Earthquakes PDF

October 31 Early Descriptions of the phenomenon Takey causes vint - They originally were considered to be a divine cause - The greeks decided a more mechanistic explanation (subterranean fluids) causing the...

October 31 Early Descriptions of the phenomenon Takey causes vint - They originally were considered to be a divine cause - The greeks decided a more mechanistic explanation (subterranean fluids) causing the aland to rise and fall up thought - Around 100 CE the chinese were creating seismoscopes Greeks fluid. - By the 19th century people were starting to keep track of earthquake activity subterren on Lisbon - 1755 Source - Great thinks like Immanuel kant used the destruction to try and understand the cause soa Seismic Main was faultingof the tic better th Mitta alongeas of - Collected data as reports of peoples experiences the - Described structural destruction - Thinking about the destruction in terms of a natural event not divine intervention - Invoked subterranean winds and currents as the cause the coined Naples - 1857 - studied thein-y Seismology term earthqua Investigated - Robert mallet Naples the earthquake - Measuring direction of cracks to determine the location of an earthquake first time ever an earthquake Wsreally - Systematic descriptions of destruction Where do earthquakes happen a - Data compiled by Robert Mallet PatternsinCatalebased - There are some patterns bases inresearcedits/theories - And possible biases that could influence how the data appears Development of modern seismology - Early morning of april 19 1906 an earthquake shook over 200 miles of CA including San major turning Point of Francisco in the development Modern Seismology. - The skating broke gas lines and water manes city wide Ritcher Scale was developed- Shaking and ensuing fires destroyed about 80% of the jewel of the west rebound theory- About 3,000 people died and the damage was estimated to be equivalent to the us federal Elastic Andreas Importance of San budget for that year which was about 600 million dollars Fault - The governor of CA commissioned a group of scientist to investigate the mechanics of earthquakes as a way to mitigate future damage A new theory of earthquakes - That the crust of the earth deformed elastically under some horizontal stress - The rocks withstood a certain maximum strain before breaking fault the friction making it stick until -A fault overcomes is stuck the strain built up in the rock on either side of the This theory can help estimate When the next earthquake will occur ↳The release of this energy causes Seismic Waves = Ground Shaking  - The deformed rocks returned to their restrained configuration like an elastic snapping back - Release in elastic potential energy when the brittle rocks fails - The release of energy causes the shaking we feel when an earthquake happens - The shaking is the dangerous part even for humans Body Waves - P Waves - Fastest waves - Arrive first (Primary) - Compressional Body Waves - S Waves - Slower waves - Arrive second - Shear Surface Waves - Love waves - Slower then S and P waves - Horizontal motion only - High amplitude - Very destructive Surface Waves - Rayleigh Waves - Slower than S and P waves - Horizontal and vertical motion only difference - High amplitude - Very destructive Data Analysis - Many seismic stations record the P wave based on their distance from the event - Computer calculate the origin - Map view in 2 dimensions - Cross sectional view in 3 dimensions November 4 Inge Lehman - 1888-1993 study - A mathematician by training from her SeismicSignsa b - She studied the seismic signals of hundreds of earthquakes of - The results showed inconsistencies with just the liquid core earthsSinn Core  - She postulated a solid inner core within the liquid core a model finally supported decades later with many more and more precise seismometers November 19 How the earth works diffrent people many - Many independent problems to help solve contributed of the earth - Many independent approaches the many Problems different methods - Many independent research groups with many - None especially interested in solving a global problem of continents and oceans - It was not only one persons work that seems not related to each other until someone brought it all together usedWhagnometersomagnetization During World War 2 and Submarines were - Ships towed magnetometers behind research vessels was found - They registered strange readings along the sea floor - There were areas with positive magnetisation and places with negative magnetization Lodstone is a natural Mineral Magnetism throughout History the - Lodestone - had a mineral in it called magnetite greek discoured that has magentie in it which - First written about by the greeks in about 800 BCE was used by the Chinese to make the The compass was created by the lodestone - China in 300-200 BCE Compass - Still unsure what causes it but we know it exists Grai The GAD: Geocentric Axial Dipole - We still don't