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Earthquake and Seismology Study Guide

Learn about earthquakes, seismology, fault types, and how to read seismograms in this comprehensive study guide. Includes practice problems and distance-time calculations.

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Earthquake and Seismology Study Guide

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  1. Due today: None 4/07/14 Find your new seat! Turn to your new table of contents and correct the test date. Make sure your earthquake video paper is in your notebook if you were here. Take a copy of notes from the table. Unit 5: Earthquake and Volcanoes Test: Tuesday, 4/15

  2. Earthquakes

  3. What Is Seismology? • Seismology is the study of earthquakes and seismic waves that move through and around the earth. • Earthquake activity usually originates at faults that are located on plate boundaries or at fractures in the Earth. • A seismologist is a scientist who studies earthquake locations, magnitude, etc.

  4. What is a fault? an extended break in a body of rock, marked by the displacement of strata (layers) on either side of a particular surface.

  5. Draw the chart on the blank side of your notes (5 min.)Complete the first three columns using the textbook at your table. (8 min)

  6. Normal Fault Stress: Tension = pull away

  7. Reverse Fault Stress: Compression = push together

  8. Strike-slip Fault Stress: Shear = side-to-side movement

  9. Reverse

  10. Reverse

  11. Focus and Epicenter

  12. Focus – where the earthquake happens within the Earth Epicenter – the spot on the surface above the focus Focus and Epicenter

  13. Stress causes the ground to be deformed. • An earthquake occurs when a rock passes its point of maximum elasticity. • its point of maximum elasticity.

  14. This release is measured with a seismograph to determine distance, location and magnitude. Seismograph

  15. Triangulation-using time and distance from 3 different seismograms to locate the epicenter of an earthquake.

  16. Triangulation between 3 Centers

  17. Due today: None 4/8/14

  18. Triangulation-using time and distance from 3 different seismograms to locate the epicenter of an earthquake.

  19. Triangulation between 3 Centers

  20. P Waves • Primary wave. This is the fastest wave created from an earthquake and can move through both liquid and solid rock. • Moves by compressing the earth • These are the waves that animals can sometimes sense.

  21. S Waves • Secondary wave. • S waves are slower than P waves and can only move through solid rock. • This wave moves rock up and down.

  22. Surface Waves • These waves cause the most damage during an earthquake.

  23. Reading the Seismogram • The P wave will be the first wave on the paper. P waves are the fastest seismic waves, so they will be the first ones recorded. The S waves will be second. These are usually bigger than the P waves. • The surface waves are the last, and often larger, waves marked on the seismogram. Surface waves travel a little slower than S waves so they arrive at the seismograph just after the S waves.

  24. Seismogram

  25. Earthquake Distance Chart

  26. Interpreting Seismograms Worksheet • #1-3 as a class • #4-6 Popsicle Sticks

  27. Sample Problem: A seismic station is 3000 kilometers from the epicenter of anearthquake. How long will it take P waves from this earthquake to reach theseismic station?

  28. We know the distance (3000km) We’re trying to find the time it will take P waves to travel this distance. Find 3 (really 3000km) on the bottomaxis and, using a straight edge(a ruler) draw a line up to meet theP wave line. Now, using the ruler, draw a line overto the left axis and read the traveltime: 5 minutes and 40 seconds. Notice that each small box is worth 20 seconds. Now try the same problem in reverse: It takes P waves 5 minutes and 40 seconds to travel from an epicenter to a seismic station. How far is the seismic station from the epicenter?

  29. We know the P wave travel time: 5 minutes and 40 seconds. We are trying to find the distancebetween the epicenter and theseismic station. Using a ruler, draw a line from thetime (5:40) to the P wave line. Now draw a line straight down tothe bottom axis and read the distance............. 3000 kilometers! All of these problems are the same. Given the time, find the distance. Given the distance, find the time. And it doesn’t matter whether you are given P or S wave travel time as long as you are careful to use the correct line and, most important: TAKE THE TIME TO BE CAREFUL AND ACCURATE!

