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Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Dec 24, 2015

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Hilary Sims
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Page 1: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquakes

Page 2: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Plate Boundaries

Sketch the 3 type of plate boundaries

Page 3: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Pacific-North American Plate Boundary

Page 4: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Study

• Seismology – the study of earthquakes (#27)

• Seismologist – person who studies earthquakes

Page 5: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Where?

• Most occur near tectonic plate boundaries

Page 6: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Causes

• Deformation – bending, tilting, and breaking of Earth’s crust (#28)

• Caused by plates pushing, pulling & sliding

• 2 kinds of deformation– Plastic – bends like piece of soft clay

• No earthquake

– Elastic – stretches like a rubber band• Earthquake

Page 7: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Elastic Rebound• Elastic rebound – sudden return of elastically

deformed rock to its undeformed shape– Like a stretched rubber band that breaks and returns

to its unstretched shape, now in 2 pieces– Energy released as seismic waves

Page 8: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Normal

Divergent

Reverse

Convergent

Strike-slip

Transform

Page 9: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Body Waves• Seismic waves – waves of energy that travel through Earth, away

from an earthquake in all directions (#29)• Two types of body waves that travel through interior of Earth

– P waves• Primary waves (#30)• Pressure waves (#30)• Back and forth motion (#30)• Go through solid, liquid, gas• Fastest wave

– S waves• Secondary waves (#31)• Shear waves (#31)• Side to side motion (#31) • Go through solids only• Slower wave, 2nd to arrive

Page 10: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

More Waves• Surface waves – waves

that move in top few km of the crust– Up, down, circular

motion– Back and forth motion

• Travel slower than body waves

• More destructive

Page 11: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Draw pictures of P and S Waves

Page 12: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Measurement• Seismograph – instrument that

records ground vibrations to find location and strength of earthquake

• Seismogram – tracing of earthquake motion created by a seismograph

• Epicenter – point on Earth’s surface directly above an earthquake (#32)

• Focus – point on a fault where earthquake motion first occurs (#33)

Page 13: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Location

Page 14: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Finding Epicenter – Step 1• Scientists use the S-P Time Method

– Use a time-distance graph– S and P curves are already calculated– Determine distance away from epicenter for at least 3 seismograms

Page 15: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Finding Epicenter – Step 2

Page 16: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Strength

• Richter Magnitude Scale –– Created in 1930s by Charles Richter– Magnitude measures strength of earthquake

by ground motion adjusted for distance from epicenter

– Each unit represents 10x increase in strength• 5.0 is 10x stronger than a 4.0• 6.0 is 100x stronger than a 4.0

Page 17: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Richter Magnitude Scale

Page 18: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Intensity

• Intensity – degree to which earthquake is felt and amount of damage caused

• Modified Mercalli Intensity Scale– Numerical scale from I to XII– I not felt by people– XII total destruction

• Intensity values highest near epicenter

Page 19: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Hazards

• How likely area is to have a damaging quake in the future

Page 20: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Forecasting

Page 21: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Gap Hypothesis• Areas on active faults that haven’t had many

earthquakes are likely to be sites for future strong earthquakes.– Known as seismic gaps

Page 22: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Preparations

• Resistant buildings– Mass damper– Active tendon

system– Base isolators– Cross braces– Flexible pipes

• Retrofitting– Reinforce columns– Fasten to foundation

Page 23: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

What to do in an Earthquake• Before shaking

– Put heavy objects down low– Have an emergency meeting place– Store emergency supplies

• During shaking– Crouch or lie under a strong table or desk– Outside – lay down away from buildings, trees, power

lines– Stop car and stay inside

• After shaking– Stay calm and think– Get away from danger areas– Prepare for aftershocks– Follow emergency plan

Page 24: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Examples

• Normal

• Reverse

• Strike slip

Page 25: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Normal Fault Example

Dixie Valley-Fairview Peaks, Nevada earthquakeDecember 16, 1954

Page 26: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Thrust Fault Example

Page 27: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Thrust Fault Example

Page 28: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Strike-slip Fault Example

Page 29: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Strike-slip Fault Example

1906 San Francisco Earthquake

Page 30: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects

• Ground shaking

• Liquefaction – solid earth turns to liquid

• Surface faulting

• Landslides

• Fires

• Tsunami

Page 31: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Ground Shaking

KGO-TV News ABC-7

Loma Prieta, CA 1989

Page 32: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Ground Shaking

Kobe, Japan 1995

Page 33: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Liquefaction

Source: National Geophysical Data Center

Niigata, Japan 1964

Page 34: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Surface Faulting

Landers, CA 1992

Page 35: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Landslides

Turnagain Heights, Alaska,1964 (upper left inset);Santa Cruz Mtns, California , 1989

Source: National Geophysical Data Center

Page 36: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Fires

KGO-TV News ABC-7

Loma Prieta, CA 1989

Page 37: Earthquakes. Plate Boundaries Sketch the 3 type of plate boundaries.

Earthquake Effects - Tsunamis

Photograph Credit: Henry Helbush. Source: National Geophysical Data Center

1957 Aleutian Tsunami