know what causes the magnetic filed Dipole - We still accept that there is a magnetic field despite not being able to explain it The horizontal Point the latidute What we measure determine can of the earth Inclination - The direction from horizontal that the filed points. It can indicate latitude of the earth Declination Compass mement 8 - The measurement in degrees magnetic north (Nm) is away from true north westic (rotational/geographic) ↳ Geographic Intensity north - How strong is the force The magnetic field and us  - The earths magnetic field protects life on earth from dangerous solar radiation The existence of the magnetic field - Magneticfielhappenis Patrick Maynard stewart blackett - Thought that the earths magnetic field is caused by the spinning of the earth - Borrowed several hundred pound of pure gold to test the theory feild came the earths Magnetic Keith Runcorm ↳ Thought - Blackett's former student current the earths - Thinks the magnetic field is caused by the currents of the earths motion from Attractions from the past - To understand the earths magnetic filed over time the two groups begin looking for sings of the past magnetic field in the rocks - They find that two rocks give very strong consistent magnetic signals From rich Canfind a, - Basalt is an iron rich volcanic rock and is what comprises all the sea floor find large & in - Red sandstone is also high in iron and is found in large deposits on all major continents rich , -Iron amounts everywhere Curie and his temperature - To understand the earths current magnetic field Blackett and Bullard started to try and understand the magnetic field through time - An important aspect was how rocks might become magnetized How igneous rocks get magnetized hot for iron crystals - Iron crystals do not align themselves in molten rock To into molten rock - Is is too hot to turn happens Magnetic fieldsolidified. - The magnetic field is assumed after the rock is solidified it is after In sedimentary rocks it is compressed - Sediments settle through the water collum avearesiduaary- Iron bearing minerals align their tiny magnetic field with earths ambient magnetic field When ↳i the grain magne - When compressed the grains are stuck in place rock - This leaved a residual magnetic field measured in the sedimentary rock. Challenges of measuring direction of magnetic filed - Cleaning and subsidiary magnetic signal - Accounting for folds - Need to figure out what these directions mean when we get them from the rock - Sets of multiple samples from the same layer - Grouping the data - Multiple sets of samples from different layers  Continental APW’s - Interpretation leads to continental displacements - This should be the end if permanentism but its not - Geologists just aren't geophysicists plus there were problems with the data The problems of magnetic reversals Not a Perfect - There was a problem with switching polarities by 180 degrees method Many. - Was it a local phenomenon? unanswered questions - Should we just ignore it ? - How could we test it? Development of a timescale of magnetic reversals - Samples taken globally over the next decade start to align in a pattern - Radioactive dating was become much more precise - What happens to the nature of the timescale of reversals from the late 1950’s to the late 1960’s? Allan Cox, Richard Doell, Brent Dalrymple Daa - Age dating rocks becomes more refined and accurate Tomuch b - Extraction process is more precise - Magnetometers are more sensitive ignore. be - Many many more samples - They saw that if we go offshore and drill into current sediments and pull these cores and measure the magnetic polarity they also show magnetic reversals - In igneous rocks and sedimentary rocks - Geologists could no longer ignore the data Ronald Mason and Arthur Raff Recorded a the - No one was sure what to make of these signals in " cattern - Originally detected by magnets dragged behind ships looking form enemy submarines oceanfloorthee the - They searched other oceans of the world was ridges. - The pattern was parallel to ocean ridges - Recorded the magnetic reversals perfectly  November 21 - The average elevation of the continents is 800m ASL - At 0.005mm/year all the continents would be eroded away in less than 160,000 years - Even mount everest would disappear in 1.6 million years - The earth is older than 4 billion years old - Porous earth : Aristotle - Contracting earth : Seuss, Dana - Horizontal displacement : Wegner Hypsographic curve a Becauseident - Suggests the crust had two components based on density - Makes it difficult to explain land bridges - Makes it difficult to explain alternating marine and terrestrial deposits Where geologists stood 1920’s-1950’s Some - North american and european geologes were not upset with the contraction to the point they were looking for a new theory only interested - Contraction answered their questions well enough in their own local - They were dominating the science field - Indian and south american