1. Monitoring Earthquakes Chapter 2, Section 3

2. Did you Know? The problem of predicting Earthquakes is one of the many scientific questions that remains unsolved!

3. It is important for scientists to develop ways to predict earthquakes because: A warning allows people who live in the area to protect themselves by: – Reinforcing buildings and other structures – Getting emergency supplies – Evacuating

4. Earthquakes are dangerous, so scientists are trying to monitor them (monitor =watch closely) What do scientists use to monitor and measure Earthquakes now?

5. SeismoGRAPH The machine that measures earthquake seismic waves

6. The Seismograph

9. Seismic Waves cause the seismograph’s drum to vibrate The suspended weight with the pen attached to it moves very little Pen stays in place and records the drum’s vibrations

10. Review: Which part of the Seismograph is moving?

11. The part of the Seismograph that is moving is the rotating drum http://www.youtube.com/watch?v=G bd1FcuLJLQ Modern-day Seismographs are digital and these are called “SeismoMETERS”

12. Seismogram The pattern of lines that show a record of an earthquake’s seismic waves Seismograms are produced by the Seismograph machine

13. SeismoGRAM –the written record of the seismic waves

14. Look for the P waves, S waves, and Surface waves

15. Seismic Waves on the Seismogram P waves –fastest and arrive first S waves –arrive shortly after p waves Surface waves –move the most slowly and produce the LARGEST disturbance on the seismogram

16. In order to predict WHEN earthquakes are going to happen, where do you think is the first place that Geologists look?

17. Geologists monitor FAULT LINES WHY?

18. Geologists hypothesize that along a fault, they can monitor the stress buildup in the crust to predict when an earthquake might occur

19. Geologists measure the STRESS in the Earth’s crust on either side of faults, looking for: a slight rise or fall in the elevation (height) of the crust the tilt of the crust and the distance of horizontal ground movement

20. Instruments for Monitoring Faults Tiltmeters Creep Meters Laser-Ranging Devices GPS Satellite

21. 1) Tiltmeter

22. Tiltmeters Measures the “tilting” or lift of the crust on either side of the fault Consist of two contraptions that are filled with liquid and connected by a hollow stem If the land rises or falls slightly, the liquid will flow from one contraption to the other

23. What type of faults are Tiltmeters used for?

24. Used on NORMAL and REVERSE Faults

25. 2) Creep Meter

26. Creep Meter Uses a wire stretched across a fault to measure horizontal movement of the ground One side of the fault, the wire is anchored to a post On the other side, the wire is attached to a weight that can slide if the fault moves

27. Creep Meters Used on Strike-Slip Faults

28. 3) Laser-Ranging Devices

29. Laser-Ranging Device

30. Used on Strike-Slip faults Uses a laser beam to detect horizontal fault movements The device times a laser beam as it travels to a reflector and back The device can detect any change in distance to the reflector

31. 4) GPS Satellite

32. GPS (Global Positioning System) Scientists can monitor changes in elevation AND horizontal movement along faults Scientists can see changes in elevation and horizontal movement Used for Normal, Reverse, and Strike-Slip Faults

33. The movement along faults depends on how much friction there is between the sides of the fault Friction: the force that opposes the motion of one surface as it moves across another Low Friction = no Earthquake Moderate Friction = small Earthquake High Friction = big Earthquake

34. Did You Know? Even with data from many sources, geologists cannot predict when and where an Earthquake will strike Reasons: – Sometimes stress builds up along a fault, but an Earthquake does NOT occur – Sometimes an earthquake relieves stress in an unexpected part of a fault

35. The problem of predicting Earthquakes is one of many scientific questions that remains unsolved!