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Transcript of Earthquakes
What are the different types of seismic waves?
P-waves are one type of body wave (travel inside the Earth).
The back-and-forth wave motion alternately squeezes and stretches the rock material.
Can travel through – solid rock, magma, ocean water and air.
Primary Waves: P-waves
S-waves are the second type of body wave (travel inside the Earth).
The side-to-side wave causes particles to move at right angles (perpendicular) to the direction the waves are traveling.
Can travel through solids but NOT through liquids and gases.
Secondary Waves: S-waves
Surface waves, or L-waves (long waves), move along Earth's surface and travel like ripples on a pond.
Cause the most destruction
Surface Waves: L-waves
The two types of surface waves. (We'll just call them both surface waves)
An earthquake’s seismic waves can be detected with a seismograph machine.
What instrument is used to detect seismic waves?
The basic idea
The basic idea with technology
P-waves travel fastest, and hence arrive first.
The difference in the arrival time of the P- and S-waves is used to determine the distance to the focus.
Reading a Seismogram
By measuring the S-P arrival times at 3 or more stations, circles can be drawn around each station and where they meet indicates the earthquake's location or epicenter.
Two trains leave different cities heading toward each other at different speeds. When and where do they meet?
Train A, traveling 70 miles per hour (mph), leaves Westford heading toward Eastford, 260 miles away. At the same time Train B, traveling 60 mph, leaves Eastford heading toward Westford. When do the two trains meet? How far from each city do they meet?
To solve this problem, we'll use the distance formula:
Distance = Rate x Time
It's like the infamous math problem...
By knowing the rate (wave velocities) and determining the difference in arrival times, scientists can calculate the distance to the earthquake.
Seismographs also provide a way to monitor for nuclear explosions. This helps to prevent countries from secretly building and testing nuclear weapons.
Besides detecting earthquakes and nuclear explosions, seismic waves have also helped us to map the Earth’s interior.
Compressional Wave (P-Wave) Animation
Deformation propagates. Particle motion consists of alternating
compression and dilation. Particle motion is parallel to the direction of propagation (longitudinal). Material returns to its original shape after wave passes.
P-wave & S-wave demo
Sing along! :)
What machine is actually used to detect earthquakes?
Seismology: the study of earthquakes