Earth Science Notes Earthquakes Objectives I can Identify

Earth Science Notes Earthquakes

Objectives I can… • Identify fault types – Normal, reverse, strike-slip • Explain how an Earthquake occurs – Elastic limit / Elastic Rebound / Plate Tectonics • Describe the types of waves generated by and earthquake – P-waves / Surface-waves

How Faults Form • Rocks can bend, compress or stretch • When rocks can no longer do this they break – creating a fault

Fault Types • Normal Faults – form when rocks are diverging

Normal Faults

Fault Types • Reverse Faults – form when rocks are converging

Reverse Faults

Fault Types • Strike-Slip Faults –form when rock moves past another rock Displacement is such that the material on the other side of the fault appears to be displaced to the left. Displacement is such that the material on the other side of the fault appears to be displaced to the right.

Strike-Slip Faults

What is an Earthquakes? • When plates move along faults it puts stress on rocks at the plates edge • Vibrations caused by plate movements are called earthquakes.

How Earthquakes Occur • Rocks move along faults and catch on each other. • Forces continue to build on rocks and they begin to distort. • Once the rocks reach their elastic limit they break. – Elastic rebound • Rocks readjust themselves and return to their original shape.

How Earthquakes Occur

Elastic Rebound

Elastic Limit is reached

Earthquakes Create Waves • Seismic Waves – waves that move through the earth that were created by an earthquake • Measured by a Seismograph – measures wave magnitude and time – There are horizontal and vertical LINES

Types of Seismic Waves • Primary Waves (P-Waves) – causes rocks to move back and forth in a linear manor

P - Waves

Types of Seismic Waves • Secondary Waves (S-Waves) – causes rocks to move at right angles in relation to the direction of the wave

S- Wave

S- Waves • S-waves do not travel through fluids. – Do not exist in Earth’s outer core. (inferred to be primarily liquid iron). – S waves travel slower than P waves in a solid and, therefore, arrive after the P wave.

P v. S Wave

Types of Seismic Waves • Surface Waves – causes rock to move in a backwards rolling motion – Most destructive type – Produced when earthquake energy reaches the surface Epicenter – point on the earth’s surface directly above the focus

Surface Waves

Wave Comparison

Summary Be able to… • Identify fault types – Normal, reverse, strike-slip • Explain how an Earthquake occurs – Elastic limit / Elastic Rebound / Plate Tectonics • Describe the types of waves generated by and earthquake – P-waves / Surface-waves