GEOL 106 lecture notes for final exam (with diagrams).pdf

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Department
Geological Sciences and Geological Engineering
Course
GEOL 106
Professor
John Hanes
Semester
Winter

Description
GEOL 106- Christine Hung Jan 7, 2013 The Dynamic Earth and the relationship between humankind and our ever changing planet Goals of GEOL 106 To help you ask the following questions and to find answers to them 1) what causes natural and anthropogenic hazards, disasters and catastrophes? 2) how do we minimize/maximize the risks associated with hazards, disasters and catastrophes? 3) how does an understanding of geology allow us to answer questions 1) and 2) Why has there been an increase in the impact of natural hazard events ?  increased population growth in general (and in the zones that are more disaster prone) (now at over 7 billion)  increased use of natural resources o humans can jump up and hit "nature" in the face o oil sands mining o Tanker-Train Derailment (New Brunswick, Jan 7, 2014) o the story of the Aral sea (nearly drained for irrigating the land for cotton farming, exposed dry seabed to wind, pesticides in mud were blown toward the cities, became a hazard area)  big bodies of water have a moderating effect on nearby climate (Aral sea extended the cotton growing season, as the sea shrank, the cotton growing season shortened) Jan 9, 2013  how do we manage the risks that these "natural" and anthropogenic (human created) hazards pose? o "Once a photograph of the Earth taken from outside is available ... a new idea as powerful as any in history will be let loose" Fred Hoyle (astronomer) o --> changes how we think of ourselves, when earth was seen as something so fragile from space, we realize that we have to take better care of it  increase in environmental laws, increased awareness o "it is so incredibly impressive when you look back at our planet from out there in space and you realize so forcibly that it's a closed system"  2007 = 50 year anniversary of Sputnik - Oct 4, 1957- first human made object that went into space  "the world changes as we learn to see it in new ways and the way we see the world depends on how we use it" from "hand END Technology and the Limits of Nature (1993) by David Ruthenberg  "Only one Earth- the care and maintenance of a small planet " (now the earth is seen as small and limited vs huge and vast from the early explorers)  "we made all the way to the moon to finally discover the Earth" William A Anders (1968)  view of the earth from space led to increased awareness of the fragility of the earth and the need to better understand it  the president of the USA commissioned a study of the earth system o --> what do we need to know in order to live in concert with this fragile earth? o scientific writings about "managing planet earth" "our previous planet- why saving the environment will be the next century's biggest challenge" o the "pearl" model of the earth --> it's valuable but fragile, needs to be kept in a protective shell The goal of the solid earth sciences  to understand the past, present, and future behaviour of the whole earth system . From the environment where life evolves on the surface in the interaction between the crust and its fluid envelopes (atmosphere and hydrosphere), this interest extends through the mantle and the outer core to the inner core.  a major challenge is to use this understanding to maintain an environment in which the biosphere and humankind will continue to flourish o we need to understand what's happening not only on the surface The objectives associated with this goal  a) = science, b) c) d) e) = Earth System Engineering/Managing Earth Systems a) understand the processes involved in the global earth system- with particular attention to the linkages and interactions between its parts (the geospheres) b) sustain sufficient supplies of natural resources c) mitigate geological hazards d) minimize and adjust to the effects of global and environmental change e) improving "standard of living" Earth system science - the earth system is a set of interacting subsystems  can't separate and isolate things like science tends to do, but have to look at how everything interacts  new approach to the study of our planet is referred to as earth system science.  Its practitioners strive to understand how the world works on a global scale by describing how its parts and their interactions evolved, how they function today and how they may be expected to function in both the near and distant future  in this light, the earth system is seen as a set of interacting subsystems characterized by processes that vary Earth systems Engineering: The world as Human Artifact - by Brad Allenby  "manage the earth's complex systems and their dynamics is the next great challenge for the engineering profession"  Allenby claims that: humans have been engineering/ managing the earth since the start of the human race  claims that have been conducting earth system engineering (ESE) from the start of the human race How do we study the past?  study tree rings --> cut down a tree and expose the growth rings; each year a new growth ring is formed on the outside surface o thickness of ring can tell us about climate conditions --> thick = good growing season with lots of rainfall and ideal temperatures, thin = drought/dry year, scar from forest fire o can extract a plug sample from the tree bark to avoid cutting down the tree  look at ice cores from ice sheets - Greenland ice sheet o every year a pile of snow builds up, dust in the atmosphere gets trapped in the snow o annual ice layers build up, older ones at the bottom, youngest ones on the top surface o drill a hole down into the ice sheet to extract an ice core and study the layers o winter has darker layers because wind blows in more dust vs lighter layers formed in summer o can study the amount of lead concentration in the ice (ie. significant spike from the industrial revolution)  even 2000 years ago, Romans were smelting lead and were unknowingly affecting/engineering the earth  study of lead contamination in the ice cores from the ice sheets in Greenland  can determine if a fire occurred- ie. burning off the land to grow crops  burning of vegetation releases CO2 into the atmosphere (greenhouse gas) Scale of earth system engineering/management "the earth is increasingly a product of human engineering" Brad Allenby We can certainly see the increase by simple observation (qualitatively) We can also quantitatively measure the increase  ex. how much material do humans move compared to the rest of natural processes?  