0:00:01 > 0:00:04It's Sunday 11th May, 2008.
0:00:06 > 0:00:10For millions of people, it's just another ordinary day.
0:00:10 > 0:00:14Meanwhile, at earthquake monitoring stations around the world,
0:00:14 > 0:00:17there's nothing special to report.
0:00:17 > 0:00:21What no-one knows is that 24 hours later,
0:00:21 > 0:00:24an extraordinary natural disaster is going to strike.
0:00:29 > 0:00:31TV: A massive rescue operation is under way...
0:00:31 > 0:00:35..7.28 this morning, sending shock waves around Asia.
0:00:35 > 0:00:38..a magnitude of 7.8 struck Sichuan Province...
0:00:38 > 0:00:43An enormous earthquake tears into Sichuan Province in Western China.
0:00:43 > 0:00:47Over 50 million people are affected.
0:00:47 > 0:00:52Five million lose their homes and 70,000 die.
0:00:53 > 0:00:59And all because science can't answer what seems like a simple question.
0:01:13 > 0:01:18In the last 100 years, earthquakes have killed over a million people.
0:01:18 > 0:01:21And with the growth in the world's population
0:01:21 > 0:01:26scientists predict that this century might see ten times as many deaths.
0:01:28 > 0:01:34So why can't we work out when and where the next big quake is going to happen?
0:01:34 > 0:01:37Well, the more work we do on earthquake prediction
0:01:37 > 0:01:40the more difficult it seems it's going to be.
0:01:40 > 0:01:43You start to think you see patterns and understand them
0:01:43 > 0:01:46and then when you try to play the game forward
0:01:46 > 0:01:50and look for those patterns, it just hasn't ever panned out.
0:01:50 > 0:01:54If you were a seismologist and you knew how to predict earthquakes,
0:01:54 > 0:01:56er, you've arrived.
0:01:57 > 0:02:01So why is earthquake prediction so difficult?
0:02:01 > 0:02:05And what is science doing to overcome this force of nature?
0:02:10 > 0:02:15If you want to know about earthquakes, this is the place to come -
0:02:15 > 0:02:17California.
0:02:17 > 0:02:21# They tell me the faultline
0:02:21 > 0:02:24# Runs right through here... #
0:02:24 > 0:02:30American's golden state lives in the constant shadow of an enormous earthquake,
0:02:30 > 0:02:36and because of this they throw more money into studying these disasters than anywhere else.
0:02:36 > 0:02:40# They tell me the faultline
0:02:40 > 0:02:43# Runs right through here. #
0:02:43 > 0:02:46At the heart of this effort is the United States Geological Survey,
0:02:49 > 0:02:52the nerve centre of earthquake monitoring.
0:02:52 > 0:02:58This is a map showing the global earthquakes of the last week.
0:02:58 > 0:03:03Any time you look at this picture there's going to be aspects of it that are gonna look a lot like this.
0:03:03 > 0:03:06You're gonna see this distribution down California
0:03:06 > 0:03:10because this map is showing smaller magnitude earthquakes in California.
0:03:10 > 0:03:15The red shows that we've just had an earthquake, this is at the Northern end of Japan.
0:03:15 > 0:03:20There's usually something in Japan every week that's large enough to show up here.
0:03:20 > 0:03:23The South Pacific is one of the active areas of the world right now.
0:03:23 > 0:03:28You'll see a few things spread around, somewhere through Asia essentially all the time.
0:03:28 > 0:03:31For seismologists like Lucy Jones,
0:03:31 > 0:03:35it's no longer a mystery why the earth suffers so many quakes.
0:03:38 > 0:03:41The tectonic plates that make up the world's crust
0:03:41 > 0:03:47grind against each other, building up huge amounts of stress.
0:03:47 > 0:03:50The stress produces cracks known as faults.
0:03:50 > 0:03:54Wherever there's a fault, there might one day be an earthquake.
0:03:57 > 0:03:59We know that earthquakes happen
0:03:59 > 0:04:02because stress builds up in the crust
0:04:02 > 0:04:05and finally you overcome the friction and you slip suddenly.
0:04:05 > 0:04:08Actually, an analogy is snapping your fingers.
0:04:08 > 0:04:12When you snap your fingers you have two surfaces in frictional contact.
0:04:12 > 0:04:16But, all right, now I'm trying to say what micro-second they're going to move on
0:04:16 > 0:04:20and that's going to be exactly what point the friction is overcome.
0:04:20 > 0:04:23That's, er... There's a lot of processes going on there.
0:04:23 > 0:04:27But even though scientists know how and where earthquakes happen,
0:04:27 > 0:04:31the question they can't answer is the one that matters most.
0:04:31 > 0:04:35So on May the 11th did you think there was going to be a big earthquake in China?
0:04:35 > 0:04:41No. There's nobody who on May 11th said there's gonna be an earthquake.
0:04:41 > 0:04:46There are plenty of people on May 13th said "I really did know this two days earlier."
0:04:48 > 0:04:53It's a far cry from the picture of just couple of decades ago.
0:05:01 > 0:05:03This is Parkfield,
0:05:03 > 0:05:06a tiny hamlet in the middle of California.
0:05:08 > 0:05:14Few people ever come here, and even fewer stay.
0:05:14 > 0:05:17But this village lies on top of the infamous San Andreas Fault,
0:05:17 > 0:05:22and once looked like it held the key to understanding earthquakes.
0:05:22 > 0:05:27It all began when a team of geologists led by John Langbein
0:05:27 > 0:05:30noticed something unusual about little Parkfield.
0:05:30 > 0:05:35It was, er, in the '70s and early '80s it was recognised
0:05:35 > 0:05:39that there was a sequence of magnitude six earthquakes
0:05:39 > 0:05:43that repeated the same stretch of the San Andreas Fault
0:05:43 > 0:05:48every 20-odd years and it didn't take too much imagination
0:05:48 > 0:05:53to extrapolate and say the next one ought to be in the late '80s.
0:05:53 > 0:05:59The village had always suffered from earthquakes, but these quakes followed a very distinct pattern.
0:06:00 > 0:06:06Langbein's team decided to use Parkfield for a bold and unprecedented experiment.
0:06:06 > 0:06:11To see what happened to the ground before an earthquake struck.
0:06:11 > 0:06:16Estimating that the quake would occur between 1987 and 1993,
0:06:16 > 0:06:20scores of geologists descended onto Parkfield.
0:06:24 > 0:06:27They came to town and they set up shop with instruments,
0:06:27 > 0:06:30and they're sort of hidden away and tucked away
0:06:30 > 0:06:34so they're not that obvious but there's a lot of them out there.
0:06:34 > 0:06:40And the idea was to have the instruments ready to catch the next earthquake red-handed.
0:06:40 > 0:06:46Well, what you're hoping to see, the analogy is a stick breaking,
0:06:46 > 0:06:50so in the long term you're bending the stick,
0:06:50 > 0:06:52you see it, er, deform
0:06:52 > 0:06:56and then maybe just before the stick actually goes snap
0:06:56 > 0:06:59you'll hear "crack crack crack" or something like that.
0:07:01 > 0:07:04Now that they had narrowed down the time window
0:07:04 > 0:07:06and knew where it was going to strike,
0:07:06 > 0:07:10this was science's best chance yet to see an earthquake in action.
0:07:12 > 0:07:15Millions of dollars flooded in to fund the research.
