Chapter 8 Earthquakes: Part 2
Chapter 8 Earthquakes: Part 2 Geology 101
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This 5 page Class Notes was uploaded by Alanna Wight on Wednesday December 9, 2015. The Class Notes belongs to Geology 101 at Washington State University taught by Wilkie in Fall 2015. Since its upload, it has received 19 views. For similar materials see Geology in Geology at Washington State University.
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Date Created: 12/09/15
Lecture Outline Chapter 8 Part 2 Key Points for today 0 What are some of the side a ects caused by earthquakes 0 Why do some earthquakes occur within plate interiors Can earthquakes be predicted 0 What you can do to reduce your risk from earthquakes 0 What you can do to prepare and protect yourself during and after an earthquake Effects of Earthquakes Tsunami Landslides Liquefaction Unconsolidated sediment becomes water saturated and ows Seiches Water sways back and forth over enclosed body of water lakes swimming pools Ground Shift Fires Tsunami Fast moving seismic sea waves generated by faulting Ground motion displaces sea water above generated wave Move at speeds up to 800 kmhr 500 mihr up to 100 ft high Is there a potential tsunami hazard in Washington Possibly Other possible causes for a Tsunami landslides volcanic island collapse Landslides Earthquakeinduced mass wasting So do landslides caused by earthquakes only cause property damage yes Liquefaction Unconsolidated sediment becomes water saturated and ows can cause mass movements and sinking of structures Ground Shift Uplift and Subsidence can be caused by earthquakes Fires are common after earthquakes broken gas pipelines and broken water mains are contributing factors Earthquakes Within Plates Possible Causes Reactivation of faults at old plate boundary Ex New Madrid Missouri Old faults that have been reactivated by erosion release of overlying pressure sediment load increase in overlying pressure rainfall human induced Future continental rift zones Human induced earthquakes 1 Dams Example Hoover dam 600 earthquakes in 10 years after dam was built increased water pressure lubricated faults 2 Iniection of liquids underground Example Dumping of toxic waste chemical weapons Rocky Mountain Flats CO So if man can induce earthquakes does this mean man can control or diminish the intensity of an earthquake What do you think What would be the consequences Cost More smaller earthquakes potential to small damage Can earthquakes be predicted Some animals seem to sense an EQ is coming World 39s rst successful earthquake prediction China Feb 4 1975 Magnitude 73 9 hours advance warning based on animal behavior But then July 28 1976 Magnitude 78 240000 died No prediction made Not too reliable quotRecurrence Intervalquot the average time between earthquakes on a given fault There is a relationship between the size of the earthquake and the recurrence interval the longer the interval between earthquakes the larger the probable quake energy builds up for longer period of time Seismic Hazard map for North America takes into account the intensity of seismic shaking and proximity to active faults Seismic Risk map for the US describes the damage that one can expect It takes into account the seismic hazard but also the population density building type So what can we do to reduce the risk from earthquakes Public education about hazards emergency practices Landslide policy Earthquake engineering buildings designed to withstand shaking gas lines valves that automatically shutoff redundant water systems to ght res Earthquake warning and emergency response coordinated by realtime seismic detection devices Lecture Outline Monday Dec 7 2015 Video The Day the Earth Shook NOVA This is approximately 30 minute video so I will start as soon as possible so we can have a short discussion afterwards If more time is needed we will continue the discussion in Wednesday s class As you view this video please note and answer the following questions You will be responsible for this material for the Final exam 1 List the similarities and differences between the Northridge and Kobe earthquakes Similarities Both by plate boundaries Similar ground shaking Differences Plate boundaries rub against each other and plates will crack in Kobe but not Northridge In Kobe the fault went right through the city 2 What are some of the factors which contributed to the higher number of fatalities resulting from the Kobe earthquake Quake closer to densely populated area Buildings built on alluvium in narrow corridor adjacent to mountain more shaking Seismic waves re ected off mountain and when met incoming seismic waves cause 3 Why did some tall buildings pancake certain oors collapse Box stores large open areas Buildings with parking garages Hotels with big lobbies 4 What are some measures that can be taken to prevent the freeways and some buildings from collapsing Build for earthquake protection Build strong or reinforced buildings Foundation to bedrock 5 What is liquefaction Unconsolidated sediment becomes water saturated and ows 6 How are P and S waves used to prevent additional fatalities from train accidents In what other ways could this same concept be used Seismometer used to detect earthquake and shut down trains Similar technology could be used to turn off gas on gas mains and smart meters to turn off gas to a house sensors used to deploy airbags in a crash Used real time