GEOL110_NaturalHazards CH3 GEOL 110
Long Beach State
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This 5 page Class Notes was uploaded by Doris M on Wednesday April 20, 2016. The Class Notes belongs to GEOL 110 at California State University Long Beach taught by Ewa Burchard in Spring 2016. Since its upload, it has received 5 views. For similar materials see Natural Disasters in Geology at California State University Long Beach.
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Date Created: 04/20/16
CH 3: Earthquakes 2011 Tohoku Earthquake -power plant explosion -japan is prepared for earthquakes and tsunamis -even though they tried to build the best construction, it doesn’t always work out perfectly -japan trench-subduction zone, -moves 9cm/yr -pollution of the environment -radioactive debris were found near America -it wasn’t predicted to be of such a large magnitude -liquefaction and landslides Earthquakes in the US -ppl feel ~1million earthquakes a year -few are noticed very far from the source -even fewer are major earthquakes -most earthquakes occurs along plate boundaries Northridge earthquake -compression along the san Andreas fault bend Earthquake Distribution -when plates hit each other, they collide and there is huge pressure, one slides under the other Intro to Earthquakes -Faults and Faulting -features: footwall and hanging wall -fault lines contai mineral deposits -foot wall -block below the fault plane -miner would stand here -hanging wall -block above the fault plane -hang a lantern here -faulting: process of fault rupture -some rocks are strong compared to other minerals -Stress: force that results from plate tectonic movements -tensional -compressional: rock will decrease in thickness -shearing -Fault types -reverse fault: where the hanging wall block moves up -movement happens due to compression -whole area becomes smaller, shrinks -formation of mountains -slip along dip/ slip along strike -dip slip: the slips are vertical, at a vertical angle -strike slip: moves horizontally -can be measured by the slip of the horizontal slip -river valley, trees, fences can be moved and you can see how much they have moved -caused by shear forces -blind faults: form under the surface -do not extend to the surface -active and not active -normal fault: the hanging wall goes down and the foot wall goes up -you can measure the slip along the fault The Earthquake Process -active or inactive -4,600,000,000 years: inactive -200 years: active -The Earthquake Cycle -when plates move they impact each other -change in strain -accumulation before an earthquake -drop after an event -3 or 4 stages 1.long per of inactivity 2.accumulated elastic strain produces small earthquakes 3.foreshocks -hours or days before large earthquakes -may not occur 4.mainshock -epicenter -given by news reports -location on surface above the rupture -focus (hypocenter) -point of initial breaking or rupturing -displacement of rocks starts here -propagates up, down, and laterally along the fault plane -produces shock waves, called seismic waves -Seismic Waves -body waves: move underthe surface -surface waves: moves close to the surface -p waves: faster, pull and push -primary wave can move thru solid liquid and gas -s wave: slower -a rolling type of wave, a snake in a horizontal matter -create the most destruction in the building -Tectonic Creep and slow Earthquakes -creeping: slow movement -2 creepings on the san andreas fault -the rocks contain minerals and there is a slip. Movement isnt visible -doesn’t create earthquakes but causes damages to buildings -surpentimite: a rock found in the water but was found in the rock of the san andreas -a slippery rock -the slipping San Andreas was the cause of the rock -tact-the softest and slipperiest rock Earthquake shaking Shaking experience depends on 1.earthquake magnitude 2.location in relation to epicenter and direction of rupture 3.Local soil and rock conditions -Earthquake Magnitude -moment magnitude -calculated, aka absolute magnitude -takes many days to calculate -logarithmic scale -Values are close -moment magnitude can be much larger -Earthquake Intensity -based on the amount of shaking a destruction -represented by a roman numeral and shows the amount of destruction in an area -the map intensity if developed by ppl who experienced the destruction of the earthquake -depends on the amount of shaking and the kind of rock -shake maps -an ex of the Mercalli scale map -Depth of Focus -Focus is the place within the Earth where the Earthquake starts -depth of earthquakes influence the amount of shaking -deeper, less shaking -the direction of the rupture-if it moves in the same direction of the moves, it can inc the shaking -Video: Earthquake Country Los Angeles -the larger the fault the higher the frequencies and low frequencies -basins can be filled with mud -the softer rocks will shake more in an earthquake -shaking is greater amplified in soft rocks -in an open area like a park, you are pretty safe -human build structures cause deaths -how to prevent falling structures -internal structures provide strength to a house -adding cross bracings can help with waves coming from the side -if an earthquake happens in all directions, add the bracings to support it -where are the dangerous items? Secure them -Direction of Rupture -Distance to the Epicenter -The primary wave, secondary wave and then the surface wave -the time difference of the arrival can determine the distance and where the epicenter is -distance is measured around a city -where ever the circles cross, that’s where the epicenter is -Supershear -if we have an earthquake, the energy is released -the rupture happens faster -the ruptures, will become the source of the energy release -each section of the rupture will become the new source of energy release - -Local Geologic Conditions Case Study: Earthquake Catastrophes: Lessons Learned Geologic Regions at Risk from Earthquakes -Plate Boundary Earthquakes -intraplate earthquakes Effects of Earthquakes and Linkages w/ other Natural Hazards -Shaking and ground rupture -Case Study: The Denali Fault Earthquake: Estimating Potential Ground Rupture Pays off -Liquefaction -Regional Changes in Land Elevation -Landslides -Fires -Disease Natural Service Functions of Earthquakes -Groundwater and Energy Resources -Mineral Resources -Landform Development -Future Earthquake hazard Reduction Human Interaction with Earthquakes -Earthquakes caused by Human Activity -Water Reservoirs -Deep Waste Disposal -Nuclear Explosions Minimizing the Earthquake Hazard -The Natural Earthquake Hazard Reduction Program -Estimation of Seismic Risk -Short-Term Prediction -Ground Deformation -Seismic Gaps Case Study: Paleoseismic Earthquake Hazard Evaluation
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