geologists were sympathetic to drift because it did a much E Problems better job at answering their regional geologic problems liked Continental - Regionalism is a big factor in acceptance drift - Geologists only interested in answering their own localized problems - We need to understand that scientific knowledge is tentative Seeing the sea floor - It didn't give us very much information even though it was so much more than what we had - Only looked into it because we were interested in money - Sound navigation ranging sonar - Listening to the echoes of sound bouncing off the sea floor - The time it tales for the echo to arrive indicated the distance traveled Marie Tharp  Mantel Plumes is ·found oontaina - Discovered a long chain of rugged mountains running the length of the atlantic and its deep Valley Center : had a deep valley down its center Deep - Formalized the anatomy of the ocean floor Earthquakes - In that valley it was active - earthquakes - It was all over the worlds oceans - It was youngest where the warm colours, volcanically active, least sediment, seismically active. - Oldest were the coldest colors were also deepest - Hot stuff is less dense than the colder version of the same stuff - Has it cooled it would get deeper and deeper and deeper because it would get denser A verse in geopoetry - Ridges were locations of mantel convection upwelling - The rocks break magma flows into that break becoming new rock - New seafloor is generated at ridges and migrates away getting colder a Samuel Carey contientsareold - The seafloor is much younger than the condiments the than and - Homogeneous crust forms on a smaller earth (Seuss) liked Seuss - Continents break apart with the basaltic sea floor forming (Dana) ideas 1) anas - The earth has been expanding since the breakup of pangea The European APW path - The pole seems to move through time conditentsmoree the - Found that the paths didn't overlap pole. - The continents were moving independently of the pole - The problem was that rocks of the same age were all polarized the same direction - The rocks record a global phenomenon of the earth, episodically reversing its polarity Lawrence Morley - Recognizes both the pattern and a symmetry about the ridge axis Combines Magnetic with magnetic - He combines the idea of seafloor spreading anomaliesand the idea spreading - Magnetic anomalies the seafloor of - Magnetic reversal; time scale - A new ocean crust formed in ocean rifts it record the ambient magnetic field at the time - This give us time markers - The pattern is symmetric above the ridge - Submitted a paper for Nature - rejected for lack of evidence in april 1963 - Submits a paper for the journal of geophysical research - rejected in august 1963  Graduate student Fred vine and co-authors a paper - They combine the same things Lawrence morley - write the same paper - Send it to nature and theres is accepted in september 1963 - Who should get credit? - credit was given to all 3 of them This new theory - Allows for new explanations for why there are earthquakes and volcanoes within pretty well defined zones of deformation - Where crust is breaking apart Tuzo Wilson hot spots - Geophysicist at the university of Toronto volcanic caused a that don't -- Thought that drift was the answer were tectonic b Volcanic hot spots in vacation hot spots More While - He supposes that we have these mantel plumes Plates Shift - The movement of the pacific plate drags the heaf of the magma plume - This process forms volcanos - Eventually the volcano forms a hot spot and a new one forms - As it moves the older volcano goes extinct - That there is a mantel plume and that it is stationary are only assumptions - The plume is stationary the crust is moving - The direction of crustal movements is towards the older volcanoes - Had multiple models for convection in the mantel - Wilson figured out that due to the shape of the earth long linear zones of compression or extension could not exist without some lateral compensation - If the ridges are stationary then this fault represents a left lateral displacement - If the ridges are spreading then the relative motion across this line would be opposite - Measured a bunch of earthquakes and realized the spreading is happening at the ridges Wadati-Benioff Zone mantle Idea of - Higher density crust is pushed underneath the lower density crust creatin one Homeand Subduction Zones - Deepest parts of the seafloor  - Explains earthquake and volcano observations - A necessary component to account for the continual production of seafloor at ocean ridges - The earth does not have to be expanding - They are all being formed at the same time therefore all the same age New Global Tectonics the idea of - Bryan Jack, Lynn had - From columbia university in 1968 ConvectionIn the mantel - Proposed convection in the mantel - There is spreading going on. - There is subduction - Many geologist still weren't impressed - They are only interested in their localized portion