NARRATOR: Earth, a 4.5
billion year old planet, still evolving. As continents shift and clash,
volcanoes erupt and glaciers grow and recede. The Earth's crust is carved in
numerous and fascinating ways, leaving a trail of
geological mysteries behind. In this episode, an
investigation into California's San Andreas Fault, the
greatest fault line on Earth. 800 miles long, this ugly
scar on the landscape has spawned earthquake
after earthquake. But for now it waits
quietly deep under our city, building up stress
to strike once again. The San Andreas Fault is
one of the most dangerous geological features on Earth. California's greatest cities
and millions of our citizens live in constant peril. Since records began, there
have been 13 large earthquakes along the San Andreas
Fault. And now America's geologists,
her rock detectives, are warning of a
potential disaster. In the fall of 2008,
more than 300 scientists calculated what a major
earthquake would do to Southern California. We've been conducting a
special study of a magnitude 7.8 earthquake on the southern
San Andreas Fault, large enough to potentially damage
tall buildings. Fire will be very significant. NARRATOR: The definitive
scientific report presented to politicians
was codenamed Shakeout. It forecasts thousands of
deaths and billions of dollars of damage in the city
of Los Angeles, which makes it crucial to investigate
the most important question. When will the next big
earthquake hit the San Andreas Fault? The latest preparations
for disaster are the climax of an
investigation that started more than 100 years ago in
the aftermath of the great San Francisco earthquake of 1906. The earthquake struck on a
Wednesday just before dawn. The ground shook
violently for 45 seconds, igniting fires that raged
unchecked for the next four days. 28,000 buildings, a tenth of
the entire city, were destroyed. And more than 3,000 people, one
in every 100 of the population, were killed. With a magnitude of 7.8, it's
in the top 20 of North America's strongest ever earthquakes. The scale of the great
San Francisco earthquake shocked the nation. But no one understood what
had made the city shake. Native American myths
explained earthquakes as shocks from a battle between
warring spirits. Latter day explorers couldn't
understand the shocks that destroyed their
mission buildings. One Spanish missionary
wrote, the Earth shook around me from
explosions under the ground. 300 years later and science
has still made little progress. Refugees in the ruins
of San Francisco still blamed earthquakes
on mysterious underground explosions. So just three days
after the earthquake, the state of California asked
one of the world's most famous geologists, Andrew Lawson from
California State University, to investigate what
had destroyed the city. He and a team of
25 scientists began collecting damage
evidence in the city and surrounding countryside. There were roads that had
buckled, rail tracks that had twisted. The most startling
evidence of all, that came near the town of
Bolinas in Marin county, to the north of San Francisco. This picket fence had an
eight foot gap in the middle. Before the earthquake, it
was a solid boundary fence dividing two fields. But when he recreated
what had happened, Lawson realized that the land
had jolted apart and torn the fence in two. Plotting the evidence on
a map around San Francisco revealed a surprising pattern. Because connecting the
dots drew a straight line. And at every point the
Earth moved in the same way. On the coast to the north,
inland to the south, this line of weakness
was the culprit they were searching for. South of San Francisco,
the suspect line ran underneath a lake,
the Laguna de San Andreas. So now the earthquake
perpetrator at last had a name. Professor Lawson, who a decade
earlier had identified cracks in the Earth here
as a harmless rift, now rechristened it
the San Andreas Fault. In modern day San Francisco,
the buildings, the roads, and the railways have
long since been repaired. But if you know where to look,
evidence of the 1906 quake can still be found. Geologist Charlie Paull
follows in the footsteps of Lawson's team, seeking
signs of the havoc from 1906. He finds it on the cliffs at
Mussel Rock, 12 miles south of San Francisco. The cliff is not
here by accident. There's a very good reason
why this cliff is here. Half a mile or so
of the shore face apparently fell off in
the 1906 earthquake. And if you look down
below us, there's a big rotated block that's
near the present day shoreline. And it is just inboard
of the San Andreas Fault. The San Andreas Fault is about
