• 2 months ago

Category

📺
TV
Transcript
00:00Deep beneath the Pacific Ocean lurks a killer, a giant geological fault that's home to almost
00:0890% of the world's volcanoes, about 80% of the planet's major earthquake zones, and nearly
00:14one-third of the global population.
00:18On average, an earthquake or volcano erupts here once every hour.
00:23This is the Ring of Fire.
00:26Now, some new evidence suggests it is three times more active than ever before.
00:35The Ring of Fire is one of the most dangerous places on the earth.
00:48The Ring of Fire is a giant fault that runs for 25,000 miles around the edge of the Pacific
00:55Ocean floor.
00:56Now, one group of researchers have recently discovered it might be becoming more volatile.
01:03This could mean more earthquakes and volcanic eruptions.
01:11Scientists are now urgently re-examining this fault line to understand the scale of the
01:16potential threat.
01:17The first clues of this increase in volcanic activity were discovered by chance, locked
01:24deep in the ice of Antarctica.
01:33This freezer contains hundreds of cores of ice.
01:38These cores are thousands of years old.
01:41Each one contains tiny traces of chemical compounds that provide a detailed record of
01:47the earth's climatic history.
01:54New York University professor Mike Rampino specializes in using ice cores to study the
02:00history of the earth.
02:05These ice cores are like many time machines.
02:08You're going back in time.
02:10Hundreds of years, thousands of years, hundreds of thousands of years.
02:14And each layer preserves a record of what was going on in the earth at that time.
02:25These layers hold a secret as to why the Ring of Fire may be becoming more active.
02:31Earth scientist Rampino examines the chemical composition of each layer in the ice to find
02:37causes for fluctuations in the earth's climate.
02:44It's 2005, and after months of careful analysis, Rampino notices something unusual, significant
02:52traces of sulfuric acid.
02:56Sulfuric acid, to a scientist like Rampino, means only one thing.
03:03Volcanic eruptions eject vast quantities of lava, rock, and ash.
03:10But they also eject sulfur dioxide.
03:14An eruption begins as molten rock, which is mixed with carbon dioxide, builds explosive
03:20pressures.
03:22This forces the magma toward the surface and explodes through the crust as a volcano.
03:30Sulfur dioxide, an invisible gas, lies in wait in the ash column.
03:36This gas combines with water vapor to become sulfuric acid.
03:43Upper atmosphere winds spread the acid around the world, only to deposit it back in rain
03:48or snow.
03:51Antarctica only has 1% of all the world's volcanoes.
03:56So how does the acid get there?
03:59The answer lies in the snow.
04:02In Antarctica, snow never melts, so layer by layer, year after year, falling snow locks
04:09in the sulfuric acid.
04:12Rampino finds evidence of volcanic eruptions dating back over 11,000 years inside the ice.
04:21These traces increase dramatically in the youngest parts of the core.
04:25He suspects that something is going on in the world's most volcanically active area.
04:32One of the first things we thought of is that since these are explosive volcanic eruptions,
04:38they're eruptions of volcanoes that are part of the ring of fire.
04:45Rampino finds that 2,000 years ago, volcanic eruptions large enough to show up in the ice
04:51of Antarctica increased from an average of 7 per 1,000 years to 12.
04:59Then in the last millennium, this average jumped again, this time to 21 eruptions per
05:051,000 years.
05:09Volcanic activity in the last 2,000 years appears to have tripled.
05:16Finding a 300% increase in volcanism is a very exciting result.
05:22If this is true, then that increases the hazards of all of the highly populated areas around
05:31the ring of fire.
05:34One highly populated area that will bear the brunt of this increased hazard is right here
05:40in the Pacific Northwest.
05:42This part of the ring of fire is called the Cascadia Fault.
05:46It's 680 miles long and runs just 50 miles off the coast.
05:53Scientists have long considered this tranquil section of America's coastline to be one of
05:57the most harmless on the ring of fire.
06:00That's because for over 300 years, there has been no record of any major geological activity.
06:06Until recently, the accepted scientific thinking was that the fault was tectonically dead.
