Earthquake_Damage

Earthquake_Damage - Earthquake Damage & Prediction...

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Unformatted text preview: Earthquake Damage & Prediction Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Earthquakes kill people and destroy cities The damage can be heartbreaking and horrific Knowledge improves odds of survival Knowledge Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Severity of shaking and damage depends on … Severity Magnitude (energy) of the earthquake Distance from the hypocenter Intensity and duration of the vibrations The nature of the subsurface material Bedrock transmits waves quickly = less damage Sediments bounce waves = amplified damage Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Effects on buildings: Buildings “pancake” Bridges topple Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Effects on buildings: Bridge supports crush Masonry walls break apart Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Landslides and Avalanches Shaking causes slopes to fail Shaking Rockslides and avalanches follow earthquakes in uplands Rockslides Mount St. Helens erupted via an earthquake landslide Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Liquefaction – Waves liquefy H2O-filled sediments Liquefaction Waves High pore pressures force grains apart, reducing friction High Liquefied sediments flow as a slurry Sand becomes “quicksand;” clay becomes “quickclay” Sand dikes Sand volcanoes Contorted layering Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Fire is a common hazard following earthquakes Shaking topples stoves, candles, and power lines Shaking Broken gas mains and fuel tanks ignite a conflagration Broken Earthquakes destroy critical infrastructure such as water, Earthquakes sewer, telephone, and electrical lines, as well as roads sewer, Firefighters powerless No road access No water Too many hot areas Good planning is Good crucial to saving lives crucial Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Earthquake devastation fuels disease outbreaks Food, water, and medicines are scarce Basic sanitation capabilities disabled Hospitals damaged or destroyed Health professionals overtaxed There may be many decaying corpses Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Tsunamis, or seismic sea waves (not tidal waves) Tsunamis, tidal Tsunamis result when earthquakes change the seafloor Normal faulting drops the seabed; thrusting raises it This displaces an enormous volume of overlying water A giant mound (or trough) forms on the sea surface giant Feature collapse creates waves that race rapidly away Feature Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Damage Destructive tsunamis occur frequently - about 1/yr Future tsunami disasters are inevitable 94 destructive tsunamis in the last 100 years 51,000 victims (not including 12/26/04; > 200,000) Growing human population in low-lying coastal areas Growing Education about tsunamis can save many lives Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Tsunami vs. Wind Waves Wind waves Influence the upper ~100 m Influence Have wavelengths of several Have tens to hundreds of meters Wave height and wavelength Wave related to windspeed related Wave velocity maximum Wave several tens of km per hour several Waves break in shallow water Waves and expend all stored energy and Essentials of Geology, 3rd edition, by Stephen Marshak Tsunami waves Influence entire water depth Have wavelengths of several Have 10s to 100s of kilometers Wave height and wavelength Wave unaffected by windspeed Wave velocity maximum Wave several 100s of kmh several Waves come ashore as a Waves raised plateau of water that pours onto the land pours Chapter 8: A Violent Pulse: Earthquakes Tsunami Behavior Tsunamis race at jetliner speed across the ocean They may be almost imperceptible in deep water Low wave height (amplitude) Long wavelength (frequency) As water shallows, waves As slow from frictional drag slow Waves grow in height, Waves reaching 10-15 m or more reaching Maximum damage if Maximum shore is broad and low shore Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes The Indian Ocean Tsunami On December 26, 2004, a strong megathrust earthquake On (M9.0+) originated in the trench to the west of N. Sumatra The earthquake was the largest in 40 years Displacement exceeded 15 m; rupture > 1100 km long The devastating tsunami killed people in 10 countries The surrounding the Indian Ocean; displaced many others surrounding Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes The tsunami destroyed coastlines around the Indian Ocean Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Surviving a Tsunami Heed natural and official warnings Heed Expect many waves An earthquake in a coastal setting An Retreat of water from the shore is sign of an impending tsunami Retreat Bigger waves may be next Wave arrival may last for hours Abandon belongings Get to high ground and stay there Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Surviving a Tsunami Expect roads to be impassable Climb a sturdy building or a tree Grab something that floats Expect lots of debris (sediment, wreckage, corpses) Expect landscape changes Source: Brian F. Atwater and others, 1999, Surviving a Tsunami – Lessons from Chile, Hawaii and Japan, USGS Circular 1187. Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Tsunami Map of Goleta, CA Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Earthquake Prediction “Only fools, charlatans, and liars predict earthquakes.” Only (C. Richter) Can we predict earthquakes? Yes and No Predictable over the long term (tens to hundreds of years) NOT predictable over the short term (hours to months) Seismic hazards are mapped to assess risk This information is useful for: Developing building codes Land-use planning Disaster planning Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Long-Term Earthquake Prediction Probability of a certain magnitude earthquake occurring Probability on a timescale of 30 to 100 years, or more on Based on the premise that earthquakes are repetitive Based Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Long-Term Earthquake Prediction Determination of seismic zones: Mapping historical epicenters (after ~ 1950) Evidence of ancient earthquakes (before seismographs) Evidence of seismicity – Fault scarps, sand volcanoes, etc. Historical records Seismic gaps, places that haven’t slipped recently (Parkfield, CA: years overdue) Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Long-Term Earthquake Prediction Recurrence interval – Average time between events Historical records Geologic evidence – Requires radiometric dating of events Sand volcanoes Offset strata Drowned forests Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Short-Term Earthquake Prediction Currently, we can’t reliably predict short-range events Currently, with regard to location and magnitude with Earthquakes do have precursors Clustered foreshocks Crustal strain Stress triggering And, possibly … Water level changes in wells Gases (Rn, He) in wells Unusual animal behavior Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Preparing for Earthquakes We can’t stop them but we can be ready for them Understand what happens during an earthquake Map active faults and areas likely to liquefy from shaking Develop construction codes to reduce building failures Regulate land-use to control development Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Preparing for Earthquakes We can’t stop them but we can be ready for them. We Train the community in earthquake preparedness Run preparedness drills Educate individuals on safe behavior and responses Keep viable stores of emergency supplies Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes Some Useful Websites http://earthquake.usgs.gov/regional/neic/ http://earthquake.usgs.gov/earthquakes/recenteqsww/Quak http://earthquake.usgs.gov/earthquakes/recenteqsanim/ http://earthquake.usgs.gov/earthquakes/eqarchives/ http://earthquake.usgs.gov/prepare/ http://www.ready.gov/america/beinformed/earthquakes.htm “Shake Out. Don't Freak Out” http://www.shakeout.org/resources/videos.html Essentials of Geology, 3rd edition, by Stephen Marshak Chapter 8: A Violent Pulse: Earthquakes ...
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