  30. Let’s take this one step further. A seismic station is 3000 km from the epicenter of an earthquake. If P waves from that quake arrive at the station at 4:25:40 PM (4 hours, 25 minutes and 40 seconds), at what time did the earthquake occur? We do exactly the same thing we did before, we find the travel time which is 5:40 (5 minutes, 40 sec.) Now some math. If the waves arrived at 4:25:40 and they’ve been traveling for 5:40, when did they start out? Subtract: 4:25:40 5:40 ------------ 4:20:00 The quake occurred at 4:20:00 PM

  31. OK, let’s try another type of problem involving both P and S waves. Here’san example........................... It takes P waves 7:20 (7 minutes and 20 seconds) to travel from an earthquake epicenter to a seismic station. How long will it take S waves from the sameearthquake to reach the seismic station? What do weknow? We know P wave travel time is 7:20 What are we trying to find? We want to find S wave travel time. Do we have enough information to do the problem? NO! We have to divide the problem into 2 parts. First, we do just what we did inthe previous problem. We use the P wave travel time to find the distanceto the seismic station and then................................. We use the distance to the seismic station to find how long it took S wavesto travel that same distance. Let’s see how it’s one....................................

  32. We know P wave travel time is 7:20 so, using a ruler, draw a line from 7:20 over to the P wave line. Now draw a line straight down to find the distance from the epicenter......... The distance is 4200 km. Notice that each small box on the bottom axis is200 km. Now we can get on with the second half of the problem. If the seismic station is 4200 km from the quake epicenter, how long (time) did it take the S waves to travel that samedistance? Draw a line from 4200 km straight up to the S wave line. Now draw a line over to the vertical axis and read the time.......... 13 minutes exactly (13:00) And now for something completely different.......................

  33. P & S waves: Arrive at a seismic station 4 minutes and30 seconds (4:30) apart. How far is the distance from the epicenter? 1) Take a sheet of paper and line up the left edge with the vertical axis (time). Be sure that most of the paper is hanging down below the graph. Thisis important. 2) Make a small, thin, and accurate markon the paper at 0 time. Make another small, thin, and accurate, mark at 4:30 (4 minutes, 30 seconds).

  34. Now slide your paper to the right until one of your marks is exactly on the S wave line and the other is exactly on the P wave line. It isvery important to be sure your paper is straight (vertical). Now look to see where the bottomof your paper crosses the lower(epicenter distance) axis. In thiscase it crosses at exactly 3000 kmwhich is the answer. When P & S waves arrive 4 minutes and 30 seconds apart it means that the seismic station is exactly 3000 km from the epicenter of the quake. Of course we can do the sameproblem in reverse!

  35. Earthquake Practice (5 min. each then check with popsicle sticks) • #1-6 • #1-2 • #1-4 • Interpreting Seismograms Worksheet #7-9

  36. Waves refract (bend) when they enter a new medium. Even though P waves travel through the liquid outer core. They bend.

  37. S waves cannot travel through liquid so there is a shadow zone with NO WAVES and an area with only P waves.

  38. S-Wave Shadow and P-Waves • This is how scientists know the outer core is liquid!!!

  39. Practice!! • 1. Suppose you were 1000km away from an earthquake. • How many minutes would the P waves need to arrive at your seismograph? • How many minutes would the S waves need to arrive? • How many minutes apart are the P waves and S waves from each other on your seismogram? • 2. If the S wave arrives 4 min, 30 sec after the P wave, how far is the earthquake’s epicenter?

  40. Due today: None 4/9/14 • Take one of the highlighted sheets at your table. • Take a copy of the P-S wave graph as well. • Use the information given AND the graph to complete the blank squares in your highlighted sections. (10 minutes)

  41. Magnitude • Reading and Questions • What two factors are used to determine magnitude? • What scale is used to measure magnitude? • True / False: You probably would not notice or feel the effects of an Earthquake rated 2. • Calculations • VOLCANOES! Introduction/ 2.1 10 pts. • Write 5 facts about Volcanoes on your paper. • Write a list of 5 vocabulary terms (not defined)

  42. Tsunami Long shallow waves that develop from earthquake activity and become giants upon reaching shore.

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