean. This is what we saw:

 

Many people found that anti-climactic, especially in comparison to this famous video of the 2004 Indian Ocean tsunami pouring into Patong Beach, or this dramatic one of the ’04 tsunami crashing ashore at another resort hotel on Phuket, or this disturbing video of the same surge tearing through a hotel restaurant. I, however, found the Hawaii video marvelously awesome, and rather less distressing to boot. I prefer videos of 2010’s rather “anti-climactic” and largely forgotten tsunami because their lack of flashy, splashy drama allows a more nuanced view that reveals the impressive power underlying these waves.

Tsunamis tend to be conceptualized incorrectly by newcasters, artists, and even eye-witnesses. They differ substantially from regular ocean waves, and are thus not well characterized simply as giant versions of their every-day cousins. I myself had difficulty imagining their nature until the eye-opening collection of tourists’ videos emerged documenting the tremendous 2004 Indian Ocean tsunami. Since then YouTube has enabled us to witness nearly every major tsunami that has crashed ashore somewhere in the world, and the videos lend substantial aid to our imaginations in understanding what a tsunami really is.

A tsunami occurs when a large portion of the ocean floor moves–imagine the water in a bathtub when you shift your body from one side to the other. Although submarine landslides may generate tsunamis, more commonly the giant displacements caused by undersea earthquakes heave immense volumes of water upward to spawn these waves. When a fault slips beneath the ocean it lifts a huge column of water by a few to a few tens of meters. This water then has to settle its newly gained gravitational potential and equilibrate back to global sea level. To move back downward, some of it must be displaced outward to account for the new protrusion of land caused by the earthquake below. The energy of the displaced water is transmitted rapidly through the ocean, shoving other water out of the way laterally and rolling along as a large area of elevated sea level.

Whereas regular, wind-driven ocean waves are merely surface disturbances, excited by moving air pushing gently over large areas of the ocean and extending no deeper than a few meters, tsunamis involve motion of the entire water column, top to bottom. As all that moving water approaches a shallowing shore (and especially one where the coast line funnels it to a point), it piles up, growing taller and slower until the leading edge of it begins to crest like an ordinary wave. The difference is the volume of water involved. Because tsunamis are generated by the rapid uplift of entire swaths of the ocean floor, their areal extent is huge. Behind even a modest-height crest are literally kilometers of water at that same elevation, ready to pour up onto shore. In effect we perceive tsunamis as large areas of elevated sea level, like a rapid shift in the tide, not like a steep short wave that merely reaches great heights. Once a tsunami hits, it continues pouring inland, as you can see in all of these videos, until the trough of the multi-kilometer-wavelength wave arrives and the water can finally drain back out to sea.

In the milder videos from the much smaller Chilean tsunami, this effect is very apparent, especially in time lapse. The relative calm with which the tsunami arrives belies the massive force driving it as this humongous ripple inexorably laps up over shorelines around the globe.

As the Chilean tsunami arrived at the northern California coast it merely appeared as a rapid decrease in the period of the tides, with an ebb and a rise accentuated by the narrow geometry of the harbor:

 

The rapid rise and dramatic drawback is even apparent along the wide, flat beach at Santa Monica Pier as the tsunami sweeps past Los Angeles:

 

 

Tsunamis are not predominantly impressive nor dangerous because of their height, but because of their width, or wavelength.

There you have it. I encourage you all to peruse NOAA’s National Center for Tsunami Research website (also in sidebar at right) for some great graphics and model animations of recent and historic tsunamis, like this map of modeled wave amplitude in the Feb 27-28 Chile tsunami last year.

 

Measured and modeled tsunami wave heights from the 2010 M8.8 Chile earthquake, from NOAA / PMEL / Center for Tsunami Research.

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