a quarter of a mile offshore here. And of course that's one of
the major crustal junctions on this side of North America. NARRATOR: Modern computers
can now trace how damage waves spread out across the city. And that pinpoints where the
quake originated along the San Andreas. It was offshore, about two miles
out to sea from the Golden Gate Bridge. So to continue
tracking the fault, the investigation
must head out to sea. Marine geologists use
remote operating vehicles, mini submarines to
map the seafloor. What you would see is subtle
variations in the topography or topography that would
not naturally line up. So there might be a
line on the ocean floor that is higher or
lower on one side and you can use
various techniques to determine that this
actually is a fault instead of some other process. NARRATOR: Running south
across the seabed, the San Andreas finally runs
out of ocean and hits the land. This broken line of rocks
stretching in from the sea marks where the San Andreas
hits land 12 miles south of San Francisco. And we're here at Mussel Rock. And we're essentially standing
on the San Andreas Fault right now. And if there was
an earthquake, I don't know what would
happen right here. But I wouldn't want to be here. NARRATOR: This Pacific coastline
where cliffs crumble slowly into the sea is the boundary
between two of the Earth's massive continental plates. Separated by the
San Andreas Fault, two vast separate blocks
of the Earth's crust lie directly
alongside each other. Here, the continent
of North America lies slightly on top of the
adjacent section of crust which holds the Pacific Ocean. The join can be seen where these
lower darker rocks are overlaid by light colored
sedimentary rocks. CHARLES PAULL: These rock types
differ by more than 100 million years in age. Two rock bodies that are
not similar in any way have been brought together. NARRATOR: The fault line was
exposed to geologists when the cliffs collapsed here
in the 1906 earthquake. But back then, nobody
understood how and why the two different types of
rock were next to each other. Until around 40 years ago,
when the answer was finally revealed by the theory
of plate tectonics. The theory showed that
the Earth's crust consists of separate moving plates on
which the oceans and continents sit. Around 200 million years ago,
the heavy Pacific Ocean plate collided with North
America and started sinking underneath
the lighter continent. Professor of geophysics Mark
Zoback studies that process, called subduction,
in his laboratory at Stanford University. For many millions of
years prior to the existence of the San Andreas
Fault, the Pacific plate was subducting
beneath North America. The oceanic plate
was diving down. And that process went on for
well over 100 million years. So a tremendous amount of
activity was occurring. NARRATOR: As the unstoppable
force of one plate met the immovable
object of the other, they were forced to
change direction. MARK ZOBACK: About 20 million
years ago, the plate motions were such that the Pacific
Plate had to start sliding north with respect to North America. And now, the principal motion
is this sliding process between the two plates. And 20 million years ago, the
San Andreas Fault was born. NARRATOR: It was the
moving plates that crushed different
types of rock together, just as here at Mussel Rock. At last, the investigation
knows what it is dealing with. The San Andreas Fault
is 800 miles long, emerging from the seabed
north of Point Arena in northern California and
running down to the Salton Sea in the south. The evidence is coming together. Clues from the 1906 earthquake,
such as the picket fence that was torn apart, prove
that the land was moving. Connecting the dots identifies
the straight line of the San Andreas Fault. And Mussel
Rock uncovers different plates of the Earth's crust on
either side of the fault line. But investigators still
need more information about how often the San
Andreas has spawned earthquakes in the past. It might help them answer
the all important question-- when will the San
Andreas strike again? Andreas Fault will strike again, the investigation needs to know
about ancient earthquakes that have struck along
the fault line. But there's an
immediate problem. Here in California, it's
a particular challenge. Some of the earliest written
records were from the missions and from the early explorers,
so only dating back into the 18th century here. Other parts of the world, we
have an earthquake history going back millennia. NARRATOR: The investigation
moves 350 miles south of San Francisco to a
desert where the San Andreas may have been active
