Earthquakes

March 14, 2011

Announcements- write these on your homework sheet

• Open notes Earthquakes quiz _____________________!

• Your Unit 3 Part 2 vocab is due _________________

• Earthquakes and Volcanoes test is ___________________!–Review (maybe do quiz corrections)

and STUDY your quiz and notes before then!

Discuss:• What type of plate boundary creates

Earthquakes?

• What do you think causes the earth to shake during an earthquake?

Objectives

• I will be able to describe an earthquake’s features such as epicenter, focus, magnitude, and intensity

• I will be able to analyze the energies of seismic earthquake waves

• I will be able to determine earthquake location from a travel-time graph

Key Points• To describe the location of earthquakes, we use the

terms _______________and _____________________• When analyzing how earthquakes travel, we talk about

the 3 main types of earthquake waves: _____________________________________________– These waves travel at different speeds and cause differing

amounts of destruction– The ______________________of an earthquake measures

the _______________________of the largest wave• Major earthquakes can be preceded by foreshocks and

followed by aftershocks• The _______________________of an earthquake

describes the ______________________ at a specific location

What are Earthquakes?

• Earthquake video

• Take note of at least 4 facts

1.______________________2.______________________3.______________________4.______________________

Cause of Earthquakes

• What causes earthquakes to occur?

• Where do we usually find earthquakes occurring?

Cause of Earthquakes

• Earthquakes are the vibration or shaking of the Earth __________________________________

• When rocks are subjected to large forces, such as those associated with plate movement, the rocks are stressed and strained

• When rocks cannot withstand the stress any longer, they break or shift and energy is released

• Faults are fractures in the earth where movement has occurred

• ________________________________________

Earthquake features1. Location– Focus: the place ________________________-

the source• Energy radiates out in __________________________

_________________________

– Epicenter: the ____________________________ directly above the focus

Earthquake features2. __________________: _____________________ that

precede or _________________________ major earthquakes

3. __________________: smaller earthquakes that occur after major earthquakes

4. __________________: the ______________________ produced by an earthquake at a given location

5. __________________: the “size” of the earthquake- ______________________________: determined from the ___________________________________________ ______________________________________________- Moment magnitude: determined from the displacement (movement) of the fault zone

Earthquake Waves

• All of the above features are a result of the ____________________________________ from the focus outward in all directions

• Two general categories– _______________________: travel along Earth’s

surface– _______________________: travel from the focus

through Earth’s layers

Earthquake Waves

• ___________________________________– Travel along Earth’s outer layer– Their motion is complex• Like waves move a ship on the ocean• _________________________________________

– The ___________________________________ of earthquake wave• Because they travel along the ground they cause

anything resting on the land to move

Earthquake Waves

• Body waves- 2 types1. ____________________• Primary waves- they ________________• Travel the ________________• Classified as “compressional waves”-

push-pull motion• Can travel through solids, liquids, and

gases

Earthquake Waves

• Body waves2. ________________• ________________/seismic waves- they

arrive ______________________• _______________________than P-

waves• Travel at right angles to the direction

they move• Travel through ________________only

Check In – Answer the following on a SEPARATE piece of paper in

COMPLETE sentences:1. What is the epicenter of an earthquake?2. What is the source of an earthquake called?3. What are the smaller earthquakes that precede

major earthquakes called?4. Which type of seismic wave travels the fastest?5. Which type of seismic wave travels the slowest?6. Which type of seismic wave causes the most

destruction?7. What is the amount of shaking produced by an

earthquake at a given location?

Objectives

• Today I will be able to:– Analyze the number of seismic stations necessary

to locate an earthquake epicenter– Describe other natural side effects of earthquakes– Analyze how earthquake waves provide

information about earth’s interior– Describe earthquake safety measures

Locating Earthquakes- Part II

• Using earthquake waves to locate an epicenter

• ESSENTIAL QUESTION WHILE YOU’RE WATCHING…

HOW MANY SEISMIC STATIONS WOULD YOU NEED TO ACCURATELY LOCATE AN EARTHQUAKE EPICENTER? _____________

Other useful information from earthquake waves

• Earthquake _______________tell us the __________________of an earthquake’s _______________________________________

• Earthquake waves also tell us about the ________________________________________– This information is available because s- waves and p-

waves travel at different speeds and are able to pass through different materials

• BOTTOM LINE: most of the information we know about the earth’s interior was obtained ________________________________________

Effects of Earthquakes

• Main effect of earthquakes… A lot of destruction

• Side effects:– _____________________________ triggered by

earthquakes occurring underwater• Ocean waves caused by submarine earthquakes

– _______________- ground movement and _________________________

– ____________- ____________________________ _________________________________________

Earthquake Safety

• Structures that withstood the shaking…– Candlestick park

• Built on ____________________________

• Structures that did not withstand the shaking…– Bay Bridge- too stiff and ________________________– Freeway in Oakland- ______________or reinforced– Landfill

• Soft land• Buildings sank and collapsed, ____________________broke

Earthquake Safety• Buildings can sink!?– The process is known as ________________________

– Let’s see how it works– Liquefaction

Bottom line: The _______________ location during a major earthquake would be an area with _______________________________________… and if possible a location that has been _____________________________

Check In – Answer on a separate piece of paper in complete sentences:

8. Most of the information about Earth’s interior was obtained by studying what?

9. What is the minimum number of seismic stations needed to determine the location of an earthquake?

10. Describe the type of building that would be safest during an earthquake.

11. How would the lives of people living in areas affected by tsunamis be effected if earthquakes stopped happening?

Recent Earthquakes

• Listen as I describe and we watch footage from recent earthquakes in Haiti, Chile, and Japan.

• All suffered devastating earthquakes in the past 2 years, while you watch thing of things they have in common and things that are different about them.

– http://www.boston.com/bigpicture/2010/01/earthquake_in_haiti.html

– http://www.boston.com/bigpicture/2010/02/earthquake_in_chile.html