human movement- ie. metal production, mining, oil, gas, rock; agriculture (measuring how much produce is grown) How do you measure the amount moved by other natural processes  measure sediment carried by rivers to the sea  humans move 4 TIMES AS MUCH AS OTHER NATURAL PROCESSES o BUT we can't produce and use Earth's materials without generating waste by-products so our waste production has also increased exponentially Jan 10, 2014 Chapter 1: pages 2-11  introduction  1.1 why studying natural hazards is Important  1.2 Magnitude and frequency of hazardous events  1.3 rule of time in understanding hazards pages 19-27  1.5 fundamental concepts for understanding natural concepts for understanding natural pressures hazards  1.6 many hazards provide natural service function  1.7 climate change and natural hazards We can QUANTITIVELY MEAUSRE THE INCREASE  ex. how much carbon dioxide have humans added to the atmosphere?  from coal production: ever since the industrial revolution there's been a significant growth o companies have to tell the government how much coal is being mined o coal = mainly carbon (C) o burn it with oxygen (O2) o produces carbon dioxide (CO ) which is a GREENHOUSE GAS --> gas warms the atmosphere, 2 increase of global temperature) 1) measure it directly day after day (collect bottles of gas and measure how much 2O is in the gas (ppm))  we've only been doing this since the 1950's  Charles Keeling began measuring it at the top of Manua Loa volcano (Hawaii) 2) to go back farther in time, measure CO2 in air bubbles trapped in ice sheets in Antarctic and Greenland glaciers  this take us back to over 400 000 years ago  the levels of C2 had a constant (roughly) plateau until the industrial revolution o evidence that humans made such a huge impact on the environment How does past ESE compare to future ESE? 2 main differences 1) SCALE --> in past, was more local, less global 2) INTENT --> in past, regional/global effects were unintended and unanticipated ie. The first automobile --> lead to many negative environmental and health effects another example: Thomas Midgely "had more impact on the atmosphere than any other single organism in earth history"  in 1921, Midgley invented leaded gasoline (tetra-ethyl lead) o was used in white paint, had toxic effects on babies that chewed on paint in their cribs o --> negative heath effects (lead poisoning and neurological damage) so lead was eventually banned  in 1930-31 Midgley invented Freon to be used in refrigerators o the first of the CFCs: chlorofluorcarbons --> breaks down OZONE in the upper atmosphere which protects the earth from the sun's UV rays Species Extinctions since 1800 --> ever since the 1900s, there's been an exponential number of species extinctions (a negative result of human impact) "The earth, as it now exists, is a human artifact" "It reflects the (frequently unintended and unconscious, but nonetheless real) design of a single species" - Allenby Why has there been such a dramatic increase in the impact of humans on the earth system?  exponential POPULATION GROWTH  advances in our TECHNOOGICAL CAPABILITY to make an impact on the environment o exponential increase in total amount of earth moved by humans o exponential increase of world oil consumption (even more rapid growth than world population)  in USA from 1900-2000, population grew 3.6 times, energy use went up 10 times  demand for increased HUMAN LEVEL OF AFFLUENCE o our rate of material production has been greater than our rate of population growth --> therefore our average level of affluence has gone up (abundance of money, property, goods, wealth) In the Allenby paper, he mainly discusses the "big picture" issues  But I would argue that ANYTHING THAT ANY OF US DOES IS EARTH-SYSTEMS ENGINEERING/MANAGEMENT  "when I hear the sigh and rustle of my young woodlands, planted with my own hands, then I know that I have some slight share in controlling the climate" - Anton Chekhov (1899) - Russian playwright o plants consume carbon dioxide and release oxygen as a waste by-product  Earth-system Engineering/Management credo: THINK GLOBALLY ACT LOCALLY o --> everything you do has an impact on the earth  "there are no passengers on spaceship earth, we are all crew members" Marshall McLuham (1911-1980) Canadian philosopher of communication theory  "if the success or failure of the planet and of human beings depended on how I am and what I do, how would I be? What would I do?" R Buckminster Fuller - discovered the geodesic dome (very lightweight and strong structure) THERE IS GOOD MANAGEMENT AND BAD MANAGEMENT --> which will we choose? so Allenby calls for CONSCIOUS, CONTROLLED management/engineering or earth systems  Allenby: the question "to what end are humans engineering, or should humans engineer, the earth" o is a MORAL one, not a technical one! o we can do it, but should we? and if yes, to what extent? towards what end?  "the issue, then, is not whether we should begin Earth System engineering, because we have been doing it for a long time, albeit unintentionally. The issue is where we will assume the ethical responsibility to do ESE rationally an responsibly"  --> WE HAVE A MORAL AND ETHICAL RESPONSBILTY In managing earth systems, THERE IS AN ETHICAL DIMENSION  you need to define your DESIRED ENDPOINTS  ie. you need to know where you are going  is the ultimate endpoint SUSTAINABILITY? (to not run out of resources) SUSTAINABLE DEVELOPEMNT  development that meets the needs of the present without compromising the ability of future generations to meet their own needs -(our common future, world commission on environment and development - WCED 1987) "The sight of the immense masses of timber passing my window every morning constantly suggests to my mind the absolute necessity there is for looking into the future of this great trade. We are recklessly destroying the timber of Canada and there is scarcely a possibility of replacing it. " - Sir John A Macdonald 1815-1891 IS THIS SUSTAINABLE?  