- 15 minutes ago
The episode, hosted by Leonard Nimoy, focuses specifically on the San Andreas Fault in California, a major transform plate boundary where the Pacific Plate slides past the North American Plate.
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00:00This series presents information based in part on theory and conjecture.
00:15The producer's purpose is to suggest some possible explanations, but not necessarily the only ones, to the mysteries we will examine.
00:23In the Earth's crust slashes across 700 miles of California, the San Andreas Fault.
00:32It borders both San Francisco and Los Angeles and creates one of the world's most dangerous earthquake zones.
00:41Scientists are racing to find ways of predicting the next disastrous movement of the fault.
00:48When will the great earthquake strike California?
00:53California is famous for its warm and sunny climate.
01:03Its diverse lifestyles and spectacular vistas are as varied as any other land on Earth.
01:09Much of California's rugged beauty derives from violent Earth upheavals.
01:23The product of a phenomenon called faulting.
01:31Deep cracks or faults in the Earth's crust scar the state from one end to the other.
01:36Of these, the San Andreas Fault is the longest and most dangerous.
01:41At 6 a.m. on February 9th, 1971, Californians were jolted into awareness of the powerful forces that molded their state.
01:54A sudden earthquake just north of Los Angeles caused massive devastation.
02:0750 people were killed in the collapse of two hospitals.
02:10Since the quake was of only moderate size, engineers were shocked by the heavy damage to supposedly earthquake-resistant buildings and freeways.
02:21The Richter magnitude was 6.6, releasing several hundred times less energy than the San Francisco earthquake of 1906.
02:33Had the shaking continued for another few seconds, the San Fernando disaster would have been far worse.
02:41Two dams holding 7 billion gallons of water threatened 80,000 sleeping people.
02:47When the dams began to collapse, only the abnormally low water level prevented catastrophe.
02:57Geologists soon pinpointed the quake on a minor branch of the San Andreas Fault.
03:03The San Andreas Fault system is part of a grid of faults, mountain chains, and trenches in the ocean floor.
03:17These features mark the boundaries between huge moving slabs of the Earth's crust called plates.
03:23Carrying continents and oceans with them, the plates float on a hot liquid layer of the planet.
03:29Along the fault in California, two plates slip and grind against each other due to movement deep within the Earth.
03:40Dr. Tim Hall has studied the San Andreas Fault for 15 years.
03:45I visualize the San Andreas Fault as a 700-mile-long vertical curtain of clay that runs the length of California down to a depth of about 10 miles
03:56that separates two moving plates from each other, the American plate and the Pacific plate.
04:02In places along that clay boundary, the fault can move along year by year, and we call that creep.
04:09In other places along the fault, the rocks are stuck together, locked.
04:14A large amount of energy gets stored in these surface rocks, which is released periodically by sudden large earthquakes.
04:22With its many branches, the San Andreas cuts a broad swath through California, from San Francisco, Oakland, San Jose, to Los Angeles.
04:32All are in fault zones.
04:3415 million people are vulnerable.
04:37We shall travel along the fault, seeing places where the danger is great, and observing sites where crucial research is underway.
04:44The trip begins at Southern California's Salton Sea.
04:53Repeated fault movement has lifted and exposed the reddish band of rock.
04:58The twisted cliffs were gouged by the fault's immense power.
05:05Nearby, the San Andreas has made pockets of groundwater.
05:09Lines of palm trees and brush mark the fault's passage beneath the bleak sands.
05:14Outside Palm Springs, two-mile-high mountains were thrust up by millions of years of fault movement.
05:28The fault skirts the Los Angeles basin.
05:32Its numerous sub-branches, including the one which shook San Fernando, threatened more than 10 million people.
05:38North of Los Angeles County, the fault carves a broad valley.
05:47Near Palmdale, Dr. Kerry C. dug into the San Andreas and found a treasure trove of prehistoric earthquakes.
05:55Using carbon dating, each event is identified.
06:03The fault goes down through many distorted layers, which mark earthquakes going back to the time of Christ.
06:09The intervals between major quakes range from a maximum of 300 years to only half a century.
06:16The earthquake of 1857, largest ever recorded in Southern California, shows up as a sand blow,
06:26where sand and water spouted from the earth in an eerie fountain.
06:29Trees along the fault had their roots sheared during the quake, causing growth to slow abruptly at the 1857 ring.
06:42In 1975, researchers found that a broad area of desert along the fault had risen about one foot during the last 15 years.
06:56They began a massive survey program to monitor this Palmdale bulge.
07:03Survey teams worked their way tediously up from Los Angeles, measuring the land level.
07:09They began a massive storm.
07:11Ominously, part of the bulge recently subsided.
07:17This pattern of uplift and collapse also happened before the devastating Alaskan and Chilean earthquakes.
07:26In Southern California, the pattern occurred once before, without an earthquake.
07:31Does the Palmdale bulge reflect the harmless cycle or warn of a major jolt on the San Andreas Fault?
