106 Course Notes (pre midterm).doc

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Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
Rob Beamish
Semester
Spring

Description
1 Geology 106: Natural Hazards Lecture #1: Introduction Lecture #2: Introduction to Earth-System Science and Earth System Management/Engineering - Geology is now earth system science 1969 - We had the landing on the moon 1948 - Once a photograph of the earth taken from outside is available a new idea as powerful as and in history will be let loose – Fred Hoyle - Edgar Dean Mitchell: Quote about looking out to earth and referring to it as home - We see this vibrant dynamic earth in contrast to the dead moon - Documenting of the moon was a very important event - What was felt was way beyond science and technology Diagram (Graph) - Time from 1870 to 1990 - Number of USAlaws on environmental protection versus the year - There is a big sharp bend in the curve sudden takeoff in the environmental laws right around the time when we landed on the moon - Going into space gave us a different perspective of the earth - View of earth from space led to increased awareness of the fragility of the earth and the need to better understand it - The president of the USAcommissioned a study of the earth system (appointed science people) - What needs to be done to live in concert with the fragile earth? Sheet handed out*** - We need to understand the whole earth middle and surface - Use this understanding to maintain our environment - 4 objectives are ways of reaching their goal - Of objectivesAis science and the other 4 are earth systems engineering (there all about doing things for human needs. Earth System Science: how the globe works and parts interacts and how they function today and future 5 “Reservoirs” of Earth System 1. Atmosphere 2. Hydrosphere (water and ice) 3. Solid earth (rocks and soil) 4. Life (biota) 5. Stars and Planets Geologists were most interested with the first three not realizing the importance of life on earth system functions 2 - Even when that was understood effect of stars and planets were not understood (tides/moon) - These interact in complex ways Lecture #3 - There are no passengers on earth we are all crew members - The world is a human artifact (created by humans) - Earth systems engineering = managing earth systems Allenby claims - Humans have been conducting earth system engineering from the start of human race - Ex) the ice in the arctic, drill down and count the layers to determine age - Looked at lead in the ice, which contains evidence of the atmosphere at the time. Back to the roman empire - The amount of lead increased during the industrial revolution, we were effecting the earth even when our population was smaller - Lead dropped again when we went to unleaded gasoline (toxicity) Allenby - Talks about how E.S.E. in the past compares to E.S.E. now or in the future 2 main differences 1. Scale: the past it was more local and less global 2. Intent: in past regional/global effects were unintended and unanticipated Thomas Midgely: had greater impact on the atmosphere than any other organism in history - Engineer - Cars weren’t running properly so in 1921 he invented lead gasoline to reduce engine knocking - Significant impact on the atmosphere - He invented a refrigerator coolant or Freon the first chlorofluorocarbons (CFC) which will destroy the ozone. Coal Production - Cheap energy source used in the industrial revolution - Chart of coal produced over time but amount increased dramatically since then - There is 7000x as much as we did - Coal- mainly made of carbon, burn it with O2, and we get carbon dioxide (GHG warms the atmosphere) Producing materials - Steel production from mining for iron to make steel - Steel is represented by production and mining of iron - Exponential rise in the production of steel and aluminum and metals (metal production took off dramatically from the industrial revolution) 3 Years before Present Chart: Earth movement - Dramatic increase of earth movement at revolution - Shows both the movement for agriculture and movement for construction - Think about how other stuff is moved naturally (water is the largest mover by natural process) - Worldwide total consumption of resources (compared to the natural movement) - Humans move annually more stuff every year than all the other natural processes (humans move 4 times as much as other natural processes) BUT - Humans can’t produce and use earth materials without generating waste - Waste production has also gone up exponentially - Faces effects such as mass extinctions, human health effects, etc. - Chart: # of species lost each year, since industrial revolution the number of species lost each year has increased dramatically. This poses great concern. - Waste production is associated with species extinction. Why has there been such a dramatic increase in the impact of humans on the earth system? 