1. Earthquakes

2. Do Now: Read the following text and attempt to answer the questions in your notebook.
Well before dawn on January 17, 1994, a powerful earthquake struck Los Angeles, California. Bridges collapsed, roads buckled, and buildings toppled. Five thousand people were injured, and damages totaled about $20 billion.
Earthquakes are much more common in California and the West than in other parts of the United States. As Californians know, a strong earthquake can strike their region suddenly and without warning.
Why can a strong earthquake cause so much damage?
How can people prepare for an earthquake?

3. Do Now: Read the following text and answer the questions in your notebook.
Why can a strong earthquake cause so much damage?
The vibrations from a severe earthquake can transfer to any structure that has contact with the ground, including roads, buildings, power lines, and water mains. Damages to a city’s infrastructure can impede rescue workers and make emergency situations even worse.
2. How can people prepare for an earthquake?
People can learn and practice how to stay safe during an earthquake, and they can keep emergency supply kits handy. Buildings and roads can be built to better withstand earthquakes.

4. Normal vs. Reverse Fault: Pay attention to the angle of the fault
Normal Fault
If you were to hold the foot wall stationary, gravity will normally want to pull the hanging wall down.
Reverse Fault
If you were to hold the foot wall stationary and reversed gravity, then the hanging wall would slide upwards.

5. Types of Faults California (M 6.9 in 1979) Moab, Utah Arizona Reverse
Strike-Slip
Normal
California (M 6.9 in 1979)
Moab, Utah
Arizona

6. Parts of an earthquake
When rocks move along a fault, they release seismic waves: energy that travels as vibrations on and in Earth.
Onda sismica: energia que viaja en forma de vibraciones por encima y dentro de la Tierra.
Focus: a location inside Earth where seismic waves originate and rocks first move along a fault
Foco: lugar en el interior de la Tierra donde se originan las ondas sismicas, las cuales son producidas por el movimiento de las rocas a lo largo de un falla.

7. Parts of an earthquake
Epicenter: the location on Earth’s surface directly above the earthquake’s focus.
epicentro: lugar en la superficie de la Tierra justo encima del foco de un terremoto.

8. Seismic Waves
During an earthquake, a rapid release of energy along a fault produces seismic waves, similar to dropping a stone into water.
Seismic waves transfer energy through the ground and produce motion that you feel during an earthquake.

9. Seismic Waves
When an earthquake occurs, particles in the ground can move back and forth, up and down, or in an elliptical motion.
Scientists use wave motion, wave speed, and the type of material that the waves travel through to classify seismic waves.
The three types of seismic waves are primary waves, secondary waves, and surface waves.

10. Rock particles vibrate in same direction waves travel
Primary waves: also called P-waves, a type of seismic wave which cause particles in the ground to move in a push-pull motion similar to a coiled spring.
Onda primaria (tambien, onda P): tipo de onda sismica que causa un movimiento de atraccion y repulsion en las particulas del suelo, similar a un resorte.
Rock particles vibrate in same direction waves travel
Fastest seismic waves
First to be detected and recorded
Travel through solids and liquids

11. Rock particles vibrate perpendicular to direction waves travel
Secondary wave:, also called S-wave, a type of seismic wave that causes particles to move at right angles relative to the direction the wave travels
Onda secundaria (tambien, onda S): tipo de onda sismica que causa que las particulas se muevan en angulos rectos respecto a la direccion en que la onda viaja.
Rock particles vibrate perpendicular to direction waves travel
Slower than P-waves, but faster than surface waves
Only travel through solids

12. Generally cause the most damage at Earth’s surface.
Surface wave: a type of seismic wave that causes particles in the ground to move up and down in a rolling motion.
Onda superficial: tipo de onda sismica que causa un movimiento de rodamiento hacia arriba y hacia debajo de las particular en el suelo.
Rock particles move in a rolling or elliptical motion in the same direction as waves travel.
Slowest seismic wave
Generally cause the most damage at Earth’s surface.