06:15Ten million people have been living in the cities of Portland, Vancouver, and Seattle,
06:20safe in the knowledge that this part of the ring of fire is benign.
06:24However, Cascadia holds a dark and terrifying secret.
06:31For thousands of years, Native Americans have handed down oral legends about the Thunderbird,
06:37a mythical beast that caused the ground to shake violently.
06:43The great Thunderbird finally carried the whale to its nest in the Loft Mountains.
06:50There were shaking, jumping up, and trembling of the earth beneath.
07:02In the mid-1980s, a proposal to build a nuclear power station on the Cascadia coast prompts
07:09geologists to investigate whether this area is as safe as it seems.
07:17Geologist Brian Atwater starts his search on the Copalis River in Washington State.
07:25He scours the landscape, looking for any clues in the mud that might tell him what has gone
07:30on here in the distant past.
07:32I showed up here with a background working in mud, and using mud as a recorder of changes
07:39in the level of the sea relative to the land.
07:44The scientific thinking when Atwater begins his investigation is that the two tectonic
07:49plates along Cascadia's fault slide harmlessly one over the other.
07:55Evidence of gradual sea level rise will confirm this, but as he digs, Atwater turns up something
08:02unexpected.
08:03Tree roots, lots of them in the mud.
08:09These are the roots of the Sitka spruce.
08:12It is a common tree around here, but like most trees, it cannot grow in a salt marsh.
08:19So how did the roots get here?
08:22Atwater continues to dig.
08:23He finds three distinct layers.
08:27Where there was a forest marked by this peaty soil and the tree roots, and it suddenly became
08:33a salt marsh marked by this mud.
08:36So this is not an ordinary sea level change.
08:40Something very abrupt happened here.
08:43The sharply defined layers suggest something sudden, a dramatic lowering of the land, allowing
08:49poisonous salt water to rush in here, killing the forest.
08:54But how could the land just suddenly shift levels like this?
08:59One explanation is that if the two crustal plates lock and do not slip freely past one
09:05another, then over time, the uppermost plate will begin to bulge, forcing the land above
09:11to rise.
09:12Eventually, as the upper plate springs free, a massive earthquake will occur and the land
09:19behind the bulge will drop away.
09:26This model represents how a fault like this, known as a subduction zone, works.
09:32The two plates grind against each other, and we can see the land above begin to bulge.
09:37Then, as the stress reaches critical, the top plate springs free, releasing enormous
09:44energy in the form of a megathrust earthquake.
09:48The land also drops away, just like Atwater's, and this explains what happened to the trees.
09:58This marsh used to be a thriving forest of Sitka spruce, until a large earthquake caused
10:04the land to drop suddenly.
10:07This allowed salt water to rush in, killing off the trees and creating the salt marsh
10:12of today.
10:15Atwater continues to dig and finds another surprise.
10:20The gray layer between the forest floor and the salt marsh above is sand.
10:27Soil, sand sheet, mud.
10:31This sand layer could only have come from the sea two miles away.
10:37The only possible explanation, a tsunami, created by the earthquake, must have brought
10:43the sand here.
10:57The Cascadia fault line lies 50 miles off the Pacific coast.
11:02The action of the plates springing up during the earthquake would lift the sea floor and
11:07the giant body of water above.
11:10Meanwhile on the coast, the water would recede way beyond the low tide point, only to return
11:16as a tsunami that inundates the coastline.
11:21This wave would destroy everything in its path and leave sand in its wake.
11:27Atwater finds more and more evidence up and down the 680 miles of the Cascadia coast.
11:34Having found the first tantalizing clues at one estuary, to drive out to the next one
11:42and then get in the mud here and see what was there.
11:47And each one, dependably, had this style.
11:50There were shaking, jumping up, and trembling of the earth beneath.
11:55The legend of the Thunderbird is true after all.
12:00Atwater's discovery has now unearthed a previously unknown threat.
12:05The Cascadia subduction zone is capable of creating earthquakes.
12:10History tells us that if it's triggered once, it will trigger again.
