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Izmit Turkey Seismogram

Differences in density and other physical properties affect the velocity of seismic waves.

Granite (and Average Continental Crust)

6.0 km/sec

3.5 km/sec

2.5 km/sec

3.0 km/sec

Continental Crust:P-wave Velocity = 6 km/sec“Granite”

Oceanic Crust:P-wave Velocity = 7 km/sec“Basalt”

Crust6-7 km/sec

Mantle8-13 km/sec

Outer Core8-10 km/sec

Inner Core10-11 km/sec

P-wave Velocitie

s

speed of light in a vacuum = 300,000,000 m/s

speed of light in glass = 200,000,000 m/s

From:www.what-is-the-speed-of-light.com

Slow

SlowFast

Fast

T

Distanced measured in degrees from epicenter.

Travel-time versus Distance Curves

Distanced measured in degrees from epicenter.

Travel-time versus Distance Curves

P-wave reflected from Core-Mantle Boundary

PcP

Fast

Slow

Slow

Fast

Slow

Fast

“Moho”Andrija Mohorovicic

Zagreb Seismological Observatory1909

“Moho”Andrija Mohorovicic

Zagreb Seismological Observatory1909

Inner Core discovered by Inge Lehmann in 1936

Copenhagen Seismological Observatory

Inner Core discovered by Inge Lehmann in 1936

Copenhagen Seismological Observatory

Low Velocity Zone in Upper Mantle

Low Velocity Zone in Upper Mantle

Low Velocity Zone = Asthenosphere of Plate Tectonics

Mechanism of Plate Tectonics

Crust6-7 km/sec

Mantle8-13 km/sec

Outer Core8-10 km/sec

Inner Core10-11 km/sec

P-wave Velocitie

s

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