Measuring Earthquakes

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 Newscasters say “Richter” but it is really moment magnitude

Mercalli