0:07:15 > 0:07:20All they had to do now was just sit and wait.
0:07:20 > 0:07:25This ranch house is the high-tech outpost for a team of scientists from the US Geological Survey.
0:07:25 > 0:07:28Every morning they check sophisticated sensors,
0:07:28 > 0:07:32looking for signs that the Earth is ready to rumble.
0:07:32 > 0:07:35So how many instruments are buried here in Parkfield?
0:07:35 > 0:07:37You know, it's a little hard to count.
0:07:37 > 0:07:40There's probably about two to three hundred.
0:07:40 > 0:07:43We had some creep meters that measure fault slip,
0:07:43 > 0:07:45some geo-chemical experiments,
0:07:45 > 0:07:48strain metres, pole positioning system.
0:07:48 > 0:07:52- TV:- And on the fault line itself, TV cameras are constantly recording.
0:07:52 > 0:07:55The instruments may provide a perfect...
0:07:55 > 0:08:00As 1993 approached, excitement mounted amongst the geologists.
0:08:00 > 0:08:03- TV:- For five years scientists have been preparing this experiment
0:08:03 > 0:08:08for the quake of '93. Now that it's built, they're hoping it will come.
0:08:13 > 0:08:16But then, 1993 passed without incident.
0:08:17 > 0:08:20'94.
0:08:20 > 0:08:22'95.
0:08:22 > 0:08:24'96.
0:08:24 > 0:08:26There was still nothing.
0:08:30 > 0:08:34Our guess was basically, what you'd call...
0:08:34 > 0:08:37um, ambitious or optimistic.
0:08:40 > 0:08:43It wasn't until September 28th 2004
0:08:43 > 0:08:46that the earthquake finally struck,
0:08:46 > 0:08:50and when it came, it wasn't what the scientists were hoping for.
0:08:50 > 0:08:53It was like the fault was quiet quiet quiet
0:08:53 > 0:08:56and then it broke,
0:08:56 > 0:08:58and it was sort of, it was a fairly negative result.
0:08:58 > 0:09:01You know, we were sort of waiting to catch that precursor
0:09:01 > 0:09:05with all these instruments, and nothing happened.
0:09:05 > 0:09:09Instead of finding signals that might predict an earthquake,
0:09:09 > 0:09:12all that the Parkfield experiment seemed to prove
0:09:12 > 0:09:14was that these natural disasters
0:09:14 > 0:09:18were far more complex than anyone had ever imagined.
0:09:18 > 0:09:21You know it was sort of taken as a negative result
0:09:21 > 0:09:24and some people were saying "Time to put the nail in the coffin.
0:09:24 > 0:09:26"Earthquake prediction is dead."
0:09:26 > 0:09:29And I think that's a bit extreme.
0:09:29 > 0:09:32One possibility is that earthquakes are different.
0:09:32 > 0:09:38In '66 there was quite a large foreshock and in '34 there was quite a large foreshock
0:09:38 > 0:09:43and in both of those cases the quake started up here and went that way.
0:09:43 > 0:09:46And in 2004 there was no foreshock and it started in the South
0:09:46 > 0:09:51and went the other way. So earthquakes are complicated.
0:09:52 > 0:09:57Many people thought that Parkfield might solve the mystery of earthquake prediction for good.
0:09:57 > 0:10:01But instead it was back to the drawing board for science.
0:10:05 > 0:10:07Holy shit!
0:10:07 > 0:10:09Holy shit.
0:10:09 > 0:10:11Oh, my God.
0:10:11 > 0:10:13Holy cow.
0:10:13 > 0:10:18And as every year goes past, more earthquakes continue to plague our planet.
0:10:18 > 0:10:22- Out here, out here!- What happened to the telescope?- Destroyed.
0:10:22 > 0:10:24Go, go, go, come on!
0:10:24 > 0:10:26It may fall.
0:10:26 > 0:10:28I got it on tape!
0:10:32 > 0:10:34Holy shit.
0:10:34 > 0:10:37I got it on tape.
0:10:37 > 0:10:39Go, come on.
0:10:40 > 0:10:45In the last decade alone, tens of thousands have died
0:10:45 > 0:10:49in Turkey, India, Iran and Pakistan.
0:10:49 > 0:10:53And it was an earthquake that caused the Boxing Day Tsunami,
0:10:53 > 0:10:56killing a quarter of a million people in 2004.
0:11:03 > 0:11:06Then in May 2008, it happened again.
0:11:06 > 0:11:09This time in Sichuan Province, China.
0:11:22 > 0:11:25Six months after the disaster, geologist Mike Ellis
0:11:25 > 0:11:30is travelling to China to investigate the earthquake.
0:11:30 > 0:11:32Mike has worked in this region before
0:11:32 > 0:11:36so he always knew there could be a major quake here one day,
0:11:36 > 0:11:40but he didn't think he'd ever get to see it in his lifetime.
0:11:42 > 0:11:48I've chased quite a few earthquakes, as we call it, um, Taiwan downwards.
0:11:48 > 0:11:54Big earthquakes like this happen in the ocean all the time but of course you can't go there to see them
0:11:54 > 0:11:56so academically and scientifically it's a treat
0:11:56 > 0:11:59to come to an earthquake like this
0:11:59 > 0:12:02but of course it's a very sobering experience as well.
0:12:04 > 0:12:10For the inhabitants of Sichuan Province, Monday May 12th was a day like any other.
0:12:10 > 0:12:14Many people were at work, their children in school,
0:12:14 > 0:12:17while others were simply out enjoying the sunshine.
0:12:24 > 0:12:28Little did they know that the ground beneath their feet
0:12:28 > 0:12:31was about to be ripped apart by a rupture that would travel
0:12:31 > 0:12:35100km in just 50 seconds.
0:12:46 > 0:12:49REPORTER: A massive rescue operation is underway after a powerful..
0:12:49 > 0:12:53..thousands are killed after a massive earthquake hit South West China.
0:12:58 > 0:13:00At magnitude 7.9,
0:13:00 > 0:13:05it was one of the world's most powerful earthquakes in decades.
0:13:07 > 0:13:11But even after the shaking had stopped, the real drama was only just beginning.
0:13:19 > 0:13:23As entire towns collapsed, thousands of people
0:13:23 > 0:13:26were crushed to death or killed by falling masonry.
0:13:26 > 0:13:30And strong aftershocks, some higher than magnitude six,
0:13:30 > 0:13:35continued to strike across the region causing new casualties and damage.
0:13:35 > 0:13:39REPORTER: The rescue operation is one of the biggest ever.
0:13:39 > 0:13:4150,000 troops have been mobilised....
0:13:41 > 0:13:44..mourning for victims of the Sichuan earthquake.
0:13:44 > 0:13:48Rescue work continues but very few victims are being found alive.
0:13:55 > 0:14:00Months on, and Sichuan still lies in ruins,
0:14:00 > 0:14:04but Mike hopes to find answers among the broken houses and upturned soil.
0:14:07 > 0:14:09He'll be travelling with Jing Liu,
0:14:09 > 0:14:14a Chinese earthquake geologist who's been mapping the rupture since May.
0:14:19 > 0:14:25The county town of Beichuan is 138km from the earthquake's epicentre,
0:14:25 > 0:14:29but it lies in one of the worst-affected areas.
