Hazards in California

Hazards in California

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  • Created by: naomi
  • Created on: 19-12-12 17:26

Hazards in California

State: California

Population: 36,756,666

Land Area (sq Kms): 403,931.96

Population Density (sq Kms) 91.00

Land Area (sq miles): 155,959

Population Density (sw miles): 235.68

Population growth p/yeear: 10% - expected to fall to 1.5% in coming decades due to fall in in-migration

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Dealing with earthquake threats

What if there was another major earthquake? To protect themselves, most Californians insure their property against earthquake damage. After the Loma Prieta and Northridge earthquakes, demand for insurance rose sharply. But, by 1996, it had dropped to below 1989 levels, and has declined further since. Many people avoid the cost of taking out insurance. Insurers despair about this - asking what people would do in the event of another earthquake. In San Francisco, people say that no earthquake occured between 1906 and 1989, so why bother with odds that low?

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Physical Geography of California

The Midwestern to Southwestern area of California is on the Pacific plate, while the rest of California is on the North American plate. The area is dominated by northwest trending of strike slip faults and folds. California is location on the San Andreas Fault, a conservative plate boundary, which defines approximately 1300km (800 miles) of the boundary between the Pacific and North American plates. California is also situated in the 'ring of fire' and due to there being 'hot spots' there are numerous active volcanoes in the state.

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California: Location

California is positioned in both the northern and western hemispheres, and is location in the western region of the United States of America - Over recent decades, Southwest America has been experiencing many hazards due to climate change. Natural hazards such as drought, flash floods and wildfires occur in this region, making the population vulnerable.

California is not located within the tropics, but is reasonably close to the tropic of cancer - California's population is becoming more vulnerable to storms (only in El Nino years) and other effects of climate change due to its position near the tropic of cancer.  

California's coast faces the Pacific Ocean - The Pacific Ocean is prone to earthquakes and therefore tsunamis, causing its highly populated coastal regions to be at a very high risk of these hazards. 

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California: Location

California is positioned in both the northern and western hemispheres, and is location in the western region of the United States of America - Over recent decades, Southwest America has been experiencing many hazards due to climate change. Natural hazards such as drought, flash floods and wildfires occur in this region, making the population vulnerable.

California is not located within the tropics, but is reasonably close to the tropic of cancer - California's population is becoming more vulnerable to storms (only in El Nino years) and other effects of climate change due to its position near the tropic of cancer.  

California's coast faces the Pacific Ocean - The Pacific Ocean is prone to earthquakes and therefore tsunamis, causing its highly populated coastal regions to be at a very high risk of these hazards. 

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California: Distribution of the population

A large propotion of the population of California live in its megacities, and capital cities of Los Angeles (3,792,621) and San Diego (1,307,402), both of which are situated on the coast of California facing the Pacific Ocean, making the people who live here vulnerable to the hazards this ocean can bring.

People have tended to make themselves vulnerable in California; 6% of the State's population lives on a floodplain, and millions live on active faults in huge urban centres; the high canyons and ridges which are perfect for wild fires have become favoured locations for the rich and famous. The reliance on the car and transport adds to California's vulnerability, as earthquakes often disrupt road transport. 

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California: Climatic Patterns

California suffers periodic changes which can be hazardous. Sometimes drought occurs and forest fires threaten, and also floods and landslides can occur. Flood risks in California vary, but they coincide with El Nino; forest fires and drought coincide with La Nina. The 2012 drought in California caused there to be: series shortage of water for cultivation and cattle farms, rising food prices (in the U.S.), and population migration. 

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California: Level of Human Development

  • Coping capacity is high. Efforts are co-ordinated by FEMA (Federal Emergency Management Agency) and by the Governers Office. The State tends to lead relief efforts, with FEMA following later, rather than the siuation during Katrina, where the state waited for FEMA's lead.
  • The State is well-used to dealing with disasters and tends to react well e.g. the evacuation of over 1 million people during the 2007 fires.
  • The USGS advises on earthquakes and provides detailed informationon on ground shaking risk. This allows emergency services to target areas where damage is likely to occur e.g. zones of known liquefaction risk, and it informs land use planning.
  • Building codes are strictly enforced, although land use planning in fire-risk hills leaves a lot to be desired.
  • Numerous preparedness systems are in place, from widespread education, to advice on household emergency kits, and warming systems for floods and tsunamis. 
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Hazards of the California Coast

Hazard: Earthquake

Causes: A network of active faults (e.g. San Andreas fault) underlies the Los Angeles region and the San Francisco Bay Area (e.g. Hayward and San Gregoria faults).

