Published on: July 31, 2007
The magnitude 9.2 quake was just the start of it. Underwater landslides gave way to several local tsunamis that destroyed coastlines from British Columbia to California. After a massive rebuilding effort, the sixth of our 10 Worst Disasters of the Last 101 Years has led to round-the-clock seismic monitoring. For expert survival advice and tips, visit our ultimate guide to getting ready for any disaster.
At 5:36 pm on March 27, 1964, the largest earthquake ever recorded in North America, and the second largest in history, rattled coastal Alaska for close to 4 minutes. Though the epicenter of the Great Alaskan Earthquake was deep beneath Prince William Sound — 75 miles east of Anchorage and 56 miles west of Valdez — the magnitude 9.2 temblor rippled water as far away as Louisiana and even made parts of Florida and Texas jump a couple of inches.
Every year the Pacific tectonic plate barges roughly 2 in. into, and under, the North American plate near southern Alaska. Under intense pressure from the friction, the crust bends and strains until it eventually snaps back into place, as it did that March evening. In downtown Anchorage, the quake caused the streets to become asphalt waves, bouncing cars into the air. Parts of the city dropped as much as 30 ft., bringing the Denali Theater marquee on Fourth Avenue to sidewalk level. One block over, the concrete facade of the new J.C. Penney crashed into the sidewalk, killing a crouching pedestrian and a passing driver. At the airport, the control tower toppled over and killed an air traffic controller.
The ground in the Turnagain Heights subdivision simultaneously sank and surged up. "Our whole lawn broke up into chunks of dirt, rock, snow and ice," Turnagain resident Tay Pryor Thomas wrote in National Geographic shortly after the quake. "We were left on a wildly bucking slab; suddenly it tilted sharply, and we had to hang on to keep from slipping into a yawning chasm."
A "tectonic tsunami," different from the landslide-generated local tsunamis, was caused as the quake heaved 100,000 square miles of Prince William Sound either up or down. Near Kodiak, the ground surged permanently out of the water by 30 ft., while near Portage it dropped by eight. The displaced water went pulsing down and across the Pacific Ocean and didn't stop until it hit Japan.
The local tsunamis struck within seconds; it took longer for the tectonic tsunami to radiate out. Twenty minutes after the local wave set Seward on fire, the tectonic tsunami rolled in looking as if it, too, was aflame. "[As] the fire was really roaring, the wave came up Resurrection Bay there and spread it everywhere. It was an eerie thing to see — a huge tide of fire washing ashore," recalled railroad employee Gene Kirkpatrick to National Geographic a few days later.
Back in Cordova, which had suffered only minor damage, the crew of the Sedge finally got underway and was ordered to Valdez. The cutter was in Cordova's 60-ft. shipping channel when it began to drop.
"Our Fathometer just kept dropping," remembers Pete Corson, who realized the tide was being sucked out of the channel. "It was very strange. It was incredibly dark outside, and these giant snowflakes were falling so it was very hard to see, but we could hear this loud clapping — which were halibut flapping on the seabed." The Sedge came to rest on the channel bottom and 10 minutes later the water rushed back in. "We rode it out under anchor and then went on our way."
The tsunami continued its inexorable southerly push at 415 mph. For the next 2 hours it rolled down the British Columbia coastline, damaging a logging camp in Shield's Bay and destroying 16 houses in Hot Springs Cove. It did more of the same in Washington state.
In Newport, Ore., around 11 pm, it came ashore at Beverly Beach State Park, where a family of five was camping. The mother and father survived, but all three children were swept away.
At 11:52, the first of four tsunami waves struck Crescent City, Calif., just south of the Oregon border. All 10 deaths, and nearly all of the damage, were a result of the final 15.7-ft. wave that struck at 1:45 am.
"It was like a violent explosion. A thunderous roar mingled with all the confusion. Everywhere we looked, buildings, cars, lumber and boats shifted around like crazy. The whole beachfront moved, changing before our very eyes. By this time, the fire had spread to the Texaco bulk tanks. They started exploding one after another, lighting up the sky," recalled Peggy Coons in The Raging Sea by Dennis Powers.
By the time it got to San Francisco, the wave was just a couple of feet high. It damaged several yachts and did more of the same in Hilo, Hawaii. When it reached Japan it was barely visible, but it was still strong enough to damage pearl farms along the eastern coast.
The Aftermath
The Great Alaskan Earthquake and Tsunami of 1964 caused more than $300 million in damage along the Pacific Coast from Anchorage to Los Angeles, according to a report compiled by the West Coast and Alaska Tsunami Warning Center. In fact, the '64 tsunami was responsible for the creation of the center, located in Palmer, Alaska. Since 1967 scientists on round-the-clock duty monitor seismic activity, tidal gauges and data-collection buoys in order to determine when to issue tsunami warnings. Besides being broadcast to the public, the warnings also trigger alerts to local, state and federal emergency officials as well as to the military and the Coast Guard.
After the quake, the State of Alaska and the federal government went to work cleaning up. The U.S. Army Corps of Engineers spent $110 million dollars rebuilding roads and clearing debris in Alaska. The native village of Chenega, which was completely destroyed, was moved to higher ground. Likewise the town of Valdez, which sat at the mouth of a silty glacial drainage, was abandoned and rebuilt a few miles west atop a foundation of solid bedrock.
The structural damage to downtown Anchorage was extensive, but the timing of the earthquake, Good Friday evening, undoubtedly spared many lives. As part of its Advanced National Seismic System, the U.S. Geological Survey has recently outfitted a few buildings with complex motion sensors to understand how they respond to quakes. Because of Anchorage's seismically active location — Alaska's 5000 to 6000 annual earthquakes are more than occur in the rest of the U.S. combined — its 20-story Robert Atwood Building is one of the most thoroughly monitored structures in the country.
The building is outfitted with 32 instruments from basement to ceiling to detect the "swaying," "twisting," "rocking" and "drift" that result from seismic waves. Seven boreholes, ranging from the surface to a depth of 200 ft., also contain instruments to monitor seismic activity. "We want to see what designs work, and what kind of damage, often structurally hidden, appears," says Mehmet Celebi, a research engineer with the USGS. "In the two years since it's been instrumented we've had 20 small- to medium-size earthquakes in the area. We're waiting for a large event to see how the building really reacts."
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