0:14:29 > 0:14:3212,000 people died here,
0:14:32 > 0:14:34three quarters of the population.
0:14:36 > 0:14:39Coming back for the first time since the earthquake,
0:14:39 > 0:14:43Mike is struck by what's happened to the place he once knew well.
0:14:46 > 0:14:48It's very sobering.
0:14:48 > 0:14:52Um, not something that you want to see, really.
0:14:52 > 0:14:57On the river, there were some trees and a cafe down there, I used to sit and play Mahjong.
0:14:57 > 0:15:01Now it's completely chock full of sediment and, er...
0:15:06 > 0:15:11Mike came here before to map some of the earthquake faults in this area.
0:15:11 > 0:15:17This is one place where I think the rupture did coincide quite well with the fault, the mapped fault.
0:15:17 > 0:15:21We mapped along there and then through the valley and up over there.
0:15:23 > 0:15:29By mapping faults, Mike hopes to predict where and even when an earthquake may strike again.
0:15:29 > 0:15:33Now he has his best opportunity in years.
0:15:33 > 0:15:36The recent earthquake has revealed faults never seen before.
0:15:43 > 0:15:48Even though Mike is hundreds of kilometres from the tectonic plate boundary
0:15:48 > 0:15:53between India and Asia, this is major earthquake country.
0:15:53 > 0:15:57Geological maps of the region suggest that there are thousands of faults
0:15:57 > 0:16:01hidden in the mountain range that fringes Sichuan Province -
0:16:01 > 0:16:03the Longmen Shan.
0:16:03 > 0:16:06So here you can see the big picture
0:16:06 > 0:16:11of the India, Asia collision region I suppose you could call it.
0:16:11 > 0:16:15White area for a high elevation and the darker areas are lower.
0:16:15 > 0:16:18So here is the Himalayan arc,
0:16:18 > 0:16:21India of course, moving up into, into Eurasia,
0:16:21 > 0:16:27and that's occurring about 40, 45mm per year,
0:16:27 > 0:16:30which is pretty fast in plate tectonic terms.
0:16:30 > 0:16:33There's a series of thrust faults
0:16:33 > 0:16:37that come down and around the Himalayas.
0:16:37 > 0:16:40This is the the plate boundary
0:16:42 > 0:16:44and so there's Longmen Shan
0:16:44 > 0:16:49and it's facing the very flat and relatively low Sichuan basin.
0:16:49 > 0:16:53It actually is, geologically this is a wonderful enigma.
0:16:53 > 0:16:57It's always exciting to find a place that has not been explained yet.
0:16:57 > 0:17:01I think we're all looking for something that we can make an impact with.
0:17:04 > 0:17:09Over in California, most of the mapping work has already been done.
0:17:09 > 0:17:14Here, scientists are all too aware of the cost of not knowing where the faults are.
0:17:19 > 0:17:25Their wake-up call came in 1906, when a magnitude 7.9 earthquake
0:17:25 > 0:17:28bought San Francisco to its knees.
0:17:28 > 0:17:32The violent shaking and fires afterwards killed thousands
0:17:32 > 0:17:35and destroyed much of the city.
0:17:35 > 0:17:39Ever since, the state has learned to live with the threat
0:17:39 > 0:17:43that another major earthquake could strike at any time.
0:17:48 > 0:17:52Over 100 years later, California is now the place to be
0:17:52 > 0:17:56for seismologists and geologists the world over.
0:18:06 > 0:18:09There are not a whole lot of earthquakes in London, you know,
0:18:09 > 0:18:12and the ones that happen are piddly and not worth studying.
0:18:12 > 0:18:17So in in my game where we measure things, you'd really like...
0:18:17 > 0:18:19something bigger than a seven.
0:18:19 > 0:18:22Eight's nice, nine is terrific.
0:18:22 > 0:18:27Not so good for people, but terrific for the scientists.
0:18:32 > 0:18:37Roger Bilham was born in England but moved to America to be nearer
0:18:37 > 0:18:42to faults like the San Andreas, cause of the 1906 earthquake.
0:18:42 > 0:18:47So here look, have a look at this, this beautiful flat valley here
0:18:47 > 0:18:50with a hill on each side. The fault runs right down the middle
0:18:50 > 0:18:54and this slipped in 1906.
0:18:54 > 0:18:56It slipped only about two metres here,
0:18:56 > 0:19:00as we get further north it slips increasingly more
0:19:00 > 0:19:03until you get north of San Francisco
0:19:03 > 0:19:06where it becomes about six metres of slip in 1906.
0:19:06 > 0:19:08By mapping out California's faults,
0:19:08 > 0:19:13scientists are beginning to understand how tiny slips in one place
0:19:13 > 0:19:16could lead to huge earthquakes somewhere else.
0:19:16 > 0:19:19Roger hopes to pick up a small sign
0:19:19 > 0:19:22that might predict a future disaster.
0:19:22 > 0:19:23He travels from fault to fault
0:19:23 > 0:19:26checking on a collection of home-made instruments
0:19:26 > 0:19:31that he's buried at sites up and down the state.
0:19:31 > 0:19:33Well, I I consider them my babies.
0:19:33 > 0:19:39You plant them in the ground and then they they live out their rather dull but informative existence
0:19:39 > 0:19:43sending us information about the movement of these wonderful faults.
0:19:43 > 0:19:47So yes, I quite enjoy it, except when it rains, and it doesn't do that much.
0:19:47 > 0:19:53Ah, and sometimes the local people shoot at you, which isn't such fun.
0:19:53 > 0:19:57- Sorry?- Well, yeah. I work all over the world,
0:19:57 > 0:20:01but California is the only place where they really, really tried to shoot me,
0:20:01 > 0:20:07and, er, that's the sort of macho people that go around California with guns.
0:20:07 > 0:20:12They sit on these interesting faults and they don't want you to measure them.
0:20:12 > 0:20:14Astonishing.
0:20:14 > 0:20:17We're not going to get shot at by the owners here, are we?
0:20:17 > 0:20:19- No, not at all.- Sure?
0:20:19 > 0:20:24Yes, absolutely, they're lovely people.
0:20:24 > 0:20:29OK, so if you can squint along this fence you will see it's offset.
0:20:29 > 0:20:33Now this fence was put in after the 1906 earthquake,
0:20:33 > 0:20:36so the offset has occurred since 1906.
0:20:36 > 0:20:40And we know from measurements along the road
0:20:40 > 0:20:42and from the creek meter in the the field
0:20:42 > 0:20:46that it's moving at about a quarter of an inch a year, relentlessly,
0:20:46 > 0:20:49and when the San Andreas Fault slips,
0:20:49 > 0:20:54this side of the road is going off to the South, this side of the road is going off to the North,
0:20:54 > 0:20:57so this is stuck next, this is glued to the Pacific plate
0:20:57 > 0:21:00and you're standing on the North American plate
0:21:00 > 0:21:04going away whizzing past me down sort of Mexico direction.
0:21:04 > 0:21:09Let's go and visit the machine.
0:21:09 > 0:21:12So this is the important step -
0:21:12 > 0:21:15check the bulls are in the right place.
0:21:19 > 0:21:23So it's just over here in the grass.
0:21:26 > 0:21:29I sometimes worry there's a snake under here.
0:21:31 > 0:21:33Not this time.
0:21:37 > 0:21:41There is an element of, er, a Heath Robinson contraption about it.
