In the years after a magnitude 6. This provided an excellent opportunity to verify that ground motions observed on natural faults are similar to those observed in the laboratory, suggesting that a common underlying mechanism — fault healing — may be responsible for both. Understanding how forcefully the ground will move when an earthquake hits has been one of the biggest challenges in earthquake science. And the study suggests that, in fact, the lab setting is able to capture some of those processes correctly.
Glaser said the next steps in his lab involve measuring the seismic energy that comes from the movement of the individual contact points in the model fault to more precisely map the distribution of stress and how it changes in the run-up to a laboratory earthquake event. Mission and History. UC Berkeley. UC Santa Cruz.
UC Merced. Sutardja Dai Hall. Reserve a Room. Earthquakes can trigger landslides and mudslides, especially in areas with water-soaked soils. Landslides may result in falling rocks and debris that collide with people, trees, animals, buildings and vehicles. They also can block roads and disrupt utility lines.
Liquefaction can undermine the foundations and supports of buildings, bridges, pipelines, and roads, causing them to sink into the ground, collapse or dissolve. An earthquake generated within the Pacific Ocean floor will generate a tsunami , which is actually a series of very long waves.
Large tsunamis which travel to the ocean floor to the surface are dangerous to human health, property, and infrastructure. Long lasting effects of tsunami destruction can be felt beyond the coastline. Earthquake damage facts show fires caused by earthquakes are the second most common hazard. Gas is set free as gas lines are broken and a spark will start a firestorm.
Every region of the Golden State holds earthquake risk. Most of us live within 30 miles of an active fault. How dangerous are earthquakes? Earthquakes can shake houses off their foundations, turn soil to liquid, and cause landslides. Liquefaction can also occur and turn the soil to liquid. Ground shaking often leads to other hazards and types of damage, such as a house shifting off its foundation.
The vibrations from an earthquake can lead to ground displacement and surface rupture. The surface rupture can cause other hazards, as well as damage to roads and buildings.
In this example, the surface rupture has caused large cracks and the collapse of a paved road. This could lead to injuries, loss of life, or impede people from getting home or to work. Earthquakes often trigger landslides, which can cause catastrophic damage to homes and towns. This image of a landslide in El Salvador in shows how destructive landslides can be to people and their homes.
Lateral spreads usually break up internally, forming numerous fissures and scarps. Damage caused by lateral spreads is seldom catastrophic, but it is usually disruptive.
For example, during the Prince William Sound, Alaska, earthquake, more than bridges were damaged or destroyed by lateral spreading of flood-plain deposits toward river channels.
These spreading deposits compressed bridges over the channels, buckled decks, thrust sedimentary beds over abutments, and shifted and tilted abutments and piers. Lateral spreads are destructive particularly to pipelines. In , a number of major pipeline breaks occurred in the city of San Francisco during the earthquake because of lateral spreading.
Breaks of water mains hampered efforts to fight the fire that ignited during the earthquake. Thus, rather inconspicuous ground-failure displacements of less than 7 feet were largely responsible for the devastation to San Francisco in Flow failures, consisting of liquefied soil or blocks of intact material riding on a layer of liquefied soil, are the most catastrophic type of ground failure caused by liquefaction.
These failures commonly move several tens of feet and, if geometric conditions permit, several tens of miles. Flows travel at velocities as great as many tens of miles per hour. Flow failures usually form in loose saturated sands or silts on slopes greater than 3 degrees.
Flow failures can originate either underwater or on land. 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.
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