for thousands of years. There's crucial evidence
here about earthquakes from ancient times. This creek used to flow
straight across the San Andreas Fault here. But several earthquakes
formed a natural dam where the San Andreas Fault
wedges up here in front of me. That created a small pond. And now we're looking at the
dry sediments of that pond that record the history
of earthquakes. And that tells us quite a great
deal about the past behavior of the San Andreas Fault. NARRATOR: Some of the clues
are so small that Hudnut's detective work gets him down
and dusty among tiny cracks inside the fault. Sometimes we can find
out about the past behavior of the San Andreas Fault by
looking at the tiniest details. NARRATOR: At the bottom of
this small ancient pond, mud sediments collected
above a fine line of pebbles. Then an earthquake
shifted the land upwards on one side of the
vertical fault line. KEN HUDNUT: So this layer
was originally flat and then, in a subsequent
earthquake, it was broken like this along this
tiny fracture strand of the San Andreas Fault. NARRATOR: But finding
proof that this is the site of an
ancient earthquake is only part of the story. Hudnut needs to know how
long ago it happened. The bare rock layers are
no help in dating his find. But just above the
fracture line of the rocks, he has found the
evidence he needs. KEN HUDNUT: Here,
a bush was burned by a prehistoric wildfire. And that remnant of carbon is
why you see this black stain on the side of the trench wall. NARRATOR: The key
to unlocking the age of the rocks is carbon-14,
known as radiocarbon. Its molecular structure
means that carbon-14 is a more unstable isotope
than other forms of carbon. It's absorbed by growing plants
then radioactivity decays at a known rate
after the plant dies. So measuring carbon-14 in
vegetation burned in a wildfire reveals how long ago those
plants died and dates the rock in which the carbon is found. And through this, we can
reconstruct the evidence of the past earthquakes. NARRATOR: Radiocarbon dating
has proved that earthquakes have been happening along the
line of the San Andreas for thousands of years. The particular small earthquake
investigated by Hudnut, for example, is around
3,500 years old. It happened at a time when the
last woolly mammoths were dying out in North America. The investigation moved to
an even more remote desert spot, the Carrizo Plain, 160
miles north of Los Angeles. Here lies a dried up riverbed
which takes an unusual course. Coming down off the
hills, the creek bed takes a sudden sharp
turn to its right. A few hundred feet later, it
makes an equally odd 90 degree turn to the left. The creek crossed the line
of the San Andreas Fault. But early geologists
were mystified. Why did it bend in this way? The scientific
pioneers were limited to studies on the ground. Nowadays Hudnut
has an advantage, he can take to the air. The San Andreas Fault, where
it cuts through the Carrizo Plain, it almost
looks like a scar. And it was caused by repeated
earthquakes in the past. NARRATOR: Along the
long line of hills marking the course
of the San Andreas, Hudnut spots the puzzling
bends that he's seeking. KEN HUDNUT: If we could swoop
along the fault through here, that would be awesome. Oh, there's a great angle. See that right angle offset
channel with the elbow in it right there? That's a classic
one right there. NARRATOR: Hudnut's aerial
view of the creek bed shows that the river once flowed
straight on across the fault. But little by little, a series
of earthquakes along the San Andreas dragged the creek
away from its original course. Recreating how
the land had moved showed Hudnut that the
two parts of the creek had traveled more
than 300 feet apart. KEN HUDNUT: So if you imagine
the North American plate is fixed and the Pacific plate
is moving to the Northwest, the Wallace Creek site records
that offset because the channel is straight across the fault but
it's been offset through time. NARRATOR: Earlier investigators
had already radiocarbon dated the land on
each side of the fault here, revealing that it
took 3,000 years to change the creek's position. So knowing the distance and
the time it took to do it let's Hudnut calculate the average
speed with which the two landmasses are moving
past each other. 300 feet in 3,000 years,
1 foot per decade, just over an inch a year. But this was never
a steady, sliding, one inch a year movement. The reality was a series
of sudden small jumps whenever tension built up enough
between the two moving plates to overcome friction
between the rocks and rip the land apart
with an earthquake. It's an important moment
