# Locating an Earthquake - PowerPoint PPT Presentation

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Locating an Earthquake. Learning Goal. Analyze seismic data to predict the location and magnitude of an earthquake. Types of Waves. Primary Waves – (P-Wave) Fastest wave and moves rock particles back and forth. Secondary Wave – (S-Wave) Slower and moves rock particles up and down.

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Locating an Earthquake

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## Locating an Earthquake

### Learning Goal

• Analyze seismic data to predict the location and magnitude of an earthquake.

### Types of Waves

• Primary Waves – (P-Wave) Fastest wave and moves rock particles back and forth.

• Secondary Wave – (S-Wave) Slower and moves rock particles up and down

### Determining Distance

• By comparing the time difference between S and P waves we can calculate the distance an earthquake is from a seismograph station.

### Calculating Distance

• P waves travel between 6 and 13 km/sec. S-waves are slower and travel between 3.5 and 7.5 km/sec. In most regions, study of numerous earthquakes with well-known epicenter locations results in an empirical S-P curve, such as the one shown to the right.

### Magnitude

• The magnitude of an earthquake provides a convenient measure of its size scaled to a small number usually less than 9. It is a unitless number, derived from the amplitude of ground motion associated with S-waves, adjusted for the distance between the epicenter and the seismograph station

### Directions

• Go to the following web site: http://www.sciencecourseware.com/virtualearthquake/vquakeexecute.html

• Read through the Descriptions and directions.

• Pick an earthquake to predict its location and magnitude.

• Send your completion certificate to Jeff_Pierce@allenisd.org