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How and where are earthquake waves detected and recorded?A seismograph is an instrument
that records earthquake waves.It is also used to determine the
magnitude of an earthquake the location of its epicenter.
Compressional Wave (P-Wave) Animation
Particle motion consists of alternating compression and dilation(enlargement & reduction). Particle motion is parallel to the direction of propagation (longitudinal). Material returns to its original shape after wave passes.
Shear Wave (S-Wave) Animation
Particle motion consists of alternating transverse motion. Particle motion is perpendicular to the direction of propagation. Transverse particle motion shown here is vertical but can be in any direction
Surface Wave (L-Wave) Animation
Particle motion consists of alternating transverse motions. Particle motion is horizontal and perpendicular to the direction of propagation (transverse).
Seismology
Types of seismic waves Body waves
Travel through Earth’s interior Two types based on mode of travel Primary (P) waves Push-pull (compress and expand) motion, changing
the volume of the intervening material Travel through solids, liquids, and gases Generally, in any solid material, P waves travel about
1.7 times faster than S waves
Seismology
Types of seismic waves Surface waves
Travel along outer part of Earth Cause greatest destruction Waves exhibit greatest amplitude and slowest velocity
Waves have the greatest periods (time interval between crests)
Often referred to as long waves, or L waves
Seismology
Types of seismic waves Body waves
Secondary (S) wavesShake" motion at right angles to their direction of
travel Travel only through solids Slower velocity than P waves Slightly greater amplitude than P waves
Locating the source of earthquakes
Terms Focus - the place within Earth where
earthquake waves originate Epicenter – location on the surface
directly above the focus Epicenter is located using the difference in
velocities of P and S waves
Draw the diagram on page 215 and write down the information on each caption.
What is the relationship between particle density and seismic wave?How and where are Earthquakes recorded? (page 217)Summarize how the magnitude of an earthquake is measured.
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