do your ecological footprint at www.myfootprint.org  how many earths would it take to support the whole population at your level of affluence? Jan 14, 2014 Is the endpoint of sustainability enough? --> no! Martini glass distribution of the world wealth  85% of the wealth belonging to the richest fifth, 1% of the wealth belonging to the poorest fifth What is a suitable ethical framework for earth-systems engineering?  SUSTAINABILITY AND EQUITY (are equally as important)  "the wealth of the world's 300 wealthiest individuals is equal to the combined annual incomes of 41% of the human population" United Nations Development Programme (UNDP) 2000 report University of BC conservation biologist: "This is not rocket science. It way more complicated than that" "Minimizing the RISK and scale of unplanned or undesirable perturbations in such systems is an obvious ESE objective" -Allenby --> RISK MANAGEMENT Risk Analysis and Risk Management EARTH-SYSTEM MANAGEMENT/ENGINEERING IS ALL ABOUT RISK ANALYSIS AND RISK MANAGEMENT  how to MITIGATE (geological) HAZARDS  ie. minimize damage and loss of life/injuries (similar approach used for ALL types of risks)  ie. earthquakes caused hundreds of thousands of deaths (we will do a detailed case study) Earthquake risk analysis and risk management  The government of Ontario proposes to build a nuclear power plant on Lake Ontario shore just west of Kingston  our task: carry out a risk analysis and risk management study, for the government, focused on SEISMIC RISK (ie. earthquake risk) we need to look at the GENERAL APPROACH to Risk analysis and risk management  we 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) o ie. avalanche, landslide o there are landslides on Mars: is there a hazard from Martian landslides? --> yes! there's human property (rovers and vehicles) on mars-- > if they get damaged, costs more money that could be allocated to other human resources  there are both "NATURAL" HAZARDS and ANTHROPOGENIC (human induced) HAZARDS o ie. car crashes o both kinds are often intertwined (ie. ice storm causing car crashes) We need to distinguish HAZARD from RESOURCE  RESOURCE: something that is useful to us  HAZARD: something which may cause harm to people (death, injury, property damage)  Water as a resource: to drink, wash, hydroelectricity  water as a hazard: flooding, drought o when the amount of a resource is below or above the "DAMAGE THRESHOLD", that resource becomes a hazard o ie. too much precipitation --> flooding hazard, but too little precipitation --> drought hazard  "all substances are poison, there is none which is not a poison. The right dose differentiates a poison from a remedy" - Paracelsus  poison --> hazard, Remedy --> resource  "sewer" gas: Hydrogen sulphide o poison: when concentrations are too high, can be deadly o remedy: can help relax the blood vessels and help regulate blood pressure What's the hazard?  mosquitoes carrying malaria can kill millions of people  to kill mosquitoes, DDT was used but was then banned in most countries because of health risks  DDT- a hazard or resource? is DDT Africa's last hope to controlling deaths controlled by malaria? Hazard vs Resource  how do you decide what the DAMAGE THRESHOLD is? o partly by empirical observations and scientific studies o ultimately by societal "preferences" (ie. choices) Consider "POLLUTION" = HAZARD  the very notion of POLLUTION is culturally dependent- we define what is or is not "pollution"  note: over time, there may be changes n human tolerance/sensitivity to the hazard o therefore damage thresholds may change over time note also the consequences of SYNERGY  snowfall in Kingston --> skiing, recreation as a resource  wind turbines as a resource to generate energy  but SNOW + WIND = BLIZZARD --> HAZARD, WIND + WATER = MONSOON  each on its own might be a "resource" and no problem --> but together, they might produce a hazard Jan 16, 2014 Readings: chapter 2- Earthquakes Let's imagine a particular geographic location with a fixed human population and infrastructure (buildings/roads/hospitals/police force/ambulance/ emergency crew) ie. Kingston  let's imagine that we experience a hazard "event" (ie. we go past the damage threshold)  a flood event happens what are the 3 main factors that control how severe the hazard event is?  1) ABSOLUTE AMOUNT (intensity): ie. how much water is there? o how much higher or lower than the hazard threshold  2) DURATION OF TIME: how long do we stay in the hazard zone? o the longer it lasts for, the more damage can occur  3) RATE OF CHANGE: how rapidly the hazard zone is reached? o if the hazard zone is reached in a very short amount of time, not enough time to adjust to the change and respond Hazard event: LOSSES AND GAINS  after a hazard event, there are both losses and gains o some people lose (property damage, financial loss, loss of power, deaths, injuries) o some people gain (gave more business to restaurants, people selling candles/flashlights/energy generators, tree cutting companies etc.)  Haitian earthquake may have left clues to petroleum reservoirs that could aid economic recovery  gains from recession: less automobile accidents, less people drinking/smoking When does a HAZARD EVENT become a DISASTER? a CATASTROPHE? What are the factors that decide that?  POPULATION: the number of people killed/ injured  AMOUNT OF PROPERTY LOSS - extent of financial loss  AREA AFFECTED - geographic scale  GEOGRAPHIC AREA INFRASTRUCTURE AFFECTED- resources/industrial areas affected  RELIEF PREPAREDNESS  GROUP VS INDIVIDUAL  RECONSTRUCTION TIME  SOCIETAL REACTION Why is the distinction between a disaster and a catastrophe important? 