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Seismic waves are elastic waves.
Four types:
2 Body Waves.
So called because they travel through the Earth.
These are P & S waves.
P = primary
S = secondary or shear
2 surface waves.
So called because they travel primarily on surface.
These are Love waves and Rayleigh waves.
Two types of Surface Waves
Wavefronts and rays
Period, amplitude and frequency
Equations for Vp and Vs
Vp ~ 1.7 Vs
Since Vp > Vs > Vsw P waves generally arrive at a station first.
Mag 6.9 Earthquake in Kamchatka
Recorded in Mount Soledad
What happen when the ray/wave hits an interface?
Snell’s Law:
sin 1 sin  2

V1
V2
What happens to waves in the Earth?
Density increases due to pressure but so do the
bulk and shear moduli.
Therefore rays bend!
P-wave SZ is
between 104°
and 140°.
S-wave SZ
between 104 °
and 256°
Labeling Waves.
P = direct P
S = direct S
p = P-wave that travels up first
s = S-wave that travels up first
PP = One bounce at surface of P wave
SS = One bounce at surface of S wave
c = reflection from core
K = P wave through outer core
I = P wave through inner core
i = P wave refected from inner core
J = S wave through inner core
Combine:
PcP = P wave that bounces off outer core and goes to surface
PcS = P wave that bounces off outer core and converts to S which Travels to
the surface
ScS = S wave that bounces off outer core and goes to surface
etc
Show movies.
Homog.1.avi
Prem-path.avi
Raypath.avi