12:16But when had this earthquake happened?
12:18How large was it?
12:20And most crucially, when is another one due?
12:24All things atwater cannot yet answer.
12:30And if volcanic activity in the Ring of Fire is really on the increase,
12:35then it could generate another event far sooner than ever imagined.
12:41Scientists are now on an urgent hunt to find the trigger for such events.
12:46And it turns out their prime suspect is the sea.
12:53The Ring of Fire's long history is helping scientists identify its latest threats.
13:00New evidence locked deep in the ice of Antarctica
13:03reveals that the world might have become 300% more volcanic in the last 2,000 years.
13:11What could be causing this increase?
13:14Professor Bill McGuire of University College London thinks the answer lies in the oceans.
13:20About 14,000 years ago, at the end of the last ice age,
13:24ice caps melted, causing sea levels to rise over 50 feet in just a few hundred years.
13:31We thought, well, that has to have an impact on the stress and strain within the crust.
13:35It must change it.
13:36And maybe that change can actually trigger volcanic activity.
13:40In fact, two-thirds of the world's volcanoes are located on the coast,
13:45and the rest within 150 miles of it.
13:49McGuire needs to confirm the theory
13:51by determining how often large volcanic eruptions occurred
13:55during this period of higher sea levels.
13:58He uses data from layers of volcanic ash from the seabed.
14:02He finds that for tens of thousands of years,
14:05these eruptions occurred only once every thousand years.
14:09Then, while sea levels were 50 feet higher,
14:12they took place every 350 years.
14:16This means a rise in volcanism of 300%.
14:20The similarity to Rampinoe's findings is startling,
14:24but McGuire is cautious about their significance.
14:27I'd be a bit surprised if this was a global effect, to be honest.
14:30I wouldn't say it was a blip.
14:32I just don't know.
14:34But there's a problem.
14:36In the last 2,000 years, the sea levels have not risen enough
14:40to account for Rampinoe's increase in volcanism.
14:44The sea level theory looked doomed.
14:47Then, in 1996, one of the world's most active volcanoes
14:53erupts in a remote part of the Ring of Fire.
15:06Alaska's Aleutian Chain is home to 57 active volcanoes.
15:13In mid-September 1996, scientists
15:16working with McGuire at Alaska's Volcano Observatory
15:20record a Pavlov volcano eruption.
15:25It's a small eruption, but significant
15:28because of its timing.
15:32One of the fascinating things about Pavlov volcano
15:35is that it seems to erupt only during the winter months.
15:38But why would a volcano only erupt in the winter?
15:42McGuire looks again to the sea.
15:45In winter, atmospheric conditions around Pavlov
15:49create lower than normal air pressure.
15:51These conditions cause the ocean to expand,
15:54resulting in a small increase in sea level.
15:57In Pavlov's case, this rise can be up to a foot,
16:01a tiny increase, but perhaps enough to trigger an eruption.
16:06McGuire has a simple theory.
16:09He believes that because of Pavlov's proximity to the sea,
16:12the extra weight created by the water
16:14bends the Earth's crust and puts pressure on the magma
16:18chamber below the volcano.
16:20At the same time, this extra stress
16:22pulls the top of the volcano open,
16:25causing it to erupt, just like squeezing toothpaste
16:28from a tube.
16:30This discovery forces McGuire to re-evaluate how the Earth's
16:34tectonic system works.
16:38The whole planet is very finely poised,
16:41so you don't necessarily need huge stresses
16:44to trigger volcanic eruptions, to trigger earthquakes,
16:46landslides, all these different types of geological activity
16:49which characterize the whole of the Ring of Fire.
16:55McGuire's findings, if true, mean
16:57that tiny sea level changes could
17:00trigger new catastrophic events.
17:04Perhaps nowhere is this new discovery
17:06more worrying than here in the Japanese capital of Tokyo.
17:12Here, scientists have just discovered
17:14that something new is going on with this part
17:16of the Ring of Fire, and it's just beneath their feet.
17:2235 million people live in the Tokyo metropolitan area.