07:41North of Palmdale, geologists drill deep into the fault zone to measure the stress on underground rock.
07:58In hope of finding a new way to forecast earthquakes, the researchers pump water into the drill hole.
08:14They increase the pressure until the rock breaks.
08:21Knowing the natural strength of rock, they measure what added stress it is under from the earthquake fault.
08:27They have found that rock in the fault zone is cracked, water saturated, and close to the breaking point.
08:39Further north, the San Andreas cuts through hilly desert country.
08:47In the stark and desolate Carrizo Plain, fault features are clearer than anywhere else.
08:57Most ground movement here occurs during large earthquakes in jumps of several yards parallel to the fault.
09:03The last of these took place in 1857.
09:10The quakes also caused the ground to move vertically, forming ridges along the fault.
09:18Repeated slippage has diverted streams along the fault.
09:22According to carbon dating, this stream bed moved 125 meters in the last 3400 years.
09:33The Pacific Plate slides northwest, averaging two inches a year.
09:37At this rate, in 5 million years, it will carry Los Angeles past the Carrizo Plain on its way to San Francisco.
09:48Midway between Los Angeles and San Francisco, on the Pacific coast, is the Diablo Canyon nuclear plant.
09:55The facility was originally designed to withstand an earthquake on the San Andreas fault of Richter magnitude 8.5.
10:04During construction, however, geologists discovered a nearby fault offshore.
10:10The Hosgree fault.
10:12Ralph Vrana is a county environmental worker who lives near the site.
10:17I'm opposed to the nuclear power plant at Diablo Canyon because there's an earthquake fault running two and a half miles from the plant itself.
10:26And that fault happens to be 250 miles long, and it's a major earthquake fault in California.
10:32A very large earthquake in 1927 of magnitude 7.5 occurred on that fault.
10:38A magnitude 8 earthquake is also possible on the Hosgree fault.
10:43Richard Davin represents the plant's owner, Pacific Gas and Electric.
10:49There are earthquake faults around Diablo Canyon, of course.
10:52There's San Andreas fault 48 miles away, but there's a Hosgree fault which is closer,
10:55and that's the one that's been of the major concern in the last several years.
10:59And as a result, it's been the most thoroughly investigated fault probably in California outside of the San Andreas,
11:04and we have designed that plant to withstand the maximum earthquake that could ever be expected to occur on that fault.
11:10Those of us who live close to the plant, who are seven miles away myself,
11:15are wondering whether we happen to be guinea pigs in this experiment or not.
11:19People talk about earthquakes even bigger and bigger and bigger,
11:22the kind of earthquake that would split this containment structure in half.
11:25I think when we got that kind of an earthquake, we've reached the end of the world,
11:28because before that would happen, California would be in the ocean.
11:33After the Hosgree fault was found, PG&E strengthened the plant.
11:38The adequacy of their precautions is controversial.
11:42We're only beginning to understand the dynamics of earthquakes.
11:46Whether any possible ground shock could cause hazardous release of nuclear radiation remains unknown.
11:53Further north, the fault continues to pass through major population centers.
12:02A great earthquake would cause incalculable disaster.
12:06Is there a way to predict it?
12:10The little town of Hollister lies 80 miles south of San Francisco on the San Andreas Fault's Calaveras branch.
12:19August 6th, 1979.
12:23The strongest earthquake since 1911.
12:31Sam Pintello was outside landscaping when it struck.
12:35We stood here, and you could look out over the hills.
12:37You could see the hills rolling into each other.
12:39You know, just like, uh, they were just sort of bending.
12:43The ground was moving.
12:44Uh, the house was moving.
12:46Everything was sort of, it was, everything seems to be tilting,
12:50especially the hills tilting toward each other.
12:52And, of course, I could see the trees shimmering over here.
12:55I didn't know, it was just eerie.
12:58The fault at Hollister isn't locked.
13:01Slow creep and small shakes tear the land beneath the center of town.
13:06Houses are twisted out of shape.
13:12Streets and curbs are cracked and broken.
13:18In this region of unusual activity, instruments monitor fault movement.
13:24Hill sides are dotted with reflectors for laser beams.
13:28A unique two-color system tracks deep earth movement across the fault.
13:35Four months before the August quake, the ground began to creep.
13:41Movement lasted for 10 weeks, followed by a period of quiet.
13:46Then, the earthquake struck.
13:53It is hoped the laser will eventually provide a reliable way to forecast earthquakes.
14:01West of Hollister, the San Andreas Fault gouges a narrow valley.
14:05Geologist Tim Hall supervises excavation into the fault.
14:19We're looking for a record of earthquakes in California before recorded history.
14:23And the way that we do that is look for layers that have been displaced by the San Andreas and attempt to date them.
14:31The goal of our study is to predict how often the San Andreas will move in the future.
14:36On the northern San Andreas, the earliest known great earthquake occurred in 1838, only 68 years before the 1906 disaster.
