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Chapter 6: Earthquakes Lessons 1-4
Transcript of Chapter 6: Earthquakes Lessons 1-4
By: James Gow, Ivy Tan, Katherine Loritz, and Tanner Pulice
Lesson 1: Earthquakes and Plate Boundaries
Lesson 3: Measuring Earthquakes
Now that we know what earthquakes are and the different seismic waves, the next question you might have is how to measure them. Seismographs are used to measure them by recording and measuring movements of the ground caused by seismic waves. The way a seismograph works is by attaching a weight to a pen. When the ground shakes, the pen moves. The seismograph then records the ground motion. This is called a seismogram.
To locate an epicenter, the first step is to find the different arrival times of the varying seismic waves. The next step is to find the distance from the epicenter. And then finally, the last step is to plot the distance found in step two on a map.
The magnitude scale is used to measure earthquake sizes. This scale is based on the seismogram records. They can also be described by the amount of damage they cause.
Lesson 2: Earthquakes and Seismic Waves
At the earthquake's focus, waves flow out of them. Above the focus, there is a spot called an epicenter. The waves produced by the elastic strain cause seismic waves. They include P-waves, S-waves, and Surface waves. P-waves or Primary waves travel the fastest and go about 5 km/s to 7 km/s depending on different rock material. S-waves also called Secondary waves travel slower, they move in a formation like a undulating Slinky. Surface waves are made up of both "straggler" P-waves and S-waves. they move in a side to side swaying motion and particles also move in a rolling motion. These waves are called surface waves because they travel on the surface of the crust causing destruction to bridges and buildings. In the early twentieth century scientists found places in the Earth that none of the seismic waves can travel through, those areas are called shadow zones. S-waves cannot go through liquid in the outer core. P-waves can travel through the core but it bends them a little. the bending of the P-waves and the stopping of the S-waves cause these shadow zones.
First of all, what is an earthquake? Well, an earthquake is the rupture and sudden movement along a fault. The movement can cause complex waves to release and shake objects. Earthquakes are caused by heat energy. When the heat energy is stored in Earth's interior, it is converted into kinetic energy. The energy then causes things to move.
Earthquakes begin at the focus, which is the location on a fault where the rupture and movement begin. The closer the focus is to the Earth's surface, the stronger the earthquake will be.
Different plate boundaries can cause different types of earthquakes. For example, a divergent plate boundary causes most earthquakes to be relatively smaller. However, earthquakes that occur on convergent plate boundaries are stronger. Transform plate boundaries tend to cause relatively shallow earthquakes as well, but can cause major earthquakes.
Earthquakes can also occur away from plate boundaries. These earthquakes often occur in the middle of continents. This can be dangerous, as people normally do not expect those earthquakes, and are usually not prepared for them.
Lesson 4 Earthquake Hazards and Safety
Earthquakes have many hazards. They can kill and injure people. Earthquakes can also cause damage to buildings and other structures. Earthquakes arent the only natural disaster that is made by plate movement , earthquakes cause Fire, Landslides, Liquefactiom,and tsunamis. There are ways to protect yourself from these disasters. You should plan ahead and make a safety kit. The kit should include food, water, blankets, and a game to keep you occupied because you will most likely be trapped for several hours depending on your situtation.
Summary of Chapter 6 Lessons 1-4
Earthquake Signs And Shelters
Lesson 1: This lesson is about Earthquakes and where it starts (focus)
Lesson 2:This lesson is about seismic (P-wave, S-wave and Surface waves) wave travel.
Lesson 3:This lesson is about recording siemic waves traveling and how to locate an epicenter.
Lesson 4: This lesson is about being safe and to know what earthquake hazards there are.
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Scientists have shown that the speed with which seismic waves travel through rock changes with the level of stress. That’s because the increased pressure squeezes tiny cracks in the rock together, Niu says. Therefore, measuring seismic wave speed “could, in principle, lead to a stress meter,” he adds.
Why does the increased pressure squeeze tiny cracks in rocks?
How would measuring seismic wave speed affect earthquakes?
What would the stress meter do?