17:27The beating heart of one of the world's largest economies
17:31stands on top of where three major tectonic plates converge.
17:36A small earthquake occurs here almost every week,
17:40giving the metropolis the highest at-risk rating
17:43from natural disasters of any major city on Earth.
17:48Tokyo is a city living on borrowed time.
17:58In a bid to understand how dangerous these faults are
18:01to the city, Japanese scientists are
18:04undertaking an ambitious project to study them.
18:09These vibrating trucks hammer the ground at up
18:12to 100 times per second and create seismic waves that
18:16pass down through the Earth.
18:19Scientists measure the return time
18:21of the waves reflected by the fault
18:24to produce an accurate 3D image of it,
18:26similar to that of an ultrasound scan.
18:30Seismologist Naoshi Hirata can now
18:33see for the first time exactly where
18:36the Ring of Fire is in relation to the Japanese capital.
18:41Scientists had previously estimated
18:43that the megathrust fault was as much as 25 miles
18:46below the city.
18:48Hirata's findings change all that.
18:52What we have found is the depths of the megathrust
18:57is much shallower than previously estimated.
19:02That means the source area is closer to Tokyo area.
19:07So that's bad news for the people living in Tokyo.
19:14The megathrust fault, seen here as the large blue area,
19:19is at most 16 miles below the city, and in some places
19:24is only 2.5 miles from the surface.
19:28The closer the proximity to the surface,
19:30the more destructive the earthquake.
19:35Japan's long history of devastating earthquakes
19:39reveals the potential destruction.
19:42In 1995, a magnitude 7.2 killed over 5,000 in Kobe,
19:49just 270 miles west of the city.
19:53In 1923, a magnitude 8.3 earthquake in Tokyo
19:58killed 140,000.
20:03Today, the Japanese government warns
20:05that the probability of a major magnitude 7 earthquake occurring
20:09in Tokyo in the next 30 years is over 70%.
20:14Maybe more than 10,000 people will be killed.
20:19So that's huge damage.
20:24Evidence mounts that the Ring of Fire
20:26is a finely balanced system of faults, where small changes can
20:31have devastating effects.
20:33This is dramatically highlighted in America's Pacific Northwest,
20:38where an infamous volcano is coming back to life.
20:46New scientific evidence suggesting
20:49our planet may be more volcanic is
20:52forcing scientists to re-examine the Pacific's Ring of Fire.
20:57The majority of the planet's volcanoes and earthquake zones
21:00are located in this region.
21:02In Tokyo, it is now clear the Ring of Fire
21:05sits much shallower under the city than previously thought.
21:10Closer to home, the level of threat has also been rising.
21:15In October 2004, Mount St. Helens
21:18erupted back into life and continues
21:21to endanger the population.
21:24The very same geological fault that
21:26threatens the Cascadia coast also created
21:30the Mount St. Helens volcano.
21:36We are directly over Mount St. Helens right now,
21:38and there is no question at all that the volcanic activity
21:41has begun.
21:44On May 18, 1980, Mount St. Helens
21:48erupted with cataclysmic force.
22:03It created the biggest landslide in human history,
22:07killing 57 people and laying waste to 230 square miles.
22:14The eruption, one of the most spectacular ever filmed,
22:18changed the science of volcanology forever.
22:22Volcanologist Dan Zurichen was there.
22:251980 was a watershed for volcanology,
22:28and now St. Helens is giving us another chance.
22:34In October 2004, Mount St. Helens erupts again,
22:39but things are very different from the spectacular explosion
22:4218 years earlier.
22:45This ongoing eruption currently spews out
22:4843,000 cubic yards of solid rock per day,
22:53enough to fill more than 3,000 garbage trucks.
22:56Each day, more magma emerges as the Pacific plate slides
23:02under the Juan de Fuca plate.
23:04This rock is rebuilding St. Helens' famous lava dome.
23:09But what really intrigues scientists
23:11is the millions of tiny earthquakes
23:13the eruption triggers.
23:16Swarms of earthquakes can be a sign
23:18that the volcano is building up to its next eruption,
23:22and Zurichen is anxious to find out exactly what is going on.
