In the Turnagain Heights neighbourhood of Anchorage, the event led to catastrophe. The neighbourhood was built on a small terrace of uplifted sediment. As the ground shaking began, a layer of wet clay beneath the development turned into mud, and when this happened, the overlying layers of sediment, along with the houses built on top of them, slid seaward. In the process, the layers broke into separate blocks that tilted, turning the landscape into a chaotic jumble, and resulting in the destruction of the neighbourhood figure above d.
In , an earthquake in Christchurch, New Zealand, caused sand to erupt and produce small, cone-shaped mounds on the ground surface figure above a. The transfer of sand from underground onto the surface led to formation of depressions large enough to swallow cars figure above b.
All of these examples are manifestations of a phenomenon called sediment liquefaction. The resulting cone-shaped mounds are variously known as sand volcanoes, sand boils, or sand blows. For three days, the blaze spread through the city until fire fighters contained it by blasting a fire break. As hot air rose, cool air rushed in, creating wind gusts of over mph, which stoked the blaze and incinerated , people.
Just before a. The break started at the hypocentre and then propagated north at 2. This slip triggered a great earthquake MW 9. Because the area that rose was so broad, the volume of displaced water was immense.
As a consequence, a tragedy of an unimaginable extent was about to unfold. The displacement can be due to an earthquake, submarine landslide, or volcanic explosion. Tsunami is a Japanese word that translates literally as harbour wave, an apt name because tsunamis can be particularly damaging to harbour towns. Regardless of cause, tsunamis are very different from familiar, wind-driven storm waves. Large wind-driven waves can reach heights of 10 to 30 meters in the open ocean. But even such monsters have wavelengths of only tens of meters, and thus contain a relatively small volume of water.
In contrast, although a tsunami in deep water may cause a rise in sea level of at most only a few tens of centimetres a ship crossing one wouldn't even notice tsunamis have wavelengths of tens to hundreds of kilometres and an individual wave can be several kilometres wide, as measured perpendicular to the wave front. Thus, the wave involves a huge volume of water. In simpler terms, we can think of the width of a tsunami, in map view, as being more than times the width of a wind-driven wave.
Because of this difference, a storm wave and a tsunami have very different effects when they strike the shore. The San Francisco and Tokyo earthquakes caused fire losses that greatly exceeded the losses from ground shaking. The critical factors in creating a fire risk are wind, water and weather. If the shaking is strong enough to disrupt the water supply, winds are strong enough to spread the fire across city streets and vegetation is flammable following hot, dry weather then the scene is set for a high level of fire risk.
Back to the main earthquake page. Site map A - Z. The Latest. Policy and Plans. Info and Resources. Community Response. Contact us. Members Area requires login. Many of the largest and most damaging flow failures have taken place underwater in coastal areas. For example, submarine flow failures carried away large sections of port facilities at Seward, Whittier, and Valdez, Alaska, during the Prince William Sound earthquake.
These flow failures, in turn, generated large sea waves that overran parts of the coastal area, causing additional damage and casualties.
Flow failures on land have been catastrophic, especially in other countries. For example, the Kansu, China, earthquake induced several flow failures as much as 1 mile in length and breadth, killing an estimated , people. Loss of Bearing Strength - When the soil supporting a building or some other structure liquefies and loses strength, large deformations can occur within the soil, allowing the structure to settle and tip.
The most spectacular example of bearing-strength failures took place during the Niigata, Japan, earthquake. During that event, several four-story buildings of the Kwangishicho apartment complex tipped as much as 60 degrees. Most of the buildings were later jacked back into an upright position, underpinned with piles, and reused. Soils that liquefied at Niigata typify the general subsurface geometry required for liquefaction-caused bearing failures: a layer of saturated, cohesionless soil sand or silt extending from near the ground surface to a depth of about the width of the building.
Past experience has shown that several types of landslides take place in conjunction with earthquakes. The most abundant types of earthquake induced landslides are rock falls and slides of rock fragments that form on steep slopes. Shallow debris slides forming on steep slopes and soil and rock slumps and block slides forming on moderate to steep slopes also take place, but they are less abundant.
Reactivation of dormant slumps or block slides by earthquakes is rare. Large earthquake-induced rock avalanches, soil avalanches, and underwater landslides can be very destructive. Rock avalanches originate on over-steepened slopes in weak rocks. One of the most spectacular examples occurred during the Peruvian earthquake when a single rock avalanche killed more than 18, people; a similar, but less spectacular, failure in the Hebgen Lake, Montana, earthquake resulted in 26 deaths.
Soil avalanches occur in some weakly cemented fine-grained materials, such as loess, that form steep stable slopes under non-seismic conditions. Many loess slopes failed during the New Madrid, Missouri, earthquakes of Underwater landslides commonly involve the margins of deltas where many port facilities are located.
The failures at Seward, Alaska, during the earthquake are an example. The size of the area affected by earthquake-induced landslides depends on the magnitude of the earthquake, its focal depth , the topography and geologic conditions near the causative fault, and the amplitude , frequency composition, and duration of ground shaking.
In past earthquakes, landslides have been abundant in some areas having intensities of ground shaking as low as VI on the Modified Mercalli Intensity Scale. Tsunamis are water waves that are caused by sudden vertical movement of a large area of the sea floor during an undersea earthquake. Tsunamis are often called tidal waves, but this term is a misnomer. Unlike regular ocean tides, tsunamis are not caused by the tidal action of the Moon and Sun.
The height of a tsunami in the deep ocean is typically about 1 foot, but the distance between wave crests can be very long, more than 60 miles. The speed at which the tsunami travels decreases as water depth decreases.
In the mid-Pacific, where the water depths reach 3 miles, tsunami speeds can be more than miles per hour. As tsunamis reach shallow water around islands or on a continental shelf; the height of the waves increases many times, sometimes reaching as much as 80 feet. The great distance between wave crests prevents tsunamis from dissipating energy as a breaking surf; instead, tsunamis cause water levels to rise rapidly along coast lines.
Tsunamis and earthquake ground shaking differ in their destructive characteristics. Ground shaking causes destruction mainly in the vicinity of the causative fault, but tsunamis cause destruction both locally and at very distant locations from the area of tsunami generation. Skip to main content. Search Search. Earthquake Hazards. What are the Effects of Earthquakes?
Science Center Objects Overview The effects from earthquakes include ground shaking, surface faulting, ground failure, and less commonly, tsunamis.
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