Impacts: The Soft basin sediments in Los Angeles lead to rapid shaking. Five major earthquakes were recorded in the last 100 years. The San Francisco Bay Area has experiences several large earthquakes too.

Hazard: River Flooding

Causes: Winter storms, especially during El Nino years, lead to floods in the Los Angeles and San Gabriel rivers, exacerbated by deforested hillsides.

Impacts: Rivers are now heavily channelised, but floods can still take place, usually between October and January. 

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Hazards of the California Coast

Hazard: Coastal Flooding

Causes: The area around Long Beach, which is subsiding, sometimes floods in heavy storms.

Impacts: Increasing threat with rising sea levels in the future

Hazard: Drought

Causes: A potential summer problem in the Mediterranean climate especially in southern California, but more marked in La Nina years.

Impacts: Exacerbated by lack of water supplies in Los Angeles for the rising population.

Hazard: Wildfires/bushfires

Causes: As Los Angeles expands into rural areas, wildfires are a major hazard, especially during th dry Santa Ana wind periods.

Impacts: Likely to be an increasing hazard as people move out to hills on the fringe of Los Angeles and south of San Francisco.

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Hazards of the California Coast

Hazard: Landslides/mudslides

Causes: Landslides take place in heavy winter storms where hillsides have bene nurnt by wildfire and eroded. Also a risk along the coast near Malibu and Santa Monica.

Impacts: A growing risk as climate becomes more unpredictable in coastal areas.

Hazard: Fog and Smog

Causes: Advenction fog occurs when cool air from cold offshore currents drifts inland and meets warm air (especially in summer). Climate conditions combine with car pollution to generate photo-chemical smog, which collects in the basin

Impacts: A mega city-wide hazard, especially in late summer and autumn. 

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Hazards of the California Coast: Human Causes

  • Deforestation, soil degradation - soil erosion, landslides and mudflows
  • Urbanisation and overdevelopment - landslides, mudflows, coastal and river flooding
  • Increasing traffic/industry - smog, photochemical smog
  • Rapid population growth - water overuse and shortages
  • Tourism, farming, urban sprawl - heatwves, bushfires, Santa Ana winds
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1994 Northridge Earthquake - Los Angeles

Cause:

  • The San Andreas Fault
  • Earthquake occurred on a thrust fault along northern fringes of the valley
  • Very strong ground motion was indication of significant risk presented by thrust-fault events of moderate mangitude
  • The plates frind against each other at different speeds (conservative plate boundary)

Effects:

Immediate effects:                                                     

  • Death toll: 57
  • 1,500 seriously injured
  • 9000 homes/businesses without electricity
  • 20,000 without gas
  • 11 major roads closed 
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1994 Northridge Earthquake - Los Angeles

Long-term effects

  • Roads blocked - no transport in/out
  • Damage to buildings and water supplies/electricity/gas
  • $20 billion losses

Response

Short term/medium term:

  • U.S.G.S (United States Geological Society) started analysing data and broadcasting information to the public. Schools reopened after a week or two, and leaflets were handed out

Long term:

  • NEHRP agencies assisted local, state and federal jurisdictions to carry out recovery, reconstruction and mitigation processes.
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1989 Loma Prieta Earthquake - San Francisco

Cause:

Caused by a slip along the San Andreas Fault after a release of pressure which had been building up (7.1 magnitude)

Effects:

  • The quake killed 63 people throughout northern California, injured 3,757 and left some 3,000-12,000 people homeless.
  • Damage in San Francisco and Oakland due to unstable soil. Oakland City Hall was evacuated after the earthquake.
  • In Santa Cruz 40 buildings collapsed, killing 6 people.
  • In Moss Landing, liquefaction destroyed the causeway that carried the Moss Beach access road across tidewater basin.
  • Cost was $6-8 billion. San Francisco had 22 structural fires during the 7 hours from the time the earthquake struck untill midnight.
  • Damage to the War Memorial Opera House in San Francisco. The House was closed for 18 months, and reparied with a $49.5 million seismic retrofit, along with $28 million improvement in backstage additions.
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1989 Loma Prieta Earthquake - San Francisco

  • More than 1,000 landslides and rock falls occurred in the epicentral zone in the Santa Cruz Mountains.
  • The earthquake caused the Cypress Viaduct to collapse, resulting in 42 deaths.
  • 366 businesses were destroyed and 3530 damaged.
  • 1018 homes were destroyed and 23,408 damaged

Responses:

  • Emergency services attended areas of severe damage and prioritised 911 calls calling for help associated with the earthquake.
  • Bus signed $3.45 billion earthquake relief package for California
  • Strong media coverage - responsible for education.
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