1. Plate Tectonics: Earthquake Generation and Wave Behavior
Do Now:
Explain why New York State is not prone to high earthquake activity. Use the map of the Earth’s tectonic plates to justify your answer

3. Destruction
Earthquakes

4. What causes an earthquake? Elastic Rebound Video Link
1.) As rigid plates collide, diverge, or scrape past one another, stress builds in the crust
2.) Eventually the rock can no longer bend under such high stress, and breaks or “slips” along a fault
3.) The shock of this slip deep in the crust releases energy in the form of seismic waves

5. EVIDENCE OF CRUSTAL MOVEMENT: FAULTS
EVIDENCE OF CRUSTAL MOVEMENT: FAULTS! (BREAKS IN EARTHS CRUST SHOWING DISPLACEMENT)

6. Focus Animation

7. Seismic Waves
1.) P-waves (Primary)- Arrive first & are compression or “push/pull” waves. Travel the fastest & through S, L and G
2.) S-waves (Secondary)- Arrive next & are transverse, moving side to side like a wave in a rope and only through solid crust
3.) L-Waves- surface waves that occur once P & S wave have both arrived. MOST damaging

9. Seismographs
seismic waves are detected with a sensitive instrument called a seismograph
A seismogram is the line recorded on the paper

10. Seismographs produce seismograms
Seismographs produce seismograms. These are the recordings of the seismic waves. #1The higher the amplitude (wave height) on the seismogram—the stronger the earthquake is.

11. Reading a Seismogram
#2 The closer the P & S waves arrive to one another, or the smaller the S-P interval is, the closer the station is to the epicenter!

12. Finding The Distance to the Epicenter
How does one find the distance to an epicenter? Click here for animation
ESRT Interactive Chart

13. Origin Time P arrival time - P travel time = ORIGIN TIME*
Origin time means the actual time that the Earthquake occurred at the Epicenter
You can find this by knowing:
1.) What time the P waves first arrived at any station
2.) Finding the travel time (how long it took P-Waves to get there)
3.) Distance to the Epicenter

14. In Perspective: A friend of yours who lives a half an hour away arrives at your house at 10:45 a.m. Based on this, you know they must have left at 10:15 a.m.
Real example:
An Earthquake was recorded at station A at 2:25 p.m.
You have the following information:
The epicenter is 4000(km) away
1.) What is the travel time of the P-waves? ________
Based on the travel time, what is the origin time of the EQ? ______________

16. Locating an Earthquake Epicenter on a Map (AKA Triangulation) Triangulation
You need THREE (3) seismic stations to do this
1.) Calculate difference in P and S wave arrival times
2.) Use same method to find Epicenter Distance
3.) Draw a circle around the seismic station with a radius equal to that distance

18. Where the 3 circles intersect denotes the location of the Epicenter

19. Triangulation in our class…

20. First find Distance to Epicenter using previous method

21. Step 2: Line up your compass using the scale on your map equal to the epicenter distance you found (make sure you start 0 at where the center of the circle is!!)

22. Write down in “cm’s” where the scale ends on your compass ruler= 3
Write down in “cm’s” where the scale ends on your compass ruler= 3.6 (cm)

23. Put your pencil in the closest dot to your measurement on the compass

24. Hold firmly the middle of your compass and drag the edge around to make your circle. This means that somewhere along the boundary of this circle, the epicenter is located

25. You must do three stations to find the Epicenter
You must do three stations to find the Epicenter. Where they intersect, or form a triangle, is where the epicenter is located

26. Not all Seismic Waves make it through Earth’s interior…
*When seismic waves hit a substance with a higher density (core) they are refracted (BENT) which is why we get P-Wave SHADOW ZONES
Seismic Waves and Refraction Video Link

27. Which station is the difference between the P and S waves the least
Which station is the difference between the P and S waves the least? What about the greatest?

28. Mercalli measures impact on humans from shaking

29. Richter measures actual amplitude of seismic waves and ↑ 10x every number on the scale (1-10)

30. Damage by Earthquakes Subsidence- sinking land Landslides
Demolished Buildings and Roads
Liquifaction- sediments + ground water become fluid
AND TSUNAMIS…..

31. Tsunami: 700-800 km/hr & up to 20 (m) in height
Tsunami: km/hr & up to 20 (m) in height! Tsunami Generation Animation Link
1.) Earthquake occurs under the ocean
2.) Displaced crust “shoves” water upward , creating a massive wave

33. Right before a Tsunami hits the water recedes
Japan

34. Do Now: Where would you expect Shallow Focus vs
Do Now: Where would you expect Shallow Focus vs. Deep Focus Earthquakes to occur along plate boundaries? Where and WHAT types of boundaries?

35. Map: Chili earthquake foci depths: Depth increases as submergence depth increases Green: 0-80 km Yellow: km Red: