100% Exciting! 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 Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core km/sec P-wave Velocities 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 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 Fast Slow Fast Moho Andrija Mohorovicic Zagreb Seismological Observatory 1909 Moho Andrija Mohorovicic Zagreb Seismological Observatory 1909 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 = Asthenosphere of Plate Tectonics Mechanism of Plate Tectonics Crust 6-7 km/sec Mantle 8-13 km/sec Outer Core 8-10 km/sec Inner Core km/sec P-wave Velocities A Must-See Movie!