0:21:41 > 0:21:45It's a very simple gadget, it's a cylinder with, um, a rod,
0:21:45 > 0:21:49the rod is connected across from the other side of the fault.
0:21:49 > 0:21:55When the fault slips it pulls this rod away from the metal sensor.
0:21:55 > 0:21:58It has a range of about, er...
0:21:58 > 0:22:03This one is about 30mm and so because there's 7mm of slip here,
0:22:03 > 0:22:07about every four years I have to reset it.
0:22:07 > 0:22:10But first, download the data.
0:22:10 > 0:22:13I'll get my computer out.
0:22:14 > 0:22:177mm of slip might not sound like much
0:22:17 > 0:22:21but it could have a devastating effect.
0:22:21 > 0:22:27150km up the fault in San Francisco the tectonic plates are locked,
0:22:27 > 0:22:30and eventually this pent-up energy
0:22:30 > 0:22:34will be released in the form of an earthquake.
0:22:34 > 0:22:38Every time that Roger's machine measures the fault slipping,
0:22:38 > 0:22:40known as a creep event, this may help to calculate
0:22:40 > 0:22:43the amount of stress that's building up beneath the city.
0:22:43 > 0:22:46Oh, we've got a creep event! How exciting.
0:22:46 > 0:22:50The black line here is, er, can you see that OK?
0:22:50 > 0:22:54So the black line is the temperature decrease
0:22:54 > 0:22:58from mid-summer to... It's upside down, OK,
0:22:58 > 0:23:02we could actually turn it up the other way but let's do it like that,
0:23:02 > 0:23:05so there's the temperature decreasing as a function of time
0:23:05 > 0:23:07and here is, er, a creep event
0:23:07 > 0:23:11where the fault suddenly starts slipping at a few millimetres per second
0:23:11 > 0:23:17and then over the next day or two, in fact continuing for several weeks.
0:23:17 > 0:23:22Even if you'd been standing on the fault, you wouldn't have noticed it
0:23:22 > 0:23:26cos it's really a very slow, quiet process.
0:23:26 > 0:23:30So until people have put instruments like this on the ground,
0:23:30 > 0:23:34we had no idea that these things were occurring.
0:23:37 > 0:23:41Science has mapped every fault in California,
0:23:42 > 0:23:45but in China, the process is only just beginning.
0:23:52 > 0:23:57Xiao Yu Dong is 42km from the earthquake's epicentre.
0:23:57 > 0:23:59What was once flat farmland
0:23:59 > 0:24:03was completely transformed on May 12th.
0:24:05 > 0:24:10To find the fault here, Mike's looking for earthquake scarps -
0:24:10 > 0:24:14steps in the landscape where the rupture has lifted the ground up.
0:24:22 > 0:24:25This level I'm standing on right now used to be up there.
0:24:25 > 0:24:31That's a good two to two and a half, possibly even three metres.
0:24:31 > 0:24:36So that entire free surface is the earthquake scarp.
0:24:36 > 0:24:40And no doubt that will quickly be bricked up
0:24:40 > 0:24:43and you won't be able to distinguish it so easily.
0:24:43 > 0:24:47This is also a superb place, by the way, for finding,
0:24:47 > 0:24:51um, unambiguous lateral offset, if there is any.
0:24:51 > 0:24:54You can see where I'm standing, there's a nice straight wall,
0:24:54 > 0:24:56and I can see from here that the offset,
0:24:56 > 0:24:59the natural offset here is about about a metre,
0:24:59 > 0:25:03maybe a little bit less than a metre to this wall,
0:25:08 > 0:25:12so essentially this wall here was that one back there.
0:25:12 > 0:25:15Before the rupture actually happened,
0:25:15 > 0:25:19probably at this location there was a lot of shaking and rolling
0:25:19 > 0:25:25and then this this side of the village just rose up like this.
0:25:25 > 0:25:29It takes about between 10, 15, 20, maybe even more seconds to do that.
0:25:29 > 0:25:33That's actually quite slow when you're standing here as an eyewitness
0:25:33 > 0:25:35and seeing this thing just rise up like this
0:25:35 > 0:25:38out of the ground and then this entire part of the village
0:25:38 > 0:25:41is now a metre to two metres higher.
0:25:45 > 0:25:49It's hard to imagine what this place once looked like,
0:25:49 > 0:25:52but one villager has kept a memento.
0:25:54 > 0:25:58- TRANSLATION: - I really liked the beautiful view we had of the landscape here,
0:25:58 > 0:26:02so I took this photograph from the first floor of our house.
0:26:02 > 0:26:06Before the earthquake the road used to be completely level.
0:26:06 > 0:26:09The ground too, everywhere was level,
0:26:09 > 0:26:12but now it's dropped by one or two metres.
0:26:12 > 0:26:16The ground just slid down, it was amazing.
0:26:16 > 0:26:20For the people of Xiao Yu Dong, May 2008 was the first time
0:26:20 > 0:26:24any of them had ever experienced a major earthquake.
0:26:24 > 0:26:27But Mike is beginning to suspect
0:26:27 > 0:26:30that there have been other quakes here in the past.
0:26:30 > 0:26:36The two things that important here is that the elevation difference between where I'm standing right here
0:26:36 > 0:26:39and up there is significantly higher than it was
0:26:39 > 0:26:40further along the the rupture
0:26:40 > 0:26:45and further back along the rupture that way we saw the modern earthquake scarp
0:26:45 > 0:26:48being very irregular and this looks almost identical to that,
0:26:48 > 0:26:50so this is very suggestive.
0:26:50 > 0:26:53So I would, I would love to be able to walk,
0:26:53 > 0:26:59if I could just walk up here a long way.
0:27:03 > 0:27:07To Mike's expert eye, every rise and dip in the landscape
0:27:07 > 0:27:10could be evidence of a whole history of earthquakes.
0:27:12 > 0:27:19So right here I'm standing on an old scarp that's very gentle now.
0:27:21 > 0:27:24And it continues to be this sort of hammocky topography
0:27:24 > 0:27:27in these fields, so this sort of old scarp
0:27:27 > 0:27:31and the much greater relief here at this point
0:27:31 > 0:27:35would tell us that this has been the place of an earthquake before
0:27:35 > 0:27:37and probably several before that too,
0:27:37 > 0:27:41so points to the importance of mapping these things in great detail.
0:28:00 > 0:28:03But mapping out faults isn't always so straightforward.
0:28:03 > 0:28:07Mike and Jing have come to a valley further along the rupture
0:28:07 > 0:28:12where the ground rose up twice as high as in Xiao Yu Dong.
0:28:13 > 0:28:16They're hoping that a scarp this size will tell them
0:28:16 > 0:28:19more about earthquakes that have happened here in the past
0:28:19 > 0:28:22and those that are yet to come.
0:28:24 > 0:28:28But recent heavy storms have transformed the landscape.
0:28:33 > 0:28:38- TRANSLATION: - Hello, was there an earthquake scarp here before?
0:28:38 > 0:28:43- TRANSLATION: - Yes, but it was washed away - our village was too.
0:28:45 > 0:28:50Tons of earth fell down, part of the mountain just collapsed.
0:28:58 > 0:29:00It's probably there,
0:29:00 > 0:29:03but not where the river has incised through it
0:29:03 > 0:29:06but if you follow it up a little bit there must be some remnants...
