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Learn about the measurement of earthquakes, including seismic waves and their impact on buildings. Explore the Mercalli Scale and Richter Scale to understand earthquake strength and damage.
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Earthquakes start at the focus • Earthquakes produce seismic (sizemic) waves
Seismic waves are vibrations that travel through Earth carrying the energy released during an earthquake. • They reach the Earth’s surface at the epi-center
Seismic waves carry the energy of an earthquake away from the focus through Earth’s interior and across the surface
Three types of seismic waves • P/Primary waves first to arrive, compress and expand the ground Think p for punctual! Push/pulling • S/ secondary waves vibrate from side to side • cause buildings to contract and expand • Surface waves slowest but produces most severe ground movements
Measuring Earthquakes • Magnitude is a measurement of earthquake strength based on seismic waves and movement along faults
Mercalli Scale • not precise • 12 steps • describes how earthquakes effect buildings and how much damage may be caused by earthquakes of different strengths.
Richter Scale • Rating of the size of seismic waves as measured by a seismograph. • Accurate measurements for small nearby earthquakes not large distant ones. • 1-10 • Newscasters say “Richter” but it is really moment magnitude
