# Earthquakes Liz La Rosa http www middleschoolscience com

• Slides: 23

Earthquakes Liz La. Rosa http: //www. middleschoolscience. com 2009 for my 5 th grade science class 2009

What is an earthquake? • Used to describe both sudden slip on a fault, and the resulting ground shaking and radiated seismic energy caused by the slip • Caused by volcanic or magmatic activity, • Caused by other sudden stress changes in the earth.

Three Types of Faults Strike-Slip Thrust Normal

What causes earthquakes? • Tectonic plates move past each other causing stress. Stress causes the rock to deform – Plastic deformation – does not cause earthquakes – Elastic deformation – rock stretches then reaches a breaking point, releasing energy.

Elastic Rebound – deformed rock goes back to its original shape http: //www. uwgb. edu/dutchs/Earth. SC-

Focus – point inside the Earth where an earthquake begins Epicenter – point on Earth’s surface above focus

How Seismographs Work the pendulum remains fixed as the ground moves beneath it http: //www. uwgb. edu/dutchs/Earth. SC 102 Visuals. Index. HTM

Typical Seismogram http: //isu. indstate. edu/jspeer/Earth&Sky/Earth. Ch 11. ppt

Primary Waves (P Waves) • A type of seismic wave that compresses and expands the ground • The first wave to arrive at an earthquake http: //daphne. meccahosting. com/~a 0000 e 89/insideearth 2. htm

Secondary Waves (S Waves) • A type of seismic wave that moves the ground up and down or side to side http: //daphne. meccahosting. com/~a 0000 e 89/insideearth 2. htm

Comparing Seismic Waves

Surface Waves • Move along the Earth’s surface • Produces motion in the upper crust – Motion can be up and down – Motion can be around – Motion can be back and forth • Travel more slowly than S and P waves • More destructive

How do scientists calculate how far a location is from the epicenter of an earthquake? • Scientists calculate the difference between arrival times of the P waves and S waves • The further away an earthquake is, the greater the time between the arrival of the P waves and the S waves

Locating Earthquakes http: //www. uwgb. edu/dutchs/Earth. SC 102 Visuals. Index. HTM

Locating Earthquakes http: //www. uwgb. edu/dutchs/Earth. SC 102 Visuals. Index. HTM

Locating Earthquakes http: //www. uwgb. edu/dutchs/Earth. SC 102 Visuals. Index. HTM

How are Earthquakes Measured? Richter Scale

How are Earthquakes Measured? Mercalli Intensity Scale http: //www. iknowthat. com/mhscience/Earthquakes/Fixed. htm

Earthquake Waves & Earth’s Interior

Seismic Waves in the Earth http: //www. uwgb. edu/dutchs/Earth. SC 102 Visuals. Index. HTM

Tsunamis http: //www. uwgb. edu/dutchs/Earth. SC-

Formation of a tsunami http: //isu. indstate. edu/jspeer/Earth&Sky/Earth. Ch 11. ppt

Tsunami Warning System http: //isu. indstate. edu/jspeer/Earth&Sky/Earth. Ch 11. ppt