1. governmental/world aid 2. historical perspective - how often do really big events happen? TRUISM IN DISASTERS "the poor lose their lives while the rich lose their money"  90% of the deaths are in the less industrialized countries  75% of economic damage is in the more industrialized countries o more industrialized countries have the wealth to build more stable buildings with better quality materials, but cost a lot more to rebuild it when they get damaged What type of hazard event is responsible, on average, for the MOST DEATHS?  CIVIL STRIFE (ie. wars, wars over resources/land)  drought  earthquakes/volcanoes  storms/floods  other (ie. epidemic) How big a problem is a particular hazard? ie. how RISKY is it to be exposed to that hazard?  for a particular location what is the RISK to humans from that hazard? o RISK: (the probability of the hazard occurring) x (the severity of the consequences if the hazard happens) o risk = H x H  ie. risk of bumping toe o pH= 1/2, H = 1 so risk = 1/2  ie. risk of serious injury in an automobile accident o PH= 1/100 000, SH= 1 000 000 000, so risk = 10 000 How do we measure P anH S ? H  empirical observations and scientific studies  social/ economic impact studies (how it affects people psychologically, socially, how does it disrupt society) Should you believe the "experts" ?  wise to add a margin of safety in risk analysis  --> concept of SAFETY FACTOR o ie. need 5cm to safely skate on ice, but add a safety factor to 8cm o but if the safety factor is too big, then will miss out on opportunities to skate How much risk are we willing to incur?  once you have the "data" (the determined values of PHand SH) you make your choice  it is ultimately a matter of personal/societal choice Jan 17, 2014 Readings: Chapter 3, Tsunami Risk Analysis and Risk Management- how to mitigate hazards Fungibility- "a person, and society, needs to seek a prudent balance between the advantages of boldness and the advantages of caution"  there are almost always opportunities foregone when we take precautions, and danger accepted when we do not (there's always a trade off) People's perception of risk varies with the type of risky activity Tending to increase risk perception  involuntary hazard (radiation fallout)  dreaded hazard (cancer)  events that have many fatalities (airplane crash)  process not well understood (nuclear accident) Tending to decrease risk management  volunteering hazard (mountaineering)  common hazard (road accidents)  events that have fewer fatalities (car crash)  process well understood (snowstorm) Back to our earthquake risk analysis and risk management of building a nuclear power plant in Kingston... Generic approach to RISK ANALYSIS AND RISK MANAGEMENT RISK ANALYSIS 1. understand the hazard (in general) 2. determine the RISK from that hazard for the region of interest (risk H P H S ) RISK MANAGEMENT 3. determine ways to reduce P aHd/or S H o for example: for an avalanche hazard in a given region, how can we reduceHS (severity of consequences if the hazard happens) to essentially 0 ? (don't allow skiers to go to avalanche prone areas of the mountain) 4. do a "COST-BENEFIT" ANALYSIS o determines what you can "afford" to do o "cost-benefit" analysis --> economic + environmental + social + personal choice  what risks are we willing to take for what benefits? 5. implement mitigation techniques if warranted and to the extent that you choose The first step in a risk analysis of a natural hazard: UNDERSTAND THE HAZARD 1. what causes earthquakes? 2. where do earthquakes occur? (use seismometers) 3. what energy do they release? (use seismometers) 4. what exactly causes damage? 1) What causes earthquakes? --> MOVEMENT ON FAULTS FAULT : a break/crack in rocks along which there has been appreciable displacement  ELASTIC REBOUND THEORY : when stress is applied to something, it will bend and bounce back to its original shape when the stress is released  the rigid part of the earth can store elastic energy/strain (temporary deformation) o --> when it breaks, the elastic energy is released and the elastically deformed material returns to its original shape o if the strain continues to increase, the deformed material will eventually rupture, making the deformation permanent  earthquake cycle 1) long period of inactivity along a fault segment 2) accumulated elastic strain produces small earthquakes 3) foreshocks may occur hours or days before a large earthquake (sometimes this stage is absent) 4) mainshock/aftershocks occur Earthquakes are associated with FAULTS  earthquakes happen when either o a fault forms o or there is an episode of movement on a pre-existing fault  in both cases, STORED ENERY IS RELEASED  for a big earthquake, fault motion needs to be only a metre or so HOW DO WE "RECOGNIZE" A FAULT?  look for rock/soil layers that have been SHIFTED FAULT TERMINOLOGY  1) STRIKE-SLIP fault - horizontal motion  2) DIP-SLIP fault - sub-vertical or vertical movement (results in a FAULT SCARP) o a) NORMAL DIP-SLIP FAULT "down the ramp" o b) REVERSE DIP-SLIP FAULT "up the ramp" (most damaging because the most energy is released, like cars colliding) Note: Many rivers occur along faults  because the broken up rocks can be more easily washed away, making a deep river  and we often build major DAMS on such rivers o because the rivers make canyons 2) Where do earthquakes occur? FOCUS: the "point" source of energy release on the fault (somewhere underground) EPICENTRE: the point at the Earth's surface that is directly above the focus  important because it's the closest place at Earth's surface to the focus (likely where the most energy will be released at the surface) How do you find the FOCUS and the EPICENTRE? --> USE SEISMOMETERS Seismometers allow us to  detect the energy from a quake  measure distance to an earthquake and thus locate it  measure the energy released and in what direction it was released during an earthquake How do they do this? inertial mass: a mass at rest tends to stay at rest  an inertial mass is dangling by a spring that is fixed to an arm  there is a pen dangling from the inertial mass with its tip touching a strip of paper that slides under the pen  as an earthquake occurs and