locating earthquakes. solid inner core fluid outer core → magnetic field! flexible mantle brittle...
TRANSCRIPT
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Locating Earthquakes
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Solid Inner Core
Fluid Outer Core → magnetic field!
Flexible Mantle
Brittle Crust
What's inside the Earth...
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Convective motions in Earth’s mantle:
→ heat transfer from the core→ hot spots on the surface→ pressure on tectonic plates
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Earth’s Tectonic Plates
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The focus, which is below the Earth’s surface,is where an earthquake occurs.
The epicenter is the point on the Earth’s surfacedirectly above the focus.
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Earthquakes send out seismic waves...
...and seismometers detect them on the surface.
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Useful characteristics about the waves:
- shear waves- travel up and down- travel slowly- cannot travel through liquid
S Waves
- pressure waves- travel back and forth- travel quickly- can travel through anything
P Waves
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Useful characteristics about the waves:
- shear waves- travel up and down- travel slowly- cannot travel through liquid
S Waves
- pressure waves- travel back and forth- travel quickly- can travel through anything
P Waves
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Another useful characteristic about the waves:
Since they travel at different speeds, we canfigure out distance to the earthquake.
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Another useful characteristic about the waves:
Since they travel at different speeds, we canfigure out distance to the earthquake.
![Page 13: Locating Earthquakes. Solid Inner Core Fluid Outer Core → magnetic field! Flexible Mantle Brittle Crust What's inside the Earth](https://reader036.vdocument.in/reader036/viewer/2022062518/56649ea05503460f94ba2938/html5/thumbnails/13.jpg)
Another useful characteristic about the waves:
Since they travel at different speeds, we canfigure out distance to the earthquake.
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Another useful characteristic about the waves:
Since they travel at different speeds, we canfigure out distance to the earthquake.
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With distance data from 3 cities, we canfigure out where the earthquake occurred.
This is called triangulation.
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This is good for a shallow earthquake.
What if it's not shallow?
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This is good for a shallow earthquake.
What if it's not shallow?
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This is good for a shallow earthquake.
Not as good for a deep earthquake.
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Distance (km) to focus = δt x _____________________(P speed) x (S speed)
(P speed) – (S speed)
(Don't forget to convert to cm on your map!)
To calculate distance to the earthquake...
Arrival times are given in hrs:min:sec For example, 14:35:27.8 and 14:36:19.6
δt is the difference between those times In the above example, δt = 51.8 seconds