Locating an earthquake The difference in velocities of a P wave and S wave provides a way to locate the epicenter Use a travel-time graph Need at least three seismograph station data

Intensity and Magnitude of Earthquakes Two different types of measurements to describe the size of an earthquake (intensity and magnitude) Intensity A measure of the amount of earthquake shaking at a given location based on the amount of damage Magnitude A measure of the size of seismic waves or the amount of energy released at the source of an earthquake

The Scales Richter Scale Measures the magnitude of an earthquake Based on the amplitude of the largest seismic wave 10-fold system (ex: The amount of shaking for a 5.0 earthquake is 10 times greater than the shaking produced by an earthquake of 4.0 on the Richter Scale

The Scales Moment Magnitude More precise means of measuring earthquakes Amount of displacement that occurs along a fault zone Calculated using several factors Average amount of movement along the fault Area of the surface break Strength of the broken rock Most widely used measurement for earthquakes because it is the only magnitude scale that estimates the energy released by earthquakes

Destruction from Earthquakes Seismic Vibration-Damage to building depend on several factors Intensity and duration of vibration Nature of the material on which the structure is built Design of the structure Liquefaction Stable soil turns into a liquid that is not able to support buildings or other structure

Tsunami Seismic sea waves Triggered by an earthquake occurring where a slab of the ocean floor is displaced vertically along a fault tsunami videos

Other Dangers Landslides Fires Sinking of the ground triggered by the vibration Greatest damage to structures Fires Caused by ruptured gas lines

Predicting Earthquakes Short range Methods for short range predictions of earthquakes have not been successful Long range Based on the idea that earthquakes are repetitive Seismic gap: an area along a fault where there has not been any earthquake for a long-period of time

Virtual Earthquake http://www.sciencecourseware.com/eec/Earthquake/ Main Activities: Time travel Graph Recommended: Tutorials (top right) Tasks – use different tools to gather and record in journal at bottom of screen Show teacher after you verify your answers Main Activities: Epicenter and Magnitude