0:29:06 > 0:29:09Maybe, maybe.
0:29:09 > 0:29:13I would hope so. A six-metre scarp can't disappear completely.
0:29:20 > 0:29:22That is the scarp.
0:29:24 > 0:29:29Let's see, you can go up and I'll find this place for the grass.
0:29:36 > 0:29:40Before this September the ground was like at this level
0:29:40 > 0:29:45and this level used to be lined up over where, um, Mike is standing.
0:29:45 > 0:29:52So I'm standing here on a surface that now is occupied by Jing down below there.
0:29:52 > 0:29:55The ground on my left was pushed up six metres
0:29:55 > 0:29:59and moved to the right by six metres as well,
0:29:59 > 0:30:01so the mountains as a whole are shortening,
0:30:01 > 0:30:04the crust is shortening and moving sideways
0:30:04 > 0:30:07and that sideways motion is small,
0:30:07 > 0:30:11but it is an expression of India colliding into Asia.
0:30:11 > 0:30:15This landscape we're in now has been formed by many, many earthquakes,
0:30:15 > 0:30:18hundreds and thousands of earthquakes.
0:30:18 > 0:30:23Despite the damage from the storms, Mike is beginning to understand
0:30:23 > 0:30:27the history of earthquakes in this particular valley.
0:30:27 > 0:30:29But this evidence is fast disappearing.
0:30:33 > 0:30:39Obviously, over time, the subtle signals for any specific earthquake
0:30:39 > 0:30:42disappears very quickly, and this has virtually disappeared
0:30:42 > 0:30:48in less than six months, so as we're scrabbling around the hillsides,
0:30:48 > 0:30:55we see signals every now and then, but the data is very sparse, very difficult to put together.
0:30:55 > 0:30:59Geologists like Mike hope that by mapping the past,
0:30:59 > 0:31:02they'll come closer to predicting the future.
0:31:05 > 0:31:08But even if you know where to measure,
0:31:08 > 0:31:12every earthquake is complicated by a significant factor,
0:31:12 > 0:31:16how big it's going to be.
0:31:16 > 0:31:20We don't know what makes an earthquake start today instead of yesterday.
0:31:20 > 0:31:22We also don't know what makes it stop
0:31:22 > 0:31:24and that's what controls the size of the earthquake.
0:31:24 > 0:31:27A magnitude three starts at a point,
0:31:27 > 0:31:30you start to slip at a point and you have a rupture front that
0:31:30 > 0:31:33travels out and causes more of the fault to slip,
0:31:33 > 0:31:37and in a magnitude three, you travel out this far.
0:31:37 > 0:31:41In a magnitude five, it travels out for a kilometre or two.
0:31:41 > 0:31:46In a magnitude eight, it travels out for 500 kilometres,
0:31:46 > 0:31:51so when we're trying to predict what the earthquake will be, we're saying, it starts here,
0:31:51 > 0:31:56but does it stop after one kilometre, or does it stop after, um, 100 kilometres?
0:31:58 > 0:32:01Predicting the size of an earthquake is essential.
0:32:01 > 0:32:04Millions of quakes happen all over the world each year,
0:32:04 > 0:32:08but the vast majority are too weak even to be felt.
0:32:08 > 0:32:11The real challenge for science is to work out when one of these
0:32:11 > 0:32:15little earthquakes is going to develop into a major disaster.
0:32:17 > 0:32:21You don't want me to predict every earthquake, there's going to be 50 in California today.
0:32:21 > 0:32:24You want me to predict which of the 35,000 we record each year
0:32:24 > 0:32:28is the one or two large enough to do some damage, and really, what we want to do
0:32:28 > 0:32:33is really predict just the one that happens every five or ten years that does a lot of damage.
0:32:33 > 0:32:39'Live, Los Angeles tonight, battered and bracing for the worst.'
0:32:41 > 0:32:43The last earthquake to do a lot of damage in California
0:32:43 > 0:32:49stuck in Northridge, a suburb of Los Angles, in January 1994.
0:32:49 > 0:32:55Measuring magnitude 6.7, it killed 72 people and caused over
0:32:55 > 0:33:0120 billion in damage, making it one of the costliest natural disasters in US history.
0:33:01 > 0:33:05'The earth is literally split here.'
0:33:05 > 0:33:07'The city wakes up to a nightmare.'
0:33:09 > 0:33:11But one man saw it coming.
0:33:14 > 0:33:17Professor Vladimir Keilis-Borok, an 87-year-old
0:33:17 > 0:33:21Russian geophysicist at the University of Los Angeles
0:33:21 > 0:33:28has developed a way of predicting earthquakes, with a surprisingly high level of accuracy.
0:33:28 > 0:33:31Out of 17 earthquakes worldwide
0:33:31 > 0:33:36which happened since '92,
0:33:36 > 0:33:40we have predicted 12.
0:33:40 > 0:33:42'The Earth's fury
0:33:42 > 0:33:47'unleashes fire, and flood, and fear.'
0:33:49 > 0:33:55The prediction method doesn't come from the world of geology, but from an extraordinary branch of maths...
0:33:55 > 0:33:57chaos theory.
0:34:08 > 0:34:14Chaos theory seeks to find an underlying order in some of nature's most random processes.
0:34:14 > 0:34:16Weather systems,
0:34:16 > 0:34:22the way birds flock together, or even the distribution of leaves on a tree.
0:34:22 > 0:34:26There didn't seem to be any order to earthquakes, but Keilis-Borok
0:34:26 > 0:34:29brought together scientists from multiple disciplines
0:34:29 > 0:34:35to study the problem, including seismologist David Jackson.
0:34:35 > 0:34:39Well, the general theory is that when the earth is in a chaotic state,
0:34:39 > 0:34:42there will be some features that can be recognised.
0:34:44 > 0:34:50And typically, those features are in the smaller earthquakes that occur, and how much a small earthquake
0:34:50 > 0:34:54brings with it, some immediate follow-on earthquake.
0:34:55 > 0:34:59Looking at some of California's major earthquakes in the past,
0:34:59 > 0:35:04the UCLA team thought that they could see patterns in the smaller quakes that preceded them.
0:35:06 > 0:35:10Today, they look for similar patterns, chains of small
0:35:10 > 0:35:14earthquakes linked by their size and the time they strike.
0:35:14 > 0:35:18If they think they see a new chain that matches their historical data,
0:35:18 > 0:35:21the group then issues an earthquake alarm.
0:35:24 > 0:35:28Sometimes, humans can see the patterns and we propose
0:35:28 > 0:35:34something that seems to us logical in terms of the way earthquakes behave, but sometimes, their patterns are
0:35:34 > 0:35:40too complicated and the hope is that computers, using vast amounts of data,
0:35:40 > 0:35:45and, er, combing the data for those patterns, can out-think us in that particular way.
0:35:48 > 0:35:52But the patterns haven't always led to accurate predictions.
0:35:52 > 0:35:57Nine years after Northridge, Keilis-Borok's team announced that a major earthquake
0:35:57 > 0:36:02would strike near Palm Springs by September 5th, 2004.
0:36:02 > 0:36:07Once again, the enigmatic Russian was putting his career on the line.
0:36:10 > 0:36:12But this time, nothing happened.
0:36:16 > 0:36:21The team's work continues to be a mixture of success and failure,
0:36:21 > 0:36:25but Keilis-Borok is confident that he can improve his hit rate.
