Earthquakes: Magnitude and Intensity

## Magnitude

magnitude: a measure of energy released by an earthquake

quantitative

as magnitude increases, the earthquake tends to:

affect a broader region

shake for longer (damage more buildings, cause more harm)

## Richter Magnitude Scale

measures amplitude

amplitude: size of the waves on seismograph

logarithmic scale: each degree of magnitude is 10x bigger waves

equates to 50x more energy per degree of magnitude

not accurate for large, deep, or distant earthquakes

no longer used

## Moment Magnitude Scale

the scale that’s now used

measures strain energy along rupture surface (energy released)

logarithmic scale: each degree of magnitude is 10x more energy released

more accurate than richter

most widely accepted and used by scientists

## Intensity

qualitative

what we feel in an earthquake

modified mercalli scale

“I'“ is felt by very few people or not at all to “X” which is total destruction

## Earthquake Intensity

relates to ground motion’s effects on population and structures

rely on “felt” reports

people provide location and their own intensity rating

# Earthquakes: Magnitude and Intensity

## Magnitude

magnitude: a measure of energy released by an earthquake

quantitative

as magnitude increases, the earthquake tends to:

affect a broader region

shake for longer (damage more buildings, cause more harm)

## Richter Magnitude Scale

measures amplitude

amplitude: size of the waves on seismograph

logarithmic scale: each degree of magnitude is 10x bigger waves

equates to 50x more energy per degree of magnitude

not accurate for large, deep, or distant earthquakes

no longer used

## Moment Magnitude Scale

the scale that’s now used

measures strain energy along rupture surface (energy released)

logarithmic scale: each degree of magnitude is 10x more energy released

more accurate than richter

most widely accepted and used by scientists

## Intensity

qualitative

what we feel in an earthquake

modified mercalli scale

“I'“ is felt by very few people or not at all to “X” which is total destruction

## Earthquake Intensity

relates to ground motion’s effects on population and structures

rely on “felt” reports

people provide location and their own intensity rating