for the investigation. Knowing how fast the
land is moving not only reveals the stress
that's building up but also the risk
of an earthquake. The San Andreas Fault is
giving up its secrets. Clues from a long dried
up pond revealed the site of ancient earthquakes. Carbon from a prehistoric
fire provides the dates. And bends in a riverbed prove
how fast the plates are moving along the San Andreas. But now the investigation
has a new mystery to solve. If the land along
the San Andreas is moving one inch every
year causing earthquakes, then why has one small
town along the fault line never had any. The investigation has discovered
how fast the land is stretching and straining along each side
of the San Andreas Fault, which should help establish
when that ever increasing stress will snap the land apart in
the next major earthquake. But there's a problem. One part of the fault line
just doesn't fit the pattern. The small town of Hollister is
unique along the San Andreas Fault system. It's never had an earthquake. And the investigation is
going to find out why. Hollister has a
population of 37,000 and nothing here is quite
the way it should be. There are plenty of clues
suggesting that the land must be moving here-- sidewalks with cracks in,
curb stones way out of line, and walls that have
bent out of shape. CHARLES PAULL: Walking
through Hollister, we can see anything that man
has built that was laid out in a straight line
may have a jog in it. Every year, it
changes a little bit. And it's a progressive thing. NARRATOR: The clues add up
to one clear conclusion. Even without any
earthquakes, the Earth in this town in the heart
of the San Andreas system still slides imperceptibly
slowly and effortlessly along. In one sense, the
damage that you see here associated with the creeping is
clearly sort of under control. But as a geologist, if
you start playing that out for tens of thousands
or hundreds of thousands or millions of years,
the consequences of that become enormous. NARRATOR: For many years,
the creeping ground that moved without earthquakes
remained an unsolved mystery. But then the investigation
moved 100 miles south to another small community where
the land also creeps along. The village of Parkfield has
a population of just 37 people and a bridge which spans
right across the San Andreas Fault. The bridge separates
the Pacific plate on one side from the North American
plate on the other. And the bridge railings
have started to bend. I'm right now on the
Pacific plate on the west side of the San Andreas Fault.
And the San Andreas comes off the flank of that hill and
right across that field, right under the bridge, and
then right over by the corner of that building
or that fence post, and then on off to
Middle Mountain. NARRATOR: The movement
here around the bridge is strikingly similar
to the slow creeping ground of Hollister. But there is one important
difference here in Parkfield. Every couple of decades
or so, this village does have earthquakes. They're just little tremors
but they're big enough to be recorded on earthquake
monitoring seismographs. That's why the village proudly
boasts of being the earthquake capital of the world. But it's perhaps more accurately
called the earthquake study capital because scientists
are fascinated by the fact that earthquakes here follow
a predictable pattern. Elsewhere earthquakes always
strike without warning, the toll of death
and destruction made worse because nobody
knew they were coming. So scientists are desperate
for any clues that might help predict when an
earthquake could happen. And here in Parkfield,
the earthquakes happen with
astonishing regularity. On average, every
couple of decades or so. Minor quakes happened here in
1857, 1881, 1901, 1922, 1934, and 1966. After the '66 earthquake,
investigators set up a network of monitoring instruments to see
if the fault gave any warning before the next
earthquake arrived. They expected it sometime
between 1988 and 1993. But it was late. And months of waiting
stretched into years. But still the scientists
waited until finally, in December, 2004, the
long awaited earthquake arrived and was caught on film. From a now slightly
worn and damaged camera, the earthquake movie may not
have seemed that impressive. But the instruments collected
a mass of information. The data didn't, after all,
help with earthquake prediction. But it did pinpoint where the
earthquake started underground which told investigators
where to look next. Deep down under the
Parkfield countryside, starting slightly to
one side of the fault, the aim was to angle in and stab
into the very heart of the San Andreas. After three years of
