Transcript Chapter 8
Chapter 8 Earthquakes Recent Earthquakes • • • • • • • Kobe Earthquake 07.01.1995 Satellite Photos - Japan Before and After Tsunami - Interactive Feature NYTimes.com Video of Tsunami - Video Library - The New York Times Earthquake and Tsunami - Video Library - The New York Times Day 2: Japan's Earthquake - Video Library - The New York Times Day 3: Japan’s Nuclear Woes - Video Library - The New York Times Widespread Devastation in Japan - Video Library - The New York Times Where do earthquakes occur? • On Earth of course • Seismology is the study of earthquakes • Most quakes occur at the edge of tectonic plates • Tectonic plates are pieces of the lithosphere that move on top of the asthenosphere Plate tectonics • Plates push and pull upon one another • Faults occur when the crust breaks • Breaks occur at the edge of plate boundaries What causes Quakes • The changing of rocks due to stress is called deformation • Focus is the area in the crust where the rock under stress breaks • Epicenter is the point on Earth’s surface directly above the focus Focus and epicenter Earthquake Characteristics Plate Boundary Fault type Stress force Transform Strike-slip Shearing Convergent Reverse Compression Divergent Tension Normal E-quake Motion • Seismic Waves – Waves of energy that travel through the earth • Seismic waves classified as: – P waves – S waves – Surface P and S waves • Travel through the Earth • Released from Focus • When they reach the surface at epicenter become Surface waves P and S Wave Characteristics • • • • • P waves Primary wave Pressure wave Arrives first Travels through solid, liquid or gas • 1st wave to be detected • • • • • S waves Secondary wave Shear wave Arrives last Cannot travel through liquid Surface wave • Move the ground up and down in circles • Travel slower than P and S but are more destructive Measuring E-quakes • Common Methods – Mercalli • Rating based upon damage – Richter • Rating based upon seismic wave – Moment Magnitude • Rating based upon total energy released • Used to rate all earthquakes Earthquake Damage • Damage occurs due to: – Shaking – Liquefaction • Loose soil turns to mud – Aftershocks • Earthquake after larger earthquake – Tsunamis • Water displacement