13. Activity: Human Wave
Objective:Model how the waves are travelling through the ground, with each person representing a separate particle.
P-waves:
0:10 at es_in_the_classroom
S-waves: 2:00 at mic_waves_in_the_classroom

14. Human Wave Model Limits
Seismic waves only travel outward all directions; not just in one direction like the line of students
Seismic waves also travel at speeds that are much faster, about 3000x faster, than the waves in the Human Wave model
The particle motion of an S wave can be in any direction that is perpendicular to the direction of wave propagation; not just up and down as shown in the demo

16. Why does this matter? Mapping Earth’s Interior
Seismologists: scientists that study earthquakes.
Sismologo: cientifico que estudia los terremotos
They use the properties of seismic waves to map Earth’s interior.
P-waves and S-waves at different depths within Earth’s interior travel at different speeds.

17. Why does this matter? Mapping Earth’s Interior
Through extensive earthquake studies, seismologists discovered S- waves cannot travel through the outer core, proving that Earth’s outer core is liquid unlike the solid inner core.
By analyzing P-wave speed travelling through the core, seismologists discovered the core is made of mostly iron and nickel.

18. Why does this matter? Earthquake risk
Because earthquakes threaten people’s lives and property, seismologists study the probability that an earthquake will occur in a given area. Probability is one of several factors that contribute to earthquake risk assessment.

19. Why does this matter? Earthquake Risk
Seismometer: an instrument that measures and records ground motion and the distance and direction that seismic waves travel.
Sismometro: instrument que mide y registra el movimiento del suelo y que determina la distancia de las ondas sismicas.
Ground motion is recorded as a seismogram: a graphical illustration of earthquake waves.
sismograma: ilustracion grafica de las ondas sismicas.

20. Locating an earthquake’s epicenter
Seismologists use a method called triangulation to locate an earthquake’s epicenter. Triangulation uses the speeds and travel times of seismic waves to determine the distance to the epicenter from at least 3 different seismometers.

21. Describing Earthquake Magnitude
Scientists can use three different scales to measure and describe earthquakes.
The Richter magnitude scale uses the amount of ground motion at a given distance from an earthquake to determine magnitude.
Each increase of 1 unit represents 10x the amount of ground motion on a seismogram.
Ex: a magnitude 8 earthquakes produces 10 times greater shaking than a magnitude 7 earthquake and 100 times greater shaking than a magnitude 6 earthquake does.

22. Describing Earthquake Magnitude
The moment magnitude scale measures the total amount of energy released by the earthquake.
For each increase of one unit on the scale, the earthquake releases 31.5x more energy.
Ex: a magnitude 8 earthquake releases more than 992x the amount of energy than that of a magnitude 6 earthquake.

23. Determining Earthquake Intensity
The Modified Mercalli scale measures earthquake intensity based on descriptions of the earthquake’s effects on people and structures.

24. Earthquake Risk
Seismologists use probability and study earthquake history, the geology around a fault, the population density, and the building design in an area to evaluate risk.
Areas that experienced earthquakes in the past will likely experience earthquakes again.
Based on this information, engineers design earthquake-safe structures to withstand the shaking during an earthquake.

25. Determining Earthquake Magnitude (cont.)
How do seismologists evaluate risk?

26. Lesson 1 - VS
The focus is the area on a fault where an earthquake begins.

27. Lesson 1 - VS
Earthquakes occur along plate boundaries.

28. Lesson 1 - VS
Seismologists assess earthquake risk by studying past earthquake activity and local geology.

29. Lesson 1 – LR1 A. fault B. seismic wave C. epicenter D. seismogram
Which term refers to the location on Earth’s surface directly above an earthquake’s focus?
A. fault
B. seismic wave
C. epicenter
D. seismogram

30. Lesson 1 – LR2
Which of these uses the amount of ground motion at a given distance from an earthquake to determine magnitude?
A. the Richter magnitude scale
B. the moment magnitude scale
C. the Modified Mercalli scale
D. seismogram

31. Lesson 1 – LR3 A. primary waves B. secondary waves C. surface waves
Which of these cause particles to move at right angles relative to the direction the wave travels?
A. primary waves
B. secondary waves
C. surface waves
D. epicenter

32. Lesson 1 - Now
Do you agree or disagree?
1. Earth’s crust is broken into rigid slabs of rock that move, causing earthquakes and volcanic eruptions.
2. Earthquakes cause energy waves that travel through Earth.
3. Earthquakes can be predicted.