Exploring Earth Physical Geology (GT
Exploring Earth Physical Geology (GT GEOL 120
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This 15 page Class Notes was uploaded by Mrs. Otha Yost on Tuesday September 22, 2015. The Class Notes belongs to GEOL 120 at Colorado State University taught by Kaleb Scarberry in Fall. Since its upload, it has received 15 views. For similar materials see /class/210354/geol-120-colorado-state-university in Geoscience at Colorado State University.
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Date Created: 09/22/15
Earthquake Damage I Tsunamis or seismic sea waves not m waves a Tsunamis result when earthquakes change the seafloor 0 Normal faulting drops the seabed thrusting raises it b This displaces the entire volume of overlying water b A giant mound or trough forms on the sea surface b This feature may be enormous up to a 10000 mi2 area D Feature collapse creates waves that race rapidly away Exposed by I I Exposed by receding sea receding sea Earthquake Damage I Destructive tsunamis occur frequently about 1Iyr I Many tsunami disasters dot recorded history 0 94 destructive tsunamis in the last 100 years 0 51000 victims not including 122604 I Future tsunami disasters are inevitable 0 Growing human population in lowlying coastal areas I Education about tsunamis can save many lives Exposed by I I Exposed by receding sea receding sea Tsunami Behavior I Tsunamis race atjetliner speed across the ocean I They may be almost imperceptible in deep water 0 Low wave height amplitude 0 Long wavelength frequency I As water shallows waves slow from frictional drag o Waves grow in height reaching 1015 m or more Tsunami I Tsunami destruction of the coast depends upon 0 Offshore bathymetry gt Broad shallows increase amplitude but sap wave energy D Quick deeptoshallow transition Deadliest condition v Waves have maximum energy V quotquotquotquot v Wave heights are modest v Water pours onto land as a sheet 0 Topography of shore D Broad low land Maximum damage gt Steep rise of land Less damage I The Indian Ocean Tsunami o On December 26 2004 a strong earthquake M90 originated in the trench to the west of N Sumatra o The earthquake was the largest in 40 years 0 Displacement exceeded 15 m rupture gt 1100 km long 0 The devastating tsunami killed people in 10 countries surrounding the Indian Ocean s W1 A V w f I The Indian Ocean Tsunami I Killed more people than any tsunami on record At least 283106 deaths14100 still missing as of 92507 1126900 people were displaced I Recordsetting death toll The earthquake was r r 39 so large and the tsunami spread fast Coasts were full of Christmas tourists Source USGS Earthquake Hazards Program Most Destructive Earthquakes lu u quot 439 39 quotan aquot destructivephpl a m Destroyed coastlines around the Indian Ocean 1 Huge death tolls 0 Northern Sumatra 39 I mmmn 0 Thailand o Malaysia 0 Sri Lanka INDIA u nmt m 1 Ill s a Complete devastation below runup elevation o Dense coastal development in Banda Aceh hardest hit I Entire communities were erased buildings and people I Expect roads to be impassable I Climb a sturdy building or a tree I Grab something that floats I Expect lots of debris sediment wreckage corpses I Expect landscape changes Tsunami Prediction I Scientific modeling predicts tsunami behavior I Tsunami detection is expanding o Tsunami detectors are placed on the deep seafloor 0 Sense pressure increases from changes in sea thickness I Prediction I detection can save 1000s of lives Earthquake Prediction I Prediction would help reduce catastrophic losses I Can we predict earthquakes Yes and no 0 They CAN be predicted longterm 101005 of years 0 They CANNOT be predicted shortterm hoursmonths I Seismic hazards are mapped to assess risk I This information is useful for 0 Developing building codes o Landuse planning 0 Disaster planning Earthquake Prediction I Longterm predictions 0 Probability of a certain magnitude earthquake occurring on a time scale of 30 to 100 years or more 0 Based on the premise that earthquakes are repetitive Offset stream Offset ridge Strikeslip fault Normal fault Earthquake Prediction I Longterm predictions 0 Require determination of seismic zones by r Mapping historical epicenters after 1950 r Evidence of ancient earthquakes before seismographs v Evidence of seismicity Fault scarps sand volcanoes etc v Historical records Pullapart Sag ponds Transverse basin thrust belt Pressure 7 ridge I Longterm predictions 0 Recurrence interval Average time between events D Historical records b Geologic evidence v Sand volcanoes v Offset strata v Drowned forests Requires radiometric dating of events Tilted tree Sand volcano Asymmetric tree rings Sand volcano source layer Offset ancient soil horizon 39 paleosol Disrupted layer V Datable 39 r a wood fragment more recent fault Older fault I Longterm predictions o Seismic gaps places that haven t slipped recently are more likely candidates Greater than 60 Greater than 40 Greater than 20 Greater than 10 Greater than 5 Less than 5 39 umber of times per century the shaking lrom earthquakes wlll exceed 020 g at this level there is signi cant damage to 7 older buildings