1. More people, population growth has been overwhelming 2. Technological advancements and capabilities have increased (Ex) Midgely Allenby Ctnd. - Calls for conscious, controlled management and engineering of earth systems - In his paper he discusses the ‘big picture’issues - But we don’t have to always look to deal with the big picture, small things add up. - The idea of earth systems management is very old (Anton Chekhov) Earth system Management Credo: - Think globally but act locally - Everything you engineer or manage has an impact. Lecture #4 Chapter 1 Readings: Pages 2 to 11, 19 to 27. Continued from lecture 3 (E.S.E.) ArticleAllenby Review - Global ecosystem as a whole is reaching a stale due to human influence - Think of the concept of the tipping point 4 - Necessary to address root causes of how humans are causing biological change - The degree to which humans engineer the earth is a moral issue and not a technical one (technical aspects involved but decision needs to be made from a moral perspective) - We can do it but should we? If yes, to what extent? We have ethical responsibility to do ESE rationally and responsibly. - It’s a moral and ethical issue In managing earth systems there is an Ethical dimension - You need to define you desired endpoints, where are we headed what should we improve? What should be our ultimate goal be? Where are we heading? - The ultimate endpoint is sustainability!Asustainable earth system that can maintain itself Sustainable Development - Development that meets the needs of the present without compromising the ability of future generation to meet their own needs - Sustainable has been designated as jargon because it is used so often Allenby: Is sustainability enough? Model of the world: Martini Glass - Narrow at the bottom and wide at the top - The top wide are represents the richest fifth whom controls 85% of the wealth - The bottom is the poorest fifth whom controls only 1% of the wealth - The wealth of the worlds 300 wealthiest individuals is equal to the combined annual incomes of 41% of the human population- UN What is a suitable ethical framework for earth systems engineering? Need two things 1. Sustainability 2. Equity Managing the earth (ESE) requires: 1. Technical dimension 2. Ethical dimension 3. Economic dimension 4. Environmental dimension ***Add these 4 together and is combined to RISK MANAGEMENT (what risks are we willing to take for what benefits) RiskAnalysis and Risk Management (really what the rest of the course is about) - How to mitigate a geological hazard - All about minimizing damage, loss of life and injury - Similar approach used for all types of risk Earthquakes 5 - Several with over 100,000 deaths (Haiti and Indonesian most recent) SCENARIO - Gov’t of Ontario proposes to build a nuclear reactor on the shore of lake Ontario near Kingston - Our task: carry out a risk analysis and risk management study for the government focuses on seismic risk. - We need to carry this out in order to minimize damage from hazards, disasters and catastrophes HAZARD: something which might cause harm to people (death/injury/property damage) - ex) Avalanche causing fatalities or a landslide - There are landslides on mars is this a hazard? Yes because of mars rovers that cost billions of dollars a. Natural Hazards b. Anthropogenic Hazards: human induced (cars) - They can be intertwined: cars in the ice storm - We need to distinguish hazard from resources Hazard: Something that which may cause harm to people Resource: Something that is useful to us (ex) water too much or too little is harmful ***Diagram - Looking at water as a material - Amount of water on y-axis and time on the x-axis - For example, an up and down of the annual rainfall - Put boundaries in using green lines above and below. Between the two lines the water is acting as a resource but if you’re above or below it’s a hazard. This green line is a damage threshold. - This chart can be used for any material (Co2). It can be both a resource and a hazard. - Poison=Hazard, Remedy=Resource - Hydrogen Sulfide< too high it kills us but we all have a level of it in our blood that prevents hypertension Lecture #5 Hazard Continued How do you decide what the damage threshold is? - Partly by empirical observations and scientific studies - Ultimately by societal preference (choices) Consider “pollution” - Pollution is a hazard - The very notion of pollution is culturally dependent - We define what is or is not pollution (hazard) 6 - Think about smoking and how its evolved from smoking indoors to only outdoors - With this example we see that these green lines (damage threshold) can change over time ex) become closer together or further apart - Changes in human tolerance/sensitivity to the hazard Note also the consequences of “SYNERGY” - Snowfall: It’s a resource by boosting the water table in the spring - Wind: for turbines - Both of these are resourceful within the damage thresholds but too high or too low becomes hazard - BUT high snow and high wind in combination with each other despite each being within their individual damage threshold will become a hazard (together they might produce a hazard = blizzard) Let’s imagine a particular geographical location with a fixed human population and infrastructure (Kingston) - Lets imagine that we experience a hazard event (flood) - What are the three main factors that control how severe the hazard event is? When considering the GRAPH 1. Absolute amount (intensity): How far above or below the damage threshold 2. Duration of Event: How long it lasts above or below threshold 3. Rate of Change: too fast not enough time to adjust (Ex) sudden impact of large meteorite OR burning by humans of natural gas causing increase in CO2 resulting in global warming After a hazard event there are both LOSSES and GAINS - Some people lose and some people gain (generator sales, arborists) When does a hazard event become a: - Disaster? - Catastrophe? Deciding Factors 1. Extent of human loss of life 2. Extent of human injury 3. Extent of money loss due to property damage 4. Group versus individual 5. Reconstruction time 6. Societal reaction 7. Economic loss 8. Media coverage 9. Recovery time 10. Geographic scale: size of region 11. How