14:49If such a small interval is typical, the next major shake may be overdue in the Bay Area.
15:04Slashing north along a chain of valleys and long, narrow lakes, the San Andreas Fault cuts the San Francisco Peninsula in two.
15:13On the shore of San Francisco Bay is Marine World, where studies of animal behavior may give warning of earthquakes to come.
15:26Peter Gross is director of Land Animals.
15:29What we have here at Marine World is the entire collection of both land and sea animals being viewed on a daily basis by all the keepers and the trainers and the handlers.
15:38And what they're looking for is any kind of an unusual sustained behavior that might show flight or fear, which we can then document as happening just before an earthquake.
15:50About a half hour before the big earthquake, these animals, which ordinarily mix together and peacefully coexist amongst themselves, all separated and went into their own species.
16:00The zebras all stayed together, the antelope all went into one area, they just didn't want to mix with each other during this period of unrest and fear.
16:09I think that the animals are a lot more in tune to nature's sounds than people are.
16:17Trainer Paul Barkman recalls the morning before another earthquake.
16:21And when we finally did get them out of the barn, we watered them, we watered them down, they all refused to drink and they refused to eat all day long.
16:30We have one lead elephant, Jenny, she's the oldest, and she was thumping the whole day long and she was trumpeting, which she very seldom does.
16:37And the other elephants were answering her back and they were just really hard to control the whole day until after four o'clock when the quake hit, then they were fine.
16:47Reports of strange animal behavior before earthquakes go back thousands of years.
16:55So far, however, it has proven difficult to use such information for reliable prediction.
17:01There is still no sure way to warn of an earthquake.
17:08On the western edge of San Francisco Bay, homes are often built on compacted landfills.
17:13This kind of land can amplify ground shaking up to ten times and turn wet, sandy soil nearly to quicksand.
17:24Cracks up to three feet wide could split foundations and bring thousands of houses crashing down on their owners.
17:31On the east side of San Francisco Bay, the Hayward branch of the fault cuts through city after city.
17:41In 1836 and again in 1868, huge earthquakes here caused little damage because the area was barely inhabited.
17:50Today, however, dozens of schools and hospitals stand in the fault zone.
17:55In the aftermath of the San Fernando quake, where some buildings that met all earthquake codes collapsed, standards throughout the state were toughened.
18:06Schools along the Hayward Fault were reinforced or replaced.
18:11A dam, not unlike the ones that began collapsing at San Fernando, is being rebuilt.
18:18In Berkeley, the Hayward Fault rims the campus of the University of California.
18:25It runs beneath the football stadium, which is slowly being split in half.
18:30Dr. Bruce Bolt heads the university's seismographic station.
18:35According to the calculations that I have made, based on the work along the San Andreas Fault recently, the chances of a great earthquake affecting either the San Francisco area or the Los Angeles area in the next ten years are about 50-50.
18:54If a great earthquake of magnitude seven or eight occurred in the Bay Area, undoubtedly there would be considerable loss of life.
19:01Most Californians are not well prepared for another great earthquake like that of 1906.
19:09North of San Francisco, San Andreas slices through Marin County.
19:14The little town of Olima straddles the fault.
19:17On April 18, 1906, a giant tremor broke the earth.
19:24It shifted roads and fences an incredible 20 feet.
19:27Olima was the epicenter for California's greatest earthquake disaster, known as the San Francisco earthquake.
19:37That quake claimed 700 lives.
19:53Today, the death toll from a major shock along the San Andreas could reach the tens of thousands.
20:00Only a few miles from the fault, San Francisco remains exquisitely vulnerable.
20:12Collapse of older buildings, showers of debris, and fire would inflict a heavy toll.
20:18In Southern California, stress has been building up on the main fissure of the San Andreas for more than 120 years.
20:27If the historic pattern is followed, the stress will be relieved by a cataclysm many times larger than the San Fernando earthquake.
20:35It is frightening to imagine that disaster multiplied a hundredfold.
20:46Thousands dead, families homeless, firestorms raging out of control.
20:511906-type disaster would cause unimaginable chaos, but earthquakes recorded in Asia and Alaska dwarf any yet seen in California.
21:04Perhaps we have yet to learn the full power of the San Andreas Fault.
21:09The San Andreas is the most closely watched earthquake fault in the world.
21:18Hundreds of instruments monitor its slightest tremble.
21:23If it is possible, reliable earthquake forecasting belongs to the future.
21:29Earth's science is only in its infancy.
21:31The forces that mold our planet and cause the ground to shake beneath our feet remain mysterious.
21:42Coming up next, In Search Of continues with an investigation into the Siberian fireball.
21:48Then, on FBI, the untold stories, an agent is trapped into a dangerous meeting with drug traffickers.
21:53And later tonight, Friedrich Paulus loses at Stalingrad and defects to the Russians on Hitler's generals at 9 here on the History Channel, where the past comes alive.
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