GEOL 106 Condensed Midterm notes.docx

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Geological Sciences and Geological Engineering
GEOL 106
John Hanes

GEOL 106 Condensed Midterm Notes Why has there been an increase in the impact of humans on the earth system? • exponential population growth • advances in our technological capability to make an impact on the environment • demand for increased human level of affluence ESE/ ESM credo: think globally, act locally (everything you do has an impact on the earth) How do we study the past? • study tree rings • study ice cores from ice sheets o measure gas/lead/dust concentration How does past ESE compare to future ESE? • SCALE - in past was more local, now more global • INTENT- in past regional/global effects were unintended and unanticipated In managing earth systems, we have a MORAL AND ETHICAL RESPNSIBILITY • THE DESIRED ENDPOINTS ARE SUSTAINABILITY AND EQUITY o sustainable development: development that meets the needs of the present without compromising the ability of future generations to meet their own needs Risk Analysis and Risk Management HAZARD: something which might cause harm to people (death, injury, property damage) RESOURCE: something that is useful to us --> when the amount of a resource is above or below the "damage threshold" that resource becomes a hazard 3 main factors that control how severe the hazard event is 1. ABSOLUTE AMOUNT - how much water is there? 2. DURATION OF TIME - how long do we stay in the hazard zone? 3. RATE OF CHANGE - how rapidly was the hazard zone reached? Factors that decide when a hazard event becomes a disaster or a catastrophe 1. population- number of people killed/injured 2. amount of property loss (financial) 3. area affected - geographic scale 4. geographic area/infrastructure affected (resources/industries affected) 5. relief preparedness 6. group vs individual 7. reconstruction time 8. societal reaction Why is the distinction between a disaster and a catastrophe important? • governmental/world aid • historical perspective- how often do really big events happen? Truism in disasters • 90% of deaths are in the less industrialized countries • 75% of economic damage is in the more industrialized countries What type of hazard event is responsible for the most deaths ? • CIVIL STRIFE (WARS) • drought • earthquakes/volcanoes • storms/floods • other (ie. epidemic) RISK : the probability of the hazard occurring x the severity of the consequences if the hazard happens • P H S H • measured by empirical observations and scientific studies and social/economic studies (how the people is affected, how society is disrupted) Fungibility: seeking a prudent balance between the advantages of boldness and the advantages of caution RISK ANALYSIS 1. UNDERSTAND THE HAZARD a. WHAT CAUSES EARTHQUAKES ? i. MOVEMENT ON FAULTS (FAULT = a break/crack in rocks along which there has been appreciable displacement) 1. elastic rebound theory- when stress is applied to something, it will bend and bounce back to its original shape when the stress is released 2. earthquake cycle a. long period of inactivity b. accumulated elastic strain produces small earthquakes c. foreshocks may occur (sometimes this stage is absent) d. main shock/ aftershocks occur 3. TYPES OF FAULTS a. STRIKE-SLIP FAULT (horizontal motion) b. NORMAL DIP-SLIP FAULT (down the ramp) c. REVERSE DIP-SLIP FAULT (up the ramp) b. WHERE DO EARTHQUAKES OCCUR? i. FOCUS - the point source of energy release on the fault ii. EPICENTRE- the point at the earth's surface directly above the focus 1. how to find the focus/epicentre a. use seismometers to measure seismic waves (velocity = elasticity/density) i. BODY WAVES 1. P-WAVE (primary) push-pull compression, travels 2 times faster than S-waves 2. S-WAVE (secondary) shear up and down movement ii. SURFACE WAVES (most damaging to human structure) 1. LOVE wave - horizontal, side to side motion 2. RAYLEIGH wave - circular motion b. measure the travel time between P-S waves at 3 locations and use triangulation to locate the intersection of 3 circles iii. what DEPTH do earthquakes occur at? (in the outer 10% layer of the earth since it is rigid/sufficiently elastic to experience fault formation) (90% of earthquake foci are at depths less than 100km since deeper in the earth is too plastic) c. WHAT ENERGY DO EARTHQUAKES RELEASE ? i. measure the INTENSTY by the Mercalli scale ii. measure the Richter magnitude d. WHAT EXACTLY CAUSES DAMAGE ? (determined by empirical observations, laboratory experiments, computer modelling) i.SURFACE FAULTING (so don't build right on an active fault) ii.GROUND SHAKING 1. material amplification effect - when seismic waves slow down as they pass into another material a. ROCK = least shaking, SAND/STIFF SOIL = moderate shaking, WATER SATURATED CLAY/SOFT SOIL = most shaking iiiGROUND FAILURE 1. landslides 2. liquefaction of soils - when sand/ clay soil change strength and flow like a liquid when shaken iv.TSUNAMIS - generated by an earthquake from a fault underwater, column of water is displaced, energy translates to waves, wavelength decreases and wave amplitude increases as waves come into contact with the continental slope 1. caused by seafloor earthquakes 2. underwater landslide 3. collapse of the flank of a volcano into the sea 4. submarine volcano explosion 5. impact of meteorite into the ocean v. FIRES 1. surface faulting and ground shaking can sever electric power and gas pipelines --> causing a fire 2. appliances topple over --> gas leaks --> ignite a fire vi. DISRUPTION OF WATER SUPPLIES / DISEASE 1. water pipelines disrupted so fires can't be put out 2. cholera epidemic 3. parasites, diarrhea, sanitary facilities compromised 4. water supplies contaminated vii.HUMAN INDUCED SEISMIC HAZARDS 1. dam construction causing stress on faults
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