of the earth - Tanya Atwater brings tectonic onto land in 1970 - The San Andreas fault is a long transform fault connecting two ridge systems All of this evidence is circumstantial How can we find a way to substantiate motion of continents? - in order to find some direct evidence of this motion - find actual measurements - measure plate motion with gps - Measure direction and magnitude of portions of the crust Why are there still mountains? - The earth is dynamic - Collision of continental plates lead to deformation and thickening of the crust - New magmas is continually added to the crust above - Looks kinda like an iceberg - Keeps the iceberg 10% above water - The mountains as they wether and erode we lose the top layers new rocks rise to take their place  November 26 What runs the machinery? - Earths internal heat or gravity - Energy is leaving a place of high concentration to a place of low concentration - Earth is cooling itself off - Convectively mainly Heat heat forms things - Heat of formation - Radigenic - Latent heat at the core continues to solidify - Rock turns out to be excellent insulation - Plastic mantel either makes the plates move or allows for plate movement The Mechanism theory for- Jason morgan arbitrarily places those plumes at the core mantel boundary his efrom - This model resonates fantastically due to its concreteness and elegance mantleplumes - Mantel plumes becomes the default explanation of otherwise ambiguous tectonic the cure observations - went from having about 10 around the earth to 100’s - Mantel plume publication also increase ten fold during this time while alternative explanations are not getting published - Simple model but it explained our observations very well - We cant see these with seismic data - they are too small Plume Vs Plate Model 100% agreed - Not settled yet for some people Not - There is a plate group who think we can use a bunch of different explanations to what we way the on one or saw other answer - There is a plume group who is settled on the answer that plumes correct plume-only - Need to rely on “listening” to the earth to determine what is really going on answers Plate= Many - The real revolution is when we figure out what is going on with the mantel - John Verhoogan  Things important to note - Plate tectonics is not continental drift - except for horizontal displacement - There were 5 major models all trying to explain the same data - Regionality plated a role in whose model you excepted - Science and technology are coupled - science drives tech and tech drives science - Scientific advancement leads explanations closer to realty it is self correcting - Reality does not decide who wins a controversy its the winner of the controversy who decides what reality is - Bruno Latour 1987 - We don’t know what reality is so we can never solve the controversy November 28 Constructing knowledge in science and learning Why this title - Use your previous knoweldge as building blocks and as a foundation for new learning What is a model? - A model is a made up representation thats the source that represents an object or showthatoncea phenomenon (target). Is a simplification that describes or explains the real world object or phenomenon and aids in study and understanding. It is based on empirical observations about the object or phenomenon in question. - Something that we create that represents something else Why not just study the real thing? - Some of the things you want to study are not obtainable - Helps us comprehend something that may be difficult to Characteristics of a model - Artificial - constructs of the human mind - They are utilitarian - serving a particular purpose - They are simplified - data is missing to enhance utility - They are interpreted - meaning is also constructed by the human mind - They are imperfect - incomplete analogues When using models  1. They highlight a certain aspect or aspects of the target 2. They hide aspects of the target in Concrete models physical - Models that you can hold in your hand some way - Physical entity - Some of them are functional models - Scale Models - hardly ever work Visual Models no - Those models that you see - Something that is 2d Gestural Models - Things we do with our bodies with body show - Example - hand slide = heat and sound language Verbal Models - Similes - a p wave is like a sound wave only speaking - Analogies - Metaphor - Semantics are listening to the earth Mathematical Models - Descriptions of reality mathematical - The most abstract equation Stochastic the future - Forecasting Predict the past - We don’t know when something is going to happen, but we can model a certain tendency using Deterministic - They have a specific answer at the end Dosen't have a concrete answer - There are no probabilities, this is what it is Models and Learing - Experiential - you experienced it, you did it - Collaborative - someone helped you - Amalogical - already had prior knowledge, muscle memory All subject to your past