drilling, long cores of rock were extracted from the exact
spot where the earthquake occurred. This was the first time that
team leader geologist Mark Zoback had ever seen rocks from
the center of the San Andreas. MARK ZOBACK: What
we're looking at here are cores from the
active San Andreas Fault from a depth of about two miles. So for the Earth
science community, these are like moon rocks. As we are trying to
exhume these cores, we had a great deal of
drilling difficulty. The San Andreas Fault was
literally fighting back. After nine weeks of attempting
to recover the cores, in the middle of a
huge lightning storm, almost a scene directly out
of Hollywood, with the thunder and lightning these cores
came to the surface. And so it was a tremendous
feeling of satisfaction. The lightning and
thunder just made it that much more dramatic. And we're all wearing gloves. We didn't want the oil from
our fingers to affect the core. And the rule was that you
touched the core as little as possible, obviously. I'm not going to
wait for you guys. Oh, look at this beautiful rock. The reality was we
couldn't help ourselves and it was just such
a remarkable thing to be actually looking at the
San Andreas Fault for the very first time that we all got
to touch it a little bit. NARRATOR: Buried
within the rock cores, they found a vital
clue about the way that land slips along
the San Andreas. They found serpentinite. Serpentinite is an
unusual rock type. It was originally formed at
the base in the ocean crust and exhumed up
onto the continent. But the reason that
serpentinite is so interesting is that serpentinite is
very easily altered to talc. It allows the rock to slide
at very low force levels. Talcum powder is very slippery. NARRATOR: Talc's
crystalline structure of soft sliding
flat plates makes it one of the slipperiest
rocks known to science. So talc could well
be a key mineral in deciding how the
fault is actually working in central California. We see that the secret of the
slipping San Andreas Fault is actually the
rocks themselves. NARRATOR: The talc explains the
tiny earthquakes of Parkfield. Nobody's yet drilled to
investigate the rocks at Hollister, but scientists
suspect the talc is present there, too. Cracks in the wall show the
land creeps in Hollister. And a bend in the bridge
reveals the same creeping ground in a nearby town. Rock cores extracted
from the fault contain serpentinite,
leading investigators to the softest and slippieriest
mineral, talc, which lubricates some parts of the
fault. The investigation is having success. But one crucial question
remains to be answered. What will the San
Andreas Fault do next? The investigation into
the San Andreas Fault is trying to predict when and
where its next major earthquake will strike. So far, the only
certain prediction is the far distant future
of the San Andreas. Look 20 million years ahead,
if the plate movements continue to follow their
pattern, Los Angeles will end up becoming a
suburb of San Francisco. But predictions on a shorter
timescale are more difficult. If you were to
ask the question, can we predict earthquakes,
my answer would be no. Because I know what your
question really meant is can we predict that an
earthquake is going to occur on a certain fault
at a certain time that we can specify
in the future. And we cannot do that. But there are many
things we can predict. We can predict which faults
are likely to produce the big earthquakes. We can predict how big the
earthquakes are likely to be. And we can even predict the
probability of the earthquake occurrence over some
period of several decades. NARRATOR: Predictions are most
crucial where the San Andreas runs to the south of LA. Here in the Coachella
Valley Desert, geological evidence
of earthquakes stretches back 1,500
years and more. And they follow a
regular pattern. Major earthquake strike here
with monotonous regularity every 200 years. But the latest one
is long overdue. There hasn't been an earthquake
here for more than 300 years. That's a concern because parts
of the San Andreas Fault system run straight from here towards
the city of Los Angeles. The faults will transmit
earthquake shocks in a straight line towards
California's biggest city. Geologist Yuri Fialko
regularly monitors how the ground moves on
either side of the fault line. He lines up his GPS equipment
precisely over a series of metal pegs fixed
into the ground. YURI FIALKO: This information
is crucial for estimating how fast the fault
slips at depths and what is the rate of
accumulation of strain in the crust. In other words, how close the
