1 Earthquakes What Is An Earthquake? Click here to find outLiz LaRosa 2009 for my 5th grade science class 2009 What Is An Earthquake? Click here to find out

2 What is an earthquake? Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip Caused by volcanic or plate activity, The map above shows the distribution of earthquakes with magnitudes greater than 5.0 that occurred between 1965 and 1995.

3 Three Types of Faults Strike-Slip Normal ReverseAnimation of fault movement Strike-Slip Reverse Three types of faults Form depending on type of plate motion and complex reaction of earth’s lithospheric blocks Strike-slip Normal Thrust Normal

4 Normal fault Pulls on the crust stretching rock so that it becomes thinner (like pulling on bubble gum) = tension Occurs when plates are moving apart Hanging wall Foot wall Results in hanging wall slipping downward animation

5 What type of fault? normal Hanging wall Foot wallNormal fault - Results in hanging wall slipping downward

6 What causes earthquakes?Tectonic plates move past each other causing stress. Stress causes the rock to deform What type of fault boundary is this? What type of stress is shown? transform shearing Transform plate boundary showing shearing stress.

7 Strike – slip fault Rocks on either side of fault slip past each other sideways with little up or down motion - What type of stress is produced? shearing Occurs at a plate boundary transform Animation of strike-slip motion

8 Fault rupture across road in western Kaynasli, right-lateral strike slip displacement was about 4.0 m (13 feet) at this location

9 Reverse fault Pushes on the crust squeezing rock until it folds or breaks (like a trash compactor) = Occurs when plates are moving together compression Hanging wall Foot wall Results in hanging wall slipping upward animation

10 What type of fault? reverse Hanging wall Foot wallReverse fault – hanging wall has moved upward

11 What type of fault?

12 Focus – 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly Epicenter 2 1

13 How Seismographs Work A seismograph is an instrument used for recording the intensity and duration of an earthquake. the pendulum remains fixed as the ground moves beneath it Contrary to intuition, an earthquake does not make the pendulum swing. Instead, the pendulum remains fixed as the ground moves beneath it. A pendulum with a short period (left) moves along with the support and registers no motion. A pendulum with a long period (right) tends to remain in place while the support moves. The boundary between the two types of behavior is the natural period of the pendulum. Only motions faster than the natural period will be detected; any motion slower will not. 

14 Earthquakes How are earthquakes measured?Seismogram – seismic wave display record Seismograph machine

15 Seismic Waves

16 Primary Waves (P Waves)A type of seismic wave that compresses and expands the ground The first wave to arrive at an earthquake

17 Secondary Waves (S Waves)A type of seismic wave that moves the ground up and down or side to side

18 Comparing Seismic Waves

19 Surface Waves Move along the Earth’s surfaceProduces motion in the upper crust Motion can be up and down Motion can be around Motion can be back and forth Travel more slowly than S and P waves More destructive Animation of wave types

20 How do scientists calculate how far a location is from the epicenter of an earthquake?Scientists calculate the difference between arrival times of the P waves and S waves The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

21 Typical Seismogram How much time elapsed between the arrival of theP wave (start) and the arrival of the S wave (finish)? finish start Approximately 5 minutes and 20 seconds.

22 Locating Earthquakes

23 Locating Earthquakes

24 Now you are going to be seismologists and locate an Earthquake Go to: Click here to go to virtual earthquake site

25 National Geographic earthquake information

26 How are Earthquakes Measured? Richter ScaleA logarithmic scale used to express the total amount of energy released ___________ of an earthquake. Its values typically fall between 0 and 9, with each increase of 1 representing a _________ increase in energy. magnitude 10-fold

27 How are Earthquakes Measured? Mercalli Intensity ScaleA scale of earthquake intensity based on ___________ and ranging from I (detectable only with instruments) to XII (causing almost total destruction). observed effects Click for Interactive Demo Go to

28 Earthquake Waves & Earth’s InteriorSeismic wave animation

29 Seismic Waves in the EarthClick here for animation

30 Click here for explanation of a tsunamiTsunamis Click here for explanation of a tsunami

31 Formation of a tsunami a large ocean wave usually caused by an underwater earthquake or a volcanic explosion. PBS –tsunami animation

32 With typical waves, water flows in circles, but with a tsunami, water flows straight. This is why tsunamis cause so much damage! Click here for Japan helicopter view of tsunami

33 Tsunami Warning System

34 Review Questions 1. A large ocean wave usually caused by an underwater earthquake or a volcanic explosion. tsunami 2. Used to describe both a sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip earthquake

35 How are Earthquakes Measured?3. Which one uses a logarithmic scale to express the total amount of energy released or magnitude of an earthquake. Richter Scale 4. Which uses a scale of earthquake intensity based on observed effects and ranging from I (detectable only with instruments) to XII (causing almost total destruction). Modified Mercalli Scale

36 What type of fault is shown by each picture?1. 2. Normal Reverse Transverse or strike-slip 3.

37 Which type of wave travels through solids only?S-wave

38 Which type of wave causes the most destruction?Surface or Love waves

39 What type of fault? B A Strike –slip or transverse faultA – reverse fault - hanging wall has moved upward B - Strike-slip fault // Source: indiana.edu Source: indiana.edu B A Strike –slip or transverse fault Hanging wall has moved upward Reverse fault

40 Focus – 1. point inside the Earth where an earthquake begins – 2. point on Earth’s surface above focus where earthquake is FELT most strongly Epicenter 2 1

41 People walk along a damaged road in the province of Bohol on Tuesday, October 15, 2013.Do you think this was a major earthquake? Why or why not?

42 Yes, it was a major quake. It crumbled a number of buildings Such as this church 7.1 magnitude earthquake hit the Philippines

43 Earthquakes 3. Surface 1. P-wave 2. S-wave Seismogram____________ seismic wave display record 4. Seismograph 5. __________ machine