preventable it was? 7 Why is the Distinction important? a. Government/world aid: influences the assistance provided b. Historical perspective: how often do really big events occur Truism in Disasters - The poor lose their lives while the rich lose their money - 90% of deaths are in the less industrialized countries - 75% of economic damage is in the more industrialized communities How big a problem is a Particular hazard? - How RISKY is it to be exposed to that hazard (for a particular location; Kingston) - The whole globe can still be your location (global warming) but most are more geographically specific RISK: the probability of the hazard occurring (Ph) X the severity of the consequences if the hazard happens (Sh) - Risk = Ph X Sh Ex) risk of bumping my toe - Ph (½) X Sh (1) = ½ Ex) Risk of serious injury in a car accident - Ph (1/100,000) X Sh (1,000,000,000) = 10,000 How do we “measure” Ph and Sh? 1. Empirical observations and scientific studies 2. Social/economic impact studies Lecture #6 Get the Hazard City Disk: www.mygeoscienceplace.ca Chapter 2 readings: Earthquakes Should we believe the experts with regards to a Hazard? - Wise to add a margin of safety in risk analysis - Ex) thickness of ice, experts will add a safety margin - Concept of Safety Factor (estimate of probability of failure) - Experts have probably already added a margin of safety How much risk are we willing to incur? - Once you have the data (ie. The determined values of Ph and Sh) you make your choice - It is entirely a matter of personal/societal choice! 8 Cost-benefit Analysis - Economic + environmental + social + personal choice - What risks are we willing to take for what benefits People’s perception of risk 1. Volunteer hazard: something you choose to do which makes it seem less risky 2. Non Volunteer Hazard: perceived to be much more risky - Common hazards such as a road accident we decrease risk because it’s so common Case study of Chlorinating Water in Peru - U.S.A. studies showed that chlorine in water elevates the incidence of bladder cancer - So in Peru they took the evidence in account they decided not to chlorinate the walls - In an ensuing cholera epidemic more than 3500 people were saved from bladder cancer by an early death **There are almost always opportunities foregone when we take precautions and danger accepted when we do not What is a life worth? - Is this a question we should be asking? - To whom is the life important? a. Individual person b. Relatives c. Company looking at employees d. Government e. Society as a whole - Apersons worth to society - Young vs. old, educated vs. non educated, present value vs. future value, rich vs. poor. Generic Approach to RiskAnalysis and Risk Management RiskAnalysis 1. Understand the hazard (in general) 2. Determine the RISK from that hazard for the region of interest (risk = Ph X Sh) Risk Management 3. Determine ways to reduce Ph and/or Sh 4. Do a cost-benefit analysis (determine what you can afford to do) 5. Implement mitigation techniques if warranted Lecture #7: NO CLASS Lecture #8 Movie Lecture #9 9 First step in a risk analysis of a natural hazard: Understand the Hazard 1. What causes earthquakes 2. Where do earthquakes occur 3. What energy do they release 4. What exactly causes damage - Faults What exactly causes earthquakes: They said the ground was behaving like a piece of wood - Apply stress to stick it’ll bend but it bends back (elastic material) - Too much stress and it will break (rupture) - They fault which is how the earth is behaving, the energy is released when the stick breaks (movement and noise) Elastic Rebound Theory: The rigid part of the earth can store elastic energy - When it breaks the elastic energy is released Earth quakes are associated with faults - Earthquakes happen when either a. Afault forms b. There is an episode of movement on a pre-existing fault - In both cases, stored energy si released Fault: a break/crack in rocks along which there has been appreciable displacement - For a big earthquake fault motion needs to be only a meter or so 1. Strike-Slip Faults: Horizontal motion - Shown in brick diagram - There are offsets in stream 2. Dip-Slip Faults: vertical motion or sub-vertical - Results in a FAULT SCARP - Two kinds: one where they move away from each other but in the fault plane or one where they move towards each other. A. Normal Dip Slip: “down the ramp” - Need to have force pulling away from each other away from the fault line - Top block moves down the ramp (text book on table analogy) B. Reverse Dip Slip: “up the ramp” biggest ones - Top block moves up the ramp - Need to have a force pushing against each other towards fault line (cars colliding) When rocks rub against each other in earthquake: rocks ground up - Look for features like a valley within the rocks because rocks have been washed away - Fault Breccia: a bunch of broken up rock pieces 10 - Body of water will often come in on the fault (rivers) - Humans like to occupy these areas (dams and reservoirs) - The rivers make canyons Where do earthquakes occur?? What energy do they release?? - There is a single point on fault surface where the energy is initiated (initial movement) Focus: The ‘point’source of energy release on the fault Epicenter: the point at the earth’s surface that is directly above the focus (why care?) - The closest distance at the surface is where the damage will be the greatest, we want to be far from the focus as possible Seismometer: instrument allowing us to do three things 1. Detect the energy from a quake 2. Measure distance to an earthquake