23:27Is St. Helens set to dramatically explode once
23:30again?
23:31In some cases at volcanoes, we see a gradual buildup
23:37in earthquakes, small ones occurring infrequently
23:43to bigger ones occurring more frequently
23:45to magnitude threes and fours occurring almost continuously
23:48and then an eruption.
23:50However, something is different this time around.
23:54These little red wiggles each represent an earthquake,
23:58and each one is identical.
24:01Named drumbeat earthquakes because they
24:03occur so regularly, with nearly 2 million
24:06recorded since the eruption began,
24:09Zurichen has several theories.
24:13The first explains the phenomenon
24:15as the opening and closing of cracks in the volcano's base
24:19caused by escaping steam, working
24:21much like a set of bellows.
24:24The second, called stick slip, theorizes
24:27that inside the volcano, pressure builds up,
24:31forcing a giant plug of solid rock higher and higher.
24:36Each move of the plug accounts for an earthquake.
24:40This second theory has ominous implications.
24:46If the stick slip model is right,
24:48then when you do the mathematics and the physics,
24:51it says that over time, it takes more and more pressure
24:55to cause this big rock column to slip.
24:59We could reach a point where the pressure is great enough
25:01to overcome the strength of the rock surrounding it,
25:04and we could trigger an explosive eruption.
25:07Just as the model predicts, the earthquakes
25:10have now begun to slow and are less frequent.
25:14Is this a sign that the column of rock
25:16has become lodged inside the volcano?
25:19And is St. Helens counting down once more
25:22to its next explosive eruption?
25:24Volcanoes are very complicated systems.
25:27Sometimes volcanoes swell up before they erupt.
25:30Sometimes they don't.
25:31Sometimes they produce a tremendous amount
25:33of earthquakes and erupt.
25:34Sometimes they produce very few earthquakes and erupt.
25:38This is Zorichian's dilemma.
25:41Accurate prediction is not yet an exact science,
25:45and a wrong call has almost as many repercussions
25:48as not predicting it at all.
25:52Meanwhile, as the world awaits the next St. Helens eruption,
25:56our inability to make accurate predictions
25:59burdens scientists all around the Ring of Fire.
26:02Geologist Brian Atwater still worries about his own countdown
26:07as he tries to crack when the next catastrophic earthquake
26:10might hit the Pacific Northwest.
26:15There was an urgency to figure it out
26:17because we earth scientists had said,
26:22oh, there's a threat here.
26:24But we had not defined the threat very well.
26:26We had not defined the threat.
26:29There's a threat here, but we had not defined the threat very well.
26:33It's hard for people to take action against threats
26:35that are ill-defined.
26:38To identify the scale of this threat,
26:41Atwater must solve Cascadia's history.
26:44But the last piece of the puzzle still eludes him.
26:48When did the last great earthquake occur,
26:51and how large was it?
26:54Little does he know, the answer lies on the other side
26:58of the Ring of Fire.
27:12Tsunami expert Kenji Satake
27:15has been trying to solve the riddle of the Orphan Tsunami,
27:20a giant wave that crashed onto Japan's eastern shore
27:24for no apparent reason.
27:27Most tsunamis around Japan are caused by earthquakes around Japan.
27:31And so typically, people on the coast
27:34feel earthquake, ground shaking first,
27:37then followed by tsunamis in 20 minutes or 10 minutes.
27:42For nearly 300 years,
27:44the location of the earthquake that created the tsunami
27:47has eluded scientists,
27:49which is why, in written records,
27:51it is known as the Orphan Tsunami.
27:55By the early 90s, the task of solving the mystery falls to Satake.
28:01Early accounts rule out South America,
28:03so he turns his attention to Alaska,
28:06which has a long history of earthquakes generating tsunamis.
28:11In 1964, a magnitude 9.2 earthquake
28:16leveled the Alaskan capital of Anchorage
28:19and created a tsunami that devastated the Pacific coast
28:22as far south as California.
28:26By the time the waves had reached Japan,
28:28they were too small to account for the damage recorded in 1700.