0:36:27 > 0:36:30There is no such thing as
0:36:30 > 0:36:35100% accuracy, but...
0:36:35 > 0:36:41we believe the accuracy can be increased by factor at least five.
0:36:44 > 0:36:51It remains to be seen if chaos theory and maths are the answer to earthquake prediction.
0:36:51 > 0:36:55In the meantime, science has been forced to explore other,
0:36:55 > 0:36:58sometimes stranger avenues, to try and solve this problem.
0:37:02 > 0:37:06Since time began, people have been reporting weird goings on
0:37:06 > 0:37:12in the days, or hours, before an earthquake. Sudden upsurges in migraines...
0:37:13 > 0:37:16..mysterious changes in ground water levels,
0:37:16 > 0:37:22but perhaps the most bizarre phenomenon involves animals.
0:37:30 > 0:37:33Guangxi province, South West China.
0:37:33 > 0:37:38This farms lies at the centre of an intriguing experiment to predict earthquakes...
0:37:41 > 0:37:44..using snakes.
0:37:48 > 0:37:51TRANSLATION: We call this snake Dragon,
0:37:51 > 0:37:54or Earth Dragon, here in China.
0:37:54 > 0:37:59In Chinese culture, we think of ourselves as children of the dragon,
0:37:59 > 0:38:02so there is no need to be afraid of snakes.
0:38:04 > 0:38:09Jiang Weisong, head of the local earthquake bureau, has a team
0:38:09 > 0:38:14monitoring these snakes 24 hours a day using webcams.
0:38:14 > 0:38:18It's thought that snakes may be able to sense earthquakes in the same way
0:38:18 > 0:38:21that they locate their prey.
0:38:21 > 0:38:25Using their inner ears to pick up vibrations in the ground.
0:38:30 > 0:38:35If a small earthquake happens within 120 kilometres of this region,
0:38:35 > 0:38:37for example, a magnitude five,
0:38:37 > 0:38:41then the snakes will come out of their holes
0:38:41 > 0:38:44and crawl along the walls, trying to escape.
0:38:48 > 0:38:51If a major earthquake happens nearer, then the snakes would
0:38:51 > 0:38:54smash themselves against the wall continuously,
0:38:54 > 0:38:56until they killed themselves.
0:38:56 > 0:38:58It has a very powerful effect on them.
0:39:03 > 0:39:07We'd like to see this happen three to five days in advance,
0:39:07 > 0:39:11then we'd have time to analyse it and make an accurate prediction.
0:39:16 > 0:39:19Animal predictions aren't without foundation in China.
0:39:22 > 0:39:27They've been attributed to saving tens of thousands of lives.
0:39:27 > 0:39:31At the height of the cultural revolution, the city of Haicheng was
0:39:31 > 0:39:36evacuated after many people reported seeing animals behaving strangely.
0:39:42 > 0:39:48When a magnitude seven earthquake struck days later, Haicheng was heralded as the first time
0:39:48 > 0:39:52one of these disasters had been predicted using animals.
0:40:02 > 0:40:06But since then, no-one has ever been able to replicate the results.
0:40:09 > 0:40:13As far as I know, I'm the only person doing research in this area.
0:40:13 > 0:40:16Even in China.
0:40:16 > 0:40:21I can understand why other scientists might not recognise my work, but I think the reason they distrust it
0:40:21 > 0:40:25is that they haven't done the practical experiments themselves.
0:40:32 > 0:40:40If we can have more observation stations, then our predictions would be more scientific and more accurate.
0:40:40 > 0:40:45One flower doesn't make a spring, but hundreds of flowers can definitely make spring.
0:40:47 > 0:40:53In the hours, or days, before an earthquake, it's not just animals that can be affected.
0:40:53 > 0:40:58There's another even stranger phenomenon that can be used for prediction.
0:40:58 > 0:41:01Bright lights that appear in the sky.
0:41:01 > 0:41:06This photograph was taken in September 1966,
0:41:06 > 0:41:10before an earthquake struck the town of Matsushiro, in Japan.
0:41:11 > 0:41:14Many other people have reported seeing these lights,
0:41:14 > 0:41:18but no-one has ever been able to prove why they might happen.
0:41:22 > 0:41:28Today, however, NASA physicist Friedemann Freund believes he may have found the answer.
0:41:30 > 0:41:33Gary, will you tell us when you make contact?
0:41:36 > 0:41:37Now, it starts.
0:41:39 > 0:41:44In 2005, Freund made a peculiar discovery that if you crush a rock
0:41:44 > 0:41:49to almost breaking point, it produces a tiny electrical current.
0:41:49 > 0:41:51Now, we are already driving
0:41:51 > 0:41:54something like four nanoamps
0:41:54 > 0:41:56through this rock,
0:41:56 > 0:41:59the pressure increases more and more,
0:41:59 > 0:42:01the current increases,
0:42:01 > 0:42:07now the pressure has already reached its maximum value and the current
0:42:07 > 0:42:12will stay up there, and as long as the load stays on the rock,
0:42:12 > 0:42:15the current will continue to flow,
0:42:15 > 0:42:18and that is the simulation for what we believe to be happening
0:42:18 > 0:42:26in the Earth prior to an earthquake, before they rupture. If you can imagine
0:42:26 > 0:42:32that you have a cubic kilometre of rock being stressed or...the currents translate
0:42:32 > 0:42:36into thousands, ten thousand, sometimes hundreds of thousands of amperes
0:42:36 > 0:42:39that could flow out of a cubic kilometre of rock.
0:42:41 > 0:42:47The currents going through the rock can give rise to other oddities, including one that Freund believes
0:42:47 > 0:42:50may explain the lights in the sky before an earthquake.
0:42:50 > 0:42:58If it were dark here, we would start seeing little flashes of light forming along the edges
0:42:58 > 0:43:00of these rocks. Maybe in nature,
0:43:00 > 0:43:06they are sufficiently strong that they couldn't become luminous
0:43:06 > 0:43:10phenomenon known as earthquake lights that can happen before
0:43:10 > 0:43:14earthquakes, during earthquakes and also during the aftershock series.
0:43:14 > 0:43:16You think there's a connection between this and...?
0:43:16 > 0:43:20Oh, yes, yes, there's definitely a connection.
0:43:20 > 0:43:24Friedemann Freund is fighting a tide of opposition from mainstream science,
0:43:24 > 0:43:31but he's convinced that he's right and he's prepared to put his money where his mouth is.
0:43:34 > 0:43:40So far, everything that I've shown you was essentially done on a shoe-string budget,
0:43:40 > 0:43:44with lots of private money going in there
0:43:44 > 0:43:49and very, very little funding from any government sources.
0:43:49 > 0:43:51Who's been funding it up until now?
0:43:52 > 0:43:58Well, I eventually paid most of it out of pocket, we are still
0:43:58 > 0:44:01having a very, very minimal funding level.
0:44:01 > 0:44:06- Just out of your own wallet?- Yes, I've spent close to a million dollars
0:44:06 > 0:44:11on funding this research, because nobody believed me.
0:44:11 > 0:44:13That's a hell of a lot of money just to try and...
0:44:13 > 0:44:19Well, because I know that I'm on the right track, so I will pursue this
0:44:19 > 0:44:24and bring it to the end. Now, people start to listen, and yes, now they are convinced.
