1994 Northridge, California earthquakeIn the early morning hours of January 17, 1994, most residents of Los Angeles were still asleep. At 4:30 that morning, a major earthquake hit the area. The ground shook violently over a large region. Many houses and buildings were shaken off their foundations and some collapsed. Frightened residents ran into the streets. Soon fire trucks were racing to fires caused by broken gas mains. Rescue teams were struggling to reach people trapped in collapsed buildings. It was a scene of widespread chaos.
The magnitude 6.7 Northridge earthquake-with an epicenter just north of Los Angeles and lasting just 15 seconds-was one of the costliest natural disasters in U.S. history. Around 9000 people were injured, some 1600 of these seriously, and 57 people were killed. Over 22,000 people were displaced from their homes. The region suffered an estimated $40 billion in economic losses. Thousands of buildings were damaged. Of these, 1600 were subsequently "red-tagged" as being unsafe to enter, while 7300 were "yellow-tagged" as being safe for only limited entry. Nine hospitals were closed, with 2500 beds lost. Nine parking garages collapsed. Portions of eleven major roads were impassable. Sections of seven freeways collapsed and 170 bridges were damaged to some extent. (http://pubs.usgs.gov/of/1996/ofr-96-0263/)
Californians live with earthquake hazard on a daily basis. Small earthquakes occur frequently, but it is well known that occasionally large earthquakes do occur-they have throughout the recorded history of the region-and when they occur in an urban setting they can be devastating. A source of particular dread in southern California is The Big One, a great earthquake of magnitude approaching 8.0, like the one that destroyed much of San Francisco in 1906. Californians live with the knowledge that sooner or later another such earthquake will occur somewhere in California. A magnitude 8 earthquake today in the San Francisco or Los Angeles areas-or in other large metropolitan areas around the world where similar earthquake hazard exists-could cause damage in the hundreds of billions of dollars and take many thousands of lives. The enormous costs of hurricanes Katrina (2005) or Andrew (1992) in lives and property pale in comparison. This case study of an "urban earthquake," will consider scientific observations related to the earthquake, the consequences of the earthquake, and why variations in earthquake hazard exist within a seismically active region such as Los Angeles using the tools of a geographic information system (GIS). It will explore not just what scientists know about earthquake hazards but how they know what they know.
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On May 3, 1999, eight supercell thunderstorms spawned 58 tornadoes that devastated areas in and around the Oklahoma City metropolitan area. Forty people lost their lives, 675 were injured, and the total economic impact was estimated at 1.2 billion dollars. Almost exactly four years later, another outbreak of tornadoes from May 4 through May 9, 2003 killed 37 people and caused hundreds of millions of dollars in damage across large portions of the south central US. This case study will use GIS to investigate both tornado outbreaks from both scientific and societal perspectives. What were the atmospheric conditions that helped spawn the enormous supercell thunderstorms from which the tornadoes developed? Students will explore temperature, humidity and wind direction datasets, investigate the location and intensity of the 250 millibar Jet stream winds and examine the National Weather Service forecasting tools to see if they can predict where severe "tornadic" weather is likely to occur. The National Weather Service predicted severe weather two days before the tornadoes actually occurred - given the same information, how well will the students do? Using NexRad weather radar data, students will identify the locations of individual tornadoes by finding the characteristic "hook" radar signature, determine which way the tornadoes were moving, and then consider how much warning and evacuation time residents have given direction and rate of travel information. Again, the National Weather Service gave residents 20-30 minute lead times on several of the 2003 tornadoes. Examining the tornado damage tracks superimposed over digital aerial photography will show students how the Fujita scale rating correlates with the density of houses and buildings. Finally, by translating the tornado tracks from the Oklahoma City outbreak to a major metropolitan area like Houston or Dallas, students will use the Federal Emergency Management Agency's HAZUS disaster management data layers to determine the impact on both people and urban infrastructure.
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There are numerous oral accounts of a massive earthquake followed by a catastrophic flood from native people from the whole of the coastal zone from British Columbia to northern California, collectively known as Cascadia. But when did it happen? And do all such stories tell of one event-or were there many? The written record of Cascadia is relatively short. European settlement of the region only began in 1778, when Captain James Cook sailed his ship Resolution into Nootka Sound in what is now British Columbia. Before that time, European maps showed the Pacific Northwest as terra incognita. In more recent history, we know that towns along the coast of Cascadia have experienced numerous tsunamis generated by distant earthquakes, notably a tsunami from the great earthquake off Anchorage, Alaska, on Good Friday in 1964. Although these tsunamis in some cases caused local damage and some deaths, they were not massive tsunamis, nor did a great earthquake nearby precede them. In this case study, you will explore the geologic evidence that can help answer the question of whether the historical accounts of a tsunami were caused by a great Cascadian earthquake? And if so, what does this imply about another such earthquake in the (possibly not-very-distant) future?
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Coming soon...
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