28:33Satake runs out of ideas.
28:36Then in 1995,
28:37he hears about Atwater's work on the other side of the Ring of Fire.
28:41Around 1995, I met Brian Atwater
28:45and other North American geologists,
28:48and I was impressed by their work.
28:53Could they both be looking at evidence from the same tsunami?
28:58The only way to find out is to recreate it,
29:01this time in the computer.
29:04Satake models a number of different scenarios.
29:07Finally, he manages to create a huge rupture
29:10along the whole length of the Cascadia subduction zone.
29:14The results speak for themselves.
29:17At about 10 hours after the earthquake in Cascadia,
29:21the waves cross the Pacific
29:23and crash onto Japan's eastern shore,
29:25just as in 1700.
29:28This evidence, coupled with all that Atwater has found on the Cascadia coast,
29:33leaves little doubt in both scientists' minds.
29:36The last great Cascadia earthquake caused the 1700 Japanese tsunami.
29:42They know the time, the date and the location.
29:45Now, what about the size?
29:48And it turns out the earthquake magnitude is about nine.
29:51Only magnitude nine earthquake can generate a tsunami
29:55that travels across the Pacific Ocean
29:57that causes even damage in Japan.
29:59A magnitude nine is one of the largest earthquakes the planet can create,
30:05and its effects are truly awesome.
30:09At 9pm on January 26th, 1700,
30:13the 680-mile Cascadia Fault
30:16ruptured along its entire length,
30:19creating an earthquake that released more energy
30:23than the United States uses in a whole month.
30:26Ever since then, the fault has been locked,
30:29building up stress like a ticking geological time bomb.
30:33The questions remain.
30:35When will it happen again?
30:38How big will it be?
30:40And what damage will it inflict?
30:44All questions scientists race to answer in the face of new evidence
30:49that suggests an increased threat from the Ring of Fire.
31:00The clock is ticking for cities all around the Ring of Fire,
31:04as new research suggests it may be more active than ever before.
31:09Now, scientists in these cities are finding ingenious ways
31:13to provide vital extra seconds of warning
31:16that may just save lives the next time the Ring of Fire strikes.
31:37Professor Matthew D'Alessio has come from Northern California
31:42to work at Tokyo's Earthquake Research Institute.
31:45He is only too aware that a giant megathrust earthquake
31:49will one day devastate Tokyo.
31:52He's just getting used to the daily threat that all Japanese face.
31:57Pretty much the entire time I've been here, I feel an earthquake
32:00about once every three weeks, once every two weeks.
32:03And these are not small earthquakes by the standards that I'm used to.
32:09Here, D'Alessio demonstrates a simulation at the Hanzo Disaster Center.
32:17When I lived in California, I felt an earthquake or two every year,
32:22and they were magnitude threes, sometimes a magnitude four.
32:26Well, here it's a magnitude four every couple of weeks.
32:31This simulator reaches a magnitude seven quake,
32:34virtually identical to the one that devastated the Japanese city of Kobe in 1995.
32:42These events always strike with virtually no warning,
32:46and the focus of D'Alessio's research is to change those odds.
32:54All the techniques that we developed in seismology were based upon
32:57looking at earthquakes long after they happened.
33:00All of a sudden now, we want to look at earthquakes while they're happening.
33:05And that's a lot like getting into a car with somebody
33:09and trying to figure out how fast they're going to drive
33:12and how far they're going to travel,
33:14all from the moment they hit the accelerator.
33:17A new discovery may now give the scientists this edge.
33:21The earthquake itself provides its own warning.
33:25The earthquake releases energy in the form of two different types of seismic waves.
33:30The first, called P, or primary waves,
33:33travel at almost 18,000 miles per hour, shown in blue.
33:39These are compression waves and move like the slinky in a forward and back motion.
33:45The P waves arrive first and cause little damage.
33:49The lethal S waves, or secondary waves, shown in red, quickly follow.
33:55These shear waves move left and right and create the destructive ground shaking.
34:01It's actually a lot like thunder and lightning.