0:44:24 > 0:44:27With something like this,
0:44:27 > 0:44:32as clear as you can hope you would get it.
0:44:35 > 0:44:41The scientific community may still be sceptical about Friedemann Freund's rock experiments,
0:44:41 > 0:44:45but his research is now being used in a commercial application...
0:44:45 > 0:44:48QuakeFinder - a device that measures electromagnetic changes
0:44:48 > 0:44:53in the ground to sense if an earthquake is coming.
0:44:53 > 0:44:58It's, er, basically, a computer system, er, set of electronics
0:44:58 > 0:45:03to process the data, a simple hard drive from a laptop to record it,
0:45:03 > 0:45:09a radio link to bring it into, er, a farmer's house maybe 200, or 300 feet away, and then we have
0:45:09 > 0:45:11a satellite dish that takes the data
0:45:11 > 0:45:16and brings it through a satellite link up to our site here in Palo Alto.
0:45:16 > 0:45:22It's still early days for QuakeFinder, but it may have already had a minor breakthrough.
0:45:22 > 0:45:28In October 2007, the little white boxes picked up electromagnetic
0:45:28 > 0:45:32signals shortly before an earthquake struck Alum Rock.
0:45:32 > 0:45:35A small community south of San Francisco.
0:45:36 > 0:45:41This is the, er, the actual data from the, er, Alum Rock earthquake,
0:45:41 > 0:45:45if you're interested in that, these are the days prior to the earthquake
0:45:45 > 0:45:52so the, er, magnetic pulsations that we see are very, very few and far between, this large one here
0:45:52 > 0:45:57is a calibration signal that we generated ourselves just to make sure everything was working OK.
0:45:57 > 0:46:01About two weeks before the earthquake, we started to get these
0:46:01 > 0:46:06very large pulsations, the next few days, it got busier and busier
0:46:06 > 0:46:08it spread out over more of the day
0:46:08 > 0:46:11until finally, right there, the earthquake hit.
0:46:11 > 0:46:15But was there a moment, Tom, when this data was, you know,
0:46:15 > 0:46:19more and more data's coming in from Alum Rock, were you thinking, "Crikey, this must be an earthquake?"
0:46:19 > 0:46:22I'll be honest with you, no.
0:46:22 > 0:46:26Because we're still trying to discover what the pattern is,
0:46:26 > 0:46:29we're not quite sure how many days it should be there.
0:46:29 > 0:46:33This was, we didn't know if it was a large earthquake or a small earthquake, all we knew was that
0:46:33 > 0:46:38it was only happening at that one station, not at any of the other stations.
0:46:40 > 0:46:44It's going to take a great deal of research and a lot more earthquakes
0:46:44 > 0:46:49before theories about rocks or animals are ever proven.
0:46:49 > 0:46:55But mainstream science has practically given up on funding these kinds of experiments,
0:46:55 > 0:47:02and many geologists even question the value of prediction.
0:47:02 > 0:47:05Well, what would you do with it? Let's imagine I can tell you
0:47:05 > 0:47:07there'll be an earthquake in a hour, what would you do?
0:47:07 > 0:47:09You'd get your camera out, or your tape recorder or something,
0:47:09 > 0:47:13if you were in a building, you'd probably go outside because you
0:47:13 > 0:47:16might think it's gonna fall down, that's not particularly useful,
0:47:16 > 0:47:18the building is gonna fall down, that is the problem.
0:47:18 > 0:47:23Would you rather have an hour to get out of a building or a building that didn't fall down in the first place?
0:47:24 > 0:47:30It's a real possibility that we'd have more people dying on the freeway trying to get away when we made
0:47:30 > 0:47:33a prediction than we would have killed in the earthquake when it happened.
0:47:37 > 0:47:41Unable to predict these disasters, California has turned itself into
0:47:41 > 0:47:44one of the most earthquake-proof places on the planet.
0:47:44 > 0:47:50In Los Angeles, every new skyscraper has been built following strict construction codes.
0:47:50 > 0:47:56Hundreds of freeway flyovers have been retro-fitted and re-enforced, and as the city expands
0:47:56 > 0:48:02into the surrounding counties, the fault lines are what matters when it comes to choosing real estate.
0:48:05 > 0:48:07Would you live directly on it, Ken?
0:48:07 > 0:48:11No, when we were looking for a house, we looked at some houses that were right on top of
0:48:11 > 0:48:14the Sierra Madre fault and we decided to keep looking.
0:48:14 > 0:48:19Similarly, when we were looking at the house, I was probably
0:48:19 > 0:48:26more interested in the structural integrity of it and the construction of it than most people would be.
0:48:26 > 0:48:33Geologist Ken Hudnut works for the US GS, preparing Los Angeles for the next big earthquake.
0:48:33 > 0:48:40You can see here a brand new development going right up to the Cucamonga Falls.
0:48:40 > 0:48:43We think that that fault is capable of a magnitude 7.5,
0:48:43 > 0:48:467.6 earthquake on its own,
0:48:46 > 0:48:50without any involvement of the San Andreas Fault itself.
0:48:50 > 0:48:55That gap is there because they have to set back away from the fault,
0:48:55 > 0:48:59that's the case for any fault that's considered active,
0:48:59 > 0:49:02and by that, the state law says if it has had
0:49:02 > 0:49:07surface faulting within the last 10,000 years, you need to set back from it.
0:49:15 > 0:49:20Over in China, the devastation in Sichuan Province serves as a stark reminder
0:49:20 > 0:49:24of the potential cost of building on earthquake faults.
0:49:31 > 0:49:32Mike and Jing have come to Bailu,
0:49:32 > 0:49:37a mountain town around 50 kilometres from the earthquake's epicentre.
0:49:37 > 0:49:42The fault passes right through this valley, heading straight for the town's middle school.
0:49:47 > 0:49:50Well, this is quite something.
0:49:50 > 0:49:53Thanks to an astonishing stroke of luck,
0:49:53 > 0:49:57the rupture missed both of the buildings containing classrooms,
0:49:57 > 0:49:59but at the end of the playground,
0:49:59 > 0:50:04the earthquake demolished a block of housing, killing several teachers.
0:50:09 > 0:50:14What we would, er, be very happy about seeing here,
0:50:14 > 0:50:20um, extraordinarily happy, is that these buildings that are built either side of the rupture didn't collapse,
0:50:20 > 0:50:26and that one over there appears to have very little damage, you know, apart from broken windows,
0:50:26 > 0:50:30but, er, this rupture goes through
0:50:30 > 0:50:35what used to be the dormitory for the school teachers and that's completely gone.
0:50:35 > 0:50:39Um, so first lesson, don't build across a rupture.
0:50:39 > 0:50:44The school has now become a tourist attraction,
0:50:44 > 0:50:50but Mike and Jing can see clues in the landscape that suggest this disaster could have been avoided.
0:50:50 > 0:50:56The fact that beyond the school buildings, the land is higher
0:50:56 > 0:50:59and it may be there was an old scarp here.
0:50:59 > 0:51:03In the topography, you can see the long-term effect of this fault
0:51:03 > 0:51:06slicing straight up that valley and giving that notch.
0:51:10 > 0:51:14To be fair to the authorities, there are many fault scarps in these mountains
0:51:14 > 0:51:20and they're very, very difficult to find, we had only just begun to find some of them,
0:51:20 > 0:51:22it takes a long and sustained effort.