shakes the machine, the inertial mass stays at rest while the pen draws squiggles on the paper that correspond with the amount of energy released o can also detect the weakest of earthquakes by using very sensitive seismometers that use a magnet as the inertial mass, and as a metal coil rubs against the magnet, a metal wire connected to a voltmeter will generate an electric current that is recorded How do we actually 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  seismic waves: seismic energy waves radiate from the FOCUS of an earthquake as BODY WAVES o (which translate to SURFACE WAVES - on the earth's surface and into the atmosphere)  when body waves reach the earth's surface, some of the motion gets transformed into surface wave motion o 2 kinds of surface waves o RAYLEIGH: circular motion o LOVE: horizontal, side-to-side  surface wave motion is the most damaging to human structures Body waves (2 kinds) 1. P-WAVES : push-pull (compression-rarefaction) a. the crust vibrates forward and back along the path of motion 2. S-WAVE: shear (up and down) What is the VELOCITY (speed) of seismic waves? how fast do they move?) And what does the velocity depend on? the VELOCITY of P and S waves depends on ELASTICITY/(divided by) DENSITY of the material they are passing through  the more ELASTIC a material is, the HIGHER the seismic velocity  the more DENSE a material is, the LOWER the seismic velocity o so both the P-WAVE and S-WAVE velocities change when they move into a different material Speed of P-waves = sqrt((K + 4/3mu)/e) Speed of S-waves = sqrt (mu/e)  (how compressible the material is has no bearing on S-waves)  P-wave travel faster than S-waves because both the K and mu are in the numerator, and mu is multiplied by 4/3 o so P- actually stands for PRIMARY, and S- stands for SECONDARY  where e = density  K and mu = elastic model o K = how compressible the material is o mu = how easy it is to change the shape seismic velocities for rocks at earth's surface  P-WAVES = 5.6 Km / second  S-WAVES = 3.3 km/second o just know that P-WAVES (approx 6km/s) travel twice as fast as S-WAVES (approx 3km/s)  for an earthquake in Toronto : ~ 250 km from Kingston o how long until the first P-WAVE reaches Kingston? o ~50 sec- 1 minute! not much warning time! So finally, to measure distance to an earthquake focus, we use TRAVEL TIMES  travel time: the time between the P- and S-WAVE arrivals at your seismometer  shorter the time gap, the closer you are to the focus of the earthquake o think about THUNDER = S and LIGHTNING = P (lightning travels faster than thunder) o the longer the time gap between the flash of lightning and the peal of thunder, 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 earthquakes of KNOWN LOCATION and TIME, obtain the P-S ARRIVAL-TIME DIFFERENCES from seismometers around the world  plot the time difference on the empirical travel-time graph to measure the distance to the focus  need a min of 3 seismic stations to locate the focus of an earthquake o where the 3 spheres (radius being the distance to the focus) intersect underground is where the epicentre is (process called "triangulation") o the epicenter is directly above the focus at the surface of the earth o if the focus is deep in the ground, won't cause as much difference as if it was very close to the surface of the earth What DEPTH do earthquakes occur at?  radius of earth (ie. distance from surface to center) = approx 6000 km  earthquakes occur at less than 700 km depth  ie. in the outer 10% layer of the earth (700km/6600 km)  and 90% of earthquake foci are at depths less than 100 km Why do earthquakes only occur in the outer 10% of the earth?  only the outer part of the earth is RIGID enough (ie. sufficiently ELASTIC) to experience BRITTE FAILURE (FAULT FORMATION)  deeper in the earth, it is too PLASTIC (or liquid?) (3) WHAT ENERGY IS RELEASED? --> How do we estimate energy released from a earthquake? 1) Measure the INTENSITY (energy estimate)  based on observed damage (eg. the MERCALLI SCALE)  does not make use of seismometers o --> subjective/qualitative measurement o --> varies with distance from the epicenter Jan 24, 2014 How do we actually measure the energy released? 2) Measure the RICHTER MAGNITUDE - a qualitative measure of energy released  determined from the MAXIMUM S-WAVE AMPLITUDE on a seismogram (corrected for distance) o maximum amplitude of ground shaking determines Richter magnitude  each integer on the scale represents an amplitude difference of a factor of 10 (logarithmic scale) o ie. magnitude 2 = 10x the amplitude of magnitude 1 o each magnitude integer step corresponds to approximately a 30-FOLD difference in energy release  how much more energy is released in a magnitude 7 earthquake than in a magnitude 5 earthquake? (30 x 30 = 900 times more energy is released)  how about a magnitude 8 earthquake? (30^3 = 27 000)  how about magnitude 9? (30^4) o it is an open-ended scale --> we don't know the absolute maximum value  the largest earthquakes ever recorded are ~9 on the Richter scale  earthquakes <2.5 magnitude are not felt by humans o but these low-energy earthquakes might be important for our nuclear reactor How do you calibrate the Richter magnitude? What do the Richter numbers mean in terms of actual energy released?  compare to known explosions (eg. nuclear blasts, world trade towers collapsing) What is the range of earthquake magnitude  largest recorded earthquake - Chile 1960 (M 9.)  equivalent to annual USA energy use How Frequent are earthquakes?  about 100 000 M3 small earthquakes  big earthquakes happen rarely , >7 = 20/year POWER-LAW RELATIONSHIPS  on a LOG-LOG plot (both x and y axes use a logarithmic scale) you get a straight line (4) WHAT EXACTLY CAUSES DAMAGE?  