EESA05 Study Guide Chapters 3, 8, 10, 11, 12, 13

17 Pages

Environmental Science
Course Code
Mandy Meriano

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EESA05 Hazards TextbookChapters 3810111213Chapter 3 TsunamiTsunami the waves generated by a sudden upward or downward movement of a large area of the seafloor or by an asteroid impact Causes of tsunami include subduction earthquakes collapse of the flank of a volcano large landslides and asteroid impactsCatastrophe in the Indian Ocean y December 2004 230000 people killed in costal areas around Indian Ocean y Caused by 91 earthquake just off the Indonesian island of Sumatra y The movement of this fault displaces the entire mass of overlying water and produced a series of waves that moved rapidly away from the seafloor y Tsunami are less common in Indian Ocean as Pacific Ocean y Need for effective warning systems y Emergency procedures are needed y Earthquake and tsunami educated is needed for coastal areasIntroduction to TsunamiEarthquakeTriggered Tsunami y An earthquake can cause a tsunami by displacing the seafloor or the floor of a large lake or by triggering a larger landslide y Generally takes a 71 mag earthquake to generate a tsunami y Sets in motion oscillatory waves that transmit energy outwards and upward from source y Not notice a passing tsunami in deep ocean y The decrease in velocity is accompanied by a decrease in the spacing between wave crests and an increase in wave height y During some tsunami the trough of the wave arrives first causing the sea to recede and exposing the seafloor y Misconception that tsunami is just one big wave o Waves are typically turbulent onrushing surges of debrisladen water y The runup of the tsunami is the maximum horizontal and vertical distances that the largest wave of a tsunami reaches as it travels inland y Commonly strike coast over a period of several hours y Earthquake can produce distant or local tsunamis o Distant tsunami or teletsunami travels thousands of kilometers across the open ocean and strikes remote shorelines with little loss of energy o Local Tsunami affects shorelines near the source of the earthquakeLandslideTriggered Tsunami y Large landslide that fall from mountains and into a large body of water can generate tsunamiVolcanoTriggered Tsunami y Less common that earthquake generated or landslide generatedRegions at Risk y Coats in proximity to a major subduction zone or directly across the ocean basin from a subduction zone capable of generating M9 earthquakes are at greatest risk y 85 in Pacific Ocean association with earthquakes at subduction zones o Japan Kamchatka Hawaii Islands of east and west pacific Chile Peru Mexico Alaska and California o Parts of Mediterranean and Indian OceanEffects of Tsunami and Linkages with Other Natural Hazards y Primary effects impact of onrushing water and its entrained debris and to the resulting flooding and erosion o Energy sufficient to tear up beached move costal vegetation and houses buildings o Deaths from drowning o Deaths and injury from physical impacts of debris y Secondary Effects time following event o Fires may start from ruptured gas lines or flammable chemical tanks o Polluted water supply o Damaged wastewater system o Rotting animal carcasses and plants o Disease from polluted water malaria and cholera mosquito breeding grounds o Trauma and mental health y Linked to offshore earthquakes some landslides and explosive volcano eruptions o Costal erosionNatural Service Functions of Tsunami y May leave thin sheet of sand inland from shore Beneficial for costal ecosystem and contribute to costal sand dunesMinimizing the Tsunami Hazard y Detection and warning y Structural control y Construction of tsunami inundation maps y Land use y Probability analysis y Education y Tsunami readinessDetection and Warning y PacificWide system the pacific tsunami warning center regional systems and local systems y Network seismography and realtime estimates of earthquake magnitudes and locations y Warning sensors on buoys y 100 km away generally insufficient time to warn people and evacuate y Warning sirensStructural Control y Elevation of buildings and other types of flood proofing o Installing seals for basement windows and bolting houses to their foundation y Most building codes in jurisdictions exposed to tsunami are not adequate y Dykes and walls to prevent waves from reaching areas o ExpensiveTsunami Inundation Maps y Flood mapping Off of historic data o To guide development and educate dwellersLand use y Vegetation as a protective buffer o But areas are of value to homes and tourismProbability Analysis y Provides information on location and possible severity of damage y Identification and specification of potential earthquake sources and their associated uncertainties
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