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South Asia Earthquake Last SATURDAY, October 8th, 2005 30,000 current death toll…on the rise • The magnitude -7.6 earthquake hit South Asia Saturday, • Left a wake of damage spanning at least 250 miles from Jalalabad, Afghanistan, to the northern Indian territory. • It was the largest earthquake ever to rock the region! Indonesian Tsunami • December 2004 224,000 death toll • Sumatra, on the western most end of the Indonesian archipelago was the hardest hit, losing 131-thousand people in the region of Aceh alone. • In all, more than 176-thousand people in 11 countries were killed. Anatomy of an EARTHQUAKE Rock Deformations: o Elastic~ Earthquakes stem from this type, and can suddenly fracture if stretched too far. o Plastic~ Earthquakes do not come from this type, and the earth molds like putty. o Tectonic Plate~ Earthquakes also come from this type, and formation and movements cause them. Earthquakes and Tectonic Plates! • Plate boundaries occur in three sections: o Circum~ Pacific Belt. o Mediterranean Belt. o Himalayan Belt. More on Tectonic Plates… o They move between 1 and 16 cm/yr. That’s as o o o fast as a fingernail grows! Friction prevents plates from slipping past one another When the strain on the plates reaches a critical value, the rock fractures and an EARTHQUAKE ensues. Strong rock near plate boundary is elastic, while the edges are solid and immobile. Earth composed of thin crust, thick mantle, and core. Discovery of the Crust-Mantle Boundary • 1909 Andrija Mohrovicic discovered that seismic waves from a distant earthquake traveled more rapidly than those from a nearby earthquake • By analyzing the arrival times of the earthquake waves to many different seismographs, Mohrovicic identified the boundary between the crust and mantle • Mohrovicic discontinuity or the Moho Mantle • Seismic waves sped up abruptly at the crust-mantle boundary • Slowed down once they entered the asthenosphere (75 and 125 kilometers) • At the base of the asthenosphere (350 km) seismic waves sped up again • Then again seismic wave velocities increase again at 660 kilometers Core • Seismologists detect direct P and S waves up to 150 ° from the focus of an earthquake. • Between 105° and 140° “shadow zone” • No S waves arrive beyond 150° – not transmitted through liquids • Refraction patters of P waves liquid outer core and solid inner core