34:04People are kind of used to that effect where you can see lightning, a flash,
34:08and then it isn't for a few more seconds
34:10until that big roaring thunder comes along and hits you.
34:15The system uses this phenomenon and issues a warning
34:18as soon as it detects the faster P waves.
34:21This warning only ranges from a few seconds to a few minutes,
34:25but it can be a lifesaver as people take cover.
34:29Manufacturing shuts down, and even Japan's famous bullet train comes to a stop.
34:37Tokyo now leads the world in earthquake preparedness,
34:41with many new buildings built on giant shock absorbers like these.
34:46It's just one example of how scientists all around the Ring of Fire
34:50are learning to deal with the increased threats.
34:53But the key to conquering earthquakes still eludes even those in Japan.
35:00We don't even know if prediction is possible.
35:02We don't even know if earthquakes are predictable.
35:05And that's really something that we're working on,
35:08is understanding what is the physics of this process.
35:15Earthquake prediction may have just taken a significant step forward,
35:20thanks to a recent discovery back on the Cascadia coast.
35:25Scientists from the Plate Boundary Observatory
35:28are installing a network of 960 ultra-sensitive strain meters and GPS monitors.
35:35These record tiny changes in the Earth's surface
35:39to shed light on when and where Cascadia will rupture again.
35:47Research scientist Herb Dragert is one of the pioneers of the study.
35:53What we're looking at now is the next level of scientific investigation
35:59in terms of can we say anything more definitive
36:03about when these earthquakes are more likely,
36:07as opposed to simply saying statistically every 500 years.
36:11Up until now, scientists assumed that subduction zones
36:16reload their stress in one long continuous motion.
36:20This stress continues until it becomes too great and creates an earthquake.
36:28Dragert begins to analyze the data from the strain meters.
36:32He anticipates a continuous motion, illustrated here by the green line.
36:39But what he finds might revolutionize our understanding of how and why earthquakes occur.
36:47Instead of just one continuous kind of squeezing,
36:52we discovered that there was structure to the motion,
36:57a totally unexpected structure.
37:01Dragert has discovered a sawtooth pattern to this false movement.
37:07What we found out is that for about 14-15 months in this area of Cascadia,
37:13I'm being squeezed eastward, and then over a two-week period,
37:18there's a slight release in the opposite direction.
37:22Dragert's findings highlight a new type of earthquake event called a slow slip.
37:28Could this hold the key to predicting when Cascadia will rupture again?
37:33Dragert believes the fault operates in much the same way as tuning a guitar.
37:38Each turn of the tuning peg tightens the string and brings it closer and closer to the point of failure.
37:45The same principle applies to Cascadia.
37:49The longer we go without a major earthquake,
37:55we know we must be getting close to that critical stress level.
38:01And so, in effect, your guitar string is getting tighter and tighter and tighter,
38:09until you just say to yourself, I can't believe this string is not going to break.
38:17There's another surprise.
38:19Dragert believes it is during one of the slow slip events in the Cascadia Fault
38:24that the next earthquake will hit the Pacific Northwest.
38:27The instability created as the fault changes direction during these brief periods
38:32makes an earthquake more likely.
38:35The probability of a very large earthquake coming next week
38:40is something like 1 in 200,000 during that 14-month period when no slip occurs.
38:48During the two-week period that the slip occurs,
38:52that probability is changed by a factor of 50.
38:56So then it becomes the probability of 1 in 4,000.
39:03The next great Cascadia earthquake is both inevitable and unstoppable.
39:11A major megathrust earthquake has never hit a modern high-rise city like Seattle.
39:18But the clock is ticking, and disaster looms large.
39:27In 1700, the Ring of Fire unleashed one of its most awesome forces,
39:32rupturing the 680-mile-length subduction zone known as Cascadia.
39:38This fault, located just 50 miles off the Pacific Northwest coast,
39:43generated a magnitude-9 megathrust earthquake
39:46and shook the ground for nearly five minutes.
39:50Since then, the fault has been reloading,
39:53and scientists now know an earthquake will happen again, possibly soon.