experiences - Everyone's past experiences is going to be different  Accommodation - Getting information in and making stuff up on the fly - Same data, but different meanings Projection - Once you see it you can not unsee it Your brain fills in the spaces where there is missing data. It tires to make sense of the whole situation Hierarchy of Models Mental Models - We create models in our mind - Private and personal representation - Something fully makes sense to you but you cant express it in a way that makes sense to others - When that model changes we learn something Expressed Model Takingsomethineg ng - Making the private public - Express it Private - Describing a dream Public it - Tell them, show them - Is a model of a model Consensus Model everyone - Social groups agrees that a particular model is useful Not 100% agree - Not a vote to has - Have a conversation about it Scientific Model consensus, same as - When the social group is made up of scientists al but group is - Not everyone agrees but most scientists agree scientists Historical Model - Replaced by something more useful Descriptive Models What we - What do we observe Watch  - Scientific laws Explanatory Models - Why or how is this happening - Scientific theories December 3 What is geology? - The verb is what is happening today - process - The noun is the actually rocks and the structures that the rocks make up Where do we learn how to do geology? - Textbook - Geology for dummies - Online There Many are - By just doing it diffrent Methods Textbooks to learn Marshak geology - Recognizance - Collect - Propose - Test Fletcher - Make - Create - Use - Test - Reject We can consider that a rock formation is a book with indications of its history In order to read the book we need to understand the language first Signs and Causes - Many causes create multiple signs a and - Multiple causes can wind up causing the same signs many causesca many have Visversa - Mountains is a sign - 4 different causes all to explain mountains - Need to find which causes have more signs then we can see - narrow it down Example - Sign is a magnetic signal in rock  Causes: - The earths magnetic field - Process during lithification - Process during deformation - Process of extraction and testing Test: orderspecific - Multiple sample from the same location, same age In you - Samples from different locations of same age define a use to it - Multiple samples from different ages, same location eatest sign ar - Fold test - Magnetic “cleaning” - want to get rid of the different magnetic fields and see the of one When faced with multiple causes for the same sign we need to find ways (tests) to distinguish one cause from the others Along the way we also need to make assumptions We need to assume a set of rules the universe is working by Assumptions - We assume the magnetic field is not produced by a bar magnetic = Geocentric axis dipole - We also assume that magnetism is stable through time Paleo Climats Climate The - Along the equator it is warm and it is wet Past - On either side of the equator north and south it is really dry a during age geological - North and south of that is gets really wet again of Mounds ~sand created formed byWater- derived dunes vs Aeolian (Wind) derived dunes by Wink The GAD is a reasonable assumption because is is supported by evidence outside of strong palomagneticism, but it is still an assumption - The origin stability of the paleomagnetic signal is reasonable based on the results of the different tests fun and the coherence of the data across time and space - Geology is building an argument and looking for a building evidence to support our case - Measurements statistically averaged into clusters - Clusters become points - Points direct the line The Scientific Method and - We don't do the scientific method in geology Methods Many don't - This idea of a linear progression of scientific knowledge is a fantasy we ideologies - Renne Cart = All the method is, is a way to report science in a way that is not messy Proveanything juesnts - There is no order in which is took place - there is just doing it  - There are many methods to investigate and solve problems - We don't “prove” anything in science we build arguments - Try to have the most reliability not the truth Geology is a historical science not an experimental science - We are trying to figure out the past which makes it historical - There are limitations with this - unlike chemistry or physics Explanation of - Hypothesis are predicted form explanatory accuracy - historical events Past is - Hypothesis are predicted for predictive accuracy - experimental Hypothesis that experiments tested through Hypothesis leads to observations and data which leads to hypothesis which leats to observations and data which leads to hypothesis which leads to observations and data which leads to enginghypothesis thesis knowledge- Your hypothesis is always changing based on the new observations and data you learn - Increasing explanatory power