determine this by (1) empirical observations, (2) laboratory experiments, (3) computer modelling In general 1. the CLOSER you are to the quake, the GREATER the damage 2. the GREATER the magnitude of the quake, the GREATER the damage but this is modified by natural and anthropogenic conditions  natural: nature of soils/rocks  anthropogenic: nature of the structures that we build Earthquake hazards - (what exactly causes damage) (1) surface faulting (2) ground shaking (3) ground failure (4) tsunamis (5) fires (6) disruption of water supplies/disease (7) human -induced seismic hazards 1. SURFACE FAULTING a. structures built on the fault will be disrupted by the tearing motion b. so don't build right on an ACTIVE FAULT c. but people do! eg. San Francisco, and other parts of the San Andreas fault 2. GROUND SHAKING a. this is generally the greatest threat to buildings and people b. in a big earthquake, the shaking can be severe; even hundreds of km away from the epicentre c. most ground-shaking damage is generally a direct consequence of SURFACE WAVE motion i. (since they're always bigger than the P-and S-waves) d. and if you are close to the epicenter, the P- and S- waves will affect you Jan 28, 2014 (2. Ground Shaking) Material Amplification Effect  when seismic waves SLOW DOWN as they pass into another material  some of the energy is transferred into GREATER SHAKING  the amount of shaking also depends on the NATURE OF THE SOIL/ROCKS in the area even if 2 locations are at the same distance away from the epicenter o ROCK= least shaking (higher velocity) o SAND/STIFF SOIL= intermediate shaking (medium velocity) o CLAY/SOFT SOIL= most shaking (lower velocity) o the most severe shaking is in WATER-SATURATED CLAY SOIL  ie. Loma Prieta earthquake near San Francisco (1989)  ie. 1985 earthquake near Acapulco, AFTER-SHOCKS  smaller earthquakes that occur SOON (minutes after up to a year after) after the MAIN-SHOCK, with epicentres in the same area as the main shock  --> aftershocks can cause collapse of already-damaged buildings o since the still standing buildings are compromised in stability, sometimes rescue missions are called off because they can't risk the workers being trapped in a building rescuing people (WHAT EXACTLY CAUSES DAMAGE) 3. GROUND FAILURE A. LANDSLIDES (rocks and/or soils) a. eg. Hegben, Montana 1959 b. eg. Yungary, Peru --> Mt. Huascaran 1970 (M8) (15 km in 4 min --> 220 km/hour) B. LIQUEFACTION OF SOILS a. sand or clay soil that changes strength when shaken b. can flow like a liquid (only some specific types of clay soil/sand will act this way) (ie. quicksand) c. clay is made of tiny particles (like sheets/cards), when shaken particles lie parallel to each other and slide against each other and flow like a liquid d. eg. Alaska 1964 (M 9.2) e. eg. St. Jean Vainney, Quebec 1971 4. TSUNAMIS  Japanese word for "harbour-wave"  colloquial: "tidal wave"  --> SEISMIC SEA WAVE  generated by earthquake at sea (fault line under the sea, energy is released into the water--> creating a huge wave)  ordinary (wind- produced) waves: 10-20 m in wavelength, up to 30 m in amplitude  tsunami waves: wavelength up to several 100 km, amplitude only 1 m high o velocity in open ocean = 500-800 km/hour (speed of a passenger jet plane) o as the wave approaches the sloping sea floor near shore, the wave SLOWS, friction is created and the water piles up to huge waves with heights as much as 60 m or more (an 18-storey building) o THERE WILL BE MORE THAN ONE TSUNAMI WAVE! o note: a side to side strike-slip fault motion will NOT cause a tsunami since it doesn't push the water upwards What about a tsunami in lake Ontario?  probably not very big! maximum of around 2 m  why? because of the shallow water depth o a) which leads to only a small amount of water is displaced o b) speed of the tsunami waves is low  BUT a big lake tsunami can happen if it is triggered by a major LANDSLIDE o fortunately, there are no high, steep mountain sides around lake Ontario TSUNAMI CAUSES 1. Seafloor earthquakes 2. Underwater landslide 3. Collapse of the flank of a volcano into the sea 4. submarine volcanic explosion 5. impact of meteorite into the ocean 5. FIRES  surface faulting and ground shaking can sever electrical power and gas pipelines --> causing a fire  these fires may be difficult to suppress because firefighting equipment may be damaged, streets, roads, and bridges blocked, and water mains broken  appliances such as gas water heaters may topple when shaken --> produce gas leaks that may ignite  eg. the 1906 "fire" in San Francisco 6. DISRUPTION OF WATER SUPPLIES AND DISEASE  water pipelines disrupted so fires can't be put out  cholera epidemic (Haiti 2010)  parasites, diarrhea, sanitary facilities compromised, water supplies contaminated 7. HUMAN INDUCED SEISMIC HAZARDS a) Dam construction  loading of the earth by water changes the stress regions --> quakes can happen  the large reservoir of water held by the dam can be hazardous when the dam is damaged and water is released  water infiltration (percolation) below dam into the ground can "lubricate" faults --> quakes can happen --> possible dam failure (et. malpasset dam 1959, France)  possibility of earthquake control by injecting water into the fault to create various small earthquakes to release the stress b) Mining Underground  the rocks will "squeeze" into the newly opened space  due to the release of pressure, can result in sudden ROCKBURSTS in the mine (eg. Sudbury Ontario) (Risk Analysis) 1) understand the hazard 2) determine the risk from that hazard for the region of interest (riskH= PHx S ) (Risk Management) 3) determine ways to reduce P Hnd/or S H 4) do a cost-benefit analysis --> determines what you can "afford" to do 5) implement mitigation techniques if warranted (and to the extent that you choose) Jan 31, 2014 (2) ASSESS SEISMIC RISK OF AREA 1. locate and determine NATURE OF FAULTS in the area  look on the ground, and from the air (and space!) --> but there can be HIDDEN FAULTS  set up seismometers to help locate faults o only effective for faults that have moved since seismometers were set up  note: fault zones are very complex (not just a single fault, there could be several in an area)  but does every fault produce earthquakes? --> NO, SOME FAULTS ARE INACTIVE if it has not moved in the last 2 million years  some are POTENTIALLY ACTIVE if it has moved in the last 2 million years  some are ACTIVE if it has moved in the last 10 000 years are there faults in the Kingston area?  yes! all the way from small ones, up to very big ones (ie. the St. Lawrence River)  but are any of them ACTIVE? 