28 regional changes in land elevation alaska 1964 m

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Unformatted text preview: ridge earthquake. 28 Regional changes in land elevation Alaska 1964; M 8.25 • Uplift up to 10m • Subsidence 2m High and dry (8m) A serious fracture! 29 - improperly known as tidal waves Tsunamis, or seismic sea waves Result from vertical displacement along a fault located on the ocean f loor In _________ coastal waters the water piles up to heights that shallower occasionally exceed 30 metres Can be very destructive - waves experience friction as they get closer to shore - if troff hits first, water will start to recede Formation of a tsunami 30 10 Risk assessment: Probabilistic: Calculate probibility _____________ of the event or the amount shaking likely to occur in an event 31 Prediction: Short term: days to months 1. Patterns and frequency of foreshocks 2. Deformation of ground surface 3. Changes in electrical conductivity of ground 4. Abrupt changes in well water levels 5. Emissions of radon gas 6. Anomalous behavior of ________ animals Problems????? 32 Prediction: Long term: years to hundreds of years Periodicity of Earthquakes EQ cycle Paleoseismicity: historical evidence recurrence intervals seismic _______ gaps (areas of little or no seismic activity along active faults “locked zones”) 33 11 Lecture 9: Earthquakes - places where there hasn't been much activity are most at risk Seismic Gaps •Areas along faults with unusually ___ low seismic activity 34 Damage Mitigation: Earth...
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