Earthquakes What are Earthquakes Earthquakes the sudden movement

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Earthquakes

Earthquakes

What are Earthquakes?

What are Earthquakes?

Earthquakes: the sudden movement of Earth’s Crust!

Earthquakes: the sudden movement of Earth’s Crust!

Where Do Earthquakes Occur? • Mostly occur near tectonic plate • A break in

Where Do Earthquakes Occur? • Mostly occur near tectonic plate • A break in the Earth’s crust where movement occurs is called a fault.

The Three Types of Faults Plate Motion Transform Boundary (shearing) Convergent Boundary (compression) Divergent

The Three Types of Faults Plate Motion Transform Boundary (shearing) Convergent Boundary (compression) Divergent Boundary (tension) Fault Name Strike Slip Fault Reverse Fault Normal Fault Movement

What Causes Earthquakes? • Deformation of the plates! Rocks that are under stress can

What Causes Earthquakes? • Deformation of the plates! Rocks that are under stress can eventually break = EQ! • Elastic Rebound = when rocks suddenly break and spring back to their original shape. Check out the DEMO: http: //projects. crustal. ucsb. edu/understanding/elastic/rebound. html

How Do Earthquake Waves Travel? There are 3 types of seismic waves: 1. Primary

How Do Earthquake Waves Travel? There are 3 types of seismic waves: 1. Primary Waves: P-Waves 2. Secondary Waves: S-Waves 3. Surface Waves Click Here for animation!

Primary Waves (P-Waves) • • Move the fastest Move in a straight line Compress

Primary Waves (P-Waves) • • Move the fastest Move in a straight line Compress and expand like an accordion Move through solids, liquids, and gases

P-Wave

P-Wave

Secondary Waves (S-Waves) • 2 nd fastest • Vibrate side to side and up

Secondary Waves (S-Waves) • 2 nd fastest • Vibrate side to side and up and down • Can only move through solids

S-Wave

S-Wave

Surface Waves • Result of P-waves and S-waves when they reach the surface •

Surface Waves • Result of P-waves and S-waves when they reach the surface • Only travel in the crust! • Slowest seismic waves • Make the ground roll like ocean waves • Responsible for surface damage and falling buildings.

Surface Waves Notice the top is moving more than the bottom!

Surface Waves Notice the top is moving more than the bottom!

Surface Wave Diagram

Surface Wave Diagram

How are earthquakes measured? • Seismograph: records ground movements of earthquakes • The pendulum

How are earthquakes measured? • Seismograph: records ground movements of earthquakes • The pendulum sits still while the ground moves. http: //www. wwnorton. com/college/geo/egeo/flash/8_3. swf

What is the seismograph measuring? • Epicenter: Center of earthquake ABOVE GROUND • Focus:

What is the seismograph measuring? • Epicenter: Center of earthquake ABOVE GROUND • Focus: Point where rocks break UNDERGROUND

Earthquake Location

Earthquake Location

Earthquake Effects - Ground Shaking Loma Prieta, CA 1989 KGO-TV News ABC-7

Earthquake Effects - Ground Shaking Loma Prieta, CA 1989 KGO-TV News ABC-7

Earthquake Effects - Ground Shaking Kobe, Japan 1995

Earthquake Effects - Ground Shaking Kobe, Japan 1995

Earthquake Effects - Ground Shaking Kobe, Japan 1995

Earthquake Effects - Ground Shaking Kobe, Japan 1995

Earthquake Effects - Surface Faulting Landers, CA 1992

Earthquake Effects - Surface Faulting Landers, CA 1992

Earthquake Effects - Landslides Source: National Geophysical Data Center Turnagain Heights, Alaska, 1964 (upper

Earthquake Effects - Landslides Source: National Geophysical Data Center Turnagain Heights, Alaska, 1964 (upper left inset); Santa Cruz Mtns, California , 1989