2. study past earthquake HISTORY in the area a) which faults are most active? b) what sort of energy is released by earthquakes? c) how often do big earthquakes occur? 1) set up SEISMOMETERS  gives an idea of which faults are most active  gives some idea of frequency and magnitude of earthquakes  CRITICAL TO COLLECT AS LONG A SEISMIC RECORD AS POSSIBLE o for example, let's look at Canada- where are the zones that are prone to earthquakes? o western Canada, Arctic, Eastern Canada o is the arctic region high risk? --> no! because the population there is low. therefore more money will be invested to mitigate risks in the west and east coast 2) determine RECURRENCE INTERVAL for big (>M7) earthquakes in the area  recurrence interval- the time (# of years) between successive earthquakes  power-law relationship (big earthquakes don't happen very often, lots of small ones) how do we determine RECURRENCE INTERVAL? a) look at human historical records (goes back before seismometers) b) Dig trenches and pits on the active faults to identify ancient (big) fault movements that would have created big earthquakes Feb 4, 2014 Determining the age of the layers in relative time  "Law of superposition" (layers at the bottom are older, layers at the top are younger)  "Law of Cross-cutting relationship" - fault cuts across the layers, therefore the fault is younger than the layers Step 1: determine the RELATIVE age of the fault Step 2: determine the ABSOLUTE age (bracket) for fault movement using carbon-14 dating of organic PEAT layers (dead organic matter) --> the time since the organic matter died can be determined by the C method  most of the carbon in the atmosphere is C , the C is created when N is converted into 14 14 C by trees. After the tree dies, the amount of C in the tree decreases at a fixed rate --> we measure the ratio of C / C as the C is converted into N again (1 half-life for C is 14 5730 years)  so C dating (and other radiometric dating methods) can be used to determine when a fault last moved (if your seismometers haven't already told you if it's active or not)  but it is a "subjective" determination to decide if a particular movement event was a "BIG" earthquake or just a small one c) Look for evidence of ancient tsunamis, and ground elevation/subsidence  use carbon 14 dating on the buried swamp layers (dead organic matter) beneath the tsunami sand layer to determine the age of the earthquake  ground elevation and ground subsidence: ie. there was originally a forest but it died because a tsunami came in and flooded that area with water-- trees died  Los Angeles, California--> 9 major events in 1400 years --> therefore recurrence interval of 160 years (last big one was in 1857 AD but note that events are not evenly spaced) 3) construct PROBABILITY and EARTHQUAKE HAZARD MAPS  to help future planning --> show where the earthquake-prone areas Feb 6, 2014 3. determine the GEOLOGIC/GEOGRAPHIC FACTORS in the area (nature of soils/rocks in area) a) Map out locations of different rocks/sand soils/ clay soils that have VARIABLE SHKAING CHARACTERISTICS b) map out zones of sand and clay that are PRONE TO LIQUEFACTION c) map out locations of CLIFFS AND HILLS that are at risk of LANDSLIDES d) map out TSUNAMI-HAZARD ZONES  shorelines of oceans and lakes (but tsunamis will be small) 4. determine HUMAN INTERACTIONS with the potential hazard in the area (population and property) a) what is the distribution of the population in the zone? Particular attention to proximity of people to HIGH HAZARD ZONES  if the population is high in the high-hazard zone, it is also a HIGH-RISK ZONE. if that area isn't inhabited, then it isn't a high-risk zone b) what is the nature of the human INFRASTRUCTURE ?  where are the buildings, roads, bridges, tunnels with respect to high-hazard zone?  what are the buildings made of, and how are they designed (Risk Management) 3) determine ways to reduce P aHd/or S H 1. apply land-use planning and zoning a) use high-hazard areas for low population use (eg. parks, golf courses) b) don't build in areas of soft soil or soils that might liquefy 2. apply stringent building codes a) choose appropriate building MATERIALS  GOOD MATERIALS are all FLEXIBLE: wood, steel, reinforced concrete (concrete with an internal framework of steel bars)  tends to be more developed countries that can build with these materials because they have the money to do so  BAD MATERIALS are all INFLEXIBLE (rigid) : heavy masonry, stucco, adobe, unreinforced concrete  tends to be in the less developed countries since they don't have the money to use the good materials b) choose resistant building DESIGN  for example, the worst damage occurs when the PERIOD OF VIBRATION of the ground and THE PERIOD VIBRATION OF THE BUILDING are the SAME  buildings have a natural period of vibration of # of stories/10 seconds  if the periods of vibration match, the shaking will be amplified o (like gaining momentum on a swing to get higher, to slow down swing against the momentum direction)  GROUND PERIODS: soft soils = several seconds, solid rock = < 1 second  BUILDING PERIODS: tall building = several seconds, short building ~ 1 second Feb 7, 2014  how to build a house to resist seismic waves (to build extra stability)  BOLT IT (in place)  BRACKET IT (using L-shaped brackets in corners)  BRACE IT (cross braces integrated into the support frame) (or piston cross braces - viscous fluid absorbs energy) (or springs with dampers) (tuned mass-damper in Taipei 101 to absorb the seismic energy)  BLOCK IT (add blocks between vertical supports)  PANEL IT (overtop)  BUTTRESS IT  ISOLATE IT  study/test building stability via outdoor shake tables to simulate an earthquake  Trans-Alaska oil pipeline survives large earthquake since each joint was mounted on a roller/slider beam so as the ground shakes, the pipeline is flexible enough to move from side to side on the tracks with the earthquake instead of snapping/cracking (along a strike- slip