How do be bridge the present to the past? - Geology is a historical science - Trying to understand the past - How can we bridge from where we are here to a billion years ago - The present is the key to the past - james hutton Progression of the 4 - Uniformitainism, made is like a doctrine very rigid - the progression of the earth is the earth is the throughout same throughout history - charles lyell same Change happened all at - Catastrophism - layers of lots of dead things and then above that none of those dead Once. things exist - not a slow change, must have happened all of a sudden , global catastrope- george cuvier Same Process used - Actualism : we must allow for these moments of chaos to happen is also in the Past used today - Taking the best parts of two ideas and putting them together was one explanation for the signs in the rock - The modern consensus models usually contain different parts of competing models from the past The earth's crust is positioned - Pratt Model vertically based on it's density and thickness - The crust Airy Model - The crust is all the same density, but where there are mountains there are also stuff in the mantels ↳ The earths crust b same density is more rigid Shell floating.  Practice Test MC T/F 1 A. B 11 TrueV.. 2 C 12. True B 3 C 13 False True.. 4 B ~ 14 False. B. 5 /D 15 True. 6 Bu.. 7. BV 8 9. AV 10. B 4482% Practice Test. Divine Cause 1 B. Subterran 2 fluids C.TheChinese 3 C 4. Described structural destruction B. 5 Measuring the direction of cracks B 6. Earth crust deforms elastically under stress B 7. Pwaves C. 8 Rayleigh Naves C 9. The had both solid inner and core core a liquid inner core B 10. Magnometers A 11 A. theory explaing the earths magnetic field B 1 2. Solar radiation B. 13.They can Lawrence record past Morley A magnetic signals when solidifieda 15. Blackett ModelB 16 Subductiona. 17 A. Sonar and magnometers 18. Regionalism and intrest in losal Phenomenon B 19 Plate. tectonics B 20 Tuzo Wilson B. 21. Mantle convection D Radioactive Decay B 22. The magnetic field is casued by the earths Spin C 23 Plate tectonic. theory 13 24 Mountains. formed by Continental theory Earthquakes and Volcanic activity 25. A flexible Cyclical Process , of Observations and hypotheses B 26. Earthquakes were seen as a punishment from the Gods A 27 creating -0 There was no scientific too to measure a seismograph to measure tremors e collecting. 28. He measured the a reports based direction of cracks on peoples experiences B 29 The crust deformed elastically under. horizontal Stress A 30 P-waves B. 3! Love-waves D outer liquid -0 The Made Solid tiner the layers Core was up op 32. The earths was solid and core inner core was 33. The use of Magnometers A -o The development of sonar to map the sea floor 34. Magnetite B 35. A model that describes earths magnetic field as originating from the Poles B 36. Shielding against harmful solar radiation C 37 The creation of a timescale for 38. It was unclear if the reversal magnetic reversals using age-dated rocks B was local a or global Phenomenon B 39. She discoured a chain of rugged moutains in the atlantic ocean B 40. The contientsSink into the earths mantel overtime a 41 The fit of the contients the atlantic. along ocean B - > The discovery of deep sea trenches 42 Some geologists were skeptikal due to regional diffrences geological thinkingB. in 43. Mantle convection currents B 44 Volcanic activity. is related to Plate moument B - Plumes of Magma cause volcanic islandsto form Practice test06 intervention 1 B Divine natural B Subterranean Winds and currents. Phenomenon Dismissed the event a -u as. D 2 3 B. Measuring cracks to locate earthquakes 4 B. A group of scientists to investigate earthquake Mechanics 5 C They are shear waves within the liquid. core. B A solid inner core 6 is unknown the cause 7. C The earth has magnetic field but a , - A sedimentary rocks rocks 8C. Igneous it's center. B It had 9 a chain of mountains running down 10. Plate tectonics accounts for both horizontal displacement and seafloor Spreading Il B Mantel Plumes are responsible for volcanic hot spots due to movement of the plates. 12 B.. They are deep areas of ocean floor where high density crust is pushed below low density crust 13. B Earth internal heat causing convection currents in the mantel 14.B It measures the direction and magnitude plate movements of of rocks minerals and Processes that shape the earth 15.C The study , Practice Test 1. B Divine Causes causes of earthquakes 2 B understand the natural. 3. CHe measured the directions of the cracks. 4 B Predict future earthquakes brittle rocks fail. 5 B Release of Elastic Potential energey wihen. 6. A P waves Elastic rebound 7 C. theory earth from solar rays 8. B protects life on dangerous within a liquid outer core core 1. B Revealed the earth has a solid inner 10 A Alfred Wagner. 1. A she mapped the seafr and identified ocean ridges 12. A Earths direction de to pole shifts magnetic field has Changed 13 B. 14 C. Practice Test