8.2 measuring earthquakesnewburyparkhighschool.net/stillwagon/geoscp/notes/8.2...travels the...
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Earthquake Zones
• About 95% of major earthquakes occur in a few narrow zones
(plate boundaries)
http://www.iris.edu/seismon/
Seismographs (seismometer) - instruments
that record earthquake waves.
Seismograms - traces of amplified,
electronically recorded ground motion
made by seismographs.
Seismograph Seismogram
Types of Waves
#1: P-waves: primary waves
- LONGITUDINAL waves: push (compress) &
pull (expand) in the direction that the
waves travel
- Fastest speed (velocity) of all quake waves
- Travel through solids, liquids & gases
Earthquake Waves
Body Waves – (2 types) P or S waves
#2: S-waves: secondary waves
- TRANSVERSE waves: shake particles
at right angles to the direction that they
travel
- Travel along Earth’s outer layers
- Travel only through solids!!!!!
- Cause more damage than p-waves
Surface waves
- only move across Earth’s surface
- Combination of Earth moving up &
down and back & forth
- Most destruction due to longer
wavelengths
Locating an Earthquake - TRIANGULATION
• Convert the arrival time difference into
distance with a Distance -Time graph
Step 2: Find the Earthquakes Distance
Step 1: Measure the difference in arrival times
between P and S waves from a seismograph
Explaining Earthquakes
• Plot the possible locations
of an earthquake from 3 or
more seismic recordings
TRIANGULATION
Step 3: Find the Earthquakes Direction
Travels the fastest; the first wave to pass seismic stations
Does not travel through Earth’s Body
Waves can only travel through solids
Are push-pull or compression waves
Traverse waves: move particles at right angles compared to the direction that they
travel and are known as
Waves move up and down and side to side
Waves can travel through solids, liquids, or gases
The second wave to arrive a seismic station
The most destructive but are the last waves to arrive at a seismic station
Label the blank areas with one of the three seismic waves