• Measures the strength of shaking produced by an earthquake on a certain location.

• Intensity varies with different locations and depends on the distance from the epicenter.

Intensity

• Measure of energy ​released by an earthquake.

• ​An earthquake has only one magnitude.

Magnitude

​Magnitude Vs. Intensity

• Qualitative (Descriptive)

• Determined by the effects on people, human structures, and natural environment.

• ​The severity of an earthquake can be determined using Mercalli Intensity Scale.

Intensity

• Quantitative (measurable)

• ​Recorded through a seismograph.

• Scale used to determine the strength of an earthquake: ​Richter's Magnitude Scale.

Magnitude

​Magnitude Vs. Intensity

​Seismology

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​Seismology

Definition:

• The study of earthquakes ​and seismic waves that move through and around the earth.

Seismograph

• The instrument used to measure ground movement during an earthquake

​Seismology

Seismic waves

• The vibrations generated by a sudden impulse on the earth.

Seismogram

• The recording of ground shaking produced by the seismograph.

​Types of Seismic Waves

Body Waves

• Travel through the interior of the earth.

  1. P-waves (Primary or Compressional Waves)

  2. S-waves (Secondary or Shear Waves)

• Travels the slower (~3.5km/s in the upper crust)

• Oscillate side to side

• It shears the rock they pass through

S-waves

• Travels the fastest (~6km/s in the upper crust)

• Cause the matter to oscillate forward and backward.

• P-waves push and pull the rock they pass through.

P-waves

​Types of Seismic Waves

​Types of Seismic Waves

Surface Waves

• Travel along the earth's surface.

• Slower than body waves but ​do the damage in earthquakes.

  1. Love Waves - shake the ground side to side (like s waves)

  2. Rayleigh Waves - displace the ground like rolling ocean waves.