39:58The question now is, what will happen to major cities in Cascadia like Seattle?
40:04Full of high-rise buildings and modern infrastructure,
40:07it's just one of the major mechanics of the future.
40:13Like metropolises in Cascadia's firing line,
40:16almost 10 million people are under threat,
40:19and the potential for disaster is virtually unimaginable.
40:25Though we know it will certainly happen,
40:28the details of how the Cascadia fault will rupture,
40:31and the effect it will have, remain speculative.
40:35But it is hard to imagine the consequences being anything less than disastrous.
40:41Any increased activity will compound many future threats all around the Ring of Fire.
40:47But Cascadia looks like it may be one of the most serious.
40:52I think of all the Ring of Fire threats,
40:55the next big Cascadia earthquake is a real worry.
40:59It'll be like unzipping a zipper.
41:03The shaking will be intense all up and down the Cascadia zone.
41:10One can predict a repeat of what happened several hundred years ago,
41:16the Magnitude 9 earthquake.
41:20And that is a thousand times bigger than, for example, the San Francisco earthquake of 1906.
41:29Now we can visualize what our Pacific coast might look like
41:33if a Magnitude 9 earthquake happened tomorrow.
41:37The earthquake begins at one end of the 680-mile Cascadia fault.
41:42It spreads at more than 7,000 miles per hour.
41:46It will take as long as five minutes to rupture completely.
41:49The seafloor, forced up by the fault, lifts a huge body of water above it,
41:54setting off a series of giant waves traveling at the speed of a jetliner.
42:01The seismic waves race at almost 18,000 miles per hour
42:05and quickly reach the Cascadia coast, erupting the coastline in violent shaking.
42:12Okay. All right. Thank you.
42:14Okay.
42:15The Washington State Emergency Operations Center's first warning
42:19is when their earthquake-proof building starts to shake.
42:25I have a verified 9.2.
42:28155 miles west-northwest of Bandon, Oregon.
42:34One minute into the quake, the P waves hit Seattle,
42:39the city's inhabitants' first clue that something is wrong.
42:45Forty seconds later, the lethal S waves arrive,
42:49and the city erupts in violent sideways shaking.
42:57The shaking continues to build, and now brick buildings begin to fail.
43:05Seagulls
43:13Minutes into the quake, the land along Seattle's harbor area begins to collapse.
43:18As the seawall ruptures, the streets open up.
43:29The foundations of the city's main highway start to fail,
43:33and the collapse of the Alaskan Way Viaduct becomes Seattle's final indignity.
43:42The shaking finally subsides.
43:45A shattered city will lay in its wake.
43:53I can't believe what I'm seeing.
43:55Seattle is devastated.
43:58The End
44:03But this is just our scenario of what could happen.
44:06Such an eruption in Cascadia is one example of the awesome power
44:11that will someday be unleashed all around the Ring of Fire.
44:15Evidence from the frozen wastes of the Antarctic
44:18suggests that it has become more and more active,
44:21and events like this may well occur more frequently.
44:25We need better activity at the Ring of Fire.
44:27We're going to see big events happening maybe every few decades,
44:31either volcanic eruptions or earthquakes, as far as we can look into the future.
44:38For now, scientists in the U.S. and Japan do all they can with new underground sensors
44:45and the latest seismic techniques to better understand the Earth's tectonic system.
44:51More understanding will bring advances in both forecasting and preparedness,
44:55but accurate predictions of events like those in Cascadia for now remain elusive.
45:02Prediction implies specific time, place, and magnitude,
45:07and we're not close to being able to do that.
45:13Mount St. Helens and thousands of other volcanoes,
45:18Tokyo's megathrust fault, Cascadia.
45:22All these threats located along the Ring of Fire could be triggered
45:26if the evidence for this increased activity found in the ice is true.
45:31Either way, it's only a matter of time before the Ring of Fire humbles the world again.
45:37But while this geological time bomb ticks,
45:40scientists are doing their best to better protect us against whatever comes next.
45:47NASA Jet Propulsion Laboratory, California Institute of Technology