EARTHQUAKES INTRODUCTION TO EARTHQUAKES • Earthquake = • a vibration of the Earth produced by the release of energy. Seismology is the study of earthquakes and seismic waves that move through and around the earth. A seismologist is a scientist who studies earthquakes and seismic waves What is the epicenter and focus of an earthquake? • Energy that creates an earthquake moves out from the focus. • The focus is the place within the Earth where the rocks breaks, producing an earthquake. • The epicenter of an earthquake is the point on the ground’s surface directly above the focus. Waves associated with earthquakes • Energy moving outward from the focus of an earthquake travels in the form of seismic waves. TYPES OF SEISMIC WAVES • The two main types of seismic waves are body waves and surface waves. Body Waves Surface Waves HOW DO SCIENTISTS MEASURE EARTHQUAKES • There are two ways in which scientists quantify the size of earthquakes: magnitude and intensity • Earthquake magnitudes are measured using the Richter Scale. WHERE ARE EARTHQUAKES MOST COMMON? • No part of the Earth’s surface is safe from earthquakes. But some areas experience them more frequently than others. • Earthquakes are most common at plate boundaries, where different tectonic plates meet. The largest events usually happen where two plates are colliding- this is where a large amounts of stress can build up rapidly About 80 percent of all recorded earthquakes occur at the circum-Pacific seismic belt, commonly known as the Rim of Fire due to the prevalence of seismic and volcanic activity Other facts about Earthquakes put together… • Tectonic earthquakes are most common • Earthquake is in other words, a shaking or trembling of the earth that accompanies rock movements extending anywhere from the crust to 680 km below the Earth's surface. • The tsunami that hit Indonesia and killed more than 150,000 people would be measured at 9.0 in Richter Scale. • Earthquakes release stress which causes permanent change in the Earth's crust.