fault) c) legislate and enforce regulations about construction -  this ensures that builders actually do a) and b)  aim of all three is to minimize damage to structures  BUT all three lead to an increased (initial) COST 3. set up warning systems and emergency-response plans a) set up earthquake warning systems and tsunami early-warning system Earthquake warning system  radio waves travel faster than seismic waves --> so we can set up seismometers near faults  when they detect an earthquake, they transmit a RADIO SIGNAL to the more distant cities  provides a warning (5 seconds up to 1 minute before seismic waves arrive at the cities ) o enough time to shut off gas valves, stop drains, seek cover Tsunami warning system 1. early warning system --> sensors on ocean floor that detect sudden changes in ocean depth 2. maintain natural shorelines --> mangrove trees lessen impact of tsunami wave 3. limit population centres along shoreline 4. provide tsunami education/training b) provide appropriate emergency equipment and personnel  prepare emergency response planes b) education of the public  information booklets (what to do before/during/after an earthquake), information presentations in schools, conduct earthquake drills 4. try predicting earthquakes so you can evacuate, prepare supplies etc (1-4 are to try to reduHe S ) a) LONG TERM PREDICTION -  use RECURRENCE INTERVALS (limited use, since it only gives you a broad sense of what might happen in the general future)  look for SEISMIC GAPS (these are high-risk areas where the fault is "locked"- the stored energy is not being released - when it finally does, look out!) Feb 11, 2014 b) SHORT TERM PREDICTION  difficult (impossible?!) to pin-point precise times of upcoming earthquakes because earthquake behaviour is CHAOTIC  (self-organized criticality - chaotic behaviour organizes itself o ie. dropping grains of sand, makes a pile, can't predict when a single grain will cause a landslide -or predict the size of the landslide)  therefore short-term prediction is not likely to work  However, changes preceding an earthquake might provide some short-term warning  the main change as stress builds up is the formation of micro-cracks in rocks  a process known as DILATANCY - ie. expansion in volume by cracks opening up  this leads to (1) GROUND BULGE  (2) MICRO-SEISMICITY and FORESHOCKS o we can monitor micro-seismicity in the mine shaft to try to predict rock- bursts and warn miners - we are "listening" to the rock "crackle"  (3) INCREASE IN RADON GAS LEVELS IN WELLS (as rocks crack, radon gas is released and pressure builds up) 5. try "controlling" earthquakes (to try to reduceHP ) a) perhaps lubricate faults with WATER to release stress on faults (bit by bit to avoid the stress being released in a big earthquake)  problem: how many earthquakes of M2 would you need to release the energy of a M9 earthquake  problem: a lot of water needed, how deep to drill, how much water  problem: if you happen to pump the water the day before a big earthquake was going to happen anyway, blame will be put on you / risk of accidentally triggering a big earthquake? 4) do a cost-benefit analysis --> determines what you can "afford" to do 5) implement mitigation techniques if warranted (and to the extent that you choose) Readings (2nd Canadian Edition) Chapter 1: pg 11-19, 1.4 Geologic Cycle (Rock Cycle, Plate Tectonic Cycle, Hydrologic Cycle) Introduction to the ROCK CYCLE and the PLATE TECTONIC CYCLE What causes earthquakes? --> movement on faults What causes faults? --> stress (pressure) on rocks in the earth What causes stress inside the earth? --> release of earth's internal heat energy (the plate tectonic cycle) Energy acting on the earth  1) EXTERNAL ENERGY: "wears down" the earth's surface o mostly from the SUN (37 000 x 10 calories /day), the heat moves around the earth through  the hydrologic cycle  the oceanic conveyor belt which creates water currents  air currents o GRAVITY (0.6 x 10 ) (mainly the moon) which creates TIDAL ENERGY  we can convert the tidal energy as the tides go in and out into electrical energy from dams  moon stabilizes earth's tilt o METEORITES/COMETS (small amount) Feb 13-14, 2014  2) INTERNAL ENERGY: "builds up" the Earth's surface o the earth is a heat engine (6.6 x 10 calories/day) --> compare this to energy of the sun o causes earthquakes, volcanoes, mountains, etc o daily, the earth's surface receives 6000 times as much energy from the sun as from the inside of the earth. Therefore, EXTERNAL ENERGY dominates the biosphere. But INTERNAL ENERGY over time, has a profound effect The Rock Cycle  summarizes the interaction of external and internal energy  rocks are in constant change from one type into another (cycle)  IGNEOUS: molten material, consequence of internal energy, liquid magma cools, hardens, and "crystallizes" to become igneous rock  SEDIMENTARY: consequence of external energy, formed when weathered "particles" get deposited and converted to sedimentary rock by a process called lithification (compaction and cementation of sediment during burial)  METAMORPHIC: consequence of internal energy, formed when a pre-existing rock is changed under higher TEMPERATURE and PRESSURE in the solid state PLATE TECTONIC CYCLE: Summarizes how internal energy is released from the Earth's interior SOURCES OF INTERNAL ENERGY 1. Formation of Solar System (ca. 4500 million years ago)  from 4600 M years ago, Solar Nebula (gas) --> collapsed inward and kept spinning into Dust Cloud -- > cloud with embryos --> Planetesimals --> Proto-Planets --> Planets, 4500 M years ago the earth grew like a "snowball rolling down a hill", and adding heat  A) impact of "planetesimals"  B) sinking of iron to form core of earth  differentiation: Iron (Fe) sinks towards center, when cooled formed an iron rich core of the earth  by 4400 million years ago, the earth became differentiated --> Iron (Fe) core and lighter silicate mantle  earth was originally homogeneous and became layered with an iron core 2. Decay of Radioactive Elements (eg. Uranium etc)  how does the e
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