Great Alaskan earthquake of 1964 was the most powerful earthquake ever known to hit North America . The quake struck southern Alaska on March 27, causing great damage in Anchorage , Valdez, and other cities. The earthquake generated a tsunami (series of huge, destructive ocean waves) that caused most of the 131 deaths during the disaster. The tsunami killed people as far south as California. The quake occurred on the Friday before the 1964 Easter holiday, causing some to label it the Good Friday Earthquake.
Earthquake and tsunami.
The earthquake struck at 5:36 p.m. local time on March 27, 1964. Its focus or hypocenter—the point deep in Earth where it originated—was about 16 miles (25 kilometers) below Earth’s surface. The quake’s epicenter—the point on Earth’s surface directly above the focus—was in Prince William Sound, about 75 miles (120 kilometers) east of Anchorage. This area lies along the border between two tectonic plates—the North American Plate and the Pacific Plate. Tectonic plates are large, rigid sections of Earth’s rocky outer shell. The movements of the plates in relation to one another can cause earthquakes.
The earth shook violently for about four minutes. Anchorage—by far the state’s most populous area—experienced severe damage as buildings shook and collapsed. Landslides occurred throughout the area as the ground rose and fell, and avalanches rumbled in the surrounding mountains. Some areas rose by more than 30 feet (9 meters), while others fell about 8 feet (2.4) meters. Seismologists—people who study earthquakes and other movements of Earth’s crust—reported that the quake had a moment magnitude of 9.2. The moment magnitude scale measures the ground movements produced by an earthquake and is used especially for large earthquakes. Nine people in the Anchorage area were killed.
Tectonic uplift—that is, the rise of an area as a result of plate tectonics —led parts of the sea floor near the epicenter of the earthquake to rise. The greatest uplift—about 50 feet (15 meters)—occurred southwest of Montague Island, near the entrance of Prince William Sound. The uplift displaced massive amounts of water in the Pacific Ocean and set into motion a large tsunami. The quake also triggered underwater landslides that generated numerous smaller, local tsunamis. Ships were tossed in the violent waves, and dock buildings were carried out to sea. Oil tanks ruptured and caught fire. In total, the tsunamis were responsible for 106 of the 115 deaths that occurred in Alaska during the earthquake. The communities of Valdez, Chenega, Seward, Whittier, and Kodiak suffered some of the worst damage and loss of life. Wave heights of up to 220 feet (67 meters) were recorded at Valdez Arm, a section of the Prince William Sound.
Effects of the large tsunami were experienced in Canada, Hawaii, Japan, and other areas bordering on the Pacific Ocean. Huge waves killed 12 people in California and 4 campers on a beach in Oregon.
Later developments.
The earthquake and its resultant tsunamis caused more than $300 million in damage. Rebuilding in Anchorage and other affected areas began in the weeks after the quake. Some towns—including Valdez, which was rebuilt 4 miles (6.4 kilometers) from its original location—were relocated atop more stable ground. Other municipalities rezoned affected areas as parkland in efforts to prevent building collapses during future earthquakes.
Scientists have credited seismographic data and other observations of the 1964 Alaska quake with helping to confirm the theory of plate tectonics. Plate tectonics is the theory that the earth’s crust is divided into a series of vast, platelike parts that move or drift as distinct land masses. In the decades after the 1964 quake, authorities expanded seismographic systems and other networks to improve earthquake and tsunami monitoring.
