EESA05 - Lec 4 - near verbatim

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Environmental Science
Mandy Meriano

EESA05 Lecture 4: PY Date: Oct 2, 2012 Library Liaison available for assignment help: Sarah Forbes Ask Chat with a librarian; or make appt Library guide Assignment: o Critical paper = describe environmental hazard o Health impacts of arsenic release o Discuss that hazard o Comparative, management methods, overview of what this is actually; case study kind of approach o What countries are affected? Why? Is there a model thats being used? Management of the hazard? Mitigation o Negative and positive things that have been found? o 5 pages, double spaced o APA citation refer to guide o Once found topic, then go to search strategies Deconstruct; what are the keywords; whats another way you can say that? Truncation or wildcards Oil spill* put root word and then put * to get other similar words o After in databases, use Boolean operators (AND, OR, NOT) o Use database to find words for you Journal Articles tab o o GEOBASE o Environmental Sciences and Pollution Management o Web of Science o Referee shirt = peer reviewed article Midterm: Saturday October 27, 2012; 5-7 PM, AC223 not dates, unless its important and has been repeated EARTHQUAKES: Slide 2: Learning Objectives: o Knowing what an EQ is o Understand how scientists measure EQs o Be familiar w/ earthquake processes such as faulthing, tectonic creep, and the formation of seismic waves o Know which regions are most at risk for EQs and why o Know and understand the effects of EQs such as shaking, ground rupture, tsunami and liquefaction o Know the important natural service functions of EQs 1 EESA05 Lecture 4: PY Date: Oct 2, 2012 o Know how human beings interact w/ and affect EQ hazards o Understand how we can minimize seismic risk and recognize adjustments we can make to protect ourselves o Slide 5: Figure shows locations of EQs are around the Earth Concentrated around plate boundaries; most of the NRG of moving and shaking is happening at plate boundaries N.America, not too much around where we live; were not near plate boundary; theres some inter-plate EQ that happen but not so much EQ actitvity Slide 6: Earthquake Description: o Result from rupture of rocks along a fault Fault = break in the Earths lithosphere where theres relative mvt of the different parts of the plate along that fault; can have horizontal or vertical mvt When the rocks move, NRG released in the form of seismic waves o They are mapped according to the epicenter Epicentre Focus is directly below the epicenter; where focus of EQ is below the surface o They are measured by seismographs Instruments that are put in the EQ, sit quietly until theres some NRG release Record waves as they travel thru Earth material Give seismograms Used to learn about EQ, how fast they travel and where epicentre is o They are compared based on: Magnitude Intensity Slide 7: EQs EQ = sudden motion of a rock body along a fault (break in the rock). A fault is a plane of fracture in the lithosphere, where rock masses can move past each other. o If theres no motion of the rocks along the break, then all you have is a JOINT; NOT a fault; only a fault once you get mvt of rocks along that faultline The focus or hypocentre is the point on the fault where the rupture begins (where the first shake/mvt takes place) Diagram: focus/hypocentre = deep w/in earth or shallow; can have deep/shallow focus EQ o Shallow focus EQ will cause more damage; closer to the surface; travel much easier, the waves will travel easier to the Earth where we are The epicentre is the point on the Earths surface directly above the focus 2 EESA05 Lecture 4: PY Date: Oct 2, 2012 Slide 8: Elastic Rebound Elasticity is a property that allows some reversibility; can deform and turn back to the way it was; some rocks are more elastic than others The NRG released from an EQ comes from the sudden release of strain stored in rocks as they deform o If a lot of stress applied to the rocks, causes strain in rocks, the strain stored in rocks, when strain becomes greater than the strength of the rocks, then breaks - collapse Slow tectonic motion causes blocks of rock to gradually slide past one another, but if theyre prevented from sliding then strain NRG will build up in the rocks o NRG isnt released continuously b/c rocks have a certain amount of strength (some rocks have more strength than other rocks); but depending on what the strength of the rock is, they can actually take a lot of that stress b4 they break o Once threshold is reached, then the break is very sudden which is why EQs are so damaging NRG released in a sudden discrete event Slide 9: Types of Faults Faults classified according to type of motion; 2 major types of motion: o Horizontal move past one another o Vertical one rock goes up or down relative to the other rock Joints are faults along which no motion occurs When they move past one another like in the top diagram, this is referred to as a strike-slip fault o Diagram: theres a river; b/c of the path of where the fault is and because of the movement, can see very clearly that the direction of the river has now changed (theres a bend) because the rocks have moved horizontally relative to one another A strike-slip fault is one in which the motion is horizontal A dip-slip fault is one in which the motion is vertical o Comes in 2 flavors, b/c the motion is vertical (normal) relative to the fault: o 1) can have one block of rock dropping compared to the other rock normal fault o 2) can have block of rock pushed up reverse fault Thrust fault is pretty much a reverse fault, but the dip-slip (degree of the dip) is kind of shallow (less than 45 degrees); but in terms of relative motion, its the same thing as reverse fault just the dip is a bit shallower Hanging wall: o Lot of underground mines are located around major fault lines o Metals concentrated around these fault lines due to NRG o Make tunnels along the fault lines o So miners would walk on one side, at the bottom part = footwall o And then hang their lanterns on the wall above them = hanging wall 3
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