Disaster hotspot case studies- Califrnia coastline

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  • Created on: 08-03-15 11:14
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  • Disaster hotspot case studies- Califrnia coastline
    • Location
      • California is located on the south west coast of North America.
      • 3rd biggest US state with an area of 163,696sqmi and biggest in terms of population with 38,802,500 residents
      • The San Andreas fault (the conservative plate boundary between N. American plate and Pacific Plate) runs through California.
      • Vunerability
        • >70% of the population live within 50km of a fault line.
        • An increasing population has led to buildings being developed on unstable land. This leads to liquefaction during EQs and can also increase the risk of landslides
        • The coast is very developed meaning many people are at risk from Tsnamis
        • 20% of residents live below the poverty line. These people have the lowest capacity to cope with disaster
        • California is a highly developed area with state of the art technology that predicts disasters (e.g seismographs) as well as prevent them (e.g. building reinforcement, disaster training)
          • It has a massive economy which means, combined with it's advanced prevention measures, that losses are mainly economic rather than human
    • Earthquakes
      • The San Andreas fault is a conservative plate boundary which runs through California making it very earthquake prone
        • EQs occur when the parallel plates snag creating a build up of pressure which is suddenly released sending seismic waves in all directions.
          • These EQs are usually shallow in California making them more destructive
      • Facts
        • These is a high chance that a 7.0+ magnitude EQ will hit San Francisco bay in the next 25 years
        • 15-20 4.0+ magnitude EQs each year.
        • More than 70% of California's population live within 50km of a fault line
        • California has lots of building on unstable land which causes severe liquefaction
      • Loma Prieta EQ- 1989
        • A magnitude 7.1 struck in the Santa Cruz mountains 60 miles south of San Fransisco at 5:04 pm on 17 October 1989
          • A magnitude 5.2 aftershock struck 37 mins after the main EQ
        • 63 people were killed (mainly by a collapsed freeway); 13 750 were injured; 1081 homes were destroyed; 23 408 homes were damaged; just under 4000 businesses were destroyed or damaged; total cost US$6 billion
          • The death toll was low due to the freeways being unusually clear due to the world series baseball game
      • Northridge EQ Los Angeles- 1994
        • 57 killed; 1500 injured; 12 500 buildings damaged; 9000 homes and businesses without electricity; 20 000 without gas; 48 500 without water; damage to several freeways
        • A magnitude 6.7 Eq struck the densely populated San Fernando VAlley at 4:31 on 17 Jan 1994
          • 1000s of after =shocks of magnitude 4.0-5.0 occurred in the following weeks
    • Volcanoes
      • The last major volcanic activity was in 1915 when Lassen Peak erupted.
      • Despite this many volcanoes are being monitored for activity such as Lassen Peak, Mount Shasta etc
    • Tsnamis
      • Caused by an EQ under the Pacific Ocean, a tsunami could devastate the many cities on the coast such as LA and San Francisco
      • Crescent City Tsunami 1964
        • On 28 March 1964 an underwater EQ of the coast of Alaska generated a tsunami which affected the entire Californian coastline. Crescent city was the worst affected with waves of up to 20ft.
        • 11 people killed; $7,414,000 worth of damage; a further $1,500,000 along the rest of the Californian coast; fires broke out due to overturned gas truck;
    • Droughts
      • They occur during La Nina years in which the waters of the Eastern Pacific are cooler
        • This results in less evaporation of surface water so less rainfall
      • They are also caused by anticyclones (long lasting spells of high air pressure and sinking dry air)
      • Also caused by an increase in dry, desert winds blowing form the east.
      • Puts pressure on densely populated areas such as LA where there is a shortage of water.
      • Wildfires
        • Wildfires are one of the most dangerous effects of drought periods.
        • Southern California wildfires 2007
          • 14 people killed; 160 injured; 1,500 homes destroted; 3,900sqkm of land burned; approx. 1,000,000 people evacuated. There were also concerns about the effect of particulates on health
          • Causes
            • Dorught, hot weather and strong Santa Ana
            • Sources include: damaged power lines, an over turned truck and even arsonists.
          • A series of wildfires beginning 20th October 2007 swept across southern California. The fires were visible from  space
            • 17 of the fires were classified as major fire incidents
        • As cities such as LA and San Francisco expand or people relocate into the hills fires become more hazardous to the population with more potential for damage.
    • Landslides
      • They are often caused by EQs during which sediment is shaken lose.
        • The effect of this is magnified by wildfires which destroy plants that bind soil.
        • Winter storms also erode soil causing landslides.
          • Coastal erosion may also be a cause of landslides along the coast. Coastal climates are becoming more unpredictable increasing the risk of landslides
      • The risk of landslide disaster is increased by building on steep, unstable land.
      • La Conchita landslide 2005
        • On the 10th Jan 2005 a major landslide (200,000 cubic meters) occurred in La Conchita on the site of a previous landslide (1995)
        • 10 people were killed; 13 houses destroyed; 23 damaged
        • The owners of the La Conchita Ranch (located at the top of the slope) were held partially accountable due to their inadequate drainage systems

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