The U. Scientists at the U. Geological Survey USGS have developed a new mapping tool, the Pedestrian Evacuation Analyst, for use by researchers and emergency managers to estimate how long it would take for someone to travel on foot out of a tsunami-hazard zone.
The magnitude 9. The earthquake was felt throughout most of mainland Alaska, as far west as Dutch Harbor in the Aleutian Islands The tsunami scenario is a collaboration between the U. On March 11, , the Tohoku earthquake and the resulting tsunami devastated Japan with a disaster of unfathomable proportions. Although this pales in comparison to the loss of lives and property in Japan, the U. Government must ask whether Geological Survey and cooperating scientists have recently assessed the effects of a magnitude 7.
A quake of comparable magnitude struck the southern Puget Sound region about 1, years ago, and similar earthquakes are almost certain to occur in the future. The region is In December , when a tsunami killed more than , people in 11 countries around the Indian Ocean, the United States was reminded of its own tsunami risks. In fact, devastating tsunamis have struck North America before and are sure to strike again. Executive SummaryPuerto Rico and the Virgin Islands are located at an active plate boundary between the North American plate and the northeast corner of the Caribbean plate.
The region was subject in historical times to large magnitude earthquakes and devastating tsunamis. A major downward tilt of the sea floor north of Puerto Rico and the Virgin USGS science provides part of the foundation for emergency preparedness whenever and wherever disaster strikes. Recent geological studies of a key section of the Aleutian Island chain of Alaska suggest Aleutian tsunamis may occur more frequently than previously understood. Minutes after the magnitude The images of destruction coming from Japan have caused those who dwell on America's West Coast to wonder: Could a devastating tsunami hit here?
The answer is a resounding yes. Our coast is under threat from two types of tsunamis. Map of coastal communities in a tsunami-hazard zone in the state of Washington. Animation of what a potential tsunami would look like generated from a large and hypothetical magnitude 9 subduction earthquake in the U.
Pacific Northwest. The height of the tsunami waves is exaggerated compared to the land surface. Tsunami Preparedness explains how and why tsunamis occur, how to know that a tsunami is approaching, and what you should do.
These issues are addressed by scientists, emergency managers, and first responders. By Eric L. Geist, geophysicist, Bruce E. Jaffe, oceanographer, and Brian F. Atwater, geologist. Skip to main content. Search Search. Natural Hazards. Large tsunamis have occurred in the United States and will undoubtedly occur again. Learn more : Can it Happen Here? Tsunamis and Tsunami Hazards. Apply Filter. How do landslides cause tsunamis?
Tsunamis are large, potentially deadly and destructive sea waves, most of which are formed as a result of submarine earthquakes. They can also result from the eruption or collapse of island or coastal volcanoes and from giant landslides on marine margins. Why do P-waves travel faster than S-waves? Why is the interior of the Earth hot?
What is the magnetic field of the Earth? Earthquakes and Faults Why do tectonic plates move? Brief history of the plate tectonics theory Before colliding with Asia, where was India? What is an earthquake? What is the highest magnitude an earthquake can reach? What are the biggest historical earthquakes? Why do earthquakes happen in clusters? Where are earthquakes expected in the world, especially in Asia?
What is a supercontinent? Are all the faults on Earth active? How can human activities cause climate change? Why do urbanisation and deforestation make flooding more likely? Earthquake Hazards Is Singapore threatened by earthquakes? Can we predict earthquakes? Why does a building on solid bedrock resist better to an earthquake than a building on sediment or reclaimed land?
Why does a building with base isolation resist better to an earthquake than a building without base isolation? Why does a building with full bracing resist better to an earthquake than a building with no bracing? Tsunamis race across the sea at up to miles kilometers an hour—about as fast as a jet airplane. At that pace, they can cross the entire expanse of the Pacific Ocean in less than a day.
And their long wavelengths mean they lose very little energy along the way. In deep ocean, tsunami waves may appear only a foot or so high. But as they approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously. When it does, it produces a vacuum effect that sucks coastal water seaward and exposes harbor and sea floors.
Recognizing this phenomenon can save lives. A tsunami is usually composed of a series of waves, called a wave train, so its destructive force may be compounded as successive waves reach shore. People experiencing a tsunami should remember that the danger may not have passed with the first wave and should await official word that it is safe to return to vulnerable locations. Some tsunamis do not appear on shore as massive breaking waves but instead resemble a quickly surging tide that inundates coastal areas.
The best defense against any tsunami is early warning that allows people to seek higher ground. The Pacific Tsunami Warning System, a coalition of 26 nations headquartered in Hawaii, maintains a web of seismic equipment and water level gauges to identify tsunamis at sea.
Similar systems are proposed to protect coastal areas worldwide. A supercell thunderstorm strikes in South Dakota. Among the most severe storms, supercells can bring strong winds, hail, and even tornadoes. See more extreme weather pictures. All rights reserved. Tsunamis
0コメント