0:51:22 > 0:51:30It took people in California decades to map out the fault scarps in any sort of precision.
0:51:36 > 0:51:40There were fifteen million people displaced by the earthquake. The Chinese authorities
0:51:40 > 0:51:44don't have time to wait until they've mapped the precise location of Sichuan's faults.
0:51:48 > 0:51:52TRANSLATION: If someone shouts "earthquake," put your hands on your heads.
0:51:54 > 0:51:59Hands on your heads and hide under the desk.
0:52:00 > 0:52:03The best that many schools can do now
0:52:03 > 0:52:07is simply rehearse for the moment an earthquake strikes again.
0:52:12 > 0:52:16Elsewhere in Sichuan, they're rebuilding at a rapid rate.
0:52:19 > 0:52:25But the vast majority of these new homes won't be strong enough to survive another major earthquake.
0:52:29 > 0:52:34For Roger Bilham, this is a problem that's endemic throughout the developing world.
0:52:38 > 0:52:43I can go here here, here OK, where my fingers stab the map,
0:52:43 > 0:52:46there will be a magnitude seven earthquake within,
0:52:46 > 0:52:52you know, a few inches of it in the next 30 years maybe in the next year.
0:52:52 > 0:52:57I've made a forecast that it's possible right now
0:52:57 > 0:53:01for one million people to be killed by a single earthquake, OK?
0:53:01 > 0:53:04Now, that's a terrible thing to say and it's a thing that has
0:53:04 > 0:53:08no precedent, it's never happened in the past,
0:53:08 > 0:53:10why can I make such a crazy statement?
0:53:10 > 0:53:17Because there are now cities of eight and ten and twelve million people along this earthquake belt
0:53:17 > 0:53:24that have never been there in the past and that knowledge is sufficient, surely,
0:53:24 > 0:53:29to drive those countries, if they're responsible to mandate earthquake resistance.
0:53:29 > 0:53:31And it only costs about another 10% more.
0:53:31 > 0:53:33What it means is...
0:53:33 > 0:53:37buying fewer guns and better concrete instead.
0:53:38 > 0:53:43Modern seismology has been with us for over 100 years,
0:53:43 > 0:53:47but scientists are still no closer to predicting earthquakes.
0:53:47 > 0:53:51However, they haven't completely given up.
0:53:51 > 0:53:54But where they once thought it might be possible to predict months in advance,
0:53:54 > 0:53:58now, it's come down to a matter of seconds.
0:53:59 > 0:54:05We are prototyping earthquake early warning, this is also sometimes called now casting,
0:54:05 > 0:54:11because it's not saying there's going to be earthquake, its rather saying an earthquake has already begun
0:54:11 > 0:54:16and we're giving you that information before the waves have travelled from the fault to where you are.
0:54:18 > 0:54:24The warning system will start from stations like this, located along the San Andreas Fault.
0:54:24 > 0:54:27Instruments buried deep underground will track
0:54:27 > 0:54:32how much the fault is moving, using high-precision GPS satellites.
0:54:32 > 0:54:37The, er, antenna itself is inside of this hemispherical shell and it's
0:54:37 > 0:54:41constantly locked onto the radio signals from the GPS satellites.
0:54:41 > 0:54:46Each leg of this tripod goes down about 30 feet,
0:54:46 > 0:54:50ten metres into the ground and firmly attached to the bedrock here.
0:54:51 > 0:54:55But to have this system up and running, these instruments need
0:54:55 > 0:55:00to be able to feed back data the moment the ground starts to shake.
0:55:00 > 0:55:05In a big San Andreas earthquake, this station would move more than a metre
0:55:05 > 0:55:10within a matter of less than ten seconds, so other stations like this positioned all along
0:55:10 > 0:55:14the San Andreas Fault could actually track the rupture as it's progressing.
0:55:14 > 0:55:17We're seeing it here coming up the fault
0:55:17 > 0:55:21and the red is where there's a lot of damage, so we could have
0:55:21 > 0:55:24used our stations in this area, at this point, 20 seconds into the earthquake.
0:55:24 > 0:55:28Know that it's underway, we've got a big earthquake started and send
0:55:28 > 0:55:31that information to Los Angeles that the earthquake's underway.
0:55:38 > 0:55:41We could potentially get up to a minute's warning.
0:55:41 > 0:55:46You could hook this up to your elevator and have your elevator moved to the nearest floor and open
0:55:46 > 0:55:49the doors, so people weren't trapped for the next few days after the power goes out.
0:55:52 > 0:55:58We could ring an alarm in operating room, so the surgeon pulls the scalpel out of your chest.
0:55:59 > 0:56:05You could ring an alarm where they're handling toxic materials, so you're not pouring out chlorine.
0:56:06 > 0:56:12You could shut down critical computer facilities, we could also be stopping any rail lines, we could be flashing
0:56:12 > 0:56:17the messages up on freeways, you know, "earthquake coming, slow down."
0:56:17 > 0:56:22Earthquake prediction doesn't come any more high-tech than this, and now casting
0:56:22 > 0:56:27is not only possible, it's surprisingly affordable.
0:56:27 > 0:56:32Well, I think the public expects us to be able to predict earthquakes, and of course, we really can't.
0:56:32 > 0:56:38But this is something that we can do, we have the technology, we've tested it, we've developed systems
0:56:38 > 0:56:43that work and we know that we could build an early-warning system, at this point in time, we don't have
0:56:43 > 0:56:48nearly the instrumentation in place to be able to do that kind of earthquake early warning,
0:56:48 > 0:56:52some estimates, we think it could cost about 100 million in all.
0:56:52 > 0:56:58And the price tag we're looking at for a big earthquake on the San Andreas is, er, 200 billion
0:56:58 > 0:57:05and up, so a 100 million system to help reduce the damages seems like a good investment.
0:57:07 > 0:57:12This kind of early-warning system might work for California one day,
0:57:12 > 0:57:16but for most places in the world, science's best answer to the threat of earthquakes
0:57:16 > 0:57:23is to construct better buildings and map all the faults in potential disaster zones.
0:57:23 > 0:57:27It's really important to know where these active faults are exactly,
0:57:27 > 0:57:31so that at least if you can't predict the earthquakes,
0:57:31 > 0:57:34then we know where not to build.
0:57:34 > 0:57:38But not everyone thinks that prediction is totally dead,
0:57:38 > 0:57:45there's still a sneaking hope that someone, someday, may find the Holy Grail of seismology.
0:57:45 > 0:57:50Some seismologists would say, "No, it's impossible and I'm not willing to go that far,
0:57:50 > 0:57:52"because we don't understand
0:57:52 > 0:57:57"why exactly earthquakes happen, so if we don't understand that, we can't say they're not predictable."
0:57:58 > 0:58:03It's an interesting challenge, we might get closer to it, there are obviously certain things
0:58:03 > 0:58:06we're going to learn and have learnt, maybe one day,
0:58:06 > 0:58:09we'll get lucky and find that we've been looking at the wrong thing,
0:58:09 > 0:58:15but right now, whatever we do has resulted in, well, I have to say failure, but you know,
0:58:15 > 0:58:18we're trying, we're doing our bit, we think we'll get there one day.
0:58:41 > 0:58:44Subtitles by Red Bee Media Ltd
0:58:44 > 0:58:48E-mail subtitling@bbc.co.uk