crust is brought to failure by a slip of the
fault at depths. NARRATOR: The repeated ultra
precise measurements reveal that land here on the
surface hardly moves at all. This is a problem because
deep underground the stresses and strains are
still building up. YURI FIALKO: The
fault is launching at depths at fairly high speed. And this deformation
is growing and growing and growing with time. NARRATOR: Miles
underground, the deep fault is moving at more than an inch
a year, which tells Fialko that in the centuries
since the last quake, the surface should have shifted
300 inches, 25 feet or more. But it hasn't. So sooner or later,
something's got to give. And Fialko knows what
that something will be-- the rocks themselves. YURI FIALKO: And one example
is this type of rock, which is called granite. Or this is, in fact, the
rock out of which most of the Earth's crust is made. NARRATOR: A microscope reveals
the crystalline structure of the granite. The crystals make
the rocks tough. But they have a hidden weakness. The bonds between them may
suddenly crack under stress. Basically once this
material solidifies, it is able to crack and be
sheared on the fault surface. And the brittle
behavior of these rocks is what lies behind the
physics of earthquakes. NARRATOR: Granite rocks underlie
all of the San Andreas Fault. But right here, the rock's under
greater stress than anywhere else because it's so many
centuries since a major quake occurred. And now we're over
the 300 year limit. And so it means that the strain,
the modest strain that has been accumulating on the
fault at this point, is very close to
the maximum strain that this fault has ever seen
through its geologic record. And this is a fault that
is capable of generating great destructive earthquakes. NARRATOR: Fialko believes
the coming quake could be the big one that people have
been talking about for years. And the effects
could be horrific because of the population
density of southern California. When the last huge quake
occurred 300 years ago, Los Angeles was just a tiny
Spanish mission community with fewer than 100 people. Now it's America's
second largest city with almost 11 million people
living in the earthquake vulnerable metropolitan area. People who live in
California probably experience a small or a moderate
size earthquake every year, few things moving in your house. But it's really
actually kind of fun. There is no major destruction. People just go on
with their life. Much bigger events, on the
other hand, are quite a bit different story. NARRATOR: With the threat to Los
Angeles becoming ever clearer, the investigation is
nearing its conclusion. Data from repeated GPS
measurements in the desert reveal evidence that
stress is building up. While examination of the
rocks of the crust show they may not take the
strain for much longer. All the evidence points towards
a potentially huge earthquake building up in
southern California. And new experiments suggest the
coming quake could be far worse than anyone had ever imagined. There is new urgency in the
investigation into the San Andreas Fault, as revealed by
recent evidence compiled by 300 of America's most
respected scientists. They warn that Los Angeles will
be devastated if a major quake strikes along the southern
section of the fault line. While there hasn't been a major
quake for hundreds of years, even small ones can
still be deadly, like the Northridge earthquake
which struck this LA suburb in 1994. Rupturing along an offshoot
of the main San Andreas Fault, the quake was only a magnitude
6.7, considered moderate on the scale of
earthquake measurement. But it still killed 72 people
and injured 12,000 more. And new evidence suggests mother
nature might have a lot more in store for Los Angeles. Scientists have long known
that earthquakes generate several distinct sets of waves. They travel at
different speeds, each spreading damage and destruction
out from the epicenter. Modern city buildings in
earthquake prone areas like California are engineered
to cope with such waves. Now new research by geophysicist
professor Ares Rosakis suggests that the San Andreas
may offer a new and even more deadly threat. Rosakis researches how
earthquakes rupture along straight line faults,
just like the San Andreas where it approaches Los Angeles. He creates his own
mini earthquakes representing the San Andreas
Fault by a hairline crack in a thick transparent block. This special material shows
up internal stress lines when it's lit by a laser. And the earthquake is
triggered by a tiny explosion. 3, 2, 1, zero. A node has dropped. And the explosion was big enough
that we even have a crack. NARRATOR: An ultra
high speed camera capturing 10 million frames
a second reveals a startling and newly discovered phenomenon. This frozen picture reveals
stress lines speeding along the mini San Andreas
in the milliseconds after the explosion. The cone to the
left of this frame is a previously
unrecognized type of shockwave racing
along the rupture line from the earthquake center. On a microscopic scale,
it looks and moves exactly like the sonic
boom produced when a supersonic aircraft
such as Concorde breaks the sound barrier. Because we also
see mach cones, lines that are emitted
from the rupture tips, as from the tips of
moving airplanes. NARRATOR: And just like a
sonic boom it can be dangerous. In the same sense that
we hear the sonic boom from the Concorde, you're
going to feel the sonic boom from the rupture. NARRATOR: The danger comes
because many high rises just aren't built to cope
with extra stress from this newly discovered
type of shockwave. So if you are an old
building, for example, you'll shake one way. You will accumulate some damage. And very soon after that,
you'll get very strong ground shaking because of other
types of waves coming also. NARRATOR: The high speed
ruptures that Rosakis calls super shear happen where faults
run in a straight line, which might help explain a
100-year-old mystery surrounding the
great San Francisco quake, the natural disaster
which launched the entire San Andreas investigation. The overwhelming
damage in San Francisco has long seemed surprisingly
out of proportion to the 7.8 magnitude
of the quake. And there is a particularly
straight section of the San Andreas
approaching San Francisco. So many scientists now believe
that the damage was greater than expected because the
1906 quake had traveled at super shear speed. Of greater concern
to modern emergency services is not what
happened a century ago but what could happen
tomorrow because there is a similar straight section of
faulted ground heading straight towards Los Angeles. And if a super shear earthquake
develops on that line, then the consequences
could be disastrous. All of the investigation's
warnings about the San Andreas came together in
the fall of 2008 with the biggest earthquake
drill ever held in California. ARNOLD SCHWARZENEGGER: If this
earthquake would have happened in reality, those would have
been buildings coming down. We know that there would be
no water now in certain areas. So that's what this
exercise is all about. NARRATOR: But what are the real
chances of Los Angeles soon being hit by a
massive earthquake? Frightening. The best scientific
consensus now warns that there's a 99%
chance of a major quake in southern California
within the next 30 years. To better understand
the threat to LA, the geologists produced
their study jointly with experts in charge of
the city's disaster planning. And none of them doubt that
the big quake is coming. It really isn't even a
question of if anymore. The shaking is going
to be severe for two to three minutes. And then it's going to stop. And then you're going to have
that moment of silence that often happens before you start
hearing the car alarms and all those other sounds that you
have in a disaster like this. NARRATOR: The study estimates
that a major earthquake in the LA Metro area would cause
2,000 deaths, 50,000 injuries, and $200 billion of damage. You're going to have
conflagrations developing, tens of blocks will be on fire. That's the kind of nightmare
scenario that we're looking at. NARRATOR: This specter of
disaster to California's people and cities motivates
the search to unravel the secrets of the San Andreas
Fault. All the evidence is finally in. The damage reports
from the 1906 disaster show the fault's 800 mile path. The different types
of rock at Mussel Rock provide clues to how the fault
was created 20 million years ago. The riverbed is proof how
fast the land is moving. The mineral talc
explains why some parts slip without major quakes. The brittle granite rocks
reveal a threat to Los Angeles. And recent lab experiments
uncover new and more dangerous earthquake shock waves. But one goal has eluded
the rock detectives who study the greatest
fault line on Earth. When will the
sleeping San Andreas come to life once again? It could be any time. The only certainty
is that nothing is certain in the ever evolving
story of how the Earth was made.
San Andreas is there and has potential to really make a mess of things, but anyone trying to make that point should head eastward and have a look at the Hayward fault. It’s not glitzy and glamorous like the SA, but it will be so much worse when it ruptures.