Earthquake Magnitude and Measurement

Earthquake Magnitude

• Magnitude is a measure of the energy released during an earthquake, quantifying its size and strength.
• It is a critical concept in seismology for comparing and understanding the relative power of different earthquakes.

Measuring Magnitude

• The Richter Scale:
  • Uses a logarithmic scale to quantify the amplitude of seismic waves recorded by seismographs.
  • Each whole number increase on the Richter scale represents a tenfold increase in measured amplitude and roughly 31.6 times more energy release.

Moment Magnitude Scale (Mw)

• The most commonly used scale today, which measures the total energy released by an earthquake.
• Calculated based on the seismic moment, considering:
  • Area of the fault that slipped
  • Average amount of slip
  • Force required to overcome the friction holding the rocks together
• Provides a more accurate representation of an earthquake's size, especially for very large earthquakes.

Magnitude vs. Intensity

• Magnitude:
  • Measures the energy release of an earthquake at its source.
  • A single, quantitative value.
• Intensity:
  • Measures the effects of an earthquake at different locations on the Earth's surface.
  • Describes the severity of shaking and damage experienced.
  • Varies from place to place and is described using scales like the Modified Mercalli Intensity (MMI) scale.