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Unformatted text preview: 3/10/2008 Monday, March 10, 2008 10:13 AM Earthquakes and plate tectonics divergent, convergent, and transform boundaries intraplate earthquakes Earthquake hazards (ground motion, failure of structures, uplift/subsidence, mass movement, fires/ exposure, seiche/tsunami) Planning- building in an EQ zone Prediction evidence that stress has/can accumulated evidence that rocks are nearing yield point Human caused- prevention? What to do in an EQ? 1. Liquifaction o There are a lot of unconsolidated clay particles in wet clay o All configured, interlocking o There's water in it. o When the there's an EQ, the particles align and flow. o Ground loses strength to hold stuff up o Relatively gentle slopes 2. Mudslides o Higher grade slopes than liquifaction 3. Landslides o Flows until the grade becomes too low 4. Collapse of buildings and other structures o Wood frame houses fare best o Steel frame buildings can fare well o Masonry (brick) buildings fare worse o Slab and pillar Particularly unstable o Fires and exposure Gas pipes that dont sway during earthquakes Break and start fires o Tsunami 5. New Madrid Earthquakes o 1811-12 o Series of 3 earthquakes 7.5-8.5 o Rang church bells as far away as Boston, MA o Changed course of Mississippi River, created Reelfoot Lake o Earthquake occurred from slip on faults in a Precambrian rift that underlies the Mississippi Valley 3/12/2008 Wednesday, March 12, 2008 10:10 AM Living with earthquakes Planning- building in an EQ zone Prediction evidence that stress has/can accumulated evidence that rocks are nearing yield point Prevention? What to do in an EQ? Physical and compositional layers of the Earth P &amp; S waves properties (review) travel paths through the earth Seismically recognizable regions Crust (continental vs. oceanic) Crust-Mantle Boundary (Mohorovicic discontinuity or Moho) Asthenosphere Transitions in upper mantle Outer core (liquid) Inner core (solid) Living with earthquakes o If you dont want to be in an earthquake. Obviously dont move or live near the faults o Locate and avoid critical structure on faults o Avoid construction on unconsolidated material Seismic waves travel more slowly in unconsolidated sediment (fill, loose sand and mud) than in bed rock. Because the energy of the wave doesnt change, the amplitude goes up and there is more damage to structures o Build well Wood frame houses fare best Steel frame buildings can fare well Masonry buildings fare the worst o Past history of large EQ's, recent history of movement o Evidence that the rock is starting to fracture Swelling in the rock Drop in water levels in wells. Cracks allowing for escape of water Prevention?...
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