What is the mystery of the Alaska earthquake?

Alaska is located in the northernmost part of the United States, which has entered the Arctic Circle in the north, adjacent to Canada in the east and facing Russia across the Bering Strait in the west. On March 27, 1964, at 17: 36: 13, an earthquake of magnitude 8.5 occurred in Prince William Strait, Alaska. The epicenter was located at the seaside about 12 kilometers east of Anchorage City with a focal depth of about 2 kilometers. The earthquake is accompanied by a wide range of vertical dislocation, ranging from 44, to 52, square kilometers. The main uplift area is from the south of Kodiak Island to Prince William Strait, with the vertical dislocation rising by 11.5 meters and falling by 2.3 meters.

The earthquake destroyed 215 civil buildings and 157 commercial buildings. Several buildings were razed to the ground, and high-rise buildings or buildings covering a wide area were almost destroyed. In earthquake disasters, the liquefaction of sand layer (that is, sand layer flow) causes the most serious earthquake damage. For example, the biggest disaster in Anchorage comes from four landslides. The reason for the landslide is that there is a thin sand layer 18 meters underground in the city. The largest landslide is 24 meters long and 18 ~ 36 meters wide. This landslide slides from a 2-meter-high cliff and slips out about 15 meters. The end of the landslide extends into the sea, and at least 7 houses are destroyed by this landslide. Streets not affected by landslides have also produced ground fissures parallel to the landslide edges, which have aggravated the earthquake damage of houses. Ancoretti Middle School also suffered serious damage. In addition, water mains, gas, sewers, telephone lines and power systems were all damaged.

During the earthquake, the whole earth shook violently, and people were tossed around for four minutes like a boat sitting on the top of a wave trough. Atwood, president of Time Daily in Anchorage, ran out of the house as soon as he felt the first earthquake, and found himself facing a crazy world. The trees are folded upside down, the houses are tilted, and the frozen ground is warped and arched. Just as he watched his house collapse, suddenly a big hole opened in the ground under his feet, and he fell in. When he climbed out with great efforts, he looked back at the beach and saw that his home had become a pile of waste wood by the sea.

When the earthquake happened, Mrs. Thomas, Atwood's neighbor, was watching TV with her two children with relish. She forgot the ice and snow outside and ran out with her children barefoot. Three people snuggled up to a cracked piece of frozen soil in front of the door, and suddenly the frozen soil cracked again, separating the mother and the child. She desperately grabbed her daughter. Although her hands and feet were frozen, they crawled in the rough snow for 15 minutes. Rescuers later found them and took them to safety.

Other families are not so lucky. Neurologist Meade left four children when he went to the hospital this afternoon. During the earthquake, the 12-year-old son escaped with his sister and brother. When he went in again to pick up the little brother trapped in the room, he fell into an ice crack and left no body.

Valdez Town, located 72km east of the epicenter, is a port built on the soft foundation of Robichuan Delta, with more than 5 residents all the year round (about doubled in the fishing season). During the earthquake, the underwater foundation at the front of the delta collapsed, and the ground, all buildings and equipment within 1 meters from the dock to the inland all fell into the water, and the collapsed body was nearly 75 million cubic meters. After the landslide, it was attacked by five wild waves, and the wharf and adjacent coastal areas were looted. In the inland areas a little far from the sea, dust was flying everywhere during the earthquake, and the ground churned like an ocean, and the cracks opened and closed, and closed and opened again. Ground fissures are criss-crossed, some of which are 1.8 meters wide, 75 meters long and 1.2 meters deep. About 4% of houses and many shops have ground fissures passing through, and the walls are shaken, causing houses to topple and high-voltage wires to spark, such as golden snakes dancing wildly.

The huge waves caused by the earthquake have come ashore again and again, with only 15 minutes between each ebb and flow. Seawater flooded some docks, warehouses and a cement factory. Some oil storage tanks exploded, and tens of thousands of gallons of burning oil were sprayed on the broken stones and gravel. The oil pipe that slipped into the sea stirred up a three-story wave with a burning oil layer on the top. One survivor recalled: "I have never seen such a strange sight. The huge waves beat against the coast, but there was a burning flame on the top." Almost half of the facilities and buildings in this city are immersed in seawater. After the earthquake, we had to rebuild a new town in a place with a solid foundation 6 kilometers away from the original town.

Vettel, 64 kilometers west of the epicenter, is a commercial port and military port, which was built in 1942. During the earthquake, there were 7 residents, and 13 people died because of the earthquake, accounting for about 1/5. Almost all the port facilities and buildings were destroyed, and the ground of the whole port area sank about 1 meter, and the coast collapsed seriously. After the earthquake, it was attacked by wild waves, and all the stones in the sea, including those with a diameter of 2 meters or more, were swept into the land and scattered all over the streets by wild waves. There is a large oil tank on the land, which can carry 38 cubic meters of gasoline, and it has also been tossed by the wild waves and displaced by several meters. The whole building of the timber factory was also pushed by the wild waves and displaced.

Seward Port, 153km southwest of the epicenter, is located in the small fjord delta. During the earthquake, ground fissures appeared in the area more than 1m from the wharf to the land, and the ground subsidence of the whole port area was about 1m. After the earthquake, it was attacked by tsunami and fire, all port facilities were destroyed, 86 houses collapsed and 26 buildings were damaged. Due to the destruction of the port area, it is not easy to rebuild, so the original port area can only be opened as a tourist area after the earthquake.

The earthquake caused serious damage to railways, highways, towns and villages within 16 kilometers from the epicenter due to large-scale ice collapse, landslides, ground fissures, mudslides, ground slides and collapses, and also caused the crustal deformation in a vast area nearly 1 kilometers long and 3 kilometers wide. The ground subsidence in the north of the Kodiak main Valdez line is about 1 ~ 2 meters, while the ground in the south of this line has risen. For example, the southwest end of Montague Island has risen by 11.8 meters, and the island has moved to the southeast by 15 meters. At the same time, there has been a fault nearly 6 kilometers long, and the height of its fault cliff is more than 11 meters. After the earthquake, more than 5 aftershocks of magnitude 4 or above and more than 5 strong aftershocks of magnitude 6 or above occurred in the area where ground deformation occurred.

2-3 minutes after the earthquake, tsunamis began to attack Kodiak Island and the coast of Alaska, and they attacked every 1-1.5 hours. The biggest tsunami occurred in the middle of the night, at the time of the local ocean climax, at the mouth of Valdez, the wave was as high as 3 meters. Where the tsunami affected, the damage was different. Crecente, a city in northern California on the west coast of the United States, was hit by the tsunami five times. The first wave was 6 meters high, and the largest wave was 9 meters high. After the rushing waves landed, nearly 1 buildings were washed down, more than 1 ships were sunk, and more than 2 people were killed or injured. The whole city was almost wiped out.

The earthquake in Alaska killed 178 people and caused economic losses of about 5 million dollars. The felt radius of this earthquake is 1,5 kilometers, the felt area is about 1.3 million square kilometers, the destructive earthquake area is 13, square kilometers, and the ground deformation area is over 26, square kilometers. Although the earthquake was very destructive, the local population density was relatively small, and the casualties and economic losses suffered were relatively light.