and thus locate it 3. Measure the energy release during an earthquake Diagram: - You have the ground - Then a table on top with an arm system (like hangman) - Then there’s a spring on the end of the arm that has a weight on the end (huge mass) just off the ground - The paper sitting on the table is drawn on with a pen that hangs from the weight - Ground moves a bit, so does the table and the arm and the paper on it - But the heavy mass hanging will not move, thus the pen attached to the weightwill make a scribble on the paper that is moving below - The mass at rest tends to stay at rest - The paper below is on a roll creating the seismogram Lecture #10 ***Receiving first exercise about earthquakes today through Moodle*** - Due at the end of the first half of the course Seismometer - For horizontal ground motion, the paper roll sits horizontal - For vertical ground motion, the paper roll sits vertically - You typically need three seismometers at your location (costs a lot of money) - Having three lets you determine where the earthquake was give you a bit of control - Ideally you want to put it underground so that it is not effected by human activity - The crude drawing is not very sensitive but small shaking could pose threat (nuclear station) Sensitive seismometer 11 - Replace the mass with a magnet - When energy comes everything moves with a magnet - There is electric coil through the magnet which paired with the magnet creates a current and you can pick up the electrical flow (amplifies the info) Miniaturization - Small seismometer that can be put into the ground How do we find the focus of an earthquake? - In other words how far away is the earthquake - We first need to know what seismic waves are and how they behave - We have the focus of the earthquake in the earth - Underground they are called body waves but once they reach the surface they become surface waves Seismic Waves: seismic energy waves radiate out from the FOCUS of an earth quake as body waves - Some body wave motion gets transferred into surface wave motion when the body waves reach the surface - Surface waves generally cause the most damage at the surface - Two types of seismic waves 1. Love waves: horizontal side to side 2. Rayleigh waves: rotary waves (circular motion) Let us consider the BODYWAVES in more detail: there are 2 kinds - Ground moves in two different ways which is the two types 1. P-Waves: push-pull (compression-rarefaction) 2. S-Waves: shear (Stronger) What is the Velocity of seismic waves? (How fast do they move?) What does the velocity depend on?) - The Velocity depends on: Elasticity/Density 1. The more ELASTIC a material is, the higher the seismic velocity 2. The more DENSE a material is the lower the seismic velocity - Plato vs. Lacrosse ball (returns to shape and bounces) ***So both P-wave and S-wave velocities change when they move into a different material*** - There is a difference in the elasticity in P-waves than S-waves K and Mu = elastic moduli Measure of elasticity: - K= compressibility modulus: stress needed to compress the material (Indian rubber has big K value, plato does not) - Mu= shear modulus: stress needed to change shape (plato has small Mu value) - P-wave is going to be faster 12 Lecture #11 P-Waves travel faster than S-Waves (P-Waves = Primary Waves, S-Waves = Secondary Waves) Seismic Velocities for Rocks at Earth’s Surface P-Waves = 5.6 km/second S-Waves = 3.3 km/s → If there is an earthquake in Toronto, how long would it take until the first P-Wave reaches Kingston? Answer: less than 1 minute! (not much warning time) To measure distance to an earthquake focus, we use TRAVELTIMES Travel Times are the amount of time between the P- and S-Wave arrivals at your seismometer Think of Thunder as S-Waves and Lightning as P-Waves. The longer the time gap between the lightning (P) and the peal of thunder (S), the farther away the storm is. For Earthquakes: Since we didn’t know seismic velocities at depth, we needed to first create an empirical travel-time graph. For quakes of known location and time, obtain the P and S arrival time differences from seismometers around the world. To locate ‘Quake Focus’, you need a minimum of 3 seismometer stations. Each station draws a circle, point at which all circles meet is the epicenter. All earthquakes occur at depths at less than 700KM. 90% of earthquakes foci (focuses) are at depths of less than 100 KM. This is because only the outer part of the Earth is rigid enough (sufficiently elastic) to experience BRITTLE FAILURE (fault formation). Deeper into the earth is too plastic (unelastic) OR liquid?? Lecture #12 Earthquakes: How do we estimate the energy released by an earthquake continued Seismoic Velocities for rocks - P-waves 5.6 km/sec - S-waves 3.3 km/sec - Most quakes occur within 100 km of surface (90%) - All within 700 km Measure the intensity - Based on observed damage (Mercalli scale= Physical observation the damage people see) - Subjective - Varies with distance from epicenter Charles Richter - Worked out with numbers the amount of energy released - Height of squiggles on seismograph the more energy that is outputted Measure the RICHTER MAGNITUDE 13 - Aquantitative measure of energy released - Determined from the maximum s-wave amplitude on a seismogram (corrected for distance) Empirical Travel-Time graph - Travel time on y-axis and distance to epicenter on x-axis Logarithmic scale - Each integer on a scale represents an